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Chapter 9The Upper Limb A 64-year-old woman fell down the stairs and was admitted to the emergency department with severe left shoulder pain. While she was sitting up her left arm was by her side and her left elbow was flexed and supported by her right hand. Inspection of the left shoulder showed loss of the normal rounded curvature and evidence of a slight swelling below the left clavicle. The physician then systematically tested the cutaneous sensibility of the left upper limb and found severe sensory deficits involving the skin of the back of the arm down as far as the elbow, the lower lateral surface of the arm down to the elbow, the middle of the posterior surface of the forearm as far as the wrist, the lateral half of the dorsal surface of the hand, and the dorsal surface of the lateral three and a half fingers proximal to the nail beds. A diagnosis of subcoracoid dislocation of the left shoulder joint was made, complicated by damage to the axillary and radial nerves. The head of the humerus was displaced downward to below the coracoid process of the scapula by the initial trauma and was displaced further by the pull of the muscles (subscapularis, pectoralis major). The loss of shoulder curvature was caused by the displacement of the humerus (greater tuberosity) medially so that it no longer pushed the overlying muscle (deltoid) laterally. The extensive loss of skin sensation to the left upper limb was the result of damage to the axillary and radial nerves. For a physician to be able to make a diagnosis in this case and to be able to interpret the clinical findings, he or she must have considerable knowledge of the anatomy of the shoulder joint. Furthermore, the physician must know the relationship of the axillary and radial nerves to the joint and the distribution of these nerves to the parts of the upper limb. P.426
Chapter Objectives

  • Pain, fractures, dislocations, and nerve injuries of the upper limb are commonly seen by the physician. Wrist and hand injuries deserve particular attention because the goal is to preserve as much function as possible. The pincer action of the thumb and index finger and the unique ability of the thumb to be drawn across the palm to the other fingers must be preserved at all costs.
  • A physician must be familiar with the nerves, bones, joints, tendons, and blood and lymphatic vessels and their anatomic relationships.
  • The basic anatomy of the breast is of considerable clinical importance because of the frequent development of cancer in the glands and the subsequent dissemination of the malignant cells along the lymph vessels to the lymph nodes in the armpit.
  • The primary concern of this chapter is to present to the student the basic anatomy of the upper limb so that as a practicing medical professional he or she will be able to make an accurate diagnosis and initiate prompt treatment.

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Basic Anatomy The upper limb is a multijointed lever that is freely movable on the trunk at the shoulder joint. At the distal end of the upper limb is the prehensile organ, the hand. Much of the importance of the hand depends on the pincerlike action of the thumb, which enables one to grasp objects between the thumb and index finger. The upper limb is divided into the shoulder (junction of the trunk with the arm), arm, elbow, forearm, wrist, and hand. The Pectoral Region and the Axilla The Breasts Location and Description The breasts are specialized accessory glands of the skin that secrete milk (Fig. 9-1). They are present in both sexes. In males and immature females, they are similar in structure. The nipples are small and surrounded by a colored area of skin called the areola. The breast tissue consists of a system of ducts embedded in connective tissue that does not extend beyond the margin of the areola. Puberty At puberty in females, the breasts gradually enlarge and assume their hemispherical shape under the influence of the ovarian hormones (Fig. 9-1). The ducts elongate, but the increased size of the glands is mainly from the deposition of fat. The base of the breast extends from the second to the sixth rib and from the lateral margin of the sternum to the midaxillary line. The greater part of the gland lies in the superficial fascia. A small part, called the axillary tail (Fig. 9-1), extends upward and laterally, pierces the deep fascia at the lower border of the pectoralis major muscle, and enters the axilla. Each breast consists of 15 to 20 lobes, which radiate out from the nipple. The main duct from each lobe opens separately on the summit of the nipple and possesses a dilated ampulla just before its termination. The base of the nipple is surrounded by the areola (Fig. 9-1). Tiny tubercles on the areola are produced by the underlying areolar glands. The lobes of the gland are separated by fibrous septa that serve as suspensory ligaments (Fig. 9-1). Behind the breasts is a space filled by loose connective tissue called the retromammary space (Fig. 9-1). Young Women In young women the breasts tend to protrude forward from a circular base. Pregnancy Early In the early months of pregnancy, there is a rapid increase in length and branching in the duct system (Fig. 9-2). The secretory alveoli develop at the ends of the smaller ducts and the connective tissue becomes filled with expanding and budding secretory alveoli. The vascularity of the connective tissue also increases to provide adequate nourishment for the developing gland. The nipple enlarges, and the areola becomes darker and more extensive as a result of increased deposits of melanin pigment in the epidermis. The areolar glands enlarge and become more active. Late During the second half of pregnancy, the growth process slows. The breasts, however, continue to enlarge, mostly because of the distention of the secretory alveoli with the fluid secretion called colostrum. Postweaning Once the baby has been weaned, the breasts return to their inactive state. The remaining milk is absorbed, the secretory alveoli shrink, and most of them disappear. The interlobular connective tissue thickens. The breasts and the nipples shrink and return nearly to their original size. The pigmentation of the areola fades, but the area never lightens to its original color. Postmenopause After the menopause, the breast atrophies (Fig. 9-2). Most of the secretory alveoli disappear, leaving behind the ducts. The amount of adipose tissue may increase or decrease. The breasts tend to shrink in size and become more pendulous. The atrophy after menopause is caused by an absence of ovarian estrogens and progesterone. Blood Supply Arteries The branches to the breasts include the perforating branches of the internal thoracic artery and the intercostal arteries. The axillary artery also supplies the gland via its lateral thoracic and thoracoacromial branches. Veins The veins correspond to the arteries. Lymph Drainage The lymph drainage of the mammary gland is of great clinical importance because of the frequent development of cancer in the gland and the subsequent dissemination of the malignant cells along the lymph vessels to the lymph nodes. The lateral quadrants of the breast drain into the anterior axillary or pectoral group of nodes (Fig. 9-3) (situated just posterior to the lower border of the pectoralis major muscle). The medial quadrants drain by means of vessels that pierce the intercostal spaces and enter the internal thoracic group of nodes (situated within the thoracic cavity along the course of the internal thoracic artery). A few lymph vessels follow the posterior intercostal arteries and drain posteriorly into the posterior intercostal nodes (situated along the course of the posterior intercostal arteries); some vessels communicate with the lymph vessels of the opposite breast and with those of the anterior abdominal wall. Clinical Notes Witch’s Milk in the Newborn While the fetus is in the uterus, the maternal and placental hormones cross the placental barrier and cause proliferation of the duct epithelium and the surrounding connective tissue. This proliferation may cause swelling of the mammary glands in both sexes during the first week of life; in some cases a milky fluid, called witch’s milk, may be expressed from the nipples. The condition is resolved spontaneously as the maternal hormone levels in the child fall. P.428

Figure 9-1 Mature breast in the female. A Anterior view with skin partially removed to show internal structure. B Sagittal section. C The axillary tail, which pierces the deep fascia and extends into the axilla.

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Figure 9-2 Extent of the development of the ducts and secretory alveoli in the breasts in both sexes at different stages of activity.

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Figure 9-3 Lymph drainage of the breast.

Clinical Notes Breast Examination The breast is one of the common sites of cancer in women. It is also the site of different types of benign tumors and may be subject to acute inflammation and abscess formation. For these reasons, the clinical personnel must be familiar with the development, structure, and lymph drainage of this organ. With the patient undressed to the waist and sitting upright, the breasts are first inspected for symmetry. Some degree of asymmetry is common and is the result of unequal breast development. Any swelling should be noted. A swelling can be caused by an underlying tumor, a cyst, or abscess formation. The nipples should be carefully examined for evidence of retraction. A carcinoma within the breast substance can cause retraction of the nipple by pulling on the lactiferous ducts. The patient is then asked to lie down so that the breasts can be palpated against the underlying thoracic wall. Finally, the patient is asked to sit up again and raise both arms above her head. With this maneuver, a carcinoma tethered to the skin, the suspensory ligaments, or the lactiferous ducts produces dimpling of the skin or retraction of the nipple. Mammography Mammography is a radiographic examination of the breast (Fig. 9-4). This technique is extensively used for screening the breasts for benign and malignant tumors and cysts. Extremely low doses of x-rays are used so that the dangers are minimal and the examination can be repeated often. Its success is based on the fact that a lesion measuring only a few millimeters in diameter can be detected long before it is felt by clinical examination. Supernumerary and Retracted Nipples Supernumerary nipples occasionally occur along a line extending from the axilla to the groin; they may or may not be associated with breast tissue (see page 432). This minor congenital anomaly may result in a mistaken diagnosis of warts or moles. A long-standing retracted nipple is a congenital deformity caused by a failure in the complete development of the nipple. A retracted nipple of recent occurrence is usually caused by an underlying carcinoma pulling on the lactiferous ducts.

Figure 9-4 Mediolateral mammogram showing the glandular tissue supported by the connective tissue septa.

The Importance of Fibrous Septa The interior of the breast is divided into 15 to 20 compartments that radiate from the nipple by fibrous septa that extend from the deep surface of the skin. Each compartment contains a lobe of the gland. Normally, the skin feels completely mobile over the breast substance. However, should the fibrous septa become involved in a scirrhous carcinoma or in a disease such as a breast abscess, which results in the production of contracting fibrous tissue, the septa will be pulled on, causing dimpling of the skin. The fibrous septa are sometimes referred to as the suspensory ligaments of the mammary gland. An acute infection of the mammary gland may occur during lactation. Pathogenic bacteria gain entrance to the breast tissue through a crack in the nipple. Because of the presence of the fibrous septa, the infection remains localized to one compartment or lobe to begin with. Abscesses should be drained through a radial incision to avoid spreading of the infection into neighboring compartments; a radial incision also minimizes the damage to the radially arranged ducts. Lymph Drainage and Carcinoma of the Breast The importance of knowing the lymph drainage of the breast in relation to the spread of cancer from that organ cannot be overemphasized. The lymph vessels from the medial quadrants of the breast pierce the second, third, and fourth intercostal spaces and enter the thorax to drain into the lymph nodes alongside the internal thoracic artery. The lymph vessels from the lateral quadrants of the breast drain into the anterior or pectoral group of axillary nodes. It follows, therefore, that a cancer occurring in the lateral quadrants of the breast tends to spread to the axillary nodes. Thoracic metastases are difficult or impossible to treat, but the lymph nodes of the axilla can be removed surgically. Approximately 60% of carcinomas of the breast occur in the upper lateral quadrant. The lymphatic spread of cancer to the opposite breast, to the abdominal cavity, or into lymph nodes in the root of the neck is caused by obstruction of the normal lymphatic pathways by malignant cells or destruction of lymph vessels by surgery or radiotherapy. The cancer cells are swept along the lymph vessels and follow the lymph stream. The entrance of cancer cells into the blood vessels accounts for the metastases in distant bones. In patients with localized cancer of the breast, most surgeons do a simple mastectomy or a lumpectomy, followed by radiotherapy to the axillary lymph nodes and/or hormone therapy. In patients with localized cancer of the breast with early metastases in the axillary lymph nodes, most authorities agree that radical mastectomy offers the best chance of cure. In patients in whom the disease has already spread beyond these areas (e.g., into the thorax), simple mastectomy, followed by radiotherapy or hormone therapy, is the treatment of choice. Radical mastectomy is designed to remove the primary tumor and the lymph vessels and nodes that drain the area. This means that the breast and the associated structures containing the lymph vessels and nodes must be removed en bloc. The excised mass is therefore made up of the following: a large area of skin overlying the tumor and including the nipple; all the breast tissue; the pectoralis major and associated fascia through which the lymph vessels pass to the internal thoracic nodes; the pectoralis minor and associated fascia related to the lymph vessels passing to the axilla; all the fat, fascia, and lymph nodes in the axilla; and the fascia covering the upper part of the rectus sheath, the serratus anterior, the subscapularis, and the latissimus dorsi muscles. The axillary blood vessels, the brachial plexus, and the nerves to the serratus anterior and the latissimus dorsi are preserved. Some degree of postoperative edema of the arm is likely to follow such a radical removal of the lymph vessels draining the upper limb. A modified form of radical mastectomy for patients with clinically localized cancer is also a common procedure and consists of a simple mastectomy in which the pectoral muscles are left intact. The axillary lymph nodes, fat, and fascia are removed. This procedure removes the primary tumor and permits pathologic examination of the lymph nodes for possible metastases. P.431
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Embryologic Notes Development of the Breasts In the young embryo a linear thickening of ectoderm appears called the milk ridge, which extends from the axilla obliquely to the inguinal region. In animals, several mammary glands are formed along this ridge. In the human, the ridge disappears except for a small part in the pectoral region. This localized area thickens, becomes slightly depressed, and sends off 15 to 20 solid cords, which grow into the underlying mesenchyme. Meanwhile, the underlying mesenchyme proliferates, and the depressed ectodermal thickening becomes raised to form the nipple. At the fifth month, the areola is recognized as a circular pigmented area of skin around the future nipple. Polythelia Supernumerary nipples occasionally occur along a line corresponding to the position of the milk ridge. They are liable to be mistaken for moles. Retracted Nipple or Inverted Nipple Retracted nipple is a failure in the development of the nipple during its later stages. It is important clinically, because normal suckling of an infant cannot take place, and the nipple is prone to infection (see also page 430). Micromastia An excessively small breast on one side occasionally occurs, resulting from lack of development. Macromastia Diffuse hypertrophy of one or both breasts occasionally occurs at puberty in otherwise normal girls. Gynecomastia Unilateral or bilateral enlargement of the male breast occasionally occurs, usually at puberty. The cause is unknown, but the condition is probably related to some form of hormonal imbalance. Bones of the Shoulder Girdle and Arm The shoulder girdle consists of the clavicle and the scapula, which articulate with one another at the acromioclavicular joint. Clavicle The clavicle is a long, slender bone that lies horizontally across the root of the neck just beneath the skin. It articulates with the sternum and first costal cartilage medially and with the acromion process of the scapula laterally (Fig. 9-5). The clavicle acts as a strut that holds the arm away from the trunk. It also transmits forces from the upper limb to the axial skeleton and provides attachment for muscles. The medial two thirds of the clavicle is convex forward and its lateral third is concave forward. The important muscles and ligaments attached to the clavicle are shown in Figure 9-6. P.433
Clinical Notes Fractures of the Clavicle The clavicle is a strut that holds the arm laterally so that it can move freely on the trunk. Unfortunately, because of its position, it is exposed to trauma and transmits forces from the upper limb to the trunk. It is the most commonly fractured bone in the body. The fracture usually occurs as a result of a fall on the shoulder or outstretched hand. The force is transmitted along the clavicle, which breaks at its weakest point, the junction of the middle and outer thirds. After the fracture, the lateral fragment is depressed by the weight of the arm, and it is pulled medially and forward by the strong adductor muscles of the shoulder joint, especially the pectoralis major. The medial end is tilted upward by the sternocleidomastoid muscle. The close relationship of the supraclavicular nerves to the clavicle may result in their involvement in callus formation after fracture of the bone. This may be the cause of persistent pain over the side of the neck. Compression of the Brachial Plexus, Subclavian Artery, and Subclavian Vein by the Clavicle The interval between the clavicle and the first rib in some patients may become narrowed and thus is responsible for compression of nerves and blood vessels. (See discussion of thoracic outlet syndrome on page 52.)

Figure 9-5 Muscle attachments to the bones of the thorax, clavicle, scapula, and humerus.

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Figure 9-6 Important muscular and ligamentous attachments to the right clavicle.

Scapula The scapula is a flat triangular bone (Fig. 9-7) that lies on the posterior chest wall between the second and the seventh ribs. On its posterior surface, the spine of the scapula projects backward. The lateral end of the spine is free and forms the acromion, which articulates with the clavicle. The superolateral angle of the scapula forms the pear-shaped glenoid cavity, or fossa, which articulates with the head of the humerus at the shoulder joint. The coracoid process projects upward and forward above the glenoid cavity and provides attachment for muscles and ligaments. Medial to the base of the coracoid process is the suprascapular notch (Fig. 9-7). The anterior surface of the scapula is concave and forms the shallow subscapular fossa. The posterior surface of the scapula is divided by the spine into the supraspinous fossa above and an infraspinous fossa below (Fig. 9-5). The inferior angle of the scapula can be palpated easily in the living subject and marks the level of the seventh rib and the spine of the seventh thoracic vertebra. The important muscles and ligaments attached to the scapula are shown in Figure 9-7. Clinical Notes Fractures of the Scapula Fractures of the scapula are usually the result of severe trauma, such as occurs in run-over accident victims or in occupants of automobiles involved in crashes. Injuries are usually associated with fractured ribs. Most fractures of the scapula require little treatment because the muscles on the anterior and posterior surfaces adequately splint the fragments. Dropped Shoulder and Winged Scapula The position of the scapula on the posterior wall of the thorax is maintained by the tone and balance of the muscles attached to it. If one of these muscles is paralyzed, the balance is upset, as in dropped shoulder, which occurs with paralysis of the trapezius, or winged scapula (Fig. 9-8), caused by paralysis of the serratus anterior. Such imbalance can be detected by careful physical examination. P.435

Figure 9-7 Important muscular and ligamentous attachments to the right scapula.

Humerus The humerus articulates with the scapula at the shoulder joint and with the radius and ulna at the elbow joint. The upper end of the humerus has a head (Fig. 9-9), which forms about one third of a sphere and articulates with the glenoid cavity of the scapula. Immediately below the head is the anatomic neck. Below the neck are the greater and lesser tuberosities, separated from each other by the bicipital groove. Where the upper end of the humerus joins the shaft is a narrow surgical neck. About halfway down the lateral aspect of the shaft is a roughened elevation called the deltoid tuberosity. Behind and below the tuberosity is a spiral groove, which accommodates the radial nerve (Fig. 9-9). The lower end of the humerus possesses the medial and lateral epicondyles for the attachment of muscles and ligaments, the rounded capitulum for articulation with the head of the radius, and the pulley-shaped trochlea for articulation with the trochlear notch of the ulna (Fig. 9-9). Above the capitulum is the radial fossa, which receives the head of the radius when the elbow is flexed. Above the trochlea anteriorly is the coronoid fossa, which during the same movement receives the coronoid process of the ulna. Above the trochlea posteriorly P.436
is the olecranon fossa, which receives the olecranon process of the ulna when the elbow joint is extended (Fig. 9-9).

Figure 9-8 Winging of the right scapula.
Figure 9-9 Important muscular and ligamentous attachments to the right humerus.

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Clinical Notes Fractures of the Proximal End of the Humerus Humeral Head Fractures Fractures of the humeral head (Fig. 9-10) can occur during the process of anterior and posterior dislocations of the shoulder joint. The fibrocartilaginous glenoid labrum of the scapula produces the fracture, and the labrum can become jammed in the defect, making reduction of the shoulder joint difficult. Greater Tuberosity Fractures The greater tuberosity of the humerus can be fractured by direct trauma, displaced by the glenoid labrum during dislocation of the shoulder joint, or avulsed by violent contractions of the supraspinatus muscle. The bone fragment will have the attachments of the supraspinatus, teres minor, and infraspinatus muscles, whose tendons form part of the rotator cuff. When associated with a shoulder dislocation, severe tearing of the cuff with the fracture can result in the greater tuberosity remaining displaced posteriorly after the shoulder joint has been reduced. In this situation, open reduction of the fracture is necessary to attach the rotator cuff back into place. Lesser Tuberosity Fractures Occasionally, a lesser tuberosity fracture accompanies posterior dislocation of the shoulder joint. The bone fragment receives the insertion of the subscapularis tendon (Fig. 9-10), a part of the rotator cuff. Surgical Neck Fractures The surgical neck of the humerus (Fig. 9-10), which lies immediately distal to the lesser tuberosity, can be fractured by a direct blow on the lateral aspect of the shoulder or in an indirect manner by falling on the outstretched hand. Fractures of the Shaft of the Humerus Fractures of the humeral shaft are common; displacement of the fragments depends on the relation of the site of fracture to the insertion of the deltoid muscle (Fig. 9-10). When the fracture line is proximal to the deltoid insertion, the proximal fragment is adducted by the pectoralis major, latissimus dorsi, and teres major muscles; the distal fragment is pulled proximally by the deltoid, biceps, and triceps. When the fracture is distal to the deltoid insertion, the proximal fragment is abducted by the deltoid, and the distal fragment is pulled proximally by the biceps and triceps. The radial nerve can be damaged where it lies in the spiral groove on the posterior surface of the humerus under cover of the triceps muscle. Fractures of the Distal End of the Humerus Supracondylar fractures (Fig. 9-10) are common in children and occur when the child falls on the outstretched hand with the elbow partially flexed. Injuries to the median, radial, and ulnar nerves are not uncommon, although function usually quickly returns after reduction of the fracture. Damage to or pressure on the brachial artery can occur at the time of the fracture or from swelling of the surrounding tissues; the circulation to the forearm may be interfered with, leading to Volkmann’s ischemic contracture (see page 483). The medial epicondyle (Fig. 9-10) can be avulsed by the medial collateral ligament of the elbow joint if the forearm is forcibly abducted. The ulnar nerve can be injured at the time of the fracture, can become involved later in the repair process of the fracture (in the callus), or can undergo irritation on the irregular bony surface after the bone fragments are reunited. The important muscles and ligaments attached to the humerus are shown in Figure 9-9. The Axilla The axilla, or armpit, is a pyramid-shaped space between the upper part of the arm and the side of the chest (Fig. 9-11). It forms an important passage for nerves, blood, and lymph vessels as they travel from the root of the neck to the upper limb. The upper end of the axilla, or apex, is directed into the root of the neck and is bounded in front by the clavicle, behind by the upper border of the scapula, and medially by the outer border of the first rib (Fig. 9-11). The lower end, or base, is bounded in front by the anterior axillary fold (formed by the lower border of the pectoralis major muscle), behind by the posterior axillary fold (formed by the tendon of latissimus dorsi and the teres major muscle), and medially by the chest wall (Fig. 9-11). Walls of the Axilla The walls of the axilla are made up as follows:

  • Anterior wall: By the pectoralis major, subclavius, and pectoralis minor muscles (Figs. 9-12, 9-13, and 9-14)
  • Posterior wall: By the subscapularis, latissimus dorsi, and teres major muscles from above down (Figs. 9-13, 9-14, 9-15, and 9-16)
  • Medial wall: By the upper four or five ribs and the intercostal spaces covered by the serratus anterior muscle (Figs. 9-14, 9-15, and 9-16)
  • Lateral wall: By the coracobrachialis and biceps muscles in the bicipital groove of the humerus (Figs. 9-14, 9-15, and 9-16)

The base is formed by the skin stretching between the anterior and posterior walls (Fig. 9-14). The axilla contains the principal vessels and nerves to the upper limb and many lymph nodes. The origins, insertions, nerve supply, and actions of the muscles forming the walls of the axilla are described in Tables 9-1, 9-2, and 9-3. P.438

Figure 9-10 A Common fractures of the humerus. B Common fractures of the radius and ulna. The displacement of the bony fragments on the site of the fracture line and the pull of the muscles. S, supraspinatus; D, deltoid; PM, pectoralis major; CF, pull of common flexure muscles; TR, triceps; SUB, subscapularis.

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Figure 9-11 Inlet, walls, and outlet of the right axilla.

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Figure 9-12 Pectoral region and axilla.
Figure 9-13 Pectoral region and axilla; the pectoralis major muscle has been removed to display the underlying structures.

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Figure 9-14 Structures that form the walls of the axilla. The lateral wall is indicated by the arrow.
Table 9-1 Muscles Connecting the Upper Limb to the Thoracic Wall
Muscle Origin Insertion Nerve Supply Nerve Rootsa Action
Pectoralis major Clavicle, sternum, and upper six costal cartilages Lateral lip of bicipital groove of humerus Medial and lateral pectoral nerves from brachial plexus C5, 6, 7, 8; T1 Adducts arm and rotates it medially; clavicular fibers also flex arm
Pectoralis minor Third, fourth, and fifth ribs Coracoid process of scapula Medial pectoral nerve from brachial plexus C6, 7, 8 Depresses point of shoulder; if the scapula is fixed, it elevates the ribs of origin
Subclavius First costal cartilage Clavicle Nerve to subclavius from upper trunk of brachial plexus C5, 6 Depresses the clavicle and steadies this bone during movements of the shoulder girdle
Serratus anterior Upper eight ribs Medial border and inferior angle of scapula Long thoracic nerve C5, 6, 7 Draws the scapula forward around the thoracic wall; rotates scapula
a The predominant nerve root supply is indicated by boldface type.

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Table 9-2 Muscles Connecting the Upper Limb to the Vertebral Column
Muscle Origin Insertion Nerve Supply Nerve Rootsa Action
Trapezius Occipital bone, ligamentum nuchae, spine of seventh cervical vertebra, spines of all thoracic vertebrae Upper fibers into lateral third of clavicle; middle and lower fibers into acromion and spine of scapula Spinal part of accessory nerve (motor) and C3 and 4 (sensory) XI cranial nerve (spinal part) Upper fibers elevate the scapula; middle fibers pull scapula medially; lower fibers pull medial border of scapula downward
Latissimus dorsi Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower three or four ribs, and inferior angle of scapula Floor of bicipital groove of humerus Thoracodorsal nerve C6, 7, 8, Extends, adducts, and medially rotates the arm
Levator scapulae Transverse processes of first four cervical vertebrae Medial border of scapula C3 and 4 and dorsal scapular nerve C3, 4, 5 Raises medial border of scapula
Rhomboid minor Ligamentum nuchae and spines of seventh cervical and first thoracic vertebrae Medial border of scapula Dorsal scapular nerve C4, 5 Raises medial border of scapula upward and medially
Rhomboid major Second to fifth thoracic spines Medial border of scapula Dorsal scapular nerve C4, 5 Raises medial border of scapula upward and medially
a The predominant nerve root supply is indicated by boldface type.
Table 9-3 Muscles Connecting the Scapula to the Humerus
Muscle Origin Insertion Nerve Supply Nerve Rootsa Action
Deltoid Lateral third of clavicle, acromion, spine of scapula Middle of lateral surface of shaft of humerus Axillary nerve C5, 6 Abducts arm; anterior fibers flex and medially rotate arm; posterior fibers extend and laterally rotate arm
Supraspinatus Supraspinous fossa of scapula Greater tuberosity of humerus; capsule of shoulder joint Suprascapular nerve C4, 5, 6 Abducts arm and stabilizes shoulder joint
Infraspinatus Infraspinous fossa of scapula Greater tuberosity of humerus; capsule of shoulder joint Suprascapular nerve (C4), 5, 6 Laterally rotates arm and stabilizes shoulder joint
Teres major Lower third of lateral border of scapula Medial lip of bicipital groove of humerus Lower subscapular nerve C6, 7 Medially rotates and adducts arm and stabilizes shoulder joint
Teres minor Upper two thirds of lateral border of scapula Greater tuberosity of humerus; capsule of shoulder joint Axillary nerve (C4), C5, 6 Laterally rotates arm and stabilizes shoulder joint
Subscapularis Subscapular fossa Lesser tuberosity of humerus Upper and lower subscapular nerves C5, 6, 7 Medially rotates arm and stabilizes shoulder joint
aThe predominant nerve root supply is indicated by boldface type.

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Figure 9-15 Pectoral region and axilla; the pectoralis major and minor muscles and the clavipectoral fascia have been removed to display the underlying structures.

Key Muscles in the Axilla Pectoralis Minor The pectoralis minor is a thin triangular muscle that lies beneath the pectoralis major (Fig. 9-13). It arises from the third, fourth, and fifth ribs and runs upwards and laterally to be inserted by its apex into the coracoid process of the scapula. It crosses the axillary artery and the brachial plexus of nerves. It is used when describing the axillary artery to divide it into three parts (see page 445). Clinical Notes Absent Pectoralis Major Occasionally, parts of the pectoralis major muscle may be absent. The sternocostal origin is the most commonly missing part, and this causes weakness in adduction and medial rotation of the shoulder joint. P.444

Figure 9-16 Dissection of the right axilla. The pectoralis major and minor muscles and the clavipectoral fascia have been removed to display the underlying structures.

Clavipectoral Fascia The clavipectoral fascia is a strong sheet of connective tissue that is attached above to the clavicle (Figs. 9-13 and 9-14). Below, it splits to enclose the pectoralis minor muscle and then continues downward as the suspensory ligament of the axilla and joins the fascial floor of the armpit. Contents of the Axilla The axilla contains the axillary artery and its branches, which supply blood to the upper limb; the axillary vein and its tributaries, which drain blood from the upper limb; and lymph vessels and lymph nodes, which drain lymph from the upper limb and the breast and from the skin of the trunk, down as far as the level of the umbilicus. Lying among these structures in the axilla is an important nerve plexus, the brachial plexus, which innervates the upper limb. These structures are embedded in fat. Axillary Artery The axillary artery (Figs. 9-12, 9-13, 9-15, and 9-16) begins at the lateral border of the first rib as a continuation of the subclavian (Fig. 9-17) and ends at the lower border of the teres major muscle, where it continues as the brachial artery. Throughout its course, the artery is closely related to the cords of the brachial plexus and their branches and is enclosed with them in a connective tissue sheath called the axillary sheath. If this sheath is traced upward into the root P.445
of the neck, it is seen to be continuous with the prevertebral fascia.

Figure 9-17 Parts of the axillary artery and its branches. Note formation of the axillary vein at the lower border of the teres major muscle.

The pectoralis minor muscle crosses in front of the axillary artery and divides it into three parts (Figs. 9-13, 9-15, and 9-17). First Part of the Axillary Artery This extends from the lateral border of the first rib to the upper border of the pectoralis minor (Fig. 9-17). Relations

  • Anteriorly: The pectoralis major and the skin. The cephalic vein crosses the artery (Figs. 9-13 and 9-15).
  • Posteriorly: The long thoracic nerve (nerve to the serratus anterior) (Fig. 9-15)
  • Laterally: The three cords of the brachial plexus (Fig. 9-15)
  • Medially: The axillary vein (Fig. 9-15 and 9-16)

Second Part of the Axillary Artery This lies behind the pectoralis minor muscle (Fig. 9-17). Relations

  • Anteriorly: The pectoralis minor, the pectoralis major, and the skin (Figs. 9-13 and 9-17)
  • Posteriorly: The posterior cord of the brachial plexus, the subscapularis muscle, and the shoulder joint (Fig. 9-15)
  • Laterally: The lateral cord of the brachial plexus (Figs. 9-13, 9-15, and 9-16)
  • Medially: The medial cord of the brachial plexus and the axillary vein (Figs. 9-15, 9-16, and 9-20)

Third Part of the Axillary Artery This extends from the lower border of the pectoralis minor to the lower border of the teres major (Fig. 9-17). Relations

  • Anteriorly: The pectoralis major for a short distance; lower down the artery it is crossed by the medial root of the median nerve (Fig. 9-13).
  • Posteriorly: The subscapularis, the latissimus dorsi, and the teres major. The axillary and radial nerves also lie behind the artery (Figs. 9-15 and 9-16).
  • Laterally: The coracobrachialis, the biceps, and the humerus. The lateral root of the median and the musculocutaneous nerves also lie on the lateral side (Figs. 9-13 and 9-16).
  • Medially: The ulnar nerve, the axillary vein, and the medial cutaneous nerve of the arm (Fig. 9-13)

Branches of the Axillary Artery From the first part:

  • The highest thoracic artery is small and runs along the upper border of the pectoralis minor.

From the second part:

  • The thoracoacromial artery immediately divides into terminal branches.
  • The lateral thoracic artery runs along the lower border of the pectoralis minor (Fig. 9-17).

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Figure 9-18 The formation of the main parts of the brachial plexus. Note the locations of the different parts.

From the third part:

  • The subscapular artery runs along the lower border of the subscapularis muscle.
  • The anterior and posterior circumflex humeral arteries wind around the front and the back of the surgical neck of the humerus, respectively (Fig. 9-17).

Clinical Notes The Axillary Sheath and a Brachial Plexus Nerve Block Because the axillary sheath encloses the axillary vessels and the brachial plexus, a brachial plexus nerve block can easily be obtained. The distal part of the sheath is closed with finger pressure, and a syringe needle is inserted into the proximal part of the sheath. The anesthetic solution is then injected into the sheath, and the solution is massaged along the sheath to produce the nerve block. The position of the sheath can be verified by feeling the pulsations of the third part of the axillary artery. Axillary Vein The axillary vein (Fig. 9-12) is formed at the lower border of the teres major muscle by the union of the venae comitantes of the brachial artery and the basilic vein (Fig. 9-17). It runs upward on the medial side of the axillary artery and ends at the lateral border of the first rib by becoming the subclavian vein. The vein receives tributaries, which correspond to the branches of the axillary artery, and the cephalic vein. Clinical Notes Spontaneous Thrombosis of the Axillary Vein Spontaneous thrombosis of the axillary vein occasionally occurs after excessive and unaccustomed movements of the arm at the shoulder joint. Brachial Plexus The nerves entering the upper limb provide the following important functions: sensory innervation to the skin and deep structures, such as the joints; motor innervation to the muscles; influence over the diameters of the blood vessels by the sympathetic vasomotor nerves; and sympathetic secretomotor supply to the sweat glands. At the root of the neck, the nerves form a complicated plexus called the brachial plexus. This allows the nerve fibers derived from different segments of the spinal cord to P.447
be arranged and distributed efficiently in different nerve trunks to the various parts of the upper limb. The brachial plexus is formed in the posterior triangle of the neck by the union of the anterior rami of the fifth, sixth, seventh, and eighth cervical and the first thoracic spinal nerves (Figs. 9-18 and 9-19). The plexus can be divided into roots, trunks, divisions, and cords (Fig. 9-18). The roots of C5 and 6 unite to form the upper trunk, the root of C7 continues as the middle trunk, and the roots of C8 and T1 unite to form the lower trunk. Each trunk then divides into anterior and posterior divisions. The anterior divisions of the upper and middle trunks unite to form the lateral cord, the anterior division of the lower trunk continues as the medial cord, and the posterior divisions of all three trunks join to form the posterior cord. The roots, trunks, and divisions of the brachial plexus reside in the lower part of the posterior triangle of the neck and are fully described on page 771. The cords become arranged around the axillary artery in the axilla (Fig. 9-15). Here, the brachial plexus and the axillary artery and vein are enclosed in the axillary sheath. Cords of the Brachial Plexus All three cords of the brachial plexus lie above and lateral to the first part of the axillary artery (Figs. 9-15 and 9-20). The medial cord crosses behind the artery to reach the medial side of the second part of the artery (Fig. 9-20). The posterior cord lies behind the second part of the artery, and the lateral cord lies on the lateral side of the second part of the artery (Fig. 9-20). Thus, the cords of the plexus have the relationship to the second part of the axillary artery that is indicated by their names.

Figure 9-19 Roots, trunks, divisions, cords, and terminal branches of the brachial plexus.

Most branches of the cords that form the main nerve trunks of the upper limb continue this relationship to the artery in its third part (Fig. 9-20). The branches of the different parts of the brachial plexus (Figs. 9-19 and 9-21) are as follows:

  • Roots Dorsal scapular nerve (C5) Long thoracic nerve (C5, 6, and 7)
  • Upper trunk Nerve to subclavius (C5 and 6) Suprascapular nerve (supplies the supraspinatus and infraspinatus muscles)
  • Lateral cord Lateral pectoral nerve Musculocutaneous nerve Lateral root of median nerve
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  • Medial cord Medial pectoral nerve Medial cutaneous nerve of arm and medial cutaneous nerve of forearm Ulnar nerve Medial root of median nerve
  • Posterior cord Upper and lower subscapular nerves Thoracodorsal nerve Axillary nerve Radial nerve
Figure 9-20 A Relations of the brachial plexus and its branches to the axillary artery and vein. B Section through the axilla at the level of the teres major muscle.

The branches of the brachial plexus and their distribution are summarized in Table 9-4. Branches of the Brachial Plexus Found in the Axilla The nerve to the subclavius (C5 and 6) supplies the subclavius muscle (Figs. 9-15, 9-19, and 9-20). It is important clinically because it may give a contribution (C5) to the phrenic nerve; this branch, when present, is referred to as the accessory phrenic nerve. The long thoracic nerve (C5, 6, and 7) arises from the roots of the brachial plexus in the neck and enters the axilla by passing down over the lateral border of the first rib behind the axillary vessels and brachial plexus (Figs. 9-15 and P.449
9-19). It descends over the lateral surface of the serratus anterior muscle, which it supplies.

Figure 9-21 Distribution of the main branches of the brachial plexus to different fascial compartments of the arm and forearm.

The lateral pectoral nerve arises from the lateral cord of the brachial plexus and supplies the pectoralis major muscle (Figs. 9-13 and 9-20). The musculocutaneous nerve arises from the lateral cord of the brachial plexus, supplies the coracobrachialis muscle, and leaves the axilla by piercing that muscle (Figs. 9-13 and 9-20). A summary of the complete distribution of the musculocutaneous nerve is given in Figure 9-22. The lateral root of the median nerve is the direct continuation of the lateral cord of the brachial plexus (Figs. 9-13 and 9-19). It is joined by the medial root to form the median nerve trunk, and this passes downward on the lateral side of the axillary artery. The median nerve gives off no branches in the axilla. The medial pectoral nerve arises from the medial cord of the brachial plexus, supplies and pierces the pectoralis minor muscle, and supplies the pectoralis major muscle (Fig. 9-19). The medial cutaneous nerve of the arm (T1) arises from the medial cord of the brachial plexus (Figs. 9-12 and 9-20) and is joined by the intercostobrachial nerve (lateral cutaneous branch of the second intercostal nerve). It supplies the skin on the medial side of the arm. The medial cutaneous nerve of the forearm arises from the medial cord of the brachial plexus and descends in front of the axillary artery (Fig. 9-20). The ulnar nerve (C8 and T1) arises from the medial cord of the brachial plexus and descends in the interval between the axillary artery and vein (Figs. 9-13 and 9-20). The ulnar nerve gives off no branches in the axilla. A summary of the complete distribution of the ulnar nerve is given in Figure 9-23. The medial root of the median nerve arises from the medial cord of the brachial plexus and crosses in front of the third part of the axillary artery to join the lateral root of the median nerve (Figs. 9-13 and 9-20). A summary diagram of the complete distribution of the median nerve is given in Figure 9-22. The upper and lower subscapular nerves arise from the posterior cord of the brachial plexus and supply the upper and lower parts of the subscapularis muscle. In addition, the lower subscapular nerve supplies the teres muscle (Figs. 9-15 and 9-19). P.450

Table 9-4 Summary of the Branches of the Brachial Plexus and Their Distribution
Branches Distribution
Roots
Dorsal scapular nerve (C5) Rhomboid minor, rhomboid major, levator scapulae muscles
Long thoracic nerve (C5, 6, 7) Serratus anterior muscle
Upper Trunk
Suprascapular nerve (C5, 6) Supraspinatus and infraspinatus muscles
Nerve to subclavius (C5, 6) Subclavius
Lateral Cord
Lateral pectoral nerve (C5, 6, 7) Pectoralis major muscle
Musculocutaneous nerve (C5, 6, 7) Coracobrachialis, biceps brachii, brachialis muscles; supplies skin along lateral border of forearm when it becomes the lateral cutaneous nerve of forearm
Lateral root of median nerve (C5, 6, 7) See medial root of median nerve
Posterior Cord
Upper subscapular nerve (C5, 6) Subscapularis muscle
Thoracodorsal nerve (C6, 7, 8) Latissimus dorsi muscle
Lower subscapular nerve (C5, 6) Subscapularis and teres major muscles
Axillary nerve (C5, 6) Deltoid and teres minor muscles; upper lateral cutaneous nerve of arm supplies skin over lower half of deltoid muscle
Radial nerve (C5, 6, 7, 8; T1) Triceps, anconeus, part of brachialis, extensor carpi radialis longus; via deepradial nerve branch supplies extensor muscles of forearm: supinator, extensorcarpi radialis brevis, extensor carpi ulnaris, extensor digitorum, extensor digitiminimi, extensor indicis, abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis; skin, lower lateral cutaneous nerve of arm, posteriorcutaneous nerve of arm, and posterior cutaneous nerve of forearm; skin onlateral side of dorsum of hand and dorsal surface of lateral three and a halffingers; articular branches to elbow, wrist, and hand
Medial Cord
Medial pectoral nerve (C8; T1) Pectoralis major and minor muscles
Medial cutaneous nerve of arm joined by intercostal brachial nerve from second intercostal nerve (C8; T1, 2) Skin of medial side of arm
Medial cutaneous nerve of forearm (C8; T1) Skin of medial side of forearm
Ulnar nerve (C8; T1) Flexor carpi ulnaris and medial half of flexor digitorum profundus, flexor digitiminimi, opponens digiti minimi, abductor digiti minimi, adductor pollicis, third and fourth lumbricals, interossei, palmaris brevis, skin of medial half ofdorsum of hand and palm, skin of palmar and dorsal surfaces of medial oneand a half fingers
Medial root of median nerve (with lateral root) forms median nerve (C5, 6, 7, 8; T1) Pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis, abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, first twolumbricals (by way of anterior interosseous branch), flexor pollicis longus, flexor digitorum profundus (lateral half), pronator quadratus; palmar cutaneousbranch to lateral half of palm and digital branches to palmar surface of lateralthree and a half fingers; articular branches to elbow, wrist, and carpal joints

The thoracodorsal nerve arises from the posterior cord of the brachial plexus and runs downward to supply the latissimus dorsi muscle (Figs. 9-15 and 9-19). The axillary nerve is one of the terminal branches of the posterior cord of the brachial plexus (Figs. 9-15 and 9-19). It turns backward and passes through the quadrangular space (see page 458). Having given off a branch to the shoulder joint, it divides into anterior and posterior branches (see page 458). A summary of the complete distribution of the axillary nerve is given in Figure 9-24. The radial nerve is the largest branch of the brachial plexus and lies behind the axillary artery (Figs. 9-15, 9-19, and 9-20). It gives off branches to the long and medial heads of the triceps muscle and the posterior cutaneous nerve of the arm (Fig. 9-13). The latter branch is distributed to the skin on the middle of the back of the arm. A summary of the complete distribution of the radial nerve is given in Figure 9-25. Lesions of the brachial plexus and its branches are described on page 536. Lymph Nodes of the Axilla The axillary lymph nodes (20 to 30 in number) drain lymph vessels from the lateral quadrants of the breast, the superficial P.451
lymph vessels from the thoracoabdominal walls above the level of the umbilicus, and the vessels from the upper limb.

Figure 9-22 Summary of the main branches of the musculocutaneous and median nerves.

The lymph nodes are arranged in six groups (Fig. 9-26).

  • Anterior (pectoral) group: Lying along the lower border of the pectoralis minor behind the pectoralis major, these nodes receive lymph vessels from the lateral quadrants of the breast and superficial vessels from the anterolateral abdominal wall above the level of the umbilicus.
  • Posterior (subscapular) group: Lying in front of the subscapularis muscle, these nodes receive superficial lymph vessels from the back, down as far as the level of the iliac crests.
  • Lateral group: Lying along the medial side of the axillary vein, these nodes receive most of the lymph vessels of the upper limb (except those superficial vessels draining the lateral side see infraclavicular nodes, below).
  • Central group: Lying in the center of the axilla in the axillary fat, these nodes receive lymph from the above three groups.
  • Infraclavicular (deltopectoral) group: These nodes are not strictly axillary nodes because they are located outside the axilla. They lie in the groove between the deltoid and pectoralis major muscles and receive superficial lymph vessels from the lateral side of the hand, forearm, and arm.
  • Apical group: Lying at the apex of the axilla at the lateral border of the first rib, these nodes receive the efferent lymph vessels from all the other axillary nodes.

The apical nodes drain into the subclavian lymph trunk. On the left side, this trunk drains into the thoracic duct; on the right side, it drains into the right lymph trunk. Alternatively, the lymph trunks may drain directly into one of the large veins at the root of the neck. P.452

Figure 9-23 Summary of the main branches of the ulnar nerve.
Figure 9-24 Summary of the main branches of the axillary nerve.

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Figure 9-25 Summary of the main branches of the radial nerve.
Figure 9-26 Different groups of lymph nodes in the axilla.

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Clinical Notes Examination of the Axillary Lymph Nodes With the patient standing or sitting, he or she is asked to place the hand of the side to be examined on the hip and push hard medially. This action of adduction of the shoulder joint causes the pectoralis major muscle to contract maximally so that it becomes hard like a board. The examiner then palpates the axillary nodes (Fig. 9-26) as follows:

  • The anterior (pectoral) nodes may be palpated by pressing forward against the posterior surface of the pectoralis major muscle on the anterior wall of the axilla.
  • The posterior (subscapular) nodes may be palpated by pressing backward against the anterior surface of the subscapularis muscle on the posterior wall of the axilla.
  • The lateral nodes may be palpated against the medial side of the axillary vein. The examiner’s fingers are pressed laterally against the subclavian vein and the pulsating axillary artery.
  • The central nodes may be palpated in the center of the axilla between the pectoralis major (anterior wall) and the subscapularis (posterior wall).
  • For the apical nodes, the patient is asked to relax the shoulder muscles and let the upper limb hang down at the side. The examiner then gently places the tips of the fingers of the examining hand high up in the axilla to the outer border of the first rib. If the nodes are enlarged they can be felt.

The examination of the axillary lymph nodes always forms part of the clinical examination of the breast. The Superficial Part of the Back and the Scapular Region Skin The sensory nerve supply to the skin of the back is from the posterior rami of the spinal nerves (see Fig. 1-24). The first and eighth cervical nerves do not supply the skin, and the posterior rami of the upper three lumbar nerves run downward to supply the skin over the buttock. The blood supply to the skin is from the posterior branches of the posterior intercostal arteries and the lumbar arteries. The veins correspond to the arteries and drain into the azygos veins and the inferior vena cava. The lymph drainage of the skin of the back above the level of the iliac crests is upward into the posterior group of axillary lymph nodes. Bones of the Back The underlying bones of the back are shown in Figure 9-27 and are described in detail in Chapter 12. Muscles The muscles on the back connecting the upper limb to the thoracic wall and the vertebral column are shown in Figure 9-28 and are described in Tables 9-1 and 9-2, and the muscles connecting the scapula to the humerus are shown in Figure 9-29 and are described in Table 9-3. Rotator Cuff The rotator cuff is the name given to the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles, which are fused to the underlying capsule of the shoulder joint (Fig. 9-34). The cuff plays a very important role in stabilizing the shoulder joint. The tone of these muscles assists in holding the head of the humerus in the glenoid cavity of the scapula during movements at the shoulder joint. The cuff lies on the anterior, superior, and posterior aspects of the joint. The cuff is deficient inferiorly, and this is a site of potential weakness. Clinical Notes Rotator Cuff Tendinitis The rotator cuff, consisting of the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles, which are fused to the underlying capsule of the shoulder joint, plays an important role in stabilizing the shoulder joint. Lesions of the cuff are a common cause of pain in the shoulder region. Excessive overhead activity of the upper limb may be the cause of tendinitis, although many cases appear spontaneously. During abduction of the shoulder joint, the supraspinatus tendon is exposed to friction against the acromion (Fig. 9-30). Under normal conditions, the amount of friction is reduced to a minimum by the large subacromial bursa, which extends laterally beneath the deltoid. Degenerative changes in the bursa are followed by degenerative changes in the underlying supraspinatus tendon, and these may extend into the other tendons of the rotator cuff. Clinically, the condition is known as subacromial bursitis, supraspinatus tendinitis, or pericapsulitis. It is characterized by the presence of a spasm of pain in the middle range of abduction (Fig. 9-30), when the diseased area impinges on the acromion. Rupture of the Supraspinatus Tendon In advanced cases of rotator cuff tendinitis, the necrotic supraspinatus tendon can become calcified or rupture. Rupture of the tendon seriously interferes with the normal abduction movement of the shoulder joint. It will be remembered that the main function of the supraspinatus muscle is to hold the head of the humerus in the glenoid fossa at the commencement of abduction. The patient with a ruptured supraspinatus tendon is unable to initiate abduction of the arm. However, if the arm is passively assisted for the first 15° of abduction, the deltoid can then take over and complete the movement to a right angle. P.455

Figure 9-27 Bones of the back.

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Figure 9-28 Superficial and deep muscles of the back.

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Figure 9-29 Muscles, nerves, and blood vessels of the scapular region. Note the close relation of the axillary nerve to the shoulder joint.
Figure 9-30 Subacromial bursitis, supraspinatus tendinitis, or pericapsulitis showing the painful arc in the middle range of abduction, when the diseased area impinges on the lateral edge of the acromion.

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Quadrangular Space The quadrangular space is an intermuscular space, located immediately below the shoulder joint. It is bounded above by the subscapularis and capsule of the shoulder joint and below by the teres major muscle. It is bounded medially by the long head of the triceps and laterally by the surgical neck of the humerus. The axillary nerve and the posterior circumflex humeral vessels pass backward through this space (Fig. 9-29). Nerves Spinal Part of the Accessory Nerve (Cranial Nerve XI) The spinal part of the accessory nerve runs downward in the posterior triangle of the neck on the levator scapulae muscle. It is accompanied by branches from the anterior rami of the third and fourth cervical nerves. The accessory nerve runs beneath the anterior border of the trapezius muscle (Fig. 9-28) at the junction of its middle and lower thirds and, together with the cervical nerves, supplies the trapezius muscle. Clinical Notes Accessory Nerve Injury The accessory nerve can be injured as the result of stab wounds to the neck. Suprascapular Nerve The suprascapular nerve arises from the upper trunk of the brachial plexus (C5 and 6) in the posterior triangle in the neck. It runs downward and laterally and passes beneath the suprascapular ligament, which bridges the suprascapular notch, to reach the supraspinous fossa (Fig. 9-29). It supplies the supraspinatus and infraspinatus muscles and the shoulder joint. Axillary Nerve The axillary nerve arises from the posterior cord of the brachial plexus (C5 and 6) in the axilla (see page 450). It passes backward and enters the quadrangular space with the posterior circumflex humeral artery (Fig. 9-29). As the nerve passes through the space, it comes into close relationship with the inferior aspect of the capsule of the shoulder joint and with the medial side of the surgical neck of the humerus. It terminates by dividing into anterior and posterior branches (Fig. 9-29). Branches The axillary nerve has the following branches:

  • An articular branch to the shoulder joint
  • An anterior terminal branch, which winds around the surgical neck of the humerus beneath the deltoid muscle; it supplies the deltoid and the skin that covers its lower part.
  • A posterior terminal branch, which gives off a branch to the teres minor muscle and a few branches to the deltoid, then emerges from the posterior border of the deltoid as the upper lateral cutaneous nerve of the arm (Fig. 9-29)

It is thus seen that the axillary nerve supplies the shoulder joint, two muscles, and the skin covering the lower half of the deltoid muscle. Clinical Notes Axillary Nerve Injury The axillary nerve can be injured in dislocations of the shoulder joint. Arterial Anastomosis Around the Shoulder Joint The extreme mobility of the shoulder joint may result in kinking of the axillary artery and a temporary occlusion of its lumen. To compensate for this, an important arterial anastomosis exists between the branches of the subclavian artery and the axillary artery, thus ensuring that an adequate blood flow takes place into the upper limb irrespective of the position of the arm (Fig. 9-31). Branches from the Subclavian Artery

  • The suprascapular artery, which is distributed to the supraspinous and infraspinous fossae of the scapula
  • The superficial cervical artery, which gives off a deep branch that runs down the medial border of the scapula

Branches from the Axillary Artery

  • The subscapular artery and its circumflex scapular branch supply the subscapular and infraspinous fossae of the scapula, respectively.
  • The anterior circumflex humeral artery
  • The posterior circumflex humeral artery

Both the circumflex arteries form an anastomosing circle around the surgical neck of the humerus (Fig. 9-31). Clinical Notes Arterial Anastomosis and Ligation of the Axillary Artery The existence of the anastomosis around the shoulder joint is vital to preserving the upper limb should it be necessary to ligate the axillary artery. P.459

Figure 9-31 Arteries that take part in anastomosis around the shoulder joint.

Sternoclavicular Joint

  • Articulation: This occurs between the sternal end of the clavicle, the manubrium sterni, and the first costal cartilage (Fig. 9-32).
  • Type: Synovial double-plane joint
  • Capsule: This surrounds the joint and is attached to the margins of the articular surfaces.
  • Ligaments: The capsule is reinforced in front of and behind the joint by the strong sternoclavicular ligaments.
  • Articular disc: This flat fibrocartilaginous disc lies within the joint and divides the joint’s interior into two compartments (Fig. 9-32). Its circumference is attached to the interior of the capsule, but it is also strongly attached to the superior margin of the articular surface of the clavicle above and to the first costal cartilage below.
  • Accessory ligament: The costoclavicular ligament is a strong ligament that runs from the junction of the first rib with the first costal cartilage to the inferior surface of the sternal end of the clavicle (Fig. 9-32).
  • Synovial membrane: This lines the capsule and is attached to the margins of the cartilage covering the articular surfaces.
  • Nerve supply: The supraclavicular nerve and the nerve to the subclavius muscle

Movements Forward and backward movement of the clavicle takes place in the medial compartment. Elevation and depression of the clavicle take place in the lateral compartment. Muscles Producing Movement The forward movement of the clavicle is produced by the serratus anterior muscle. The backward movement is produced by the trapezius and rhomboid muscles. Elevation of the clavicle is produced by the trapezius, sternocleidomastoid, levator scapulae, and rhomboid muscles. Depression of the clavicle is produced by the pectoralis minor and the subclavius muscles (Fig. 9-33). P.460

Figure 9-32 A Sternoclavicular joint. B Acromioclavicular joint.

Important Relations

  • Anteriorly: The skin and some fibers of the sternocleidomastoid and pectoralis major muscles
  • Posteriorly: The sternohyoid muscle; on the right, the brachiocephalic artery; on the left, the left brachiocephalic vein and the left common carotid artery

Clinical Notes Sternoclavicular Joint Injuries The strong costoclavicular ligament firmly holds the medial end of the clavicle to the first costal cartilage. Violent forces directed along the long axis of the clavicle usually result in fracture of that bone, but dislocation of the sternoclavicular joint takes place occasionally. Anterior dislocation results in the medial end of the clavicle projecting forward beneath the skin; it may also be pulled upward by the sternocleidomastoid muscle. Posterior dislocation usually follows direct trauma applied to the front of the joint that drives the clavicle backward. This type is the more serious because the displaced clavicle may press on the trachea, the esophagus, and major blood vessels in the root of the neck. If the costoclavicular ligament ruptures completely, it is difficult to maintain the normal position of the clavicle once reduction has been accomplished. Acromioclavicular Joint

  • Articulation: This occurs between the acromion of the scapula and the lateral end of the clavicle (Fig. 9-32).
  • Type: Synovial plane joint
  • Capsule: This surrounds the joint and is attached to the margins of the articular surfaces.
  • P.461

  • Ligaments: Superior and inferior acromioclavicular ligaments reinforce the capsule; from the capsule, a wedge-shaped fibrocartilaginous disc projects into the joint cavity from above (Fig. 9-32).
  • Accessory ligament: The very strong coracoclavicular ligament extends from the coracoid process to the undersurface of the clavicle (Fig. 9-32). It is largely responsible for suspending the weight of the scapula and the upper limb from the clavicle.
  • Synovial membrane: This lines the capsule and is attached to the margins of the cartilage covering the articular surfaces.
  • Nerve supply: The suprascapular nerve
Figure 9-33 The wide range of movements possible at the sternoclavicular and acromioclavicular joints gives great mobility to the clavicle and the upper limb.

Movements A gliding movement takes place when the scapula rotates or when the clavicle is elevated or depressed (Fig. 9-33). Important Relations

  • Anteriorly: The deltoid muscle
  • Posteriorly: The trapezius muscle
  • Superiorly: The skin

Clinical Notes Acromioclavicular Joint Injuries The plane of the articular surfaces of the acromioclavicular joint passes downward and medially so that there is a tendency for the lateral end of the clavicle to ride up over the upper surface of the acromion. The strength of the joint depends on the strong coracoclavicular ligament, which binds the coracoid process to the undersurface of the lateral part of the clavicle. The greater part of the weight of the upper limb is transmitted to the clavicle through this ligament, and rotary movements of the scapula occur at this important ligament. Acromioclavicular Dislocation A severe blow on the point of the shoulder, as is incurred during blocking or tackling in football or any severe fall, can result in the acromion being thrust beneath the lateral end of the clavicle, tearing the coracoclavicular ligament. This condition is known as shoulder separation. The displaced outer end of the clavicle is easily palpable. As in the case of the sternoclavicular joint, the dislocation is easily reduced, but withdrawal of support results in immediate redislocation. P.462
Shoulder Joint

  • Articulation: This occurs between the rounded head of the humerus and the shallow, pear-shaped glenoid cavity of the scapula. The articular surfaces are covered by hyaline articular cartilage, and the glenoid cavity is deepened by the presence of a fibrocartilaginous rim called the glenoid labrum (Figs. 9-34 and 9-35).
  • Type: Synovial ball-and-socket joint
  • Capsule: This surrounds the joint and is attached medially to the margin of the glenoid cavity outside the labrum; laterally it is attached to the anatomic neck of the humerus (Fig. 9-35). The capsule is thin and lax, allowing a wide range of movement. It is strengthened by fibrous slips from the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles (the rotator cuff muscles).
    Figure 9-34 Shoulder joint and its relations. A Anterior view. B Sagittal section.
    Figure 9-35 Interior of the shoulder joint.
  • Ligaments: The glenohumeral ligaments are three weak bands of fibrous tissue that strengthen the front of the capsule. The transverse humeral ligament strengthens the capsule and bridges the gap between the two tuberosities (Fig. 9-34). The coracohumeral P.463
    ligament strengthens the capsule above and stretches from the root of the coracoid process to the greater tuberosity of the humerus (Fig. 9-34).
  • Accessory ligaments: The coracoacromial ligament extends between the coracoid process and the acromion. Its function is to protect the superior aspect of the joint (Fig. 9-34).
  • Synovial membrane: This lines the capsule and is attached to the margins of the cartilage covering the articular surfaces (Figs. 9-34 and 9-35). It forms a tubular sheath around the tendon of the long head of the biceps brachii. It extends through the anterior wall of the capsule to form the subscapularis bursa beneath the subscapularis muscle (Fig. 9-34).
  • Nerve supply: The axillary and suprascapular nerves

Movements The shoulder joint has a wide range of movement, and the stability of the joint has been sacrificed to permit this. (Compare with the hip joint, which is stable but limited in its movements.) The strength of the joint depends on the tone of the short rotator cuff muscles that cross in front, above, and behind the joint—namely, the subscapularis, supraspinatus, infraspinatus, and teres minor. When the joint is abducted, the lower surface of the head of the humerus is supported by the long head of the triceps, which bows downward because of its length and gives little actual support to the humerus. In addition, the inferior part of the capsule is the weakest area. P.464
The following movements are possible (Fig. 9-36):

  • Flexion: Normal flexion is about 90° and is performed by the anterior fibers of the deltoid, pectoralis major, biceps, and coracobrachialis muscles.
  • Extension: Normal extension is about 45° and is performed by the posterior fibers of the deltoid, latissimus dorsi, and teres major muscles.
    Figure 9-36 The movements possible at the shoulder joint. Pure glenohumeral abduction is possible only as much as about 120°; further movement of the upper limb above the level of the shoulder requires rotation of the scapula (see text).
  • Abduction: Abduction of the upper limb occurs both at the shoulder joint and between the scapula and the thoracic wall (see scapular–humeral mechanism, page 465). The middle fibers of the deltoid, assisted by the supraspinatus, are involved. The supraspinatus muscle initiates the movement of abduction and holds the head of the humerus against the glenoid fossa of the scapula; this latter function allows the deltoid muscle P.465
    to contract and abduct the humerus at the shoulder joint.
  • Adduction: Normally, the upper limb can be swung 45° across the front of the chest. This is performed by the pectoralis major, latissimus dorsi, teres major, and teres minor muscles.
  • Lateral rotation: Normal lateral rotation is 40° to 45°. This is performed by the infraspinatus, the teres minor, and the posterior fibers of the deltoid muscle.
  • Medial rotation: Normal medial rotation is about 55°. This is performed by the subscapularis, the latissimus dorsi, the teres major, and the anterior fibers of the deltoid muscle.
  • Circumduction: This is a combination of the above movements.

Important Relations

  • Anteriorly: The subscapularis muscle and the axillary vessels and brachial plexus
  • Posteriorly: The infraspinatus and teres minor muscles
  • Superiorly: The supraspinatus muscle, subacromial bursa, coracoacromial ligament, and deltoid muscle
  • Inferiorly: The long head of the triceps muscle, the axillary nerve, and the posterior circumflex humeral vessels

The tendon of the long head of the biceps muscle passes through the joint and emerges beneath the transverse ligament. Clinical Notes Stability of the Shoulder Joint The shallowness of the glenoid fossa of the scapula and the lack of support provided by weak ligaments make this joint an unstable structure. Its strength almost entirely depends on the tone of the short muscles that bind the upper end of the humerus to the scapula—namely, the subscapularis in front, the supraspinatus above, and the infraspinatus and teres minor behind. The tendons of these muscles are fused to the underlying capsule of the shoulder joint. Together, these tendons form the rotator cuff. The least supported part of the joint lies in the inferior location, where it is unprotected by muscles. Dislocations of the Shoulder Joint The shoulder joint is the most commonly dislocated large joint. Anterior Inferior Dislocation Sudden violence applied to the humerus with the joint fully abducted tilts the humeral head downward onto the inferior weak part of the capsule, which tears, and the humeral head comes to lie inferior to the glenoid fossa. During this movement, the acromion has acted as a fulcrum. The strong flexors and adductors of the shoulder joint now usually pull the humeral head forward and upward into the subcoracoid position. Posterior Dislocations Posterior dislocations are rare and are usually caused by direct violence to the front of the joint. On inspection of the patient with shoulder dislocation, the rounded appearance of the shoulder is seen to be lost because the greater tuberosity of the humerus is no longer bulging laterally beneath the deltoid muscle. A subglenoid displacement of the head of the humerus into the quadrangular space can cause damage to the axillary nerve, as indicated by paralysis of the deltoid muscle and loss of skin sensation over the lower half of the deltoid. Downward displacement of the humerus can also stretch and damage the radial nerve. Shoulder Pain The synovial membrane, capsule, and ligaments of the shoulder joint are innervated by the axillary nerve and the suprascapular nerve. The joint is sensitive to pain, pressure, excessive traction, and distention. The muscles surrounding the joint undergo reflex spasm in response to pain originating in the joint, which in turn serves to immobilize the joint and thus reduce the pain. Injury to the shoulder joint is followed by pain, limitation of movement, and muscle atrophy owing to disuse. It is important to appreciate that pain in the shoulder region can be caused by disease elsewhere and that the shoulder joint may be normal; for example, diseases of the spinal cord and vertebral column and the pressure of a cervical rib (see page 50) can cause shoulder pain. Irritation of the diaphragmatic pleura or peritoneum can produce referred pain via the phrenic and supraclavicular nerves. The Scapular–Humeral Mechanism The scapula and upper limb are suspended from the clavicle by the strong coracoclavicular ligament assisted by the tone of muscles. When the scapula rotates on the chest wall so that the position of the glenoid fossa is altered, the axis of rotation may be considered to pass through the coracoclavicular ligament. Abduction of the arm involves rotation of the scapula as well as movement at the shoulder joint. For every 3° of abduction of the arm, a 2° abduction occurs in the shoulder joint and a 1° abduction occurs by rotation of the scapula. At about 120° of abduction of the arm, the greater tuberosity of the humerus comes into contact with the lateral edge of the acromion. Further elevation of the arm above the head is accomplished by rotating the scapula. Figure 9-37 summarizes the movements of abduction of the arm and shows the direction of pull of the muscles responsible for these movements. The Upper Arm Skin Superficial Sensory Nerves The sensory nerve supply (Fig. 9-38) to the skin over the point of the shoulder to halfway down the deltoid muscle is from the supraclavicular nerves (C3 and 4). The skin over P.466
the lower half of the deltoid is supplied by the upper lateral cutaneous nerve of the arm, a branch of the axillary nerve (C5 and 6). The skin over the lateral surface of the arm below the deltoid is supplied by the lower lateral cutaneous nerve of the arm, a branch of the radial nerve (C5 and 6). The skin of the armpit and the medial side of the arm is supplied by the medial cutaneous nerve of the arm (T1) and the intercostobrachial nerves (T2). The skin of the back of the arm (Fig. 9-38) is supplied by the posterior cutaneous nerve of the arm, a branch of the radial nerve (C8). P.467

Figure 9-37 Movements of abduction of the shoulder joint and rotation of the scapula and the muscles producing these movements. Note that for every 3° of abduction of the arm, a 2° abduction occurs in the shoulder joint, and 1° occurs by rotation of the scapula. At about 120° of abduction, the greater tuberosity of the humerus hits the lateral edge of the acromion. Elevation of the arm above the head is accomplished by rotating the scapula. S, supraspinatus; D, deltoid; T, trapezius; SA, serratus anterior.

Clinical Notes Dermatomes and Cutaneous Nerves It may be necessary for a physician to test the integrity of the spinal cord segments of C3 through T1. The diagrams in Figures 1-23 and 1-24 show the arrangement of the dermatomes of the upper limb. It is seen that the dermatomes for the upper cervical segments C3 to 6 are located along the lateral margin of the upper limb; the C7 dermatome is situated on the middle finger; and the dermatomes for C8, T1, and T2 are along the medial margin of the limb. The nerve fibers from a particular segment of the spinal cord, although they exit from the cord in a spinal nerve of the same segment, pass to the skin in two or more different cutaneous nerves. The skin over the point of the shoulder and halfway down the lateral surface of the deltoid muscle is supplied by the supraclavicular nerves (C3 and 4). Pain may be referred to this region as a result of inflammatory lesions involving the diaphragmatic pleura or peritoneum. The afferent stimuli reach the spinal cord via the phrenic nerves (C3, 4, and 5). Pleurisy, peritonitis, subphrenic abscess, or gallbladder disease may therefore be responsible for shoulder pain.

Figure 9-38 Cutaneous innervation of the upper limb.

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Figure 9-39 Superficial veins of the upper limb. Note the common variations seen in the region of the elbow.

Superficial Veins The veins of the upper limb can be divided into two groups: superficial and deep. The deep veins comprise the venae comitantes, which accompany all the large arteries, usually in pairs, and the axillary vein. The superficial veins of the arm (Fig. 9-39) lie in the superficial fascia. The cephalic vein ascends in the superficial fascia on the lateral side of the biceps and, on reaching the infraclavicular fossa, drains into the axillary vein. The basilic vein ascends in the superficial fascia on the medial side of the biceps (Fig. 9-39). Halfway up the arm, it pierces the deep fascia and at the lower border of the teres major joins the venae comitantes of the brachial artery to form the axillary vein. Nerve Supply of the Veins Like the arteries, the smooth muscle in the wall of the veins is innervated by sympathetic postgaiglionic nerve fibers that provide vasomotor tone. The origin of these fibers is similar to those of the arteries. Clinical Notes Venipuncture and Blood Transfusion The superficial veins are clinically important and are used for venipuncture, transfusion, and cardiac catheterization. Every clinical professional, in an emergency, should know where to obtain blood from the arm. When a patient is in a state of shock, the superficial veins are not always visible. The cephalic vein lies fairly constantly in the superficial fascia, immediately posterior to the styloid process of the radius. In the cubital fossa, the median cubital vein is separated from the underlying brachial artery by the bicipital aponeurosis. This is important because it protects the artery from the mistaken introduction into its lumen of irritating drugs that should have been injected into the vein. The cephalic vein, in the deltopectoral triangle, frequently communicates with the external jugular vein by a small vein that crosses in front of the clavicle. Fracture of the clavicle can result in rupture of this communicating vein, with the formation of a large hematoma. Intravenous Transfusion and Hypovolemic Shock In extreme hypovolemic shock, excessive venous tone may inhibit venous blood flow and thus delay the introduction of intravenous blood into the vascular system. Anatomy of Basilic and Cephalic Vein Catheterization The median basilic or basilic veins are the veins of choice for central venous catheterization, because from the cubital fossa until the basilic vein reaches the axillary vein, the basilic vein increases in diameter and is in direct line with the axillary vein (Fig. 9-39). The valves in the axillary vein may be troublesome, but abduction of the shoulder joint may permit the catheter to move past the obstruction. The cephalic vein does not increase in size as it ascends the arm, and it frequently divides into small branches as it lies within the deltopectoral triangle. One or more of these branches may ascend over the clavicle and join the external jugular vein. In its usual method of termination, the cephalic vein joins the axillary vein at a right angle. It may be difficult to maneuver the catheter around this angle. P.469
Superficial Lymph Vessels The superficial lymph vessels draining the superficial tissues of the upper arm pass upward to the axilla (Fig. 9-40). Those from the lateral side of the arm follow the cephalic vein to the infraclavicular group of nodes; those from the medial side follow the basilic vein to the lateral group of axillary nodes. The deep lymphatic vessels draining the muscles and deep structures of the arm drain into the lateral group of axillary nodes. Clinical Notes Lymphangitis Infection of the lymph vessels (lymphangitis) of the arm is common. Red streaks along the course of the lymph vessels are characteristic of the condition. The lymph vessels from the thumb and index finger and the lateral part of the hand follow the cephalic vein to the infraclavicular group of axillary nodes; those from the middle, ring, and little fingers and from the medial part of the hand follow the basilic vein to the supratrochlear node, which lies in the superficial fascia just above the medial epicondyle of the humerus, and thence to the lateral group of axillary nodes. Lymphadenitis Once the infection reaches the lymph nodes, they become enlarged and tender, a condition known as lymphadenitis. Most of the lymph vessels from the fingers and palm pass to the dorsum of the hand before passing up into the forearm. This explains the frequency of inflammatory edema, or even abscess formation, which may occur on the dorsum of the hand after infection of the fingers or palm. Fascial Compartments of the Upper Arm The upper arm is enclosed in a sheath of deep fascia (Fig. 9-41). Two fascial septa, one on the medial side and one on the lateral side, extend from this sheath and are attached to the medial and lateral supracondylar ridges of the humerus, respectively. By this means, the upper arm is divided into an anterior and a posterior fascial compartment, each having its muscles, nerves, and arteries. Contents of the Anterior Fascial Compartment of the Upper Arm

  • Muscles: Biceps brachii, coracobrachialis, and brachialis
  • Blood supply: Brachial artery (Fig. 9-42)
  • Nerve supply to the muscles: Musculocutaneous nerve
  • Structures passing through the compartment: Musculocutaneous, median, and ulnar nerves; brachial artery and basilic vein. The radial nerve is present in the lower part of the compartment.

Muscles of the Anterior Fascial Compartment The muscles of the anterior fascial compartment are shown in Figures 9-43 and 9-44 and are described in Table 9-5. Note that the biceps brachii is a powerful supinator and this action is made use of in twisting the corkscrew into the cork or driving the screw into wood with a screwdriver. The biceps also is a powerful flexor of the elbow joint and a weak flexor of the shoulder joint. Clinical Notes Biceps Brachii and Osteoarthritis of the Shoulder Joint The tendon of the long head of biceps is attached to the supraglenoid tubercle within the shoulder joint. Advanced osteoarthritic changes in the joint can lead to erosion and fraying of the tendon by osteophytic outgrowths, and rupture of the tendon can occur. Structures Passing Through the Anterior Fascial Compartment Brachial Artery The brachial artery (Figs. 9-42 and 9-43) begins at the lower border of the teres major muscle as a continuation of the axillary artery. It provides the main arterial supply to the arm (Fig. 9-42). It terminates opposite the neck of the radius by dividing into the radial and ulnar arteries. Relations

  • Anteriorly: The vessel is superficial and is overlapped from the lateral side by the coracobrachialis and biceps. The medial cutaneous nerve of the forearm lies in front of the upper part; the median nerve crosses its middle part; and the bicipital aponeurosis crosses its lower part (Fig. 9-43).
  • Posteriorly: The artery lies on the triceps, the coracobrachialis insertion, and the brachialis (Fig. 9-43). P.470
    Figure 9-40 Superficial lymphatics of the upper limb. Note the positions of the lymph nodes.

    P.471

    Figure 9-41 Cross section of the upper arm just below the level of insertion of the deltoid muscle. Note the division of the arm by the humerus and the medial and lateral intermuscular septa into anterior and posterior compartments.
    Figure 9-42 The main arteries of the upper limb.

    P.472

    Figure 9-43 Anterior view of the upper arm. The middle portion of the biceps brachii has been removed to show the musculocutaneous nerve lying in front of the brachialis.
  • Medially: The ulnar nerve and the basilic vein in the upper part of the arm; in the lower part of the arm, the median nerve lies on its medial side (Fig. 9-43).
  • Laterally: The median nerve and the coracobrachialis and biceps muscles above; the tendon of the biceps lies lateral to the artery in the lower part of its course (Fig. 9-43).

Branches

  • Muscular branches to the anterior compartment of the upper arm
  • The nutrient artery to the humerus
  • The profunda artery arises near the beginning of the brachial artery and follows the radial nerve into the spiral groove of the humerus (Fig. 9-45).
  • The superior ulnar collateral artery arises near the middle of the upper arm and follows the ulnar nerve (Fig. 9-45).
  • The inferior ulnar collateral artery arises near the termination of the artery and takes part in the anastomosis around the elbow joint (Fig. 9-45).

Musculocutaneous Nerve The origin of the musculocutaneous nerve from the lateral cord of the brachial plexus P.473
(C5, 6, and 7) in the axilla is described on page 449. It runs downward and laterally, pierces the coracobrachialis muscle (Fig. 9-15), and then passes downward between the biceps and brachialis muscles (Fig. 9-43). It appears at the lateral margin of the biceps tendon and pierces the deep fascia just above the elbow. It runs down the lateral aspect of the forearm as the lateral cutaneous nerve of the forearm (Fig. 9-38).

Figure 9-44 Anterior view of the upper arm showing the insertion of the deltoid and the origin and insertion of the brachialis.

Branches

  • Muscular branches to the biceps, coracobrachialis, and brachialis (Fig. 9-22)
  • Cutaneous branches; the lateral cutaneous nerve of the forearm supplies the skin of the front and lateral aspects of the forearm down as far as the root of the thumb.
  • Articular branches to the elbow joint

P.474

Figure 9-45 Main arteries of the upper arm. Note the arterial anastomosis around the elbow joint.

Median Nerve The origin of the median nerve from the medial and lateral cords of the brachial plexus in the axilla is described on page 449. It runs downward on the lateral side of the brachial artery (Fig. 9-43). Halfway down the upper arm, it crosses the brachial artery and continues downward on its medial side. The nerve, like the artery, is therefore superficial, but at the elbow, it is crossed by the bicipital aponeurosis. The further course of this nerve is described on page 489. The median nerve has no branches in the upper arm (Fig. 9-22), except for a small vasomotor nerve to the brachial artery. Ulnar Nerve The origin of the ulnar nerve from the medial cord of the brachial plexus in the axilla is described on page 449. It runs downward on the medial side of the brachial artery as far as the middle of the arm (Fig. 9-43). Here, at the insertion of the coracobrachialis, the nerve pierces the medial fascial septum, accompanied by the superior ulnar collateral artery, and enters the posterior compartment of the arm; the nerve passes behind the medial epicondyle of the humerus. The ulnar nerve has no branches in the anterior compartment of the upper arm (Fig. 9-23). Radial Nerve On leaving the axilla, the radial nerve immediately enters the posterior compartment of the arm and enters the anterior compartment just above the lateral epicondyle. Contents of the Posterior Fascial Compartment of the Upper Arm

  • Muscle: The three heads of the triceps muscle
  • Nerve supply to the muscle: Radial nerve
  • P.475

  • Blood supply: Profunda brachii and ulnar collateral arteries
  • Structures passing through the compartment: Radial nerve and ulnar nerve
Table 9-5 Muscles of the Arm
Muscle Origin Insertion Nerve Supply Nerve Rootsa Action
Anterior Compartment Biceps brachii
Long head Supraglenoid tubercle of scapula Tuberosity of radius and bicipital aponeurosis into deep fascia of forearm Musculocutaneous nerve C5, 6 Supinator of forearm and flexor of elbow joint; weak flexor of shoulder joint
Short head Coracoid process of scapula
Coracobrachialis Coracoid process of scapula Medial aspect of shaft of humerus Musculocutaneous nerve C5, 6, 7 Flexes arm and alsoprocess of weak adductor
Brachialis Front of lower half of humerus Coronoid process of ulna Musculocutaneous nerve C5, 6 Flexor of elbow joint
Posterior Compartment Triceps
Long head Infraglenoid tubercle of scapula
Lateral head Upper half of posterior surface of shaft of humerus Olecranon process of ulna Radial nerve C6, 7, 8 Extensor of elbow joint
Medial head Lower half of posterior surface of shaft of humerus
a The predominant nerve root supply is indicated by boldface type.

Muscle of the Posterior Fascial Compartment The triceps muscle is seen in Figure 9-46 and is described in Table 9-5. Structures Passing Through the Posterior Fascial Compartment Radial Nerve The origin of the radial nerve from the posterior cord of the brachial plexus in the axilla is described on page 450. The nerve winds around the back of the arm in the spiral groove on the back of the humerus between the heads of the triceps (Fig. 9-46). It pierces the lateral fascial septum above the elbow and continues downward into the cubital fossa in front of the elbow, between the brachialis and the brachioradialis muscles (Fig. 9-47). In the spiral groove, the nerve is accompanied by the profunda vessels, and it lies directly in contact with the shaft of the humerus (Fig. 9-46). Branches

  • In the axilla, branches (Fig. 9-25) are given to the long and medial heads of the triceps, and the posterior cutaneous nerve of the arm is given off.
  • In the spiral groove (Fig. 9-46), branches are given to the lateral and medial heads of the triceps and to the anconeus. The lower lateral cutaneous nerve of the arm supplies the skin over the lateral and anterior aspects of the lower part of the arm. The posterior cutaneous nerve of the forearm runs down the middle of the back of the forearm as far as the wrist.
  • In the anterior compartment of the arm, after the nerve has pierced the lateral fascial septum, it gives branches to the brachialis, the brachioradialis, and the extensor carpi radialis longus muscles (Fig. 9-47). It also gives articular branches to the elbow joint.

Ulnar Nerve Having pierced the medial fascial septum halfway down the upper arm, the ulnar nerve descends behind the septum, covered posteriorly by the medial head of P.476
the triceps. The nerve is accompanied by the superior ulnar collateral vessels. At the elbow, it lies behind the medial epicondyle of the humerus (Fig. 9-46) on the medial ligament of the elbow joint. It continues downward to enter the forearm between the two heads of origin of the flexor carpi ulnaris (see page 493).

Figure 9-46 Posterior view of the upper arm. The lateral head of the triceps has been divided to display the radial nerve and the profunda artery in the spiral groove of the humerus.

Branches The ulnar nerve has an articular branch to the elbow joint (Fig. 9-23). Profunda Brachii Artery The profunda brachii artery arises from the brachial artery near its origin (Fig. 9-45). It accompanies the radial nerve through the spiral groove, supplies the triceps muscle, and takes part in the anastomosis around the elbow joint. Superior and Inferior Ulnar Collateral Arteries The superior and inferior ulnar collateral arteries arise from the brachial artery and take part in the anastomosis around the elbow joint. The Cubital Fossa The cubital fossa is a triangular depression that lies in front of the elbow (Figs. 9-47 and 9-48). P.477

Figure 9-47 Right cubital fossa.

Boundaries

  • Laterally: The brachioradialis muscle
  • Medially: The pronator teres muscle

The base of the triangle is formed by an imaginary line drawn between the two epicondyles of the humerus. The floor of the fossa is formed by the supinator muscle laterally and the brachialis muscle medially. The roof is formed by skin and fascia and is reinforced by the bicipital aponeurosis. Contents The cubital fossa (Fig. 9-47) contains the following structures, enumerated from the medial to the lateral side: the median nerve, the bifurcation of the brachial artery into the ulnar and radial arteries, the tendon of the biceps muscle, and the radial nerve and its deep branch. The supratrochlear lymph node lies in the superficial fascia over the upper part of the fossa, above the trochlea (Fig. 9-40). It receives afferent lymph vessels from the third, fourth, and fifth fingers; the medial part of the hand; and the medial side of the forearm. The efferent lymph vessels pass up to the axilla and enter the lateral axillary group of nodes (Fig. 9-40). Bones of the Forearm The forearm contains two bones: the radius and the ulna. P.478

Figure 9-48 The cubital fossa and anterior surface of the forearm in a 27-year-old man.

Radius The radius is the lateral bone of the forearm (Fig. 9-49). Its proximal end articulates with the humerus at the elbow joint and with the ulna at the proximal radioulnar joint. Its distal end articulates with the scaphoid and lunate bones of the hand at the wrist joint and with the ulna at the distal radioulnar joint. At the proximal end of the radius is the small circular head (Fig. 9-49). The upper surface of the head is concave and articulates with the convex capitulum of the humerus. The circumference of the head articulates with the radial notch of the ulna. Below the head the bone is constricted to form the neck. Below the neck is the bicipital tuberosity for the insertion of the biceps muscle. The shaft of the radius, in contradistinction to that of the ulna, is wider below than above (Fig. 9-49). It has a sharp interosseous border medially for the attachment of the interosseous membrane that binds the radius and ulna together. The pronator tubercle, for the insertion of the pronator teres muscle, lies halfway down on its lateral side. At the distal end of the radius is the styloid process; this projects distally from its lateral margin (Fig. 9-49). On the medial surface is the ulnar notch, which articulates with the round head of the ulna. The inferior articular surface articulates with the scaphoid and lunate bones. On the posterior aspect of the distal end is a small tubercle, the dorsal tubercle, which is grooved on its medial side by the tendon of the extensor pollicis longus (Fig. 9-49). The important muscles and ligaments attached to the radius are shown in Figure 9-49. Ulna The ulna is the medial bone of the forearm (Fig. 9-49). Its proximal end articulates with the humerus at the elbow joint and with the head of the radius at the proximal radioulnar joint. Its distal end articulates with the radius at the distal radioulnar joint, but it is excluded from the wrist joint by the articular disc. The proximal end of the ulna is large and is known as the olecranon process (Fig. 9-49); this forms the prominence of the elbow. It has a notch on its anterior surface, the trochlear notch, which articulates with the trochlea of the humerus. Below the trochlear notch is the triangular coronoid process, which has on its lateral surface the radial notch for articulation with the head of the radius. The shaft of the ulna tapers from above down (Fig. 9-49). It has a sharp interosseous border laterally for the attachment of the interosseous membrane. The posterior border is rounded and subcutaneous and can be easily palpated throughout its length. Below the radial notch is the supinator crest that gives origin to the supinator muscle. At the distal end of the ulna is the small rounded head, which has projecting from its medial aspect the styloid process (Fig. 9-49). The important muscles and ligaments attached to the ulna are shown in Figure 9-49. P.479

Figure 9-49 Important muscular and ligamentous attachments to the radius and the ulna.

Clinical Notes Fractures of the Radius and Ulna Fractures of the head of the radius can occur from falls on the outstretched hand. As the force is transmitted along the radius, the head of the radius is driven sharply against the capitulum, splitting or splintering the head (Fig. 9-10). Fractures of the neck of the radius occur in young children from falls on the outstretched hand (Fig. 9-10). Fractures of the shafts of the radius and ulna may or may not occur together (Fig. 9-10). Displacement of the fragments is usually considerable and depends on the pull of the attached muscles. The proximal fragment of the radius is supinated by the supinator and the biceps brachii muscles (Fig. 9-10). The distal fragment of the radius is pronated and pulled medially by the pronator quadratus muscle. The strength of the brachioradialis and extensor carpi radialis longus and brevis shortens and angulates the forearm. In fractures of the ulna, the ulna angulates posteriorly. To restore the normal movements of pronation and supination, the normal anatomic relationship of the radius, ulna, and interosseous membrane must be regained. A fracture of one forearm bone may be associated with a dislocation of the other bone. In Monteggia’s fracture, for example, the shaft of the ulna is fractured by a force applied from behind. There is a bowing forward of the ulnar shaft and an anterior dislocation of the radial head with rupture of the anular ligament. In Galeazzi’s fracture, the proximal third of the radius is fractured and the distal end of the ulna is dislocated at the distal radioulnar joint. Fractures of the olecranon process can result from a fall on the flexed elbow or from a direct blow. Depending on the location of the fracture line, the bony fragment may be displaced by the pull of the triceps muscle, which is inserted on the olecranon process (Fig. 9-10). Avulsion fractures of part of the olecranon process can be produced by the pull of the triceps muscle. Good functional return after any of these fractures depends on the accurate anatomic reduction of the fragment. Colles’ fracture is a fracture of the distal end of the radius resulting from a fall on the outstretched hand. It commonly occurs in patients older than 50 years. The force drives the distal fragment posteriorly and superiorly, and the distal articular surface is inclined posteriorly (Fig. 9-50). This posterior displacement produces a posterior bump, sometimes referred to as the “dinner-fork deformity” because the forearm and wrist resemble the shape of that eating utensil. Failure to restore the distal articular surface to its normal position will severely limit the range of flexion of the wrist joint. Smith’s fracture is a fracture of the distal end of the radius and occurs from a fall on the back of the hand. It is a reversed Colles’ fracture because the distal fragment is displaced anteriorly (Fig. 9-50). Olecranon Bursitis A small subcutaneous bursa is present over the olecranon process of the ulna, and repeated trauma often produces chronic bursitis. P.480
Bones of the Hand There are eight carpal bones, made up of two rows of four (Figs. 9-51 and 9-52). The proximal row consists of (from lateral to medial) the scaphoid, lunate, triquetral, and pisiform bones. The distal row consists of (from lateral to medial) the trapezium, trapezoid, capitate, and hamate bones. Together, the bones of the carpus present on their anterior surface a concavity, to the lateral and medial edges of which is attached a strong membranous band called the flexor retinaculum. In this manner, an osteofascial tunnel, the carpal tunnel, is formed for the passage of the median nerve and the flexor tendons of the fingers. The bones of the hand are cartilaginous at birth. The capitate begins to ossify during the first year, and the others begin to ossify at intervals thereafter until the 12th year, when all the bones are ossified. A detailed knowledge of the bones of the hand is unnecessary. The position, shape, and size of the scaphoid bone, however, should be studied, because it is commonly fractured. The ridge of the trapezium and the hook of the hamate should be examined.

Figure 9-50 Fractures of the distal end of the radius. A Colles’ fracture. B Smith’s fracture.

The Metacarpals and Phalanges There are five metacarpal bones, each of which has a base, a shaft, and a head (Figs. 9-51 and 9-52). The first metacarpal bone of the thumb is the shortest and most mobile. It does not lie in the same plane as the others but occupies a more anterior position. It is also rotated medially through a right angle so that its extensor surface is directed laterally and not backward. The bases of the metacarpal bones articulate with the distal row of the carpal bones; the heads, which form the knuckles, articulate with the proximal phalanges (Figs. 9-51 and 9-52). The shaft of each metacarpal bone is slightly concave forward and is triangular in transverse section. Its surfaces are posterior, lateral, and medial. There are three phalanges for each of the fingers but only two for the thumb. The important muscles attached to the bones of the hand and fingers are shown in Figures 9-51 and 9-52. P.481

Figure 9-51 Important muscular attachments to the anterior surfaces of the bones of the hand.

Clinical Notes Injuries to the Bones of the Hand Fracture of the scaphoid bone is common in young adults; unless treated effectively, the fragments will not unite, and permanent weakness and pain of the wrist will result, with the subsequent development of osteoarthritis. The fracture line usually goes through the narrowest part of the bone, which, because of its location, is bathed in synovial fluid. The blood vessels to the scaphoid enter its proximal and distal ends, although the blood supply is occasionally confined to its distal end. If the latter occurs, a fracture deprives the proximal fragment of its arterial supply, and this fragment undergoes avascular necrosis. Deep tenderness in the anatomic snuffbox after a fall on the outstretched hand in a young adult makes one suspicious of a fractured scaphoid. Dislocation of the lunate bone occasionally occurs in young adults who fall on the outstretched hand in a way that causes hyperextension of the wrist joint. Involvement of the median nerve is common. Fractures of the metacarpal bones can occur as a result of direct violence, such as the clenched fist striking a hard object. The fracture always angulates dorsally. The “boxer’s fracture” commonly produces an oblique fracture of the neck of the fifth and sometimes the fourth metacarpal bones. The distal fragment is commonly displaced proximally, thus shortening the finger posteriorly. Bennett’s fracture is a fracture of the base of the metacarpal of the thumb caused when violence is applied along the long axis of the thumb or the thumb is forcefully abducted. The fracture is oblique and enters the carpometacarpal joint of the thumb, causing joint instability. Fractures of the phalanges are common and usually follow direct injury. P.482

Figure 9-52 Important muscular attachments to the posterior surfaces of the bones of the hand.

The Forearm Skin The sensory nerve supply to the skin of the forearm is from the anterior and posterior branches of the lateral cutaneous nerve of the forearm, a continuation of the musculocutaneous nerve, and from the anterior and posterior branches of the medial cutaneous nerve of the forearm (Fig. 9-38). A narrow strip of skin down the middle of the posterior surface of the forearm is supplied by the posterior cutaneous nerve of the forearm. The superficial veins of the forearm lie in the superficial fascia (Fig. 9-39). The cephalic vein arises from the lateral side of the dorsal venous arch on the back of the hand and winds around the lateral border of the forearm; it then ascends into the cubital fossa and up the front of the arm on the lateral side of the biceps. It terminates in the axillary vein in the deltopectoral triangle (see page 530). As the cephalic vein passes up the upper limb, it receives a variable number of tributaries from the lateral and posterior surfaces of the limb (Fig. 9-39). The median cubital vein, a branch of the cephalic vein in the cubital fossa, runs upward and medially and joins the basilic vein. In the cubital fossa, the median cubital vein crosses in front of the brachial artery and the median nerve, but it is separated from them by the bicipital aponeurosis. The basilic vein arises from the medial side of the dorsal venous arch on the back of the hand and winds around the medial border of the forearm; it then ascends into the cubital fossa and up the front of the arm on the medial side of the biceps (Fig. 9-39). Its termination, by joining the venae comitantes of the brachial artery to form the axillary vein, is described on page 446. It receives the median cubital vein and a variable number of tributaries from the medial and posterior surfaces of the upper limb. The superficial lymph vessels from the thumb and lateral fingers and the lateral areas of the hand and forearm follow the cephalic vein to the infraclavicular group of nodes (Fig. 9-40). Those from the medial fingers and the medial areas of the hand and forearm follow the basilic vein to the cubital fossa. Here, some of the vessels drain into the supratrochlear lymph node, whereas others bypass the node and accompany the basilic vein to the axilla, where they drain into the lateral group of axillary nodes. The efferent P.483
vessels from the supratrochlear node also drain into the lateral axillary nodes (Fig. 9-40).

Figure 9-53 Cross section of the forearm at the level of insertion of the pronator teres muscle.

Fascial Compartments of the Forearm The forearm is enclosed in a sheath of deep fascia, which is attached to the periosteum of the posterior subcutaneous border of the ulna (Fig. 9-53). This fascial sheath, together with the interosseous membrane and fibrous intermuscular septa, divides the forearm into several compartments, each having its own muscles, nerves, and blood supply. Clinical Notes Compartment Syndrome of the Forearm The forearm is enclosed in a sheath of deep fascia, which is attached to the periosteum of the posterior subcutaneous border of the ulna (Fig. 9-53). This fascial sheath, together with the interosseous membrane and fibrous intermuscular septa, divides the forearm into several compartments, each having its own muscles, nerves, and blood supply. There is very little room within each compartment, and any edema can cause secondary vascular compression of the blood vessels; the veins are first affected, and later the arteries. Soft tissue injury is a common cause, and early diagnosis is critical. Early signs include altered skin sensation (caused by ischemia of the sensory nerves passing through the compartment), pain disproportionate to any injury (caused by pressure on nerves within the compartment), pain on passive stretching of muscles that pass through the compartment (caused by muscle ischemia), tenderness of the skin over the compartment (a late sign caused by edema), and absence of capillary refill in the nail beds (caused by pressure on the arteries within the compartment). Once the diagnosis is made, the deep fascia must be incised surgically to decompress the affected compartment. A delay of as little as 4 hours can cause irreversible damage to the muscles. Volkmann’s Ischemic Contracture Volkmann’s ischemic contracture is a contracture of the muscles of the forearm that commonly follows fractures of the distal end of the humerus or fractures of the radius and ulna. In this syndrome a localized segment of the brachial artery goes into spasm, reducing the arterial flow to the flexor and the extensor muscles so that they undergo ischemic necrosis. The flexor muscles are larger than the extensor muscles, and they are therefore the ones mainly affected. The muscles are replaced by fibrous tissue, which contracts, producing the deformity. The arterial spasm is usually caused by an overtight cast, but in some cases the fracture itself may be responsible. The deformity can be explained only by understanding the anatomy of the region. Three types of deformity exist:

  • The long flexor muscles of the carpus and fingers are more contracted than the extensor muscles, and the wrist joint is flexed; the fingers are extended. If the wrist joint is extended passively, the fingers become flexed.
  • The long extensor muscles to the fingers, which are inserted into the extensor expansion that is attached to the proximal phalanx, are greatly contracted; the metacarpophalangeal joints and the wrist joint are extended, and the interphalangeal joints of the fingers are flexed.
  • Both the flexor and the extensor muscles of the forearm are contracted. The wrist joint is flexed, the metacarpophalangeal joints are extended, and the interphalangeal joints are flexed.

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Interosseous Membrane The interosseous membrane is a strong membrane that unites the shafts of the radius and the ulna; it is attached to their interosseous borders (Figs. 9-49 and 9-53). Its fibers run obliquely downward and medially so that a force applied to the lower end of the radius (e.g., falling on the outstretched hand) is transmitted from the radius to the ulna and from there to the humerus and scapula. Its fibers are taut when the forearm is in the midprone position—that is, the position of function. The interosseous membrane provides attachment for neighboring muscles. Flexor and Extensor Retinacula The flexor and extensor retinacula are strong bands of deep fascia that hold the long flexor and extensor tendons in position at the wrist.

Figure 9-54 Cross section of the hand showing the relation of the tendons, nerves, and arteries to the flexor and extensor retinacula.

Flexor Retinaculum The flexor retinaculum is a thickening of deep fascia that holds the long flexor tendons in position at the wrist. It stretches across the front of the wrist and converts the concave anterior surface of the hand into an osteofascial tunnel, the carpal tunnel, for the passage of the median nerve and the flexor tendons of the thumb and fingers (Fig. 9-54). It is attached medially to the pisiform bone and the hook of the hamate and laterally to the tubercle of the scaphoid and the trapezium bones. The attachment to the trapezium consists of superficial and deep parts and forms a synovial-lined tunnel for passage of the tendon of the flexor carpi radialis. The upper border of the retinaculum corresponds to the distal transverse skin crease in front of the wrist and is continuous with the deep fascia of the forearm. The lower border is attached to the palmar aponeurosis (Fig. 9-55). P.485

Figure 9-55 Anterior view of the palm of the hand. The palmar aponeurosis has been left in position.

Extensor Retinaculum The extensor retinaculum is a thickening of deep fascia that stretches across the back of the wrist and holds the long extensor tendons in position (Figs. 9-56 and 9-57). It converts the grooves on the posterior surface of the distal ends of the radius and ulna into six separate tunnels for the passage of the long extensor tendons. Each tunnel is lined with a synovial sheath, which extends above and below the retinaculum on the tendons. The tunnels are separated from one another by fibrous septa that pass from the deep surface of the retinaculum to the bones. The retinaculum is attached medially to the pisiform bone and the hook of the hamate and laterally to the distal end of the radius. The upper and lower borders of the retinaculum are continuous with the deep fascia of the forearm and hand, respectively. The contents of the tunnels beneath the extensor retinaculum are described on page 499. Carpal Tunnel The bones of the hand and the flexor retinaculum form the carpal tunnel (Fig. 9-54). The median nerve lies in a restricted space between the tendons of the flexor digitorum superficialis and the flexor carpi radialis muscles. For further details, see page 500. Contents of the Anterior Fascial Compartment of the Forearm

  • Muscles: A superficial group, consisting of the pronator teres, the flexor carpi radialis, the palmaris longus, and the flexor carpi ulnaris; an intermediate group consisting of the flexor digitorum superficialis; and a deep group consisting of the flexor pollicis longus, the flexor digitorum profundus, and the pronator quadratus
  • Blood supply to the muscles: Ulnar and radial arteries
  • P.486

  • Nerve supply to the muscles: All the muscles are supplied by the median nerve and its branches, except the flexor carpi ulnaris and the medial part of the flexor digitorum profundus, which are supplied by the ulnar nerve.
Figure 9-56 Dorsal surface of the hand showing the long extensor tendons and their synovial sheaths.

Clinical Notes Absent Palmaris Longus The palmaris longus muscle may be absent on one or both sides of the forearm in about 10% of persons. Others show variation in form, such as centrally or distally placed muscle belly in the place of a proximal one. Because the muscle is relatively weak, its absence produces no disability. Muscles of the Anterior Fascial Compartment of the Forearm The muscles of the anterior fascial compartment are seen in Figures 9-58, 9-59, 9-60, and 9-61 and are described in Table 9-6. Note that the superficial group of muscles possesses a common tendon of origin, which is attached to the medial epicondyle of the humerus. Arteries of the Anterior Fascial Compartment of the Forearm Ulnar Artery The ulnar artery is the larger of the two terminal branches of the brachial artery (Figs. 9-42 and 9-60). It begins in the cubital fossa at the level of the neck of the radius. It descends through the anterior compartment of the forearm and enters the palm in front of the flexor retinaculum in company with the ulnar nerve (Fig. 9-62). It ends by forming the superficial palmar arch, often anastomosing with the superficial palmar branch of the radial artery (Fig. 9-62). P.487

Figure 9-57 Dissection of the dorsal surface of the right hand showing the long extensor tendons and the extensor retinaculum.

In the upper part of its course, the ulnar artery lies deep to most of the flexor muscles. Below, it becomes superficial and lies between the tendons of the flexor carpi ulnaris and the tendons of the flexor digitorum superficialis. In front of the flexor retinaculum, it lies just lateral to the pisiform bone and is covered only by skin and fascia (site for taking ulnar pulse). Branches

  • Muscular branches to neighboring muscles
  • Recurrent branches that take part in the arterial anastomosis around the elbow joint (Fig. 9-61)
  • Branches that take part in the arterial anastomosis around the wrist joint
  • The common interosseous artery, which arises from the upper part of the ulnar artery and after a brief course divides into the anterior and posterior interosseous arteries (Fig. 9-61). The interosseous arteries are distributed to the muscles lying in front of and behind the interosseous membrane; they provide nutrient arteries to the radius and ulna bone.

Radial Artery The radial artery is the smaller of the terminal branches of the brachial artery. It begins in the cubital fossa at the level of the neck of the radius (Figs. 9-58, 9-59, and 9-60). It passes downward and laterally, beneath P.488
the brachioradialis muscle and resting on the deep muscles of the forearm. In the middle third of its course, the superficial branch of the radial nerve lies on its lateral side.

Figure 9-58 Anterior view of the forearm. The middle portion of the brachioradialis muscle has been removed to display the superficial branch of the radial nerve and the radial artery.

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Figure 9-59 Dissection of the front of the left forearm and hand showing the superficial structures.

In the distal part of the forearm, the radial artery lies on the anterior surface of the radius and is covered only by skin and fascia. Here, the artery has the tendon of brachioradialis on its lateral side and the tendon of flexor carpi radialis on its medial side (site for taking the radial pulse). The radial artery leaves the forearm by winding around the lateral aspect of the wrist to reach the posterior surface of the hand (see page 509). Branches in the Forearm

  • Muscular branches to neighboring muscles
  • Recurrent branch, which takes part in the arterial anastomosis around the elbow joint (Fig. 9-60)
  • Superficial palmar branch, which arises just above the wrist (Fig. 9-60), enters the palm of the hand, and frequently joins the ulnar artery to form the superficial palmar arch

Nerves of the Anterior Fascial Compartment of the Forearm Median Nerve The median nerve leaves the cubital fossa by passing between the two heads of the pronator teres (Fig. 9-60). It continues downward behind the flexor digitorum superficialis and rests posteriorly on the flexor digitorum profundus. At the wrist, the median nerve emerges from the lateral border of the flexor digitorum superficialis muscle and lies behind the tendon of the palmaris longus (Figs. 9-58, 9-59, and 9-60). It enters the palm by passing behind the flexor retinaculum (see pages 499 and 500). P.490

Figure 9-60 Anterior view of the forearm. Most of the superficial muscles have been removed to display the flexor digitorum superficialis, median nerve, superficial branch of the radial nerve, and radial artery. Note that the ulnar head of the pronator teres separates the median nerve from the ulnar artery.

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Figure 9-61 Anterior view of the forearm showing the deep structures.

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Table 9-6 Muscles of the Anterior Fascial Compartment of the Forearm
Muscle Origin Insertion Nerve Supply Nerve Rootsa Action
Pronator Teres
Humeral head Medial epicondyle of humerus Lateral aspect of shaft of radius Median nerve C6, 7 Pronation and flexion of forearm
Ulnar head Medial border of coronoid process of ulna
Flexor carpi radialis Medial epicondyle of humerus Bases of second and third metacarpal bones Median nerve C6, 7 Flexes and abducts hand at wrist joint
Palmaris longus Medial epicondyle of humerus Flexor retinaculum and palmar aponeurosis Median nerve C7, 8 Flexes hand
Flexor Carpi Ulnaris
Humeral head Medial epicondyle of humerus Pisiform bone, hook of the hamate, base at fifth metacarpal bone Ulnar nerve C8; T1 Flexes and adducts hand at wrist joint
Ulnar head Medial aspect of olecranon process and posterior border of ulna
Flexor Digitorum Superficialis
Humeroulnar head Medial epicondyle of humerus; medial border of coronoid process of ulna Middle phalanx of medial four fingers Median nerve C7, 8; T1 Flexes middle phalanx of fingers and assists in flexing proximal phalanx and hand
Radial head Oblique line on anterior surface of shaft of radius
Flexor pollicis longus Anterior surface of shaft of radius Distal phalanx of thumb Anterior interosseous branch of median nerve C8; T1 Flexes distal phalanx of thumb
Flexor digitorum profundus Anteromedial surface of shaft of ulna Distal phalanges of medial four fingers Ulnar (medial half) and median (lateral half) nerves C8; T1 Flexes distal phalanx of fingers; then assists in flexion of middle and proximal phalanges and wrist
Pronator quadratus Anterior surface of shaft of ulna Anterior surface of shaft of radius Anterior interosseous branch of median nerve C8; T1 Pronates forearm
aThe predominant nerve root supply is indicated by boldface type.

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Figure 9-62 Anterior view of the palm of the hand. The palmar aponeurosis and the greater part of the flexor retinaculum have been removed to display the superficial palmar arch, the median nerve, and the long flexor tendons. Segments of the tendons of the flexor digitorum superficialis have been removed to show the underlying tendons of the flexor digitorum profundus.

Branches

  • Muscular branches in the cubital fossa to the pronator teres, the flexor carpi radialis, the palmaris longus, and the flexor digitorum superficialis (Fig. 9-22)
  • Articular branches to the elbow joint
  • Anterior interosseous nerve
  • Palmar cutaneous branch. This arises in the lower part of the forearm and is distributed to the skin over the lateral part of the palm (Fig. 9-38).

Anterior Interosseous Nerve The anterior interosseous nerve arises from the median nerve as it emerges from between the two heads of the pronator teres. It passes downward on the anterior surface of the interosseous membrane, between the flexor pollicis longus and the flexor digitorum profundus (Fig. 9-61). It ends on the anterior surface of the carpus. Branches

  • Muscular branches to the flexor pollicis longus, the pronator quadratus, and the lateral half of the flexor digitorum profundus
  • Articular branches to the wrist and distal radioulnar joints. It also supplies the joints of the hand.

Ulnar Nerve The ulnar nerve (Fig. 9-61) passes from behind the medial epicondyle of the humerus, crosses the medial ligament of the elbow joint, and enters the front of the forearm by passing between the two heads of the flexor carpi ulnaris. It then runs down the forearm between the P.494
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flexor carpi ulnaris and the flexor digitorum profundus muscles. In the distal two thirds of the forearm, the ulnar artery lies on the lateral side of the ulnar nerve (Fig. 9-61). At the wrist, the ulnar nerve becomes superficial and lies between the tendons of the flexor carpi ulnaris and flexor digitorum superficialis muscles (Figs. 9-58 and 9-59). The ulnar nerve enters the palm of the hand by passing in front of the flexor retinaculum and lateral to the pisiform bone; here it has the ulnar artery lateral to it (see page 499).

Figure 9-63 Insertions of long flexor and extensor tendons in the fingers. Insertions of the lumbrical and interossei muscles are also shown. The uppermost figure illustrates the action of the lumbrical and interossei muscles in flexing the metacarpophalangeal joints and extending the interphalangeal joints.

Branches

  • Muscular branches to the flexor carpi ulnaris and to the medial half of the flexor digitorum profundus (Fig. 9-23)
  • Articular branches to the elbow joint
  • The palmar cutaneous branch is a small branch that arises in the middle of the forearm (Fig. 9-38) and supplies the skin over the hypothenar eminence.
  • The dorsal posterior cutaneous branch is a large branch that arises in the distal third of the forearm. It passes medially between the tendon of the flexor carpi ulnaris and the ulna and is distributed on the posterior surface of the hand and fingers.

Contents of the Lateral Fascial Compartment of the Forearm The lateral fascial compartment may be regarded as part of the posterior fascial compartment.

  • Muscles: Brachioradialis and extensor carpi radialis longus
  • Blood supply: Radial and brachial arteries
  • Nerve supply to the muscles: Radial nerve

Muscles of the Lateral Fascial Compartment of the Forearm The muscles of the lateral fascial compartment of the forearm are seen in Figures 9-58 and 9-60 and are described in Table 9-7. Arteries of the Lateral Compartment of the Forearm The arterial supply is derived from branches of the radial and brachial arteries. Nerve of the Lateral Compartment of the Forearm Radial Nerve The radial nerve pierces the lateral intermuscular septum in the lower part of the arm and passes forward into the cubital fossa (Fig. 9-47). It then passes downward in front of the lateral epicondyle of the humerus, lying between the brachialis on the medial side and the brachioradialis and extensor carpi radialis longus on the lateral side (Fig. 9-60). At the level of the lateral epicondyle, it divides into superficial and deep branches (Figs. 9-60 and 9-61).

Table 9-7 Muscles of the Lateral Fascial Compartment of the Forearm
Muscle Origin Insertion Nerve Supply Nerve Rootsa Action
Brachioradialis Lateral supracondylar ridge of humerus Base of styloid process of radius Radial nerve C5, 6, 7 Flexes forearm atridge of humerus elbow joint; rotates forearm to the midprone position
Extensor carpi radialis longus Lateral supracondylar ridge of humerus Posterior surface of base of second metacarpal bone Radial nerve C6, 7 Extends and abducts hand at wrist joint
a The predominant nerve root supply is indicated by boldface type.

Branches

  • Muscular branches to the brachioradialis, to the extensor carpi radialis longus, and a small branch to the lateral part of the brachialis muscle (Fig. 9-25)
  • Articular branches to the elbow joint
  • Deep branch of the radial nerve. This winds around the neck of the radius, within the supinator muscle (Fig. 9-61), and enters the posterior compartment of the forearm (Fig. 9-61).
  • Superficial branch of the radial nerve

Superficial Branch of the Radial Nerve The superficial branch of the radial nerve is the direct continuation of the nerve after its main stem has given off its deep branch in front of the lateral epicondyle of the humerus (Fig. 9-60). It runs down under cover of the brachioradialis muscle on the lateral side of the radial artery. In the distal part of the forearm, it leaves the artery and passes backward under the tendon of the brachioradialis (Fig. 9-60). It reaches the posterior surface of the wrist, where it divides into terminal branches that supply the skin on the lateral two thirds of the posterior surface of the hand (Fig. 9-38) and the posterior surface over the proximal phalanges of the lateral three and a half fingers. The area of skin supplied by the nerve on the dorsum of the hand is variable. Contents of the Posterior Fascial Compartment of the Forearm

  • Muscles: The superficial group includes the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and anconeus. These muscles possess a common tendon of origin, which is attached to the lateral epicondyle of the humerus. The deep group includes the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis.
  • Blood supply: Posterior and anterior interosseous arteries
  • Nerve supply to the muscles: Deep branch of the radial nerve

Muscles of the Posterior Fascial Compartment of the Forearm The muscles of the posterior fascial compartment are seen in Figures 9-64 and 9-65 and are described in Table 9-8. P.496

Figure 9-64 Posterior view of the forearm. Parts of the extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris have been removed to show the deep branch of the radial nerve and the posterior interosseous artery.

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Figure 9-65 Posterior view of the forearm. The superficial muscles have been removed to display the deep structures.

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Table 9-8 Muscles of the Posterior Fascial Compartment of the Forearm
Muscle Origin Insertion Nerve Supply Nerve Rootsa Action
Extensor carpi radialis brevis Lateral epicondyle of humerus Posterior surface of base of third metacarpal bone Deep branch of radial nerve C7, 8 Extends and abducts hand at wrist joint
Extensor digitorum Lateral epicondyle of humerus Middle and distal phalanges of medial four fingers Deep branch of radial nerve C7, 8 Extends fingers and hand (see text for details)
Extensor digiti minimi Lateral epicondyle of humerus Extensor expansion of little finger Deep branch of radial nerve C7, 8 Extends metacarpal phalangeal joint of little finger
Extensor carpi ulnaris Lateral epicondyle of humerus Base of fifth metacarpal bone Deep branch of radial nerve C7, 8 Extends and adducts hand at wrist joint
Anconeus Lateral epicondyle of humerus Lateral surface of olecranon process of ulna Radial nerve C7, 8; T1 Extends elbow joint
Supinator Lateral epicondyle of humerus, anular ligament of proximal radioulnar joint, and ulna Neck and shaft of radius Deep branch of radial nerve C5, 6 Supination of forearm
Abductor pollicis longus Posterior surface of shafts of radius and ulna Base of first metacarpal bone Deep branch of radial nerve C7, 8 Abducts and extends thumb
Extensor pollicis brevis Posterior surface of shaft of radius Base of proximal phalanx of thumb Deep branch of radial nerve C7, 8 Extends metacarpophalangeal joints of thumb
Extensor pollicis longus Posterior surface of shaft of ulna Base of distal phalanx of thumb Deep branch of radial nerve C7, 8 Extends distal phalanx of thumb
Extensor indicis Posterior surface of shaft of ulna Extensor expansion of index finger Deep branch of radial nerve C7, 8 Extends metacarpophalangeal joint of index finger
aThe predominant nerve root supply is indicated by boldface type.

Clinical Notes Stenosing Synovitis of the Abductor Pollicis Longus and Extensor Pollicis Brevis Tendons As a result of repeated friction between these tendons and the styloid process of the radius, they sometimes become edematous and swell. Later, fibrosis of the synovial sheath produces a condition known as stenosing tenosynovitis in which movement of the tendons becomes restricted. Advanced cases require surgical incision along the constricting sheath. Arteries of the Posterior Fascial Compartment of the Forearm The anterior and posterior interosseous arteries arise from the common interosseous artery, a branch of the ulnar artery (Figs. 9-61 and 9-65). They pass downward on the anterior and posterior surfaces of the interosseous membrane, respectively, and supply the adjoining muscles and bones. They end by taking part in the anastomosis around the wrist joint. Clinical Notes Rupture of the Extensor Pollicis Longus Tendon Rupture of this tendon can occur after fracture of the distal third of the radius. Roughening of the dorsal tubercle of the radius by the fracture line can cause excessive friction on the tendon, which can then rupture. Rheumatoid arthritis can also cause rupture of this tendon. “Anatomic Snuffbox” The anatomic snuffbox is a term commonly used to describe a triangular skin depression on the lateral side of the wrist that is bounded medially by the tendon of the extensor pollicis longus and laterally by the tendons of the abductor pollicis longus and extensor pollicis brevis (Fig. 9-64). Its clinical importance lies in the fact that the scaphoid bone is most easily palpated here and that the pulsations of the radial artery can be felt here (Fig. 9-100). P.499
Clinical Notes Tennis Elbow Tennis elbow is caused by a partial tearing or degeneration of the origin of the superficial extensor muscles from the lateral epicondyle of the humerus. It is characterized by pain and tenderness over the lateral epicondyle of the humerus, with pain radiating down the lateral side of the forearm; it is common in tennis players, violinists, and housewives. Nerve of the Posterior Fascial Compartment of the Forearm Deep Branch of the Radial Nerve The deep branch arises from the radial nerve in front of the lateral epicondyle of the humerus in the cubital fossa (Fig. 9-61). It pierces the supinator and winds around the lateral aspect of the neck of the radius in the substance of the muscle to reach the posterior compartment of the forearm. The nerve descends in the interval between the superficial and deep groups of muscles (Fig. 9-65). It eventually reaches the posterior surface of the wrist joint. Branches

  • Muscular branches to the extensor carpi radialis brevis and the supinator, the extensor digitorum, the extensor digiti minimi, the extensor carpi ulnaris, the abductor pollicis longus, the extensor pollicis brevis, the extensor pollicis longus, and the extensor indicis
  • Articular branches to the wrist and carpal joints

The Region of the Wrist Before learning the anatomy of the hand, it is essential that a student have a sound knowledge of the arrangement of the tendons, arteries, and nerves in the region of the wrist joint. From a clinical standpoint, the wrist is a common site for injury. In a transverse section through the wrist (Fig. 9-54), identify the structures from medial to lateral. At the same time, examine your own wrist and identify as many of the structures as possible. Structures on the Anterior Aspect of the Wrist The following structures pass superficial to the flexor retinaculum from medial to lateral (Fig. 9-54):

  • Flexor carpi ulnaris tendon, ending on the pisiform bone. (This tendon does not actually cross the flexor retinaculum but is included for the sake of completeness.)
  • Ulnar nerve lies lateral to the pisiform bone.
  • Ulnar artery lies lateral to the ulnar nerve.
  • Palmar cutaneous branch of the ulnar nerve
  • Palmaris longus tendon (if present), passing to its insertion into the flexor retinaculum and the palmar aponeurosis
  • Palmar cutaneous branch of the median nerve

The following structures pass beneath the flexor retinaculum from medial to lateral (Fig. 9-54):

  • Flexor digitorum superficialis tendons and, posterior to these, the tendons of the flexor digitorum profundus; both groups of tendons share a common synovial sheath.
  • Median nerve
  • Flexor pollicis longus tendon surrounded by a synovial sheath
  • Flexor carpi radialis tendon going through a split in the flexor retinaculum. The tendon is surrounded by a synovial sheath.

Structures on the Posterior Aspect of the Wrist The following structures pass superficial to the extensor retinaculum from medial to lateral (Fig. 9-54):

  • Dorsal (posterior) cutaneous branch of the ulnar nerve
  • Basilic vein
  • Cephalic vein
  • Superficial branch of the radial nerve

The following structures pass beneath the extensor retinaculum from medial to lateral (Fig. 9-54):

  • Extensor carpi ulnaris tendon, which grooves the posterior aspect of the head of the ulna
  • Extensor digiti minimi tendon is situated posterior to the distal radioulnar joint.
  • Extensor digitorum and extensor indicis tendons share a common synovial sheath and are situated on the lateral part of the posterior surface of the radius.
  • Extensor pollicis longus tendon winds around the medial side of the dorsal tubercle of the radius.
  • Extensor carpi radialis longus and brevis tendons share a common synovial sheath and are situated on the lateral part of the posterior surface of the radius.
  • Abductor pollicis longus and the extensor pollicis brevis tendons have separate synovial sheaths but share a common compartment.

Beneath the extensor retinaculum, fibrous septa pass to the underlying radius and ulna and form six compartments that contain the tendons of the extensor muscles. Each compartment is provided with a synovial sheath, which extends above and below the retinaculum. The radial artery reaches the back of the hand by passing between the lateral collateral ligament of the wrist joint and the tendons of the abductor pollicis longus and extensor pollicis brevis (Fig. 9-65). The Palm of the Hand Skin The skin of the palm of the hand is thick and hairless. It is bound down to the underlying deep fascia by numerous fibrous bands. The skin shows many flexure creases at the sites of skin movement, which are not necessarily placed at the site of joints. Sweat glands are present in large numbers. The palmaris brevis (Fig. 9-55) is a small muscle that arises from the flexor retinaculum and palmar aponeurosis P.500
and is inserted into the skin of the palm. It is supplied by the superficial branch of the ulnar nerve. Its function is to corrugate the skin at the base of the hypothenar eminence and so improve the grip of the palm in holding a rounded object. The sensory nerve supply to the skin of the palm (Figs. 9-38 and 9-55) is derived from the palmar cutaneous branch of the median nerve, which crosses in front of the flexor retinaculum and supplies the lateral part of the palm, and the palmar cutaneous branch of the ulnar nerve; the latter nerve also crosses in front of the flexor retinaculum (Fig. 9-54) and supplies the medial part of the palm. The skin over the base of the thenar eminence is supplied by the lateral cutaneous nerve of the forearm or the superficial branch of the radial nerve (Fig. 9-38). Deep Fascia The deep fascia of the wrist and palm is thickened to form the flexor retinaculum (described on page 484) and the palmar aponeurosis. The Palmar Aponeurosis The palmar aponeurosis is triangular and occupies the central area of the palm (Fig. 9-55). The apex of the palmar aponeurosis is attached to the distal border of the flexor retinaculum and receives the insertion of the palmaris longus tendon (Fig. 9-55). The base of the aponeurosis divides at the bases of the fingers into four slips. Each slip divides into two bands, one passing superficially to the skin and the other passing deeply to the root of the finger; here each deep band divides into two, which diverge around the flexor tendons and finally fuse with the fibrous flexor sheath and the deep transverse ligaments. The medial and lateral borders of the palmar aponeurosis are continuous with the thinner deep fascia covering the hypothenar and thenar muscles. From each of these borders, fibrous septa pass posteriorly into the palm and take part in the formation of the palmar fascial spaces (see page 508). The function of the palmar aponeurosis is to give firm attachment to the overlying skin and so improve the grip and to protect the underlying tendons. Clinical Notes Dupuytren’s Contracture Dupuytren’s contracture is a localized thickening and contracture of the palmar aponeurosis. It commonly starts near the root of the ring finger and draws that finger into the palm, flexing it at the metacarpophalangeal joint. Later, the condition involves the little finger in the same manner. In long-standing cases, the pull on the fibrous sheaths of these fingers results in flexion of the proximal interphalangeal joints. The distal interphalangeal joints are not involved and are actually extended by the pressure of the fingers against the palm. The Carpal Tunnel The carpus is deeply concave on its anterior surface and forms a bony gutter. The gutter is converted into a tunnel by the flexor retinaculum (Fig. 9-54). The long flexor tendons to the fingers and thumb pass through the tunnel and are accompanied by the median nerve. The four separate tendons of the flexor digitorum superficialis muscle are arranged in anterior and posterior rows, those to the middle and ring fingers lying in front of those to the index and little fingers. At the lower border of the flexor retinaculum, the four tendons diverge and become arranged on the same plane (Fig. 9-62). The tendons of the flexor digitorum profundus muscle are on the same plane and lie behind the superficialis tendons. All eight tendons of the flexor digitorum superficialis and profundus invaginate a common synovial sheath from the lateral side (Fig. 9-54). This allows the arterial supply to the tendons to enter them from the lateral side. The tendon of the flexor pollicis longus muscle runs through the lateral part of the tunnel in its own synovial sheath. The median nerve passes beneath the flexor retinaculum in a restricted space between the flexor digitorum superficialis and the flexor carpi radialis muscles (Fig. 9-54). Clinical Notes Carpal Tunnel Syndrome The carpal tunnel, formed by the concave anterior surface of the carpal bones and closed by the flexor retinaculum, is tightly packed with the long flexor tendons of the fingers, with their surrounding synovial sheaths, and the median nerve (Fig. 9-54). Clinically, the syndrome consists of a burning pain or “pins and needles” along the distribution of the median nerve to the lateral three and a half fingers and weakness of the thenar muscles. It is produced by compression of the median nerve within the tunnel. The exact cause of the compression is difficult to determine, but thickening of the synovial sheaths of the flexor tendons or arthritic changes in the carpal bones are thought to be responsible in many cases. As you would expect, no paresthesia occurs over the thenar eminence because this area of skin is supplied by the palmar cutaneous branch of the median nerve, which passes superficially to the flexor retinaculum. The condition is dramatically relieved by decompressing the tunnel by making a longitudinal incision through the flexor retinaculum. Fibrous Flexor Sheaths The anterior surface of each finger, from the head of the metacarpal to the base of the distal phalanx, is provided with a strong fibrous sheath that is attached to the sides of the phalanges (Fig. 9-66). The proximal end of the fibrous sheath is open, whereas the distal end of the sheath is closed and is attached to the base of the distal phalanx. The sheath and the bones form a blind tunnel in which the flexor tendons of the finger lie. P.501

Figure 9-66 Anterior view of the palm of the hand showing the flexor synovial sheaths. Cross section of a finger is also shown.

In the thumb, the osteofibrous tunnel contains the tendon of the flexor pollicis longus. In the case of the four medial fingers, the tunnel is occupied by the tendons of the flexor digitorum superficialis and profundus (Fig. 9-66). The fibrous sheath is thick over the phalanges but thin and lax over the joints. Synovial Flexor Sheaths In the hand, the tendons of the flexor digitorum superficialis and profundus muscles invaginate a common synovial sheath from the lateral side (Fig. 9-54). The medial part of this common sheath extends distally without interruption on the tendons of the little finger. The lateral part of the sheath stops abruptly on the middle of the palm, and the distal ends of the long flexor tendons of the index, the middle, and the ring fingers acquire digital synovial sheaths as they enter the fingers. The flexor pollicis longus tendon has its own synovial sheath that passes into the thumb. These sheaths allow the long tendons to move smoothly, with a minimum of friction, beneath the flexor retinaculum and the fibrous flexor sheaths. The synovial sheath of the flexor pollicis longus (sometimes referred to as the radial bursa) communicates with the common synovial sheath of the superficialis and profundus tendons (sometimes referred to as the ulnar bursa) at the level of the wrist in about 50% of subjects. The vincula longa and brevia are small vascular folds of synovial membrane that connect the tendons to the anterior surface of the phalanges (Fig. 9-63). They resemble a mesentery and convey blood vessels to the tendons. P.502
Clinical Notes Tenosynovitis of the Synovial Sheaths of the Flexor Tendons Tenosynovitis is an infection of a synovial sheath. It most commonly results from the introduction of bacteria into a sheath through a small penetrating wound, such as that made by the point of a needle or thorn. Rarely, the sheath may become infected by extension of a pulp-space infection. Infection of a digital sheath results in distention of the sheath with pus; the finger is held semiflexed and is swollen. Any attempt to extend the finger is accompanied by extreme pain because the distended sheath is stretched. As the inflammatory process continues, the pressure within the sheath rises and may compress the blood supply to the tendons that travel in the vincula longa and brevia (Fig. 9-63). Rupture or later severe scarring of the tendons may follow. A further increase in pressure can cause the sheath to rupture at its proximal end. Anatomically, the digital sheath of the index finger is related to the thenar space, whereas that of the ring finger is related to the midpalmar space. The sheath for the middle finger is related to both the thenar and midpalmar spaces. These relationships explain how infection can extend from the digital synovial sheaths and involve the palmar fascial spaces. In the case of infection of the digital sheaths of the little finger and thumb, the ulnar and radial bursae are quickly involved. Should such an infection be neglected, pus may burst through the proximal ends of these bursae and enter the fascial space of the forearm between the flexor digitorum profundus anteriorly and the pronator quadratus and the interosseous membrane posteriorly. This fascial space in the forearm is commonly referred to clinically as the space of Parona. Insertion of the Long Flexor Tendons Each tendon of the flexor digitorum superficialis enters the fibrous flexor sheath; opposite the proximal phalanx it divides into two halves, which pass around the profundus tendon and meet on its deep or posterior surface, where partial decussation of the fibers takes place (Fig. 9-63). The superficialis tendon, having united again, divides almost at once into two further slips, which are attached to the borders of the middle phalanx. Each tendon of the flexor digitorum profundus, having passed through the division of the superficialis tendon, continues downward, to be inserted into the anterior surface of the base of the distal phalanx (Fig. 9-63). Clinical Notes Trigger Finger In trigger finger, there is a palpable and even audible snapping when a patient is asked to flex and extend the fingers. It is caused by the presence of a localized swelling of one of the long flexor tendons that catches on a narrowing of the fibrous flexor sheath anterior to the metacarpophalangeal joint. It may take place either in flexion or in extension. A similar condition occurring in the thumb is called trigger thumb. The situation can be relieved surgically by incising the fibrous flexor sheath. Small Muscles of the Hand The small muscles of the hand include the four lumbrical muscles, the eight* interossei muscles, the short muscles of the thumb, and the short muscles of the little finger. The muscles are seen in Figures 9-55, 9-67, 9-68, and 9-69 and are described in Table 9-9. Short Muscles of the Thumb The short muscles of the thumb are the abductor pollicis brevis, the flexor pollicis brevis, the opponens pollicis, and the adductor pollicis (Figs. 9-59, 9-62, and 9-67). The first three of these muscles form the thenar eminence. Opposition of the Thumb It should be noted that the opponens pollicis muscle pulls the thumb medially and forward across the palm so that the palmar surface of the tip of the thumb may come into contact with the palmar surface of the tips of the other fingers. It is an important muscle and enables the thumb to form one claw in the pincerlike action used for picking up objects. This complex movement involves a flexion of the carpometacarpal and metacarpophalangeal joints and a small amount of abduction and medial rotation of the metacarpal bone at the carpometacarpal joint. Abduction of the Thumb Abduction of the thumb may be defined as a movement forward of the thumb in the anteroposterior plane. It takes place at the carpometacarpal joint and the metacarpophalangeal joint. Adduction of the Thumb This movement can be defined as a movement backward of the abducted thumb in the anteroposterior plane. It restores the thumb to its anatomic position, which is flush with the palm. The adductor pollicis is the muscle that, in association with the flexor pollicis longus and the opponens pollicis muscles, is largely responsible for the power of the pincers grip of the thumb. Adduction of the thumb occurs at the carpometacarpal and at the metacarpophalangeal joint. Short Muscles of the Little Finger The short muscles of the little finger are the abductor digiti minimi, the flexor digiti minimi brevis, and the opponens digiti minimi, which together form the hypothenar eminence (Figs 9-59, 9-62, and 9-67). P.503

Figure 9-67 Anterior view of the palm of the hand. The long flexor tendons have been removed from the palm, but their method of insertion into the fingers is shown.

Opposition of the Little Finger The opponens digiti minimi muscle is only capable of rotating the fifth metacarpal bone to a slight degree. However, it assists the flexor digiti minimi in flexing the carpometacarpal joint of the little finger, thereby pulling the fifth metacarpal bone forward and cupping the palm. Arteries of the Palm Ulnar Artery The ulnar artery enters the hand anterior to the flexor retinaculum on the lateral side of the ulnar nerve and the pisiform bone (Fig. 9-62). The artery gives off a deep branchand then continues into the palm as the superficial palmar arch. The superficial palmar arch is a direct continuation of the ulnar artery (Fig. 9-62). On entering the palm, it curves laterally behind the palmar aponeurosis and in front of the long flexor tendons. The arch is completed on the lateral side by one of the branches of the radial artery. The curve of the arch lies across the palm, level with the distal border of the fully extended thumb. Four digital arteries arise from the convexity of the arch and pass to the fingers (Fig. 9-62). The deep branch of the ulnar artery arises in front of the flexor retinaculum, passes between the abductor digiti minimi and the flexor digiti minimi, and joins the radial artery to complete the deep palmar arch (Figs. 9-67 and 9-68). P.504

Figure 9-68 Anterior view of the palm of the hand showing the deep palmar arch and the deep terminal branch of the ulnar nerve. The interossei are also shown.

Radial Artery The radial artery leaves the dorsum of the hand by turning forward between the proximal ends of the first and second metacarpal bones and the two heads of the first dorsal interosseous muscle (see page 509). On entering the palm, it curves medially between the oblique and transverse heads of the adductor pollicis and continues as the deep palmar arch (Figs. 9-67 and 9-68). The deep palmar arch is a direct continuation of the radial artery (Fig. 9-68). It curves medially beneath the long flexor tendons and in front of the metacarpal bones and the interosseous muscles. The arch is completed on the medial side by the deep branch of the ulnar artery. The curve of the arch lies at a level with the proximal border of the extended thumb. The deep palmar arch sends branches superiorly, which take part in the anastomosis around the wrist joint, and inferiorly, to join the digital branches of the superficial palmar arch. Branches of the Radial Artery in the Palm Immediately on entering the palm, the radial artery gives off the arteria radialis indicis, which supplies the lateral side of the index finger, and the arteria princeps pollicis, which divides into two and supplies the lateral and medial sides of the thumb. Veins of the Palm Superficial and deep palmar arterial arches are accompanied by superficial and deep palmar venous arches, receiving corresponding tributaries. Lymph Drainage of the Palm The lymph vessels of the fingers pass along their borders to reach the webs. From here the vessels ascend onto the dorsum of the hand. Lymph vessels on the palm form a plexus that is drained by vessels that ascend in front of the forearm or pass around the medial and lateral borders to join vessels on the dorsum of the hand. P.505

Figure 9-69 Origins and insertion of the palmar and the dorsal interossei muscles. The actions of these muscles are also shown.

The lymph from the medial side of the hand ascends in vessels that accompany the basilic vein; they drain into the supratrochlear nodes and then ascend to drain into the lateral axillary nodes. The lymph from the lateral side of the hand ascends in vessels that accompany the cephalic vein; they drain into the infraclavicular nodes, and some drain into the lateral axillary nodes. Nerves of the Palm Median Nerve The median nerve enters the palm by passing behind the flexor retinaculum and through the carpal tunnel. It immediately divides into lateral and medial branches. The muscular branch takes a recurrent course around the lower border of the flexor retinaculum and lies about one fingerbreadth distal to the tubercle of the scaphoid; it supplies the muscles of the thenar eminence (the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis) and the first lumbrical muscle. The cutaneous branches supply the palmar aspect of the lateral three and a half fingers and the distal half of the dorsal aspect of each finger. One of these branches also supplies the second lumbrical muscle. Note also that the palmar cutaneous branch of the median nerve given off in the front of the forearm (Fig. 9-55) crosses anterior to the flexor retinaculum and supplies the skin over the lateral part of the palm (Fig. 9-38). Ulnar Nerve The ulnar nerve enters the palm anterior to the flexor retinaculum alongside the lateral border of the pisiform bone (Figs. 9-55 and 9-62). As it crosses the retinaculum it divides into a superficial and a deep terminal branch. Superficial Branch of the Ulnar Nerve The superficial branch of the ulnar nerve descends into the palm, lying in the subcutaneous tissue between the pisiform bone and the hook of the hamate (Figs. 9-55 and 9-62). The ulnar artery is on its lateral side. Here, the nerve and artery may lie in a fibro-osseous tunnel, the tunnel of Guyon, created by fibrous tissue derived from the superficial part of the flexor retinaculum. The nerve may be compressed at this site, giving rise to clinical signs and symptoms. The nerve gives off the following branches: a muscular branch to the palmaris brevis and cutaneous branches to the palmar aspect of the medial side of the little finger and the adjacent sides of the little and ring fingers (Fig. 9-62). It also supplies the distal half of the dorsal aspect of each finger. Deep Branch of th1e Ulnar Nerve The deep branch of the ulnar nerve runs backward between the abductor digiti minimi and the flexor digiti minimi (Fig. 9-67). It pierces the opponens digiti minimi, winds around the lower border of the hook of the hamate, and passes laterally within the concavity of the deep palmar arch. The nerve lies P.506
P.507
P.508
behind the long flexor tendons and in front of the metacarpal bones and interosseous muscles. It gives off muscular branches to the three muscles of the hypothenar eminence, namely, the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. It supplies all the palmar and dorsal interossei, the third and fourth lumbrical muscles, and both heads of the adductor pollicis muscle.

Table 9-9 Small Muscles of the Hand
Muscle Origin Insertion Nerve Supply Nerve Rootsa Action
Palmaris brevis Flexor retinaculum, palmar aponeurosis Skin of palm Superficial branch of ulnar nerve C8; T1 Corrugates skin to improve grip of palm
Lumbricals (4) Tendons of flexor digitorum profundus Extensor expansion of medial four fingers First and second, (i.e., lateral two) median nerve; third and fourth deep branch of ulnar nerve C8; T1 Flex metacarpophalangeal joints and extend interphalangeal joints of fingers except thumb
Interossei (8)
Palmar (4) First arises from base of first metacarpal; remaining three from anterior surface of shafts of second, fourth, and fifth metacarpals Proximal phalanges of thumb and index, ring, and little fingers and dorsal extensor expansion of each finger (Fig. 9-69) Deep branch of ulnar nerve C8; T1 Palmar interossei adduct fingers toward center of third finger
Dorsal (4) Contiguous sides of shafts of metacarpal bones Proximal phalanges of index, middle, and ring fingers and dorsal extensor expansion (Fig. 9-69) Deep branch of ulnar nerve C8; T1 Dorsal interossei abductshafts of metacarpal fingers from center of third finger; both palmar and dorsal flex metacarpophalangeal joints and extend interphalangeal joints
Short Muscles of Thumb
Abductor pollicis brevis Scaphoid, trapezium, flexor retinaculum Base of proximal phalanx of thumb Median nerve C8; T1 Abduction of thumb
Flexor pollicis brevis Flexor retinaculum Base of proximal phalanx of thumb Median nerve C8; T1 Flexes metacarpophalangeal joint of thumb
Opponens pollicis Flexor retinaculum Shaft of metacarpal bone of thumb Median nerve C8; T1 Pulls thumb medially and forward across palm
Adductor pollicis Oblique head; second and third metacarpal bones; transverse head; third metacarpal bone Base of proximal phalanx of thumb Deep branch of ulnar nerve C8; T1 Adduction of thumb
Short Muscles of Little Finger
Abductor digiti minimi Pisiform bone Base of proximal phalanx of little finger Deep branch of ulnar nerve C8; T1 Abducts little finger
Flexor digiti minimi Flexor retinaculum Base of proximal phalanx of little finger Deep branch of ulnar nerve C8; T1 Flexes little finger
Opponens digiti minimi Flexor retinaculum Medial border fifth metacarpal bone Deep branch of ulnar nerve C8; T1 Pulls fifth metacarpal forward as in cupping the palm
a The predominant nerve root supply is indicated by boldface type.
Figure 9-70 Palmar and pulp fascial spaces.

The palmar cutaneous branch of the ulnar nerve given off in the front of the forearm crosses anterior to the flexor retinaculum (Fig. 9-54) and supplies the skin over the medial part of the palm (Fig. 9-38). Fascial Spaces of the Palm Normally, the fascial spaces of the palm are potential spaces filled with loose connective tissue. Their boundaries are important clinically because they may limit the spread of infection in the palm. The triangular palmar aponeurosis fans out from the lower border of the flexor retinaculum (Fig. 9-55). From its medial border a fibrous septum passes backward and is attached to the anterior border of the fifth metacarpal bone (Fig. 9-70). Medial to this septum is a fascial compartment containing the three hypothenar muscles; this compartment is unimportant clinically. From the lateral border of the palmar aponeurosis, a second fibrous septum passes obliquely backward to the anterior border of the third metacarpal bone (Fig. 9-70). Usually, the septum passes between the long flexor tendons of the index and middle fingers. This second septum divides the palm into the thenar space, which lies lateral to the septum (and must not be confused with the fascial compartment containing the thenar muscles), and the midpalmar space, which lies medial to the septum (Fig. 9-70). Proximally, the thenar and midpalmar spaces are closed off from the forearm by the walls of the carpal tunnel. Distally, the two spaces are continuous with the appropriate lumbrical canals (Fig. 9-70). The thenar space contains the first lumbrical muscle and lies posterior to the long flexor tendons to the index finger and in front of the adductor pollicis muscle (Fig. 9-70). The midpalmar space contains the second, third, and fourth lumbrical muscles and lies posterior to the long flexor tendons to the middle, ring, and little fingers. It lies in front of the interossei and the third, fourth, and fifth metacarpal bones (Fig. 9-70). The lumbrical canal is a potential space surrounding the tendon of each lumbrical muscle and is normally filled with connective tissue. Proximally, it is continuous with one of the palmar spaces. Clinical Notes Fascial Spaces of the Palm and Infection The fascial spaces of the palm (Fig. 9-70) are clinically important because they can become infected and distended with pus as a result of the spread of infection in acute suppurative tenosynovitis; rarely, they can become infected after penetrating wounds such as falling on a dirty nail. Pulp Space of the Fingers The deep fascia of the pulp of each finger fuses with the periosteum of the terminal phalanx just distal to the insertion of the long flexor tendons and closes off a fascial compartment known as the pulp space (Fig. 9-70). Each pulp space is subdivided by the presence of numerous septa, which pass from the deep fascia to the periosteum. Through the pulp space, which is filled with fat, runs the terminal branch of the digital artery that supplies the diaphysis of the terminal phalanx. The epiphysis of the distal phalanx receives its blood supply proximal to the pulp space. Clinical Notes Pulp-Space Infection (Felon) The pulp space of the fingers is a closed fascial compartment situated in front of the terminal phalanx of each finger (Fig. 9-70). Infection of such a space is common and serious, occurring most often in the thumb and index finger. Bacteria are usually introduced into the space by pinpricks or sewing needles. Because each space is subdivided into numerous smaller compartments by fibrous septa, it is easily understood that the accumulation of inflammatory exudate within these compartments causes the pressure in the pulp space to quickly rise. If the infection is left without decompression, infection of the terminal phalanx can occur. In children, the blood supply to the diaphysis of the phalanx passes through the pulp space, and pressure on the blood vessels could result in necrosis of the diaphysis. The proximally located epiphysis of this bone is saved because it receives its arterial supply just proximal to the pulp space. The close relationship of the proximal end of the pulp space to the digital synovial sheath accounts for the involvement of the sheath in the infectious process when the pulp-space infection has been neglected. The Dorsum of the Hand Skin The skin on the dorsum of the hand is thin, hairy, and freely mobile on the underlying tendons and bones. The sensory nerve supply to the skin on the dorsum of the hand is derived from the superficial branch of the radial nerve and the posterior cutaneous branch of the ulnar nerve. The superficial branch of the radial nerve winds around the radius deep to the brachioradialis tendon, descends over the extensor retinaculum, and supplies the lateral two thirds of the dorsum of the hand (Fig. 9-38). It divides into several dorsal digital nerves that supply the thumb, the index and middle fingers, and the lateral side of the ring finger. The area of skin on the back of the hand and fingers supplied by the radial nerve is subject to variation. Frequently, a dorsal digital nerve, a branch of the ulnar nerve, also supplies the lateral side of the ring finger. P.509
The posterior cutaneous branch of the ulnar nerve winds around the ulna deep to the flexor carpi ulnaris tendon, descends over the extensor retinaculum, and supplies the medial third of the dorsum of the hand (Fig. 9-38). It divides into several dorsal digital nerves that supply the medial side of the ring and the sides of the little fingers. The dorsal digital branches of the radial and ulnar nerves do not extend far beyond the proximal phalanx. The remainder of the dorsum of each finger receives its nerve supply from palmar digital nerves. Dorsal Venous Arch (or Network) The dorsal venous arch lies in the subcutaneous tissue proximal to the metacarpophalangeal joints and drains on the lateral side into the cephalic vein and, on the medial side, into the basilic vein (Fig. 9-100). The greater part of the blood from the whole hand drains into the arch, which receives digital veins and freely communicates with the deep veins of the palm through the interosseous spaces. Insertion of the Long Extensor Tendons The four tendons of the extensor digitorum emerge from under the extensor retinaculum and fan out over the dorsum of the hand (Figs. 9-56 and 9-57). The tendons are embedded in the deep fascia, and together they form the roof of a subfascial space, which occupies the whole width of the dorsum of the hand. Strong oblique fibrous bands connect the tendons to the little, ring, and middle fingers, proximal to the heads of the metacarpal bones. The tendon to the index finger is joined on its medial side by the tendon of the extensor indicis, and the tendon to the little finger is joined on its medial side by the two tendons of the extensor digiti minimi (Fig. 9-55). On the posterior surface of each finger, the extensor tendon joins the fascial expansion called the extensor expansion (Figs. 9-56 and 9-57). Near the proximal interphalangeal joint, the extensor expansion splits into three parts: a central part, which is inserted into the base of the middle phalanx, and two lateral parts, which converge to be inserted into the base of the distal phalanx (Fig. 9-63). The dorsal extensor expansion receives the tendon of insertion of the corresponding interosseous muscle on each side and farther distally receives the tendon of the lumbrical muscle on the lateral side (Fig. 9-63). Clinical Notes Mallet Finger Avulsion of the insertion of one of the extensor tendons into the distal phalanges can occur if the distal phalanx is forcibly flexed when the extensor tendon is taut. The last 20° of active extension is lost, resulting in a condition known as mallet finger (Fig. 9-71). Boutonnière Deformity Avulsion of the central slip of the extensor tendon proximal to its insertion into the base of the middle phalanx results in a characteristic deformity (Fig. 9-71C). The deformity results from flexing of the proximal interphalangeal joint and hyperextension of the distal interphalangeal joint. This injury can result from direct end-on trauma to the finger, direct trauma over the back of the proximal interphalangeal joint, or laceration of the dorsum of the finger. The Radial Artery on the Dorsum of the Hand The radial artery winds around the lateral margin of the wrist joint, beneath the tendons of the abductor pollicis longus and extensor pollicis brevis, and lies on the lateral ligament of the joint (Fig. 9-65). On reaching the dorsum of the hand, the artery descends beneath the tendon of the extensor pollicis longus to reach the interval between the two heads of the first dorsal interosseous muscle; here the artery turns forward to enter the palm of the hand (see page 504). Branches of the radial artery on the dorsum of the hand take part in the anastomosis around the wrist joint. Dorsal digital arteries pass to the thumb and index finger (Fig. 9-65). Joints of the Upper Limb The sternoclavicular joint, the acromioclavicular joint, and the shoulder joint are fully described on pages 459 and 460. Elbow Joint

  • Articulation: This occurs between the trochlea and capitulum of the humerus and the trochlear notch of the ulna and the head of the radius (Fig. 9-72). The articular surfaces are covered with hyaline cartilage.
  • Type: Synovial hinge joint
  • Capsule: Anteriorly it is attached above to the humerus along the upper margins of the coronoid and radial fossae and to the front of the medial and lateral epicondyles and below to the margin of the coronoid process of the ulna and to the anular ligament, which surrounds the head of the radius. Posteriorly it is attached above to the margins of the olecranon fossa of the humerus and below to the upper margin and sides of the olecranon process of the ulna and to the anular ligament.
  • Ligaments: The lateral ligament (Fig. 9-72) is triangular and is attached by its apex to the lateral epicondyle of the humerus and by its base to the upper margin of the anular ligament. The medial ligament is also triangular and consists principally of three strong bands: the anterior band, which passes from the medial epicondyle of the humerus to the medial margin of the coronoid process; the posterior band, which passes from the medial epicondyle of the humerus to the medial side of the olecranon; and the transverse band, which passes between the ulnar attachments of the two preceding bands.
  • Synovial membrane: This lines the capsule and covers fatty pads in the floors of the coronoid, radial, and olecranon P.510
    fossae; it is continuous below with the synovial membrane of the proximal radioulnar joint.
  • Nerve supply: Branches from the median, ulnar, musculocutaneous, and radial nerves
Figure 9-71 A Posterior view of normal dorsal extensor expansion. The extensor expansion near the proximal interphalangeal joint splits into three parts: a central part, which is inserted into the base of the middle phalanx, and two lateral parts, which converge to be inserted into the base of the distal phalanx. B Mallet or baseball finger. The insertion of the extensor expansion into the base of the distal phalanx ruptured; sometimes a flake of bone on the base of the phalanx is pulled off. C Boutonnière deformity. The insertion of the extensor expansion into the base of the middle phalanx is ruptured. The arrows indicate the direction of the pull of the muscles and the deformity.

Movements The elbow joint is capable of flexion and extension. Flexion is limited by the anterior surfaces of the forearm and arm coming into contact. Extension is checked by the tension of the anterior ligament and the brachialis muscle. Flexion is performed by the brachialis, biceps brachii, brachioradialis, and pronator teres muscles. Extension is performed by the triceps and anconeus muscles. It should be noted that the long axis of the extended forearm lies at an angle to the long axis of the arm. This angle, which opens laterally, is called the carrying angle and is about 170° in the male and 167° in the female. The angle disappears when the elbow joint is fully flexed. Important Relations

  • Anteriorly: The brachialis, the tendon of the biceps, the median nerve, and the brachial artery
  • Posteriorly: The triceps muscle, a small bursa intervening
  • Medially: The ulnar nerve passes behind the medial epicondyle and crosses the medial ligament of the joint.
  • Laterally: The common extensor tendon and the supinator.

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Figure 9-72 Right elbow joint. A Lateral view. B Medial view. C Anterior view of the interior of the joint. D Sagittal section.

Clinical Notes Stability of Elbow Joint The elbow joint is stable because of the wrench-shaped articular surface of the olecranon and the pulley-shaped trochlea of the humerus; it also has strong medial and lateral ligaments. When examining the elbow joint, the physician must remember the normal relations of the bony points. In extension, the medial and lateral epicondyles and the top of the olecranon process are in a straight line; in flexion, the bony points form the boundaries of an equilateral triangle. Dislocations of the Elbow Joint Elbow dislocations are common, and most are posterior. Posterior dislocation usually follows falling on the outstretched hand. Posterior dislocations of the joint are common in children because the parts of the bones that stabilize the joint are incompletely developed. Avulsion of the epiphysis of the medial epicondyle is also common in childhood because then the medial ligament is much stronger than the bond of union between the epiphysis and the diaphysis. Arthrocentesis of the Elbow Joint The anterior and posterior walls of the capsule are weak, and when the joint is distended with fluid, the posterior aspect of the joint becomes swollen. Aspiration of joint fluid can easily be performed through the back of the joint on either side of the olecranon process. Damage to the Ulnar Nerve With Elbow Joint Injuries The close relationship of the ulnar nerve to the medial side of the joint often results in its becoming damaged in dislocations of the joint or in fracture dislocations in this region. The nerve lesion can occur at the time of injury or weeks, months, or years later. The nerve can be involved in scar tissue formation or can become stretched owing to lateral deviation of the forearm in a badly reduced supracondylar fracture of the humerus. During movements of the elbow joint, the continued friction between the medial epicondyle and the stretched ulnar nerve eventually results in ulnar palsy. Radiology of the Elbow Region after Injury In examining lateral radiographs of the elbow region, it is important to remember that the lower end of the humerus is normally angulated forward 45° on the shaft; when examining a patient, the physician should see that the medial epicondyle, in the anatomic position, is directed medially and posteriorly and faces in the same direction as the head of the humerus. P.512
Proximal Radioulnar Joint

  • Articulation: Between the circumference of the head of the radius and the anular ligament and the radial notch on the ulna (Figs. 9-72 and 9-73)
  • Type: Synovial pivot joint
  • Capsule: The capsule encloses the joint and is continuous with that of the elbow joint.
  • Ligament: The anular ligament is attached to the anterior and posterior margins of the radial notch on the ulna and forms a collar around the head of the radius (Fig. 9-73). It is continuous above with the capsule of the elbow joint. It is not attached to the radius.
  • Synovial membrane: This is continuous above with that of the elbow joint. Below it is attached to the inferior margin of the articular surface of the radius and the lower margin of the radial notch of the ulna.
  • Nerve supply: Branches of the median, ulnar, musculocutaneous, and radial nerves
Figure 9-73 Ligaments of the proximal and distal radioulnar joints, wrist joint, carpal joints, and joints of the fingers.

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Movements Pronation and supination of the forearm (see below) Important Relations

  • Anteriorly: Supinator muscle and the radial nerve
  • Posteriorly: Supinator muscle and the common extensor tendon

Distal Radioulnar Joint

  • Articulation: Between the rounded head of the ulna and the ulnar notch on the radius (Fig. 9-73)
  • Type: Synovial pivot joint
  • Capsule: The capsule encloses the joint but is deficient superiorly.
  • Ligaments: Weak anterior and posterior ligaments strengthen the capsule.
  • Articular disc: This is triangular and composed of fibrocartilage. It is attached by its apex to the lateral side of the base of the styloid process of the ulna and by its base to the lower border of the ulnar notch of the radius (Figs. 9-73 and 9-74). It shuts off the distal radioulnar joint from the wrist and strongly unites the radius to the ulna.
  • Synovial membrane: This lines the capsule passing from the edge of one articular surface to that of the other.
  • Nerve supply: Anterior interosseous nerve and the deep branch of the radial nerve

Movements The movements of pronation and supination of the forearm involve a rotary movement around a vertical axis at the proximal and distal radioulnar joints. The axis passes through the head of the radius above and the attachment of the apex of the triangular articular disc below. In the movement of pronation, the head of the radius rotates within the anular ligament, whereas the distal end of the radius with the hand moves bodily forward, the ulnar notch of the radius moving around the circumference of the head of the ulna (Fig. 9-75). In addition, the distal end of the ulna moves laterally so that the hand remains in line with the upper limb and is not displaced medially. This movement of the ulna is important when using an instrument such as a screwdriver because it prevents side-to-side movement of the hand during the repetitive movements of supination and pronation. The movement of pronation results in the hand’s rotating medially in such a manner that the palm comes to face posteriorly and the thumb lies on the medial side. The movement of supination is a reversal of this process so that the hand returns to the anatomic position and the palm faces anteriorly. Pronation is performed by the pronator teres and the pronator quadratus. Supination is performed by the biceps brachii and the supinator. Supination is the more powerful of the two movements because of the strength of the biceps muscle. Because supination is the more powerful movement, screw threads and the spiral of corkscrews are made so that the screw and corkscrews are driven inward by the movement of supination in right-handed people. Important Relations

  • Anteriorly: The tendons of flexor digitorum profundus
  • Posteriorly: The tendon of extensor digiti minimi

Clinical Notes Radioulnar Joint Disease The proximal radioulnar joint communicates with the elbow joint, whereas the distal radioulnar joint does not communicate with the wrist joint. In practical terms, this means that infection of the elbow joint invariably involves the proximal radioulnar joint. The strength of the proximal radioulnar joint depends on the integrity of the strong anular ligament. Rupture of this ligament occurs in cases of anterior dislocation of the head of the radius on the capitulum of the humerus. In young children, in whom the head of the radius is still small and undeveloped, a sudden jerk on the arm can pull the radial head down through the anular ligament. Wrist Joint (Radiocarpal Joint)

  • Articulation: Between the distal end of the radius and the articular disc above and the scaphoid, lunate, and triquetral bones below (Figs. 9-73 and 9-74). The proximal articular surface forms an ellipsoid concave surface, which is adapted to the distal ellipsoid convex surface.
  • Type: Synovial ellipsoid joint
  • Capsule: The capsule encloses the joint and is attached above to the distal ends of the radius and ulna and below to the proximal row of carpal bones.
  • Ligaments: Anterior and posterior ligaments strengthen the capsule. The medial ligament is attached to the styloid process of the ulna and to the triquetral bone (Figs. 9-73 and 9-74). The lateral ligament is attached to the styloid process of the radius and to the scaphoid bone (Figs. 9-73 and 9-74).
  • Synovial membrane: This lines the capsule and is attached to the margins of the articular surfaces. The joint cavity does not communicate with that of the distal radioulnar joint or with the joint cavities of the intercarpal joints.
  • Nerve supply: Anterior interosseous nerve and the deep branch of the radial nerve

Movements The following movements are possible: flexion, extension, abduction, adduction, and circumduction. Rotation is not possible because the articular surfaces are ellipsoid shaped. The lack of rotation is compensated for by the movements of pronation and supination of the forearm. Flexion is performed by the flexor carpi radialis, the flexor carpi ulnaris, and the palmaris longus. These muscles are assisted by the flexor digitorum superficialis, the flexor digitorum profundus, and the flexor pollicis longus. P.514

Figure 9-74 Dissection of the dorsal surface of the left hand and distal end of the forearm. Note the carpal bones and the intercarpal joints; note also the wrist (radiocarpal) joint.

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Figure 9-75 Movements of supination (A) and pronation (B) of the forearm that take place at the proximal and distal radioulnar joints. C Relative positions of the radius and ulna when the forearm is fully pronated.

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Extension is performed by the extensor carpi radialis longus, the extensor carpi radialis brevis, and the extensor carpi ulnaris. These muscles are assisted by the extensor digitorum, the extensor indicis, the extensor digiti minimi, and the extensor pollicis longus. Abduction is performed by the flexor carpi radialis and the extensor carpi radialis longus and brevis. These muscles are assisted by the abductor pollicis longus and extensor pollicis longus and brevis. Adduction is performed by the flexor and extensor carpi ulnaris. Important Relations

  • Anteriorly: The tendons of the flexor digitorum profundus and superficialis, the flexor pollicis longus, the flexor carpi radialis, the flexor carpi ulnaris, and the median and ulnar nerves
  • Posteriorly: The tendons of the extensor carpi ulnaris, the extensor digiti minimi, the extensor digitorum, the extensor indicis, the extensor carpi radialis longus and brevis, the extensor pollicis longus and brevis, and the abductor pollicis longus
  • Medially: The posterior cutaneous branch of the ulnar nerve
  • Laterally: The radial artery

Clinical Notes Wrist Joint Injuries The wrist joint is essentially a synovial joint between the distal end of the radius and the proximal row of carpal bones. The head of the ulna is separated from the carpal bones by the strong triangular fibrocartilaginous ligament, which separates the wrist joint from the distal radioulnar joint. The joint is stabilized by the strong medial and lateral ligaments. Because the styloid process of the radius is longer than that of the ulna, abduction of the wrist joint is less extensive than adduction. In flexion–extension movements, the hand can be flexed about 80° but extended to only about 45°. The range of flexion is increased by movement at the midcarpal joint. A fall on the outstretched hand can strain the anterior ligament of the wrist joint, producing synovial effusion, joint pain, and limitation of movement. These symptoms and signs must not be confused with those produced by a fractured scaphoid or dislocation of the lunate bone, which are similar. Falls on the Outstretched Hand In falls on the outstretched hand, forces are transmitted from the scaphoid to the distal end of the radius, from the radius across the interosseous membrane to the ulna, and from the ulna to the humerus; thence, through the glenoid fossa of the scapula to the coracoclavicular ligament and the clavicle; and finally, to the sternum. If the forces are excessive, different parts of the upper limb give way under the strain. The area affected seems to be related to age. In a young child, for example, there may be a posterior displacement of the distal radial epiphysis; in the teenager the clavicle might fracture; in the young adult the scaphoid is commonly fractured; and in the elderly the distal end of the radius is fractured about 1 in. (2.5 cm) proximal to the wrist joint (Colles’ fracture) (Fig. 9-50). Joints of the Hand and Fingers Intercarpal Joints

  • Articulation: Between the individual bones of the proximal row of the carpus; between the individual bones of the distal row of the carpus; and finally, the midcarpal joint, between the proximal and distal rows of carpal bones (Figs. 9-73 and 9-74)
  • Type: Synovial plane joints
  • Capsule: The capsule surrounds each joint.
  • Ligaments: The bones are united by strong anterior, posterior, and interosseous ligaments.
  • Synovial membrane: This lines the capsule and is attached to the margins of the articular surfaces. The joint cavity of the midcarpal joint extends not only between the two rows of carpal bones but also upward between the individual bones forming the proximal row and downward between the bones of the distal row.
  • Nerve supply: Anterior interosseous nerve, deep branch of the radial nerve, and deep branch of the ulnar nerve

Movements A small amount of gliding movement is possible. Carpometacarpal and Intermetacarpal Joints The carpometacarpal and intermetacarpal joints are synovial plane joints possessing anterior, posterior, and interosseous ligaments. They have a common joint cavity. A small amount of gliding movement is possible (Figs. 9-73 and 9-74). Carpometacarpal Joint of the Thumb

  • Articulation: Between the trapezium and the saddle-shaped base of the first metacarpal bone (Fig. 9-73)
  • Type: Synovial saddle-shaped joint
  • Capsule: The capsule surrounds the joint.
  • Synovial membrane: This lines the capsule and forms a separate joint cavity.

Movements The following movements are possible:

  • Flexion: Flexor pollicis brevis and opponens pollicis
  • Extension: Extensor pollicis longus and brevis
  • Abduction: Abductor pollicis longus and brevis
  • Adduction: Adductor pollicis
  • Rotation (opposition): The thumb is rotated medially by the opponens pollicis.

Metacarpophalangeal Joints

  • Articulation: Between the heads of the metacarpal bones and the bases of the proximal phalanges (Fig. 9-73)
  • Type: Synovial condyloid joints
  • Capsule: The capsule surrounds the joint.
  • Ligaments: The palmar ligaments are strong and contain some fibrocartilage. They are firmly attached to the phalanx but less so to the metacarpal bone (Fig. 9-73). The palmar ligaments of the second, third, fourth, and fifth joints are united by the deep transverse metacarpal ligaments, which hold the heads of the metacarpal bones together. The collateral ligaments are cordlike bands present on each side of the joints (Fig. 9-73). Each passes downward and forward from the head of the metacarpal bone to the base of the phalanx. The P.517
    collateral ligaments are taut when the joint is in flexion and lax when the joint is in extension.
  • Synovial membrane: This lines the capsule and is attached to the margins of the articular surfaces.

Movements The following movements are possible:

  • Flexion: The lumbricals and the interossei, assisted by the flexor digitorum superficialis and profundus
  • Extension: Extensor digitorum, extensor indicis, and extensor digiti minimi
  • Abduction: Movement away from the midline of the third finger is performed by the dorsal interossei.
  • Adduction: Movement toward the midline of the third finger is performed by the palmar interossei. In the case of the metacarpophalangeal joint of the thumb, flexion is performed by the flexor pollicis longus and brevis and extension is performed by the extensor pollicis longus and brevis. The movements of abduction and adduction are performed at the carpometacarpal joint.

Interphalangeal Joints Interphalangeal joints are synovial hinge joints that have a structure similar to that of the metacarpophalangeal joints (Fig. 9-73). The Hand as a Functional Unit The upper limb is a multijointed lever freely movable on the trunk at the shoulder joint. At the distal end of the upper limb is the important prehensile organ—the hand. Much of the importance of the hand depends on the pincer action of the thumb, which enables one to grasp objects between the thumb and index finger. The extreme mobility of the first metacarpal bone makes the thumb functionally as important as all the remaining fingers combined. To comprehend fully the important positioning and movements of the hand described in this section, the reader is strongly advised to closely observe the movements in his or her own hand. Position of the Hand For the hand to be able to perform delicate movements, such as those used in the holding of small instruments in watch repairing, the forearm is placed in the semiprone position and the wrist joint is partially extended. It is interesting to note that the forearm bones are most stable in the midprone position, when the interosseous membrane is taut; in other positions of the forearm bones, the interosseous membrane is lax. With the wrist partially extended, the long flexor and extensor tendons of the fingers are working to their best mechanical advantage; at the same time, the flexors and extensors of the carpus can exert a balanced fixator action on the wrist joint, ensuring a stable base for the movements of the fingers. The position of rest is the posture adopted by the hand when the fingers are at rest and the hand is relaxed (Fig. 9-76). The forearm is in the semiprone position; the wrist joint is slightly extended; the second, third, fourth, and fifth fingers are partially flexed, although the index finger is not flexed as much as the others; and the plane of the thumbnail lies at a right angle to the plane of the other fingernails. The position of function is the posture adopted by the hand when it is about to grasp an object between the thumb and index finger (Fig. 9-76). The forearm is in the semiprone position, the wrist joint is partially extended (more so than in the position of rest), and the fingers are partially flexed, the index finger being flexed as much as the others. The metacarpal bone of the thumb is rotated in such a manner that the plane of the thumbnail lies parallel with that of the index finger, and the pulp of the thumb and index finger are in contact. The following movements are described with the hand in the anatomic position. Movements of the Thumb Flexion is the movement of the thumb across the palm in such a manner as to maintain the plane of the thumbnail at right angles to the plane of the other fingernails (Fig. 9-76). The movement takes place between the trapezium and the first metacarpal bone, at the metacarpophalangeal and interphalangeal joints. The muscles producing the movement are the flexor pollicis longus and brevis and the opponens pollicis. Extension is the movement of the thumb in a lateral or coronal plane away from the palm in such a manner as to maintain the plane of the thumbnail at right angles to the plane of the other fingernails (Figs. 9-76 and 9-77A). The movement takes place between the trapezium and the first metacarpal bone, at the metacarpophalangeal and interphalangeal joints. The muscles producing the movement are the extensor pollicis longus and brevis. Abduction is the movement of the thumb in an anteroposterior plane away from the palm, the plane of the thumbnail being kept at right angles to the plane of the other nails (Figs. 9-76 and 9-78A). The movement takes place mainly between the trapezium and the first metacarpal bone; a small amount of movement takes place at the metacarpophalangeal joint. The muscles producing the movement are the abductor pollicis longus and brevis. Adduction is the movement of the thumb in an anteroposterior plane toward the palm, the plane of the thumbnail being kept at right angles to the plane of the other fingernails (Fig. 9-76 and 9-78B). The movement takes place between the trapezium and the first metacarpal bone. The muscle producing the movement is the adductor pollicis. Opposition is the movement of the thumb across the palm in such a manner that the anterior surface of the tip comes into contact with the anterior surface of the tip of any of the other fingers (Figs. 9-76 and 9-77C). The movement is accomplished by the medial rotation of the first metacarpal bone and the attached phalanges on the trapezium. The plane of the thumbnail comes to lie parallel with the plane of the nail of the opposed finger. The muscle producing the movement is the opponens pollicis. Movements of the Index, Middle, Ring, and Little Fingers Flexion is the movement forward of the finger in an anteroposterior plane. The movement takes place at the interphalangeal P.518
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and metacarpophalangeal joints. The distal phalanx is flexed by the flexor digitorum profundus, the middle phalanx by the flexor digitorum superficialis, and the proximal phalanx by the lumbricals and the interossei.

Figure 9-76 Various positions of the hand and movements of the thumb.
Figure 9-77 Left hand with the fingers abducted and the thumb extended (A), with the fingers adducted and the thumb adducted (B), and with the thumb in the position of opposition (C).

Extension is the movement backward of the finger in an anteroposterior plane. The movements take place at the interphalangeal and metacarpophalangeal joints. The distal phalanx is extended by the lumbricals and interossei, the middle phalanx by the lumbricals and interossei, and the proximal phalanx by the extensor digitorum (in addition, by the extensor indicis for the index finger and the extensor digiti minimi for the little finger). Abduction is the movement of the fingers (including the middle finger) away from the imaginary midline of the middle finger (Figs. 9-69 and 9-77A). The movement takes place at the metacarpophalangeal joint. The muscles producing the movement are the dorsal interossei; the abductor digiti minimi abducts the little finger. Adduction is the movement of the fingers toward the midline of the middle finger (Fig. 9-77B). The movement takes place at the metacarpophalangeal joint. The muscles producing the movement are the palmar interossei. Abduction and adduction of the fingers are possible only in the extended position. In the flexed position of the finger, the articular surface of the base of the proximal phalanx lies in contact with the flattened anterior surface of the head of the metacarpal bone. The two bones are held in close contact by the collateral ligaments, which are taut in this position. In the extended position of the metacarpophalangeal joint, the base of the phalanx is in contact with the rounded part of the metacarpal head, and the collateral ligaments are slack.

Figure 9-78 Left hand with the thumb about to move the pencil away from the palm to demonstrate abduction (A) and with the thumb about to move the pencil in the direction of the palm to demonstrate adduction (B).

Cupping the Hand In the cupped position, the palm of the hand is formed into a deep concavity. To achieve this, the thumb is abducted and placed in a partially opposed position and is also slightly flexed. This has the effect of drawing the thenar eminence forward. The fourth and fifth metacarpal bones are flexed and slightly rotated at the carpometacarpal joints. This has the effect of drawing the hypothenar eminence forward. The palmaris brevis muscle contracts and pulls the skin over the hypothenar eminence medially; it also puckers the skin, which improves the gripping ability of the palm. The index, middle, ring, and little fingers are partially flexed; the fingers are also rotated slightly at the metacarpophalangeal joints to increase the general concavity of the cupped hand. Making a Fist Making a fist is accomplished by flexing the metacarpophalangeal joints and the interphalangeal joints of the fingers and thumb. It is performed by the contraction of the long flexor muscles of the fingers and thumb. For this movement to be carried out efficiently a synergic contraction of the extensor carpi radialis longus and brevis and the extensor carpi ulnaris muscles must occur to extend the wrist joint. (Try to make a “strong fist” with the wrist joint flexed—it is very difficult.) P.520
Clinical Notes Diseases of the Hand and Preservation of Function From the clinical standpoint the hand is one of the most important organs of the body. Without a normally functioning hand the patient’s livelihood is often in jeopardy. To students who doubt this statement, I would suggest that they place their right (or left) hand in a pocket for 24 hours. They will be astonished at the number of times they would like to use it if they could. From the purely mechanical point of view, the hand can be regarded as a pincerlike mechanism between the thumb and fingers, situated at the end of a multijointed lever. The most important part of the hand is the thumb, and it is the physician’s responsibility to preserve the thumb, or as much of it as possible, so that the pincerlike mechanism can be maintained. The pincerlike action of the thumb largely depends on its unique ability to be drawn across the palm and opposed to the other fingers. This movement alone, although important, is insufficient for the mechanism to work effectively. The opposing skin surfaces must have tactile sensation—and this explains why median nerve palsy is so much more disabling than ulnar nerve palsy. If the hand requires immobilization for the treatment of disease of any part of the upper limb, it should be immobilized (if possible) in the position of function. This means that if loss of movement occurs at the wrist joint, or at the joints of the hand or fingers, the patient will at least have a hand that is in a position of mechanical advantage, and one that can serve a useful purpose. Physicians should also remember that when a finger (excluding the thumb) is normally flexed into the palm, it points to the tubercle of the scaphoid; individual fingers requiring immobilization in flexion, on a splint or within a cast, should therefore always be placed in this position. Always refer to the patient’s fingers by name: thumb, index, middle, ring, and little finger. Numbering the fingers is confusing (is the thumb a finger?) and has led to such disastrous results as amputating the wrong finger. Embryologic Notes Development of the Upper Limb The limb buds appear during the sixth week of development as the result of a localized proliferation of somatopleuric mesenchyme. This causes the overlying ectoderm to bulge from the trunk as two pairs of flattened paddles (Fig. 9-79). The arm buds develop before the leg buds and lie at the level of the lower six cervical and upper two thoracic segments. The flattened limb buds have a cephalic preaxial border and a caudal postaxial border. As the limb buds elongate, the anterior rami of the spinal nerves situated opposite the bases of the limb buds start to grow into the limbs. The mesenchyme situated along the preaxial border becomes associated and innervated with the lower five cervical nerves, whereas the mesenchyme of the postaxial border becomes associated with the eighth cervical and first thoracic nerves. Later the mesenchymal masses divide into anterior and posterior groups, and the nerve trunks entering the base of each limb also divide into anterior and posterior divisions. The mesenchyme within the limbs differentiates into individual muscles that migrate within each limb. As a consequence of these two factors, the anterior rami of the spinal nerves become arranged in complicated plexuses that are found near the base of each limb so that the brachial plexus is formed. Amelia Absence of one or more limbs (amelia) or partial absence (ectromelia) may occur. A defective limb may possess a rudimentary hand at the extremity of the limb or a well-developed hand may spring from the shoulder with absence of the intermediate portion of the limb (phocomelia) (Fig. 9-80). Congenital Absence of the Radius Occasionally, the radius is congenitally absent and the growth of the ulna pushes the hand laterally (Fig. 9-81). Syndactyly In syndactyly, there is webbing of the fingers. It is usually bilateral and often familial (Fig. 9-82). Plastic repair of the fingers is carried out at the age of 5 years. Lobster Hand Lobster hand is a form of syndactyly that is associated with a central cleft dividing the hand into two parts. It is a heredofamilial disorder, for which plastic surgery is indicated where possible. Brachydactyly In brachydactyly, there is an absence of one or more phalanges in several fingers. Provided that the thumb is functioning normally, surgery is not indicated (Fig. 9-83). Floating Thumb A floating thumb results if the metacarpal bone of the thumb is absent but the phalanges are present. Plastic surgery is indicated where possible to improve the functional capabilities of the hand (Fig. 9-84). Polydactyly In polydactyly, one or more extra digits develop. It tends to run in families. The additional digits are removed surgically. Local Gigantism Macrodactyly affects one or more digits; these may be of adult size at birth, but the size usually diminishes with age (Fig. 9-85). Surgical removal may be necessary. P.521

Figure 9-79 Section through the lower cervical region and the formation of the upper limb bud. Note the presence of the developing bones and muscles from the mesenchyme.
Figure 9-80 Ectromelia. (Courtesy of G. Avery.)

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Figure 9-81 Congenital absence of the radius.
Figure 9-82 Partial syndactyly. (Courtesy of L. Thompson.)
Figure 9-83 Brachydactyly due to defects of the phalanges. (Courtesy of L. Thompson.)
Figure 9-84 Floating thumb. The metacarpal bone of the thumb is absent, but the phalanges are present. (Courtesy of R. Chase.)
Figure 9-85 Macrodactyly affecting the thumb and index finger. (Courtesy of R. Neviaser.)

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Radiographic Anatomy Radiographic Appearances of the Upper Limb Radiologic examination of the upper limb concentrates mainly on the bony structures because the muscles, tendons, and nerves blend into a homogeneous mass. The radiographic appearances of the upper limb are shown in Figures 9-86, 9-87, 9-88, 9-89, 9-90, 9-91, 9-92, 9-93. Magnetic resonance imaging of the upper limb can be useful to demonstrate the soft tissues around the bones (Fig. 9-94). Surface Anatomy Anterior Surface of the Chest Suprasternal Notch The suprasternal notch is the superior margin of the manubrium sterni and is easily palpated between the prominent medial ends of the clavicles in the midline (Figs. 9-95 and 9-96).

Figure 9-86 Anteroposterior radiograph of the shoulder region in the adult.

Sternal Angle (Angle of Louis) The sternal angle is the angle between the manubrium and the body of the sternum (Fig. 9-95); at this level the second costal cartilage joins the lateral margin of the sternum. Xiphisternal Joint The xiphisternal joint is between the xiphoid process of the sternum and the body of the sternum (Fig. 9-97). Costal Margin The costal margin is the lower boundary of the thorax and is formed by the cartilages of the 7th, 8th, 9th, and 10th ribs and the ends of the 11th and 12th cartilages (Figs. 9-95, 9-96, and 9-97). Clavicle The clavicle is situated at the root of the neck and throughout its entire length lies just beneath the skin and can be easily palpated (Figs. 9-95, 9-96, and 9-97). The positions of the sternoclavicular and acromioclavicular joints can be easily identified. Note that the medial end of the clavicle projects above the margin of the manubrium sterni. P.524

Figure 9-87 Anteroposterior radiograph of the elbow region in the adult.

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Figure 9-88 Lateral radiograph of the elbow region in the adult.
Figure 9-89 Posteroanterior radiograph of an adult wrist and hand.

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Figure 9-90 Posteroanterior radiograph of the wrist with the forearm pronated.

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Figure 9-91 Posteroanterior radiograph of the wrist and hand of an 8-year-old boy.
Figure 9-92 Lateral radiograph of an adult wrist and hand.

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Figure 9-93 Lateral radiograph of an adult wrist and hand with the fingers at different degrees of flexion.

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Figure 9-94 Transverse (axial) magnetic resonance image of the upper part of the right forearm (as seen from below).
Figure 9-95 Anterior view of the thorax and abdomen in a 29-year-old woman.

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Figure 9-96 The pectoral region in a 27-year-old man.

Ribs The first rib lies deep to the clavicle and cannot be palpated. The lateral surfaces of the remaining ribs can be felt by pressing the fingers upward into the axilla and drawing them downward over the lateral surface of the chest wall (Fig. 9-97). Each rib can be identified by first palpating the sternal angle and the second costal cartilage (see previous column) and counting down from there. Deltopectoral Triangle This small, triangular depression is situated below the outer third of the clavicle and is bounded by the pectoralis major and deltoid muscles (Figs. 9-95 and 9-96). Axillary Folds The anterior axillary fold is formed by the lower margin of the pectoralis major muscle and can be palpated between the finger and thumb (Figs. 9-95, 9-96, and 9-97). This can be made to stand out by asking the patient to press his or her hand against the ipsilateral hip. The posterior axillary fold is formed by the tendon of latissimus dorsi as it passes around the lower border of the teres major muscle. It can be easily palpated between the finger and thumb (Fig. 9-98). Axilla The axilla should be examined with the forearm supported and the pectoral muscles relaxed. With the arm by the side, the inferior part of the head of the humerus can be easily palpated through the floor of the axilla. The pulsations of the axillary artery can be felt high up in the axilla, and around the artery can be palpated the cords of the brachial plexus. The medial wall of the axilla is formed by the upper ribs covered by the serratus anterior muscle, the serrations of which can be seen and felt in a muscular subject (Fig. 9-96). The lateral wall is formed by the coracobrachialis and biceps brachii muscles and the bicipital groove of the humerus. Posterior Surface of the Chest Spinous Processes of Cervical and Thoracic Vertebrae The spinous processes can be palpated in the midline posteriorly (Fig. 9-98). The index finger should be placed on the skin in the midline on the posterior surface of the neck and drawn downward in the nuchal groove. The first spinous process to be felt is that of the seventh cervical vertebra P.531
(vertebra prominens). Below this level are the overlapping spines of the thoracic vertebrae. The spines of the first through sixth cervical vertebrae are covered by the large ligament called the ligamentum nuchae.

Figure 9-97 Surface anatomy of the chest, shoulder, and upper limb as seen anteriorly.

Scapula The tip of the coracoid process of the scapula (Fig. 9-97) can be felt on deep palpation in the lateral part of the deltopectoral triangle; it is covered by the anterior fibers of the deltoid muscle. The acromion forms the lateral extremity of the spine of the scapula. It is subcutaneous and easily located (Figs. 9-95 and 9-96). Immediately below the lateral edge of the acromion is the smooth, rounded curve of the shoulder produced by the deltoid muscle, which covers the greater tuberosity of the humerus (Figs. 9-95 and 9-96). The crest of the spine of the scapula can be palpated and traced medially to the medial border of the scapula, which it joins at the level of the third thoracic spine (Fig. 9-98). The superior angle of the scapula can be felt through the trapezius muscle and lies opposite the second thoracic spine. The inferior angle of the scapula can be palpated opposite the seventh thoracic spine (Figs. 9-98 and 9-99). The Breast In children and men, the breast anatomy is rudimentary and the glandular tissue is confined to a small area beneath the pigmented areola. In young women (Fig. 9-95) it is usually hemispherical and slightly pendulous, overlaps the second to the sixth ribs and their costal cartilages, and extends from the lateral margin of the sternum to the midaxillary line (Fig. 9-95). The greater part of the breast lies in the superficial fascia and can be moved freely in all directions. Its upper lateral edge (axillary tail) extends around the lower border of the pectoralis major and enters the axilla (Fig. 9-95), where it comes into close relationship with the axillary vessels. In middle-aged multiparous women the breast may be large and pendulous, and in older women the breast may be smaller. P.532

Figure 9-98 Surface anatomy of the scapula, shoulder, and elbow regions as seen posteriorly.
Figure 9-99 The back in a 27-year-old man.

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In the living subject, the breast is soft because the fat contained within it is fluid. On careful palpation with the open hand, the breast has a firm, overall lobulated consistency, produced by its glandular tissue. The nipple projects from the lower half of the breast (Fig. 9-95), but its position in relation to the chest wall varies greatly and depends on the development of the gland. In males and immature females, the nipples are small and usually lie over the fourth intercostal spaces about 4 in. (10 cm) from the midline. The base of the nipple is surrounded by a circular area of pigmented skin called the areola (Fig. 9-95). Pink in color in the young girl, the areola becomes darker in color in the second month of the first pregnancy and never regains its former tint. Tiny tubercles on the areola are produced by the underlying areolar glands. The Elbow Region The medial and lateral epicondyles of the humerus (Figs. 9-96 and 9-98) and the olecranon process of the ulna can be palpated (Fig. 9-98). When the elbow joint is extended, these bony points lie on the same straight line; when the elbow is flexed, these three points form the boundaries of an equilateral triangle. The head of the radius can be palpated in a depression on the posterolateral aspect of the extended elbow, distal to the lateral epicondyle. The head of the radius can be felt to rotate during pronation and supination of the forearm. The cubital fossa is a skin depression in front of the elbow (Figs. 9-48 and 9-97), and the boundaries can be seen and felt; the brachioradialis muscle forms the lateral boundary and the pronator teres forms the medial boundary. The tendon of the biceps muscle can be palpated as it passes downward into the fossa, and the bicipital aponeurosis can be felt as it leaves the tendon to join the deep fascia on the medial side of the forearm (Figs. 9-48 and 9-97). The tendon and aponeurosis are most easily felt if the elbow joint is flexed against resistance. The ulnar nerve can be palpated where it lies behind the medial epicondyle of the humerus. It feels like a rounded cord, and when it is compressed, a “pins and needles” sensation is felt along the medial part of the hand. The brachial artery can be felt to pulsate as it passes down the arm, overlapped by the medial border of the biceps muscle. In the cubital fossa, it lies beneath the bicipital aponeurosis, and, at a level just below the head of the radius, it divides into the radial and ulnar arteries. The posterior border of the ulna bone is subcutaneous and can be palpated along its entire length. The Wrist and Hand At the wrist, the styloid processes of the radius (Fig. 9-100) and ulna can be palpated. The styloid process of the radius lies about 0.75 in. (1.9 cm) distal to that of the ulna. The dorsal tubercle of the radius is palpable on the posterior surface of the distal end of the radius (Fig. 9-100). The head of the ulna is most easily felt with the forearm pronated; the head then stands out prominently on the lateral side of the wrist (Fig. 9-75). The rounded head can be distinguished from the more distal pointed styloid process. The pisiform bone can be felt on the medial side of the anterior aspect of the wrist between the two transverse creases (Figs. 9-48 and 9-100). The hook of the hamate bone can be felt on deep palpation of the hypothenar eminence, a fingerbreadth distal and lateral to the pisiform bone. The transverse creases seen in front of the wrist are important landmarks (Fig. 9-100). The proximal transverse crease lies at the level of the wrist joint. The distal transverse crease corresponds to the proximal border of the flexor retinaculum. Important Structures Lying in Front of the Wrist Radial Artery The pulsations of the radial artery can easily be felt anterior to the distal third of the radius (Figs. 9-48 and 9-100). Here it lies just beneath the skin and fascia lateral to the tendon of flexor carpi radialis muscle. Tendon of Flexor Carpi Radialis The tendon of the flexor carpi radialis lies medial to the pulsating radial artery. Tendon of Palmaris Longus (If Present) The tendon of the palmaris longus lies medial to the tendon of flexor carpi radialis and overlies the median nerve (Fig. 9-100). Tendons of Flexor Digitorum Superficialis The tendons of the flexor digitorum superficialis are a group of four that lie medial to the tendon of palmaris longus and can be seen moving beneath the skin when the fingers are flexed and extended. Tendon of Flexor Carpi Ulnaris The tendon of the flexor carpi ulnaris is the most medially placed tendon on the front of the wrist and can be followed distally to its insertion on the pisiform bone (Figs. 9-48 and 9-100). The tendon can be made prominent by asking the patient to clench the fist (the muscle contracts to assist in fixing and stabilizing the wrist joint). Ulnar Artery The pulsations of the ulnar artery can be felt lateral to the tendon of flexor carpi ulnaris (Fig. 9-100). Ulnar Nerve The ulnar nerve lies immediately medial to the ulnar artery (Fig. 9-100). Important Structures Lying on the Lateral Side of the Wrist Anatomic Snuffbox The “anatomic snuffbox” is an important area. It is a skin depression that lies distal to the styloid process of the radius. It is bounded medially by the tendon of extensor pollicis longus and laterally by the tendons of abductor pollicis P.534
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longus and extensor pollicis brevis (Fig. 9-100). In its floor can be palpated the styloid process of the radius (proximally) and the base of the first metacarpal bone of the thumb (distally); between these bones beneath the floor lie the scaphoid and the trapezium (felt but not identifiable). The radial artery can be palpated within the snuffbox as the artery winds around the lateral margin of the wrist to reach the dorsum of the hand (Fig. 9-100). The cephalic vein can also sometimes be recognized crossing the snuffbox as it ascends the forearm.

Figure 9-100 Surface anatomy of the wrist region.

Important Structures Lying on the Back of the Wrist Lunate The lunate lies in the proximal row of carpal bones. It can be palpated just distal to the dorsal tubercle of the radius when the wrist joint is flexed. Important Structures Lying in the Palm Recurrent Branch of the Median Nerve The recurrent branch to the muscles of the thenar eminence curves around the lower border of the flexor retinaculum and lies about one fingerbreadth distal to the tubercle of the scaphoid (Fig. 9-62). Superficial Palmar Arterial Arch The superficial palmar arterial arch is located in the central part of the palm (Fig. 9-100) and lies on a line drawn across the palm at the level of the distal border of the fully extended thumb. Deep Palmar Arterial Arch The deep palmar arterial arch is also located in the central part of the palm (Fig. 9-100) and lies on a line drawn across the palm at the level of the proximal border of the fully extended thumb. Metacarpophalangeal Joints The metacarpophalangeal joints lie approximately at the level of the distal transverse palmar crease. The interphalangeal joints lie at the level of the middle and distal finger creases. Important Structures Lying on the Dorsum of the Hand The tendons of extensor digitorum, the extensor indicis, and the extensor digiti minimi can be seen and felt as they pass distally to the bases of the fingers (Fig. 9-100). Dorsal Venous Network The network of superficial veins can be seen on the dorsum of the hand (Fig. 9-100). The network drains upward into the lateral cephalic vein and a medial basilic vein. The cephalic vein crosses the anatomic snuffbox and winds around onto the anterior aspect of the forearm. It then ascends into the arm and runs along the lateral border of the biceps (Fig. 9-39). It ends by piercing the deep fascia in the deltopectoral triangle and enters the axillary vein. The basilic vein can be traced from the dorsum of the hand around the medial side of the forearm and reaches the anterior aspect just below the elbow (Fig. 9-39). It pierces the deep fascia at about the middle of the arm. The median cubital vein (or median cephalic and median basilic veins) links the cephalic and basilic veins in the cubital fossa (Fig. 9-39). To identify these veins easily, apply firm pressure around the upper arm and repeatedly clench and relax the fist. By this means the veins become distended with blood. Clinical Notes on the Arteries of the Upper Limb Arterial Injury The arteries of the upper limb can be damaged by penetrating wounds or may require ligation in amputation operations. Because of the existence of an adequate collateral circulation around the shoulder, elbow, and wrist joints, ligation of the main arteries of the upper limb is not followed by tissue necrosis or gangrene, provided, of course, that the arteries forming the collateral circulation are not diseased and the patient’s general circulation is satisfactory. Nevertheless, it can take days or weeks for the collateral vessels to open sufficiently to provide the distal part of the limb with the same volume of blood as previously supplied by the main artery. Palpation and Compression of Arteries A clinician must know where the arteries of the upper limb can be palpated or compressed in an emergency. The subclavian artery, as it crosses the first rib to become the axillary artery, can be palpated in the root of the posterior triangle of the neck (Fig. 9-31). The artery can be compressed here against the first rib to stop a catastrophic hemorrhage. The third part of the axillary artery can be felt in the axilla as it lies in front of the teres major muscle (Fig. 9-17). The brachial artery can be palpated in the arm as it lies on the brachialis and is overlapped from the lateral side by the biceps brachii (Fig. 9-43). The radial artery lies superficially in front of the distal end of the radius, between the tendons of the brachioradialis and flexor carpi radialis; it is here that the clinician takes the radial pulse (Fig. 9-58). If the pulse cannot be felt, try feeling for the radial artery on the other wrist; occasionally a congenitally abnormal radial artery can be difficult to feel. The radial artery can be less easily felt as it crosses the anatomic snuffbox (Fig. 9-100). The ulnar artery can be palpated as it crosses anterior to the flexor retinaculum in company with the ulnar nerve. The artery lies lateral to the pisiform bone, separated from it by the ulnar nerve. The artery is commonly damaged here in laceration wounds in front of the wrist. Allen Test The Allen test is used to determine the patency of the ulnar and radial arteries. With the patient’s hands resting in the lap, compress the radial arteries against the anterior surface of each radius and ask the patient to tightly clench the fists. The clenching of the fists closes off the superficial and deep palmar arterial arches. When the patient is asked to open the hands, the skin of the palms is at first white, and then normally the blood quickly flows into the arches through the ulnar arteries, causing the palms to promptly turn pink. This establishes that the ulnar arteries are patent. The patency of the radial arteries can be established by repeating the test but this time compressing the ulnar arteries as they lie lateral to the pisiform bones. Arterial Innervation and Raynaud’s Disease The arteries of the upper limb are innervated by sympathetic nerves. The preganglionic fibers originate from cell bodies in the second to eighth thoracic segments of the spinal cord. They ascend in the sympathetic trunk and synapse in the middle cervical, inferior cervical, first thoracic, or stellate ganglia. The postganglionic fibers join the nerves that form the brachial plexus and are distributed to the arteries within the branches of the plexus. For example, the digital arteries of the fingers are supplied by postganglionic sympathetic fibers that run in the digital nerves. Vasospastic diseases involving digital arterioles, such as Raynaud’s disease, may require a cervicodorsal preganglionic sympathectomy to prevent necrosis of the fingers. The operation is followed by arterial vasodilatation, with consequent increased blood flow to the upper limb. P.536
Clinical Notes on the Nerves of the Upper Limb Dermatomes and Cutaneous Nerves The importance of the dermatomes and cutaneous nerves in the upper limb is discussed on page 467. Tendon Reflexes and the Segmental Innervation of Muscles The skeletal muscle receives a segmental innervation. Most muscles are innervated by several spinal nerves and therefore by several segments of the spinal cord. A physician should know the segmental innervation of the following muscles because it is possible to test them by eliciting simple muscle reflexes in the patient: Biceps brachii tendon reflex: C5 and 6 (flexion of the elbow joint by tapping the biceps tendon). Triceps tendon reflex: C6, 7, and 8 (extension of the elbow joint by tapping the triceps tendon). Brachioradialis tendon reflex: C5, 6, and 7 (supination of the radioulnar joints by tapping the insertion of the brachioradialis tendon). Brachial Plexus Injuries The roots, trunks, and divisions of the brachial plexus reside in the lower part of the posterior triangle of the neck, whereas the cords and most of the branches of the plexus lie in the axilla. Complete lesions involving all the roots of the plexus are rare. Incomplete injuries are common and are usually caused by traction or pressure; individual nerves can be divided by stab wounds. Upper Lesions of the Brachial Plexus (Erb-Duchenne Palsy) Upper lesions of the brachial plexus are injuries resulting from excessive displacement of the head to the opposite side and depression of the shoulder on the same side. This causes excessive traction or even tearing of C5 and 6 roots of the plexus. It occurs in infants during a difficult delivery or in adults after a blow to or fall on the shoulder. The suprascapular nerve, the nerve to the subclavius, and the musculocutaneous and axillary nerves all possess nerve fibers derived from C5 and 6 roots and will therefore be functionless. The following muscles will consequently be paralyzed: the supraspinatus (abductor of the shoulder) and infraspinatus (lateral rotator of the shoulder); the subclavius (depresses the clavicle); the biceps brachii (supinator of the forearm, flexor of the elbow, weak flexor of the shoulder) and the greater part of the brachialis (flexor of the elbow) and the coracobrachialis (flexes the shoulder); and the deltoid (abductor of the shoulder) and the teres minor (lateral rotator of the shoulder). Thus, the limb will hang limply by the side, medially rotated by the unopposed sternocostal part of the pectoralis major; the forearm will be pronated because of loss of the action of the biceps. The position of the upper limb in this condition has been likened to that of a porter or waiter hinting for a tip (Fig. 9-101). In addition, there will be a loss of sensation down the lateral side of the arm.

Figure 9-101 Erb-Duchenne palsy (waiter’s tip).

Lower Lesions of the Brachial Plexus (Klumpke Palsy) Lower lesions of the brachial plexus are usually traction injuries caused by excessive abduction of the arm, as occurs in the case of a person falling from a height clutching at an object to save himself or herself. The first thoracic nerve is usually torn. The nerve fibers from this segment run in the ulnar and median nerves to supply all the small muscles of the hand. The hand has a clawed appearance caused by hyperextension of the metacarpophalangeal joints and flexion of the interphalangeal joints. The extensor digitorum is unopposed by the lumbricals and interossei and extends the metacarpophalangeal joints; the flexor digitorum superficialis and profundus are unopposed by the lumbricals and interossei and flex the middle and terminal phalanges, respectively. In addition, loss of sensation will occur along the medial side of the arm. If the eighth cervical nerve is also damaged, the extent of anesthesia will be greater and will involve the medial side of the forearm, hand, and medial two fingers. Lower lesions of the brachial plexus can also be produced by the presence of a cervical rib or malignant metastases from the lungs in the lower deep cervical lymph nodes. Long Thoracic Nerve The long thoracic nerve, which arises from C5, 6, and 7 and supplies the serratus anterior muscle, can be injured by blows to or pressure on the posterior triangle of the neck or during the surgical procedure of radical mastectomy. Paralysis of the serratus anterior results in the inability to rotate the scapula during the movement of abduction of the arm above a right angle. The patient therefore experiences difficulty in raising the arm above the head. The vertebral border and inferior angle of the scapula will no longer be kept closely applied to the chest wall and will protrude posteriorly, a condition known as “winged scapula” (Fig. 9-8). Axillary Nerve The axillary nerve (Fig. 9-24), which arises from the posterior cord of the brachial plexus (C5 and 6), can be injured by the pressure of a badly adjusted crutch pressing upward into the armpit. The passage of the axillary nerve backward from the axilla through the quadrangular space makes it particularly vulnerable here to downward displacement of the humeral head in shoulder dislocations or fractures of the surgical neck of the humerus. Paralysis of the deltoid and teres minor muscles results. The cutaneous branches of the axillary nerve, including the upper lateral cutaneous nerve of the arm, are functionless, and consequently there is a loss of skin sensation over the lower half of the deltoid muscle. The paralyzed deltoid wastes rapidly, and the underlying greater tuberosity can be readily palpated. Because the supraspinatus is the only other abductor of the shoulder, this movement is much impaired. Paralysis of the teres minor is not recognizable clinically. Radial Nerve The radial nerve (Fig. 9-25), which arises from the posterior cord of the brachial plexus, characteristically gives off its branches some distance proximal to the part to be innervated. In the axilla it gives off three branches: the posterior cutaneous nerve of the arm, which supplies the skin on the back of the arm down to the elbow; the nerve to the long head of the triceps; and the nerve to the medial head of the triceps. In the spiral groove of the humerus it gives off four branches: the lower lateral cutaneous nerve of the arm, which supplies the lateral surface of the arm down to the elbow; the posterior cutaneous nerve of the forearm, which supplies the skin down the middle of the back of the forearm as far as the wrist; the nerve to the lateral head of the triceps; and the nerve to the medial head of the triceps and the anconeus. In the anterior compartment of the arm above the lateral epicondyle it gives off three branches: the nerve to a small part of the brachialis, the nerve to the brachioradialis, and the nerve to the extensor carpi radialis longus. In the cubital fossa it gives off the deep branch of the radial nerve and continues as the superficial radial nerve. The deep branch supplies the extensor carpi radialis brevis and the supinator in the cubital fossa and all the extensor muscles in the posterior compartment of the forearm. The superficial radial nerve is sensory and supplies the skin over the lateral part of the dorsum of the hand and the dorsal surface of the lateral three and a half fingers proximal to the nail beds (Fig. 9-102). (The ulnar nerve supplies the medial part of the dorsum of the hand and the dorsal surface of the medial one and a half fingers; the exact cutaneous areas innervated by the radial and ulnar nerves on the hand are subject to variation.) The radial nerve is commonly damaged in the axilla and in the spiral groove. Injuries to the Radial Nerve in the Axilla In the axilla the nerve can be injured by the pressure of the upper end of a badly fitting crutch pressing up into the armpit or by a drunkard falling asleep with one arm over the back of a chair. It can also be badly damaged in the axilla by fractures and dislocations of the proximal end of the humerus. When the humerus is displaced downward in dislocations of the shoulder, the radial nerve, which is wrapped around the back of the shaft of the bone, is pulled downward, stretching the nerve in the axilla excessively. The clinical findings in injury to the radial nerve in the axilla are as follows. Motor The triceps, the anconeus, and the long extensors of the wrist are paralyzed. The patient is unable to extend the elbow joint, the wrist joint, and the fingers. Wristdrop, or flexion of the wrist (Fig. 9-103), occurs as a result of the action of the unopposed flexor muscles of the wrist. Wristdrop is very disabling because one is unable to flex the fingers strongly for the purpose of firmly gripping an object with the wrist fully flexed. (Try it on yourself.) If the wrist and proximal phalanges are passively extended by holding them in position with the opposite hand, the middle and distal phalanges of the fingers can be extended by the action of the lumbricals and interossei, which are inserted into the extensor expansions. The brachioradialis and supinator muscles are also paralyzed, but supination is still performed well by the biceps brachii. Sensory A small loss of skin sensation occurs down the posterior surface of the lower part of the arm and down a narrow strip on the back of the forearm. A variable area of sensory loss is present on the lateral part of the dorsum of the hand and on the dorsal surface of the roots of the lateral three and a half fingers. The area of total anesthesia is relatively small because of the overlap of sensory innervation by adjacent nerves.

Figure 9-102 Sensory innervation of the skin of the volar (palmar) and dorsal aspects of the hand; the arrangement of the dermatomes is also shown.
Figure 9-103 Wristdrop.

Trophic Changes Trophic changes are slight. Injuries to the Radial Nerve in the Spiral Groove In the spiral groove of the humerus, the radial nerve can be injured at the time of fracture of the shaft of the humerus, or subsequently involved during the formation of the callus. The pressure of the back of the arm on the edge of the operating table in an unconscious patient has also been known to injure the nerve at this site. The prolonged application of a tourniquet to the arm in a person with a slender triceps muscle is often followed by temporary radial palsy. The clinical findings in injury to the radial nerve in the spiral groove are as follows. The injury to the radial nerve occurs most commonly in the distal part of the groove, beyond the origin of the nerves to the triceps and the anconeus and beyond the origin of the cutaneous nerves.

  • Motor: The patient is unable to extend the wrist and the fingers, and wristdrop occurs (see page 537).
  • Sensory: A variable small area of anesthesia is present over the dorsal surface of the hand and the dorsal surface of the roots of the lateral three and a half fingers.
  • Trophic changes: These are very slight or absent.

Injuries to the Deep Branch of the Radial Nerve The deep branch of the radial nerve is a motor nerve to the extensor muscles in the posterior compartment of the forearm. It can be damaged in fractures of the proximal end of the radius or during dislocation of the radial head. The nerve supply to the supinator and the extensor carpi radialis longus will be undamaged, and because the latter muscle is powerful, it will keep the wrist joint extended, and wristdrop will not occur. No sensory loss occurs because this is a motor nerve. Injuries to the Superficial Radial Nerve Division of the superficial radial nerve, which is sensory, as in a stab wound, results in a variable small area of anesthesia over the dorsum of the hand and the dorsal surface of the roots of the lateral three and a half fingers. Musculocutaneous Nerve The musculocutaneous nerve (Fig. 9-22) is rarely injured because of its protected position beneath the biceps brachii muscle. If it is injured high up in the arm, the biceps and coracobrachialis are paralyzed and the brachialis muscle is weakened (the latter muscle is also supplied by the radial nerve). Flexion of the forearm at the elbow joint is then produced by the remainder of the brachialis muscle and the flexors of the forearm. When the forearm is in the prone position, the extensor carpi radialis longus and the brachioradialis muscles assist in flexion of the forearm. There is also sensory loss along the lateral side of the forearm. Wounds or cuts of the forearm can sever the lateral cutaneous nerve of the forearm, a continuation of the musculocutaneous nerve beyond the cubital fossa, resulting in sensory loss along the lateral side of the forearm. Median Nerve The median nerve (Fig. 9-22), which arises from the medial and lateral cords of the brachial plexus, gives off no cutaneous or motor branches in the axilla or in the arm. In the proximal third of the front of the forearm, by unnamed branches or by its anterior interosseous branch, it supplies all the muscles of the front of the forearm except the flexor carpi ulnaris and the medial half of the flexor digitorum profundus, which are supplied by the ulnar nerve. In the distal third of the forearm, it gives rise to a palmar cutaneous branch, which crosses in front of the flexor retinaculum and supplies the skin on the lateral half of the palm (Fig. 9-102). In the palm the median nerve supplies the muscles of the thenar eminence and the first two lumbricals and gives sensory innervation to the skin of the palmar aspect of the lateral three and a half fingers, including the nail beds on the dorsum. From a clinical standpoint, the median nerve is injured occasionally in the elbow region in supracondylar fractures of the humerus. It is most commonly injured by stab wounds or broken glass just proximal to the flexor retinaculum; here it lies in the interval between the tendons of the flexor carpi radialis and flexor digitorum superficialis, overlapped by the palmaris longus. The clinical findings in injury to the median nerve are as follows. Injuries to the Median Nerve at the Elbow Motor The pronator muscles of the forearm and the long flexor muscles of the wrist and fingers, with the exception of the flexor carpi ulnaris and the medial half of the flexor digitorum profundus, will be paralyzed. As a result, the forearm is kept in the supine position; wrist flexion is weak and is accompanied by adduction. The latter deviation is caused by the paralysis of the flexor carpi radialis and the strength of the flexor carpi ulnaris and the medial half of the flexor digitorum profundus. No flexion is possible at the interphalangeal joints of the index and middle fingers, although weak flexion of the metacarpophalangeal joints of these fingers is attempted by the interossei. When the patient tries to make a fist, the index and to a lesser extent the middle fingers tend to remain straight, whereas the ring and little fingers flex (Fig. 9-104). The latter two fingers are, however, weakened by the loss of the flexor digitorum superficialis. Flexion of the terminal phalanx of the thumb is lost because of paralysis of the flexor pollicis longus. The muscles of the thenar eminence are paralyzed and wasted so that the eminence is flattened. The thumb is laterally rotated and adducted. The hand looks flattened and “apelike.”

Figure 9-104 Median nerve palsy.

Sensory Skin sensation is lost on the lateral half or less of the palm of the hand and the palmar aspect of the lateral three and a half fingers. Sensory loss also occurs on the skin of the distal part of the dorsal surfaces of the lateral three and a half fingers. The area of total anesthesia is considerably less because of the overlap of adjacent nerves. Vasomotor Changes The skin areas involved in sensory loss are warmer and drier than normal because of the arteriolar dilatation and absence of sweating resulting from loss of sympathetic control. Trophic Changes In long-standing cases, changes are found in the hand and fingers. The skin is dry and scaly, the nails crack easily, and atrophy of the pulp of the fingers is present. Injuries to the Median Nerve at the Wrist

  • Motor: The muscles of the thenar eminence are paralyzed and wasted so that the eminence becomes flattened. The thumb is laterally rotated and adducted. The hand looks flattened and “apelike.” Opposition movement of the thumb is impossible. The first two lumbricals are paralyzed, which can be recognized clinically when the patient is asked to make a fist slowly, and the index and middle fingers tend to lag behind the ring and little fingers.
  • Sensory, vasomotor, and trophic changes: These changes are identical to those found in the elbow lesions.

Perhaps the most serious disability of all in median nerve injuries is the loss of the ability to oppose the thumb to the other fingers and the loss of sensation over the lateral fingers. The delicate pincerlike action of the hand is no longer possible. Carpal Tunnel Syndrome The carpal tunnel, formed by the concave anterior surface of the carpal bones and closed by the flexor retinaculum, is tightly packed with the long flexor tendons of the fingers, with their surrounding synovial sheaths, and the median nerve. Clinically, the syndrome consists of a burning pain or “pins and needles” along the distribution of the median nerve to the lateral three and a half fingers and weakness of the thenar muscles. It is produced by compression of the median nerve within the tunnel. The exact cause of the compression is difficult to determine, but thickening of the synovial sheaths of the flexor tendons or arthritic changes in the carpal bones are thought to be responsible in many cases. As you would expect, no paresthesia occurs over the thenar eminence because this area of skin is supplied by the palmar cutaneous branch of the median nerve, which passes superficially to the flexor retinaculum. The condition is dramatically relieved by decompressing the tunnel by making a longitudinal incision through the flexor retinaculum. Ulnar Nerve The ulnar nerve (Fig. 9-23), which arises from the medial cord of the brachial plexus (C8 and T1), gives off no cutaneous or motor branches in the axilla or in the arm. As it enters the forearm from behind the medial epicondyle, it supplies the flexor carpi ulnaris and the medial half of the flexor digitorum profundus. In the distal third of the forearm, it gives off its palmar and posterior cutaneous branches. The palmar cutaneous branch supplies the skin over the hypothenar eminence; the posterior branch supplies the skin over the medial third of the dorsum of the hand and the medial one and a half fingers. Not uncommonly, the posterior branch supplies two and a half instead of one and a half fingers. It does not supply the skin over the distal part of the dorsum of these fingers. Having entered the palm by passing in front of the flexor retinaculum, the superficial branch of the ulnar nerve supplies the skin of the palmar surface of the medial one and a half fingers (Fig. 9-102), including their nail beds; it also supplies the palmaris brevis muscle. The deep branch supplies all the small muscles of the hand except the muscles of the thenar eminence and the first two lumbricals, which are supplied by the median nerve. The ulnar nerve is most commonly injured at the elbow, where it lies behind the medial epicondyle, and at the wrist, where it lies with the ulnar artery in front of the flexor retinaculum. The injuries at the elbow are usually associated with fractures of the medial epicondyle. The superficial position of the nerve at the wrist makes it vulnerable to damage from cuts and stab wounds. The clinical findings in injury to the ulnar nerve are as follows. Injuries to the Ulnar Nerve at the Elbow Motor The flexor carpi ulnaris and the medial half of the flexor digitorum profundus muscles are paralyzed. The paralysis of the flexor carpi ulnaris can be observed by asking the patient to make a tightly clenched fist. Normally, the synergistic action of the flexor carpi ulnaris tendon can be observed as it passes to the pisiform bone; the tightening of the tendon will be absent if the muscle is paralyzed. The profundus tendons to the ring and little fingers will be functionless, and the terminal phalanges of these fingers are therefore not capable of being markedly flexed. Flexion of the wrist joint will result in abduction, owing to paralysis of the flexor carpi ulnaris. The medial border of the front of the forearm will show flattening owing to the wasting of the underlying ulnaris and profundus muscles.

Figure 9-105 Ulnar nerve palsy.

The small muscles of the hand will be paralyzed, except the muscles of the thenar eminence and the first two lumbricals, which are supplied by the median nerve. The patient is unable to adduct and abduct the fingers and consequently is unable to grip a piece of paper placed between the fingers. Remember that the extensor digitorum can abduct the fingers to a small extent, but only when the metacarpophalangeal joints are hyperextended. It is impossible to adduct the thumb because the adductor pollicis muscle is paralyzed. If the patient is asked to grip a piece of paper between the thumb and the index finger, he or she does so by strongly contracting the flexor pollicis longus and flexing the terminal phalanx (Froment’s sign). The metacarpophalangeal joints become hyperextended because of the paralysis of the lumbrical and interosseous muscles, which normally flex these joints. Because the first and second lumbricals are not paralyzed (they are supplied by the median nerve), the hyperextension of the metacarpophalangeal joints is most prominent in the fourth and fifth fingers. The interphalangeal joints are flexed, owing again to the paralysis of the lumbrical and interosseous muscles, which normally extend these joints through the extensor expansion. The flexion deformity at the interphalangeal joints of the fourth and fifth fingers is obvious because the first and second lumbrical muscles of the index and middle fingers are not paralyzed. In long-standing cases the hand assumes the characteristic “claw” deformity (main en griffe). Wasting of the paralyzed muscles results in flattening of the hypothenar eminence and loss of the convex curve to the medial border of the hand. Examination of the dorsum of the hand will show hollowing between the metacarpal bones caused by wasting of the dorsal interosseous muscles (Fig. 9-105). Sensory Loss of skin sensation will be observed over the anterior and posterior surfaces of the medial third of the hand and the medial one and a half fingers. Vasomotor Changes The skin areas involved in sensory loss are warmer and drier than normal because of the arteriolar dilatation and absence of sweating resulting from loss of sympathetic control. Injuries to the Ulnar Nerve at the Wrist

  • Motor: The small muscles of the hand will be paralyzed and show wasting, except for the muscles of the thenar eminence and the first two lumbricals, as described (see previous column). The clawhand is much more obvious in wrist lesions because the flexor digitorum profundus muscle is not paralyzed, and marked flexion of the terminal phalanges occurs.
  • Sensory: The main ulnar nerve and its palmar cutaneous branch are usually severed; the posterior cutaneous branch, which arises from the ulnar nerve trunk about 2.5 in. (6.25 cm) above the pisiform bone, is usually unaffected. The sensory loss will therefore be confined to the palmar surface of the medial third of the hand and the medial one and a half fingers and to the dorsal aspects of the middle and distal phalanges of the same fingers.
  • Vasomotor and trophic changes: These are the same as those described for injuries at the elbow. It is important to remember that with ulnar nerve injuries, the higher the lesion, the less obvious the clawing deformity of the hand.

Unlike median nerve injuries, lesions of the ulnar nerve leave a relatively efficient hand. The sensation over the lateral part of the hand is intact, and the pincerlike action of the thumb and index finger is reasonably good, although there is some weakness owing to loss of the adductor pollicis. P.537
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Clinical Problem Solving Study the following case histories and select the best answers to the question following them. An 18-year-old woman complaining of severe pain and redness around the base of the nail of the right index finger visited her physician. She stated that she had trimmed the cuticle (eponychium) of her nail with scissors, and the following day the pain commenced. On examination, the skin folds around the root of the nail were red, swollen, and extremely tender. The index finger was swollen, and red streaks were seen coursing up the front of the forearm. 1. The following symptoms and signs in this patient were consistent with a diagnosis of an acute bacterial infection under the nail folds (paronychia) of the right index finger except which? (a) Some tender lymph nodules could be palpated in the infraclavicular fossa. (b) The patient’s temperature was raised. (c) The infection had spread into the lymph vessels draining the finger. (d) The red streaks on the front of the forearm were caused by the local vasodilatation of the blood vessels along the course of the lymph vessels. (e) The lymph vessels from the index finger drain into the supratrochlear node, which was inflamed and enlarged. View Answer1. E. The lymph vessels from the index finger drain into the infraclavicular nodes. A 20-year-old man, riding pillion on a snowmobile, was involved in an accident. The machine was traveling at high speed when it hit a tree stump buried in snow. The man was thrown 12 ft. and landed on his right shoulder and the right side of his head. After 3 weeks of hospitalization, it was noticed that he kept his right arm internally rotated by his side with the forearm pronated. An area of anesthesia was present along the lateral side of the upper part of the arm. 2. The following statements concerning this patient are correct except which? (a) A diagnosis of damage to the upper part of the brachial plexus (Erb-Duchenne palsy) was made. (b) A lesion of the fifth and sixth cervical roots of the brachial plexus was present. (c) The median radial ulnar nerve was made functionless. (d) The supraspinatus, infraspinatus, subclavius, biceps brachii, greater part of the brachialis, coracobrachialis, deltoid, and teres minor were paralyzed. (e) The loss of sensation down the lateral side of the right arm was caused by the lesion involving the fifth and sixth cervical dermatomes. View Answer2. C. The suprascapular nerve, the nerve to the subclavius, the musculocutaneous nerve, and the axillary nerve were made functionless. A father, seeing his 3-year-old son playing in the garden, ran up and picked him up by both hands and swung him around in a circle. The child’s enjoyment suddenly turned to tears, and he said his left elbow hurt. On examination, the child held his left elbow joint semiflexed and his forearm pronated. 3. The following statements concerning this case are consistent with the diagnosis of dislocation of the superior radioulnar joint except which? (a) The head of the radius was pulled out of the anular ligament. (b) At age 3 years, the child’s anular ligament has a large diameter and the head of the radius can easily be pulled out of the ligament by traction. (c) The incidence of this condition is equal in both sexes. (d) The pain from the joint caused reflex contraction of the surrounding muscles to protect the joint from further movement. (e) The subluxation of the joint can be treated by pulling downward on the forearm and at the same time performing the movement of pronation and supination. Finally, the elbow joint is flexed and held in that position. View Answer3. B. Under age 6 years, the child’s head of the radius is of a relatively small size and may easily be pulled out of the anular ligament by traction on the forearm. A 60-year-old woman fell down the stairs and was admitted to the emergency department with severe right shoulder pain. On examination, the patient was sitting up with her right arm by her side and her right elbow joint supported by the left hand. Inspection of the right shoulder showed loss of the normal rounded curvature and evidence of a slight swelling below the right clavicle. Any attempt at active or passive movement of the shoulder joint was stopped by severe pain in the shoulder. A diagnosis of dislocation of the right shoulder joint was made. 4. The following statements concerning this patient are consistent with the diagnosis except which? (a) This patient had a subcoracoid dislocation of the right shoulder joint. (b) The head of the humerus was dislocated downward through the weakest part of the capsule of the joint. (c) The pull of the pectoralis major and subscapularis muscles had displaced the upper end of the humerus medially. (d) The greater tuberosity of the humerus no longer displaced the deltoid muscle laterally, and the curve of the shoulder was lost. (e) The integrity of the axillary nerve should always be tested by touching the skin over the upper half of the deltoid muscle. View Answer4. E. The integrity of the axillary nerve is tested by touching the skin over the lower half of the deltoid muscle. The skin of the curve of the shoulder, including the skin covering the upper half of the deltoid muscle, is supplied by the supraclavicular nerves. A 45-year-old woman having her yearly physical examination was found the have a hard, painless lump in the upper lateral quadrant of the left breast. On examination with her arms at her sides, the left nipple was seen to be higher than the right, and a small dimple of skin was noted over the lump. On examination of the left axilla, three small, hard discrete nodules could be palpated below the lower border of the pectoralis major muscle. The right breast was normal. A diagnosis of carcinoma of the left breast was made, with secondary deposits in the axilla. 5. The following statements concerning this patient are correct except which? (a) The contracting fibrous tissue of the malignant tumor had pulled on the lactiferous ducts of the nipple, raising it above the level of the opposite nipple. (b) The dimpling of the skin was caused by the fibrous tissue pulling on the suspensory ligaments of the breast. (c) The upper lateral quadrant of the breast is drained into the pectoral or anterior axillary lymph nodes. (d) The enlarged pectoral lymph nodes could be palpated against the surgical neck of the humerus. (e) The malignant tumor had spread by way of the lymph vessels to the pectoral lymph nodes. View Answer5. D. The enlarged pectoral lymph nodes can be palpated against the posterior surface of the contracted pectoralis major muscle. A young secretary, running from her office, had a glass door swing back in her face. To protect herself, she held out her left hand, which smashed through the glass. On admission to the hospital, she was bleeding profusely from a superficial laceration in front of her left wrist. She had sensory loss over the palmar aspect of the medial one and a half fingers but normal sensation of the back of these fingers over the middle and proximal phalanges. She had difficulty in grasping a piece of paper between her left index and middle fingers. All her long flexor tendons were intact. 6. The following statements concerning this patient are correct except which? (a) The radial artery was cut in front of the flexor retinaculum, and this accounted for the profuse bleeding. (b) The loss of skin sensation on the palmar aspect of the medial one and a half fingers was caused by the severance of the ulnar nerve as it crossed in front of the flexor retinaculum. (c) The normal sensation on the back of the medial one and a half fingers over the proximal phalanges was caused by the fact that the posterior cutaneous branch of the ulnar nerve arises about 2.5 in. (6.25 cm) proximal to the flexor retinaculum and was spared. (d) The inability to hold the piece of paper was caused by the paralysis of the second palmar interosseous muscle, which is supplied by the deep branch of the ulnar nerve. (e) There was no sensory loss on the palm of the hand because the palmar cutaneous branch of the ulnar nerve was not cut. View Answer6. A. The radial artery does not enter the palm by passing in front of the flexor retinaculum; it does so by passing forward between the two heads of the first dorsal interosseous muscles between the first and second metacarpal bones. It was the ulnar artery that was cut with the ulnar nerve in front of the flexor retinaculum. A 50-year-old woman complaining of severe “pins and needles” in her right hand and lateral fingers visited her physician. She said that she had experienced difficulty in buttoning up her clothes when dressing. On physical examination the patient pointed to her thumb and index, middle, and ring fingers as the areas where she felt discomfort. No objective impairment of sensation was found in these areas. The muscles of the thenar eminence appeared to be functioning normally, although there was some loss of power compared with the activity of the muscles of the left thenar eminence. 7. The following statements concerning this patient are correct except which? (a) Altered skin sensation was felt in the skin areas supplied by the digital branches of the median nerve. (b) The muscles of the thenar eminence showed some evidence of wasting as seen by flattening of the thenar eminence. (c) The muscles of the thenar eminence are supplied by the recurrent muscular branch of the median nerve. (d) The median nerve enters the palm through the carpal tunnel. (e) The median nerve occupies a large space between the tendons behind the flexor retinaculum. (f) This patient has carpal tunnel syndrome. View Answer7. E. The median nerve occupies a small restricted space in the carpal tunnel. A 64-year-old man consulted his physician because he had noticed during the past 6 months a thickening of the skin at the base of his left ring finger. As he described it: “There appears to be a band of tissue that is pulling my ring finger into the palm.” On examination of the palms of both hands, a localized thickening of subcutaneous tissue could be felt at the base of the left ring and little fingers. The metacarpophalangeal joint of the ring finger could not be fully extended, either actively or passively. 8. The following statements concerning this patient are correct except which? (a) The deep fascia beneath the skin of the palm is thickened to form the palmar aponeurosis. (b) The distal end of the aponeurosis gives rise to five slips to the five fingers. (c) Each slip is attached to the base of the proximal phalanx and to the fibrous flexor sheath of each finger. (d) Fibrous contraction of the slip to the ring finger resulted in permanent flexion of the metacarpophalangeal joint. (e) The patient had Dupuytren’s contracture. View Answer8. B. The distal end of the palmar aponeurosis gives rise to four slips, which pass to the four medial fingers. A 15-year-old girl, while demonstrating to her friends her proficiency at standing on her hands, suddenly went off balance and put all her body weight on her left outstretched hand. A distinctive cracking noise was heard, and she felt a sudden pain in her left shoulder region. On examination in the emergency department, the smooth contour of her left shoulder was absent. The clavicle was obviously fractured, and the edges of the bony fragments could be palpated. 9. The following statements concerning this case are correct except which? (a) The clavicle is one of the most common bones in the body to be fractured. (b) Anatomically, the weakest part of the clavicle is the junction of the medial and middle thirds, and this is where the fracture commonly occurs. (c) The lateral bony fragment is depressed downward by the weight of the arm. (d) The lateral fragment is pulled forward and medially by the pectoral muscles. (e) The medial fragment is elevated by the sternocleidomastoid muscle. (f) The supraclavicular nerves or a communicating vein between the cephalic and internal jugular vein may be damaged by the bone fragments. View Answer9. B. Anatomically, the weakest part of the clavicle is the junction of the middle and lateral thirds, and that is where the fracture occurred in this patient. A 63-year-old man fell down a flight of stairs and sustained a fracture of the lower end of the left radius. On examination the distal end of the radius was displaced posteriorly. This patient had sustained a Colles’ fracture. 10. The following statements concerning this case are correct except which? (a) Occasionally the styloid process of the ulna is also fractured. (b) The median nerve may be injured at the time of the fall. (c) When the fracture is reduced, the styloid process of the radius should come to lie about 0.75 in. (1.9 cm) proximal to that of the ulna. (d) The fracture produces posterior angulation of the distal fragment of the radius. (e) On reduction of the fracture the distal end of the radius should lie at an angle of 15° anteriorly. (f) The hand should always be splinted in the position of function. View Answer10. C. The normal position of the tip of the styloid process of the radius is about 0.75 in. (1.9 cm) distal to that of the ulna. A 22-year-old medical student fell off her bicycle onto her outstretched hand. She thought she had sprained her right wrist joint and treated herself by binding her wrist with an elastic bandage. But 3 weeks later, she was still experiencing pain on moving her wrist and so decided to visit the emergency department. On examination of the dorsal surfaces of both hands, with the fingers and thumbs fully extended, a localized tenderness could be felt in the anatomic snuffbox of her right hand. A diagnosis of fracture of the right scaphoid bone was made. 11. The following statements concerning this patient are correct except which? (a) The fracture line on the scaphoid bone may deprive the proximal fragment of its arterial supply. (b) A bony fragment deprived of its blood supply may undergo ischemic necrosis. (c) Because the scaphoid bone articulates with other bones, the fracture line may enter a joint cavity and become bathed in synovial fluid, which would inhibit repair. (d) The scaphoid bone is an easy bone to immobilize because of its small size. (e) Fractures of the scaphoid bone have a high incidence of nonunion. View Answer11. D. The scaphoid bone is a difficult bone to immobilize because of its position and small size. A 6-year-old boy, running along a concrete path with a glass jam jar in his hand, slipped and fell. The glass from the broken jar pierced the skin on the front of his left wrist. On examination a small wound was present on the front of the left wrist and the palmaris longus tendon had been severed. The thumb was laterally rotated and adducted, and the boy was unable to oppose his thumb to the other fingers. There was loss of skin sensation over the lateral half of the palm and the palmar aspect of the lateral three and a half fingers. 12. The following facts concerning this patient are correct except which? (a) Sensory loss of the distal part of the dorsal surfaces of the lateral three and a half fingers was experienced. (b) The median nerve lies superficial to the palmaris longus proximal to the flexor retinaculum and was severed by the piece of glass. (c) The median nerve lies in the interval between the tendons of flexor digitorum superficialis and the flexor carpi radialis muscles just proximal to the wrist joint. (d) Adduction of the thumb was produced by the contraction of the adductor pollicis muscle, which is supplied by the ulnar nerve. (e) The palmar cutaneous branch of the median nerve had been severed. View Answer12. B. The median nerve lies deep to the palmaris longus tendon proximal to the flexor retinaculum. P.543
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Review Questions Multiple-Choice Questions Select the best answer for each question. 1. The following structures pass posterior to the flexor retinaculum except which? (a) Flexor digitorum superficialis tendons (b) Median nerve (c) Flexor pollicis longus tendon (d) Ulnar nerve (e) Anterior interosseous nerve View Answer1. D. The ulnar nerve passes superficial to the flexor retinaculum just lateral to the pisiform bone. 2. The following tendons are inserted into the base of the proximal phalanx of the thumb except which? (a) Extensor pollicis brevis (b) Abductor pollicis longus (c) Oblique head of adductor pollicis (d) Flexor pollicis brevis (e) First palmar interosseous View Answer2. B. The abductor pollicis longus is inserted into the base of the first metacarpal bone. 3. The following muscles abduct the hand at the wrist joint except which? (a) Flexor carpi radialis (b) Abductor pollicis longus (c) Extensor carpi radialis longus (d) Extensor digiti minimi (e) Extensor pollicis longus View Answer3. D. The extensor digiti minimi extends the metacarpophalangeal joint of the little finger and adducts the hand at the wrist joint. 4. The following bones form the proximal row of carpal bones except which? (a) Lunate (b) Pisiform (c) Scaphoid (d) Triquetral (e) Trapezium View Answer4. E. The trapezium is in the distal row of carpal bones. 5. The tendons of the following muscles form the rotator cuff except which? (a) Teres minor (b) Supraspinatus (c) Subscapularis (d) Teres major (e) Infraspinatus View Answer5. D. The teres major tendon is inserted into the medial lip of the bicipital groove of the humerus. 6. The quadrangular space is bounded by the following structures except which? (a) Surgical neck of the humerus (b) Long head of triceps (c) Deltoid (d) Teres major (e) Teres minor View Answer6. C 7. The radial nerve gives off the following branches in the posterior compartment of the arm except which? (a) Lateral head of the triceps (b) Lower lateral cutaneous nerve of the arm (c) Medial head of the triceps (d) Brachioradialis (e) Anconeus View Answer7. D. The branch from the radial nerve to the brachioradialis muscle leaves the nerve after it has left the posterior compartment of the arm by piercing the lateral intermuscular septum. 8. All the following statements concerning the brachial plexus are correct except which? (a) The roots C8 and T1 join to form the lower trunk. (b) The cords are named according to their position relative to the first part of the axillary artery. (c) The nerve that innervates the levator scapulae is a branch of the upper trunk. (d) The roots, trunks, and divisions are not located in the axilla. (e) No nerves originate as branches from the individual divisions of the brachial plexus. View Answer8. B. The cords are named according to their relative position to the second part of the axillary artery as it lies behind the pectoralis minor muscle. 9. The anterior fascial compartment of the forearm contains the following arteries except which? (a) Brachial (b) Anterior interosseous (c) Radial (d) Ulnar (e) Profunda View Answer9. E. The profunda artery runs through the posterior fascial compartment of the arm accompanied by the radial nerve. 10. The boundaries of the anatomic snuffbox include the following except which? (a) Abductor pollicis brevis (b) Extensor pollicis longus (c) Extensor pollicis brevis (d) Abductor pollicis longus View Answer10. A. The abductor pollicis brevis is a muscle of the thenar eminence and is not near the anatomic snuffbox. 11. The following structures are attached to the greater tuberosity of the humerus except which? (a) Supraspinatus muscle (b) Coracohumeral ligament (c) Teres minor muscle (d) Infraspinatus muscle (e) Subscapularis muscle View Answer11. E. The subscapularis muscle is inserted into the lesser tuberosity of the humerus. 12. The following structures form the boundaries to the superior entrance into the axilla except which? (a) Clavicle (b) Coracoid process (c) Upper border of the scapula (d) Outer border of the first rib View Answer12. B 13. The carpal tunnel contains the following important structures except which? (a) Flexor pollicis longus tendon (b) Flexor digitorum profundus tendons (c) Median nerve (d) Flexor carpi radialis tendon (e) Flexor digitorum superficialis tendons View Answer13. D. The flexor carpi radialis tendon enters the palm through a split in the flexor retinaculum in a groove on the trapezium. Completion Questions Select the phrase that best completes each statement. 14. Hyperextension of the proximal phalanges of the little and ring fingers (i.e., claw hand) can result from damage to the ________ nerve. (a) ulnar (b) axillary (c) radial (d) median (e) anterior interosseous View Answer14. A. The ulnar nerve supplies the lumbrical and interossei muscles, which normally flex the proximal phalanges and extend the middle and distal phalanges of the little and ring fingers. 15. Wrist drop can result from damage to the ________ nerve. (a) median (b) ulnar (c) radial (d) anterior interosseous (e) axillary View Answer15. C. see page 537 and Figure 9-103. 16. An inability to oppose the thumb to the little finger can result from damage to the ________ nerve. (a) anterior interosseous (b) posterior interosseous (c) radial (d) ulnar (e) median View Answer16. E. The opponens pollicis muscle, which is responsible for pulling the thumb medially and forward across the palm so that the palmar surface of the tip of the thumb may come into contact with the palmar surface of the tips of the other fingers, is supplied by the median nerve. 17. The sensory innervation of the nail bed of the index finger is the (a) median nerve. (b) radial nerve. (c) dorsal cutaneous branch of the ulnar nerve. (d) superficial branch of the ulnar nerve. (e) palmar cutaneous branch of the ulnar nerve. View Answer17. A 18. The sensory innervation of the medial side of the palm is the (a) radial nerve. (b) palmar cutaneous branch of the ulnar nerve. (c) dorsal cutaneous branch of the ulnar nerve. (d) median nerve. (e) superficial branch of the ulnar nerve. View Answer18. B 19. The sensory innervation of the dorsal surface of the root of the thumb is the (a) median nerve. (b) radial nerve. (c) superficial branch of the ulnar nerve. (d) dorsal cutaneous branch of the ulnar nerve. (e) posterior interosseous nerve. View Answer19. B 20. The sensory innervation of the medial side of the palmar aspect of the ring finger is the (a) radial nerve. (b) posterior interosseous nerve. (c) dorsal cutaneous branch of the ulnar nerve. (d) median nerve. (e) superficial branch of the ulnar nerve. View Answer20. E 21. The musculocutaneous nerve originates from the ________ of the brachial plexus. (a) posterior cord (b) lateral cord (c) both medial and lateral cords (d) upper trunk (e) medial cord View Answer21. B 22. The suprascapular nerve originates from the ________ of the brachial plexus. (a) medial cord (b) lower trunk (c) posterior cord (d) lateral cord (e) upper trunk View Answer22. E 23. The median nerve originates from the ________ of the brachial plexus. (a) medial and lateral cords (b) medial cord (c) posterior cord (d) upper and lower trunk (e) lateral cord View Answer23. A 24. The thoracodorsal nerve originates from the ________ of the brachial plexus. (a) lateral cord (b) posterior cord (c) medial cord (d) medial and posterior cords (e) lower trunk View Answer24. B 25. The axillary nerve originates from the ________ of the brachial plexus. (a) posterior cord (b) middle trunk (c) lateral cord (d) lower trunk (e) medial cord View Answer25. A 26. The lymph from the upper lateral quadrant of the breast drains mainly into the (a) lateral axillary nodes (b) internal thoracic nodes (c) posterior axillary nodes (d) anterior axillary nodes (e) deltopectoral group of nodes View Answer26. D 27. The medial collateral ligament of the elbow joint is closely related to the (a) brachial artery (b) radial nerve (c) ulnar nerve (d) basilic vein (e) ulnar artery View Answer27. C Multiple-Choice Questions Read the case histories and select the best answer to the question following them. A patient was seen in the emergency department with a laceration of the skin over the middle phalanx of the right index finger. After carefully examining the patient, the physician decided to suture the wound under a digital nerve block. 28. The site of the anesthetic injection depended on the following statements except which? (a) The skin of the right index finger over the middle phalanx is innervated anteriorly by two digital branches of the median nerve. (b) The skin of the right index finger over the middle phalanx is innervated posteriorly by two digital branches of the superficial radial nerve. (c) These nerves can easily be blocked by injecting small volumes of anesthetic solution around the base of the finger. (d) The digital nerves to the fingers are difficult to inject because they are imbedded in tough deep fascia. (e) Provided that the wound was clean and did not become infected, the healing process should take place without any complications and full return of skin sensation should occur. View Answer28. D. The digital nerves at the root of the fingers are relatively easy to inject and are not imbedded in tough deep fascia. A 46-year-old man was involved in an automobile accident and sustained a tear of the capsule of the carpometacarpal joint of his right thumb. In view of his history of lung disease, it was decided to repair the laceration under a brachial plexus nerve block. The orthopedic surgeon decided to inject the anesthetic into the brachial plexus below the clavicle. 29. The injection procedure depended on the following statements except which? (a) The brachial plexus lies in the axilla and is formed from the anterior rami of C5 through C8 and T1 spinal nerves. (b) The axillary sheath is formed of deep fascia and surrounds the axillary artery and the brachial plexus. (c) The arm is abducted to an angle greater than 90° so that the axillary artery could be palpated high up in the axilla. (d) The anesthetic blocking needle is inserted into the sheath. (e) The cords and branches of the brachial plexus, including the musculocutaneous nerve, lie within the sheath, and all the branches are blocked by the anesthetic using this approach. View Answer29. E. The disadvantage of the axillary approach to the brachial plexus nerve block is the difficulty sometimes experienced in blocking the musculocutaneous nerve. This nerve is a branch of the lateral cord of the plexus and the anesthetic agent may not reach high enough up in the sheath to block this nerve. To overcome this disadvantage, the axillary artery and the sheath are compressed distal to the point of injection, so that the sheath may be closed off below. By using this maneuver, the anesthetic agent rises in the sheath to the level of the musculocutaneous nerve. It is the terminal branches of the musculocutaneous nerve (lateral cutaneous nerve of the forearm) that supply the skin over the carpometacarpal joint of the thumb. Footnote * There are eight interossei, consisting of four dorsal and four palmar muscles. Some authors describe only three palmar interossei and state that the first palmar interosseous is in reality a second head to the flexor pollicis brevis: others believe that it is part of the adductor pollicis muscle.

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