//SKELETAL ACCESS SURGERY

SKELETAL ACCESS SURGERY

The craniofacial skeleton has an excellent blood supply, and so can be dismantled as a series of osteoplastic flaps. The surgical disarticulation of the craniofacial skeleton has been used to gain access to otherwise inaccessible sites in order to allow the surgeon to attend to pathology in the skull base, cervical spine and anterior and posterior cranial fossae. The aim is to provide increased and more direct exposure of both the pathology and the adjacent vital structures without the need to resect uninvolved structures. The craniofacial skeleton can be divided into a series of modular osteotomies, which permit both independent and conjoined mobilization.

The zygomatic and nasal bones and the maxilla may be exposed and mobilized, pedicled on the overlying soft tissues either unilaterally or bilaterally. These approaches improve access to the nasal cavity, maxillary, ethmoid and sphenoid sinuses, the soft palate and nasopharynx, and the infratemporal fossa and pharyngeal space. The exposures may be extended to gain access to the anterior and middle cranial fossae, cavernous sinus, clivus, craniocervical junction and upper cervical vertebrae.

A variety of different access osteotomies have been described and found to be useful in specific clinical situations. Most of the osteotomies described follow the conventional patterns of facial fractures described above. The entire hemimaxilla and zygoma can be mobilized, and pedicled on the soft tissues of the face by making bone cuts that follow the lines of a Le Fort II fracture on one side. The osteotomy is completed by dividing the upper alveolus and palate just to the side of the nasal septum and perpendicular plate of the vomer. The maxilla may be mobilized at the Le Fort I level and downfractured, pedicled on the palatoglossal muscles and soft tissue attachments. This gives good access to the nasopharynx, clivus and upper cervical spine, particularly if the palate is divided in the midline.

Lateral zygomatic osteotomies may be performed to gain access to the orbital apex and infratemporal fossa. The surgical approach is from behind using a hemi- or bicoronal flap. The zygomatic complex is mobilized inferiorly pedicled on masseter. When combined with a mandibular ramus osteotomy, access is gained to the retromaxillary area and pterygoid space as well as to the infratemporal fossa. In combination with a frontotemporal craniotomy, the zygomatic osteotomy has been used for access to the middle cranial fossa, cavernous sinus, apex of the petrous temporal bone and the interpeduncular cistern.

Dividing the lower lip in the midline, and dividing the mandible either in the midline or just in front of the mental foramen, allows the hemimandible to be swung laterally. The technique is used to give improved access to the floor of the mouth, the base of the tongue, tonsillar fossa, soft palate, oropharynx, posterior pharyngeal wall, supraglottic larynx and pterygomandibular region. By extending the dissection laterally access is gained to the pterygoid space, infratemporal fossa and parapharyngeal space. By dissecting more medially access is gained to the nasopharynx, lower part of the clivus and all seven of the cervical vertebrae. A modification of the mandibular swing procedure increases access up to the skull base, by combining the classic mandibular swing with a horizontal osteotomy of the mandibular ramus above the level of the lingula.

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