FIGURE  15.1  The temporomandibular joint region, muscles, and facial nerve location.

Reconstruction of the TMJ, regardless of the indication, attempts to preserve the function of the mandible as well as to maintain facial symmetry. Duplication of the complex functional properties of the TMJ is impossible with current techniques; however, maintaining adequate opening, functional occlusion, and acceptable facial aesthetics are the requirements of appropriate reconstruction. The surgeon must keep these goals in mind when planning reconstructive surgery involving the TMJ.

HISTORY

Patients will often have pain in the preauricular region, pressure sensations, or occlusal disturbances when presenting with processes involving the TMJ. Patients may report other symptoms such as ear pain, clicking/ grinding noises, and rarely inability to open the mouth.

PHYSICAL EXAMINATION

Often the necessity for TMJ reconstruction can be predicted by evaluating the underlying disease. The physical examination of the TMJ requiring reconstruction may range from a completely normal examination in the case where joint resection is necessary for oncologic margins to a severely abnormal examination with complete inability to open the mouth. The patient may exhibit varying levels of trismus, progressive malocclusion, and pain within the joint. Hyperplastic conditions of the condyle may result in shifting of the mandible toward the unaffected side. Conversely, destructive processes may result in mandibular shifting toward the affected side. Occlusal and mandibular excursive mobility should be evaluated and abnormalities such as midline shifts, asymmetry, or other abnormalities of function documented.

The maximum interincisal opening distance should be measured and documented (distance between the upper and lower incisor edges with maximal opening, mm). Examination of the external auditory meatus on the affected side is critical to assess for invasive disease into the meatus or erosion of the tympanic plate of the temporal bone.

Facial nerve function as well as regional sensory disturbances should be evaluated and appropriately documented as the frontal branch of the facial nerve, greater auricular nerve, and auriculotemporal nerve may be involved with pathologic processes in this area. The chest and rib cage in particular should be examined for evidence of previous surgery or trauma.

INDICATIONS

Common indications for reconstruction include benign and malignant processes of the TMJ, or malignant lesions involving the region. Sequelae from adjuvant radiotherapy or bisphosphonate therapy may require resection and reconstruction of the TMJ. Malignant lesions of the temporal bone may also rarely result in the necessity of resection and reconstruction of the TMJ. Malignant processes of the overlying soft tissues such as squamous cell carcinoma or cancer of the parotid gland may invade the temporomandibular region and require ablative procedures to the TMJ. Benign lesions of the mandibular condyle such as condylar hyperplasia, or severe osteoarthritis as well as malignant lesions such as chondrosarcoma or osteosarcoma are also indications for TMJ reconstruction. While osteonecrosis of the TMJ is rare, extensive radiation damage or trauma to the area may also be an indication for reconstruction.

Indications for TMJ reconstruction are summarized below:

• Benign condylar conditions (condylar hyperplasia, severe arthritis)

• Odontogenic tumors (ameloblastoma, myxoma)

• Malignant tumor of the TMJ/condyle (osteosarcoma, chondrosarcoma)

• Malignant tumor in the TMJ region (squamous cell carcinoma, cancer of the parotid gland, sarcoma)

• Severe traumatic injuries (gunshot wounds)

• Osteonecrosis (osteoradionecrosis [ORN], bisphosphonate related osteonecrosis of the jaws [BRONJ])

CONTRAINDICATIONS

There are no specific contraindications to reconstruction of the TMJ. In some cases, reconstruction of the condyle of the mandible must also be accompanied by reconstruction of the glenoid fossa to avoid middle cranial fossa complications (i.e., extensive temporal bone resections). It should also be noted that reconstruction of the TMJ may not be necessary in selected cases and that reasonable function and occlusion may be maintained with appropriate rehabilitation, even in the absence of articulation of the mandible with the skull base.

PREOPERATIVE PLANNING

Anatomy

The TMJ is unique in the human skeleton as it is classified as a ginglymoarthrodial joint, that is it functions as both a rotational hinge as well as providing gliding movements during wide excursions. The condyle of the mandible articulates with the glenoid fossa of the temporal bone, separated by the articular disc. This disc is composed of dense fibrocartilage, unlike the hyaline cartilage found in most other joints in the skeleton. The TMJ and its associated articular disc are supported by several ligaments that connect the condyle to the base of skull including the temporomandibular ligament and the capsular ligament, as well as the stylomandibular and sphenomandibular ligament. The muscles of mastication, namely the temporalis and masseter muscles, as well as the lateral and medial pterygoid muscles further support and provide movement of the joint. It is the anatomic arrangement of these ligaments and muscles that allow for the complexity of mandibular function. Other anatomical considerations in the region include the parotid gland, which lies directly on the capsular ligament of the TMJ directly below the zygomatic arch. The temporal branches of the facial nerve traverse the zygomatic arch in this region and are the motor nerves most commonly at risk during joint reconstruction (Fig. 15.1). In addition, sensory branches of the auriculotemporal nerve pass on the posterior–medial aspect of the condyle and supply the skin of the temporal area as well as portions of the auricle and external auditory canal. The superficial temporal artery and vein are adjacent to the auriculotemporal nerve branches and may be encountered during dissection of the condyle in this region. Medial to the glenoid fossa at the level of the skull base, the middle meningeal artery passes intracranial via the foramen spinosum. Care must be taken when resecting the condyle to avoid aggressive dissection in this area. Additionally, the external carotid artery lies posterior and medial to the mandibular ramus (as well as the maxillary branch medial to the condylar neck) and should be identified if dissection in this area is indicated. Reconstructive surgery of the TMJ requires an understanding of both the anatomy of the craniomandibular articulation as well as the surrounding structures to provide for functional reconstruction while avoiding iatrogenic sequelae.

Imaging Studies

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