Prosthetic Reconstruction of the Temporomandibular Joint

DEFINITION

Alloplastic reconstruction of the temporomandibular joint (TMJ) is frequently required to address myriad issues relating to skeletal derangements,¹^,²^,³^,⁴^,⁵^,⁶ including arthritic conditions (rheumatoid, osteoarthritis, and post-traumatic arthritis), ankyloses, avascular necrosis of the condyle, sequelae from condylar/subcondylar fractures, benign and malignant neoplasms, degenerative joint disease, and congenital deformities (eg, hemifacial microsomia).²^,³^,⁴

ANATOMY

The TMJ is a diarthrodial synovial joint.
- As a complex apparatus, it allows full range of mandibular movement.
- The condylar head of the mandible on each side articulates with a fibrocartilaginous disc to form, in conjunction with the glenoid fossa of the temporal bone, a joint for hinge and gliding movements.
Derangements of the disc and the condyle frequently necessitate autologous or alloplastic replacement.
Alloplastic joint replacement is commonly used to address endstage deformities in the adult skeleton, multiple operated joints, and those that have failed prior autologous reconstruction.

PATIENT HISTORY AND PHYSICAL FINDINGS

Patients with end-stage TMJ disease can have widely variable clinical presentations.
- Pain is a commonly reported symptom but is not, in and of itself, an indication for surgical intervention.
  
  FIG 1 • Coronal (A) and axial (B) computed tomography views of a patient with left-sided temporomandibular joint ankylosis.
The clinical history obtained should focus on discomfort, limitation of motion, difficulties with mastication/nutrition, prior operative and nonoperative interventions, and a focused dental history relating to occlusion and parafunctional habits.
A complete head and neck examination should be performed, with particular emphasis on evaluation of the occlusion, TMJ findings (tenderness, crepitus, maximal incisal opening, and right and left excursive movements) and tenderness of the muscles of mastication.

IMAGING

Magnetic resonance imaging is the preferred modality for assessing disc pathology and to obtain real-time imaging of the disc position during mandibular motion.
Thin-cut helical maxillofacial computed tomography (CT) is the preferred modality for assessing bone pathology of the joint (FIG 1).
- This may be combined with angiography in cases of ankylosis, in which the ankylotic mass shares an intimate relationship with major vessels in the region (eg, pterygoid plexus, internal maxillary artery).

NONOPERATIVE MANAGEMENT

Diagnosis is the key to treatment. Patients should be evaluated by both a surgeon and a facial pain or TMJ disorders specialist.
Many patients will benefit from trials of nonoperative therapy (muscle relaxants, nonsteroidal anti-inflammatory drugs [NSAIDs], etc.) or dental appliance therapy (mandibular repositioning appliances, occlusal equilibration, bite guards, etc.).
Patients who fail nonoperative therapy often begin with diagnostic and minimally invasive therapeutic maneuvers (arthroscopy, arthrocentesis), with invasive interventions (arthroplasty) reserved for refractory cases or end-stage deformities.

SURGICAL MANAGEMENT

Preoperative Planning

Preoperative planning for alloplastic TMJ reconstruction involves a preoperative decision about the use of custom or stock TMJ prostheses. In both situations, a maxillofacial CT scan with thin cuts is required to visualize the local bony anatomy and for construction of three-dimensional (3D) model templates for prosthesis fabrication (FIG 2).

FIG 3 • Standard views of patient preparation and positioning. A nasotracheal intubation is performed to afford access to the oral cavity for manipulation of the occlusion (A). The oral cavity is isolated from the surgical field for the majority of the case (B). (Reprinted from Granquist EJ, Quinn PD. Total temporomandibular joint replacement (Stock). In: Kademani D, Tiwana P, eds. Atlas of Oral and Maxillofacial Surgery, 2015 with permission from Elsevier.)

Patients who are candidates for alloplastic reconstruction are those who have failed conservative management and have end-stage joint disease.
Patients with active infections, those who are skeletally immature, those with muscle hyperactivity disorders (clenching and grinding), and those with active resorptive bony processes or inadequate bone stock are not candidates for alloplastic reconstruction.³

Positioning

The operation is completed with the patient in the supine position on the operating table.
Nasotracheal intubation is required, as the surgeon will have to verify the occlusion intraoperatively following prosthetic replacement (FIG 3A).
- The anesthetist should be told not to use long-acting paralysis, as monitoring of facial nerve branches may aid with dissection.
- The nasotracheal tube is secured to the nasal septum using a 2-0 Vicryl suture.
- A moistened pharyngeal pack is not required, but may be preferred by some surgeons.
The patient should have a mechanism for maxillomandibular fixation in place prior to initiation of the operation. This can be orthodontic appliances, Erich arch bars, or intermaxillary fixation screws.
- If intermaxillary fixation appliances are to be applied intraoperatively, it is necessary to do so before prepping and draping, so as to avoid contamination of the facial incision with oral secretions.
- Once the maxillomandibular fixation appliances are applied, the oral cavity can be sealed off with a clear plastic occlusive dressing, and the face can be prepared in the standard fashion (FIG 3B).
If the surgeon anticipates using fascia or fat grafts around the prostheses, the donor site should be prepped and draped as appropriate.