Residency · Residency · Oral Maxillofacial Surgery

Alloplastic TMJ Reconstruction

Overview

Total alloplastic TMJ reconstruction involves replacement of the mandibular condyle (and sometimes the glenoid fossa) with prosthetic components. It is reserved for end-stage TMJ disease unresponsive to conservative and minimally invasive treatment. Two systems are primarily used: custom devices (TMJ Concepts, formerly Techmedica) and stock devices (Zimmer Biomet, formerly TMJ Medical). Outcomes have significantly improved since the disastrous Vitek-Kent Proplast-Teflon era of the 1980s-1990s, and modern total joint prostheses provide reliable pain reduction and functional improvement.

Indications

Indications include severe degenerative joint disease with disabling pain and dysfunction, ankylosis (bony or fibrous, especially recurrent), failed previous TMJ surgery (multiple operations), condylar resorption (idiopathic, inflammatory, or autoimmune), avascular necrosis of the condyle, developmental abnormalities (condylar agenesis or severe hypoplasia), neoplastic destruction of the condyle requiring resection, failed autogenous reconstruction (costochondral graft failure), and multiply operated joints requiring salvage.

Contraindications

Contraindications include active infection in the surgical field, allergy to prosthetic materials (titanium, cobalt-chromium, ultra-high molecular weight polyethylene), skeletal immaturity in growing patients (a relative contraindication), uncontrolled systemic disease precluding general anesthesia, inability to comply with postoperative rehabilitation, and inadequate bone stock for prosthesis fixation (which may require bone grafting).

Prosthetic Systems

Custom Devices (TMJ Concepts)

The fossa component consists of an ultra-high molecular weight polyethylene (UHMWPE) fossa lined with titanium mesh backing. The condylar/ramus component features a cobalt-chromium-molybdenum alloy condylar head on a titanium ramus plate. Custom devices are designed from patient-specific CT data using CAD/CAM technology, providing precise fit to individual anatomy with reduced need for intraoperative modification. They are particularly suited for complex anatomy in patients with previous surgery, significant bone loss, or ankylosis. However, they carry higher cost and a longer lead time of 4-6 weeks for fabrication.

Stock Devices (Zimmer Biomet)

Stock devices are available in multiple sizes off-the-shelf. The fossa component has a UHMWPE articular surface on a titanium backing plate, and the condylar/ramus component features a cobalt-chromium condylar head on a titanium ramus. These devices require intraoperative bending and adaptation of the ramus component but are available for immediate use without fabrication delay. They are cost-effective for straightforward anatomy but may be less ideal for complex revision cases or significant anatomic variation.

Material Science Considerations

Titanium is biocompatible, osseointegrates with bone, and provides rigid fixation. Cobalt-chromium-molybdenum provides a hard, wear-resistant articular surface. UHMWPE serves as a low-friction bearing surface with a proven track record in orthopedic joint replacement. Particulate wear debris can cause a foreign body reaction, which is a long-term concern, though it is less problematic than in hip or knee replacements due to the lower loading forces in the TMJ.

<image>Photographs and diagrams of the two primary alloplastic TMJ prosthetic systems (custom TMJ Concepts and stock Zimmer Biomet), showing the fossa and condylar/ramus components, the materials used for each component, and a lateral view of the prosthesis seated on a mandible model</image>

Preoperative Planning

Imaging

A CT scan with fine cuts (0.5-1 mm) through the TMJ and mandibular ramus bilaterally is obtained along with 3D reconstruction for surgical planning. MRI is obtained if soft tissue pathology or tumor involvement is suspected. For custom devices, CT data are sent to the manufacturer for prosthesis design.

Virtual Surgical Planning

3D printed stereolithographic models of the patient's anatomy are created. The custom prosthesis design is reviewed by the surgeon before fabrication. Cutting guides are designed for precise condylectomy and ramus preparation. Planned screw positions avoid tooth roots and the inferior alveolar nerve. The fat graft harvest site is planned, typically from the abdominal or periumbilical region.

Medical Optimization

Autoimmune screening is performed if the condylar resorption etiology is unknown, including rheumatoid factor, ANA, ESR, and CRP. Nutritional optimization, smoking cessation, and mental health assessment are addressed, as chronic pain patients frequently have comorbid psychological conditions.

Surgical Technique

Approach

A preauricular incision provides access to the glenoid fossa and condylar stump, with the endaural or Al-Kayat and Bramley modification used for extended access. The temporal branch of the facial nerve is identified and protected. A submandibular or retromandibular incision (Risdon incision, 2 cm below the angle of the mandible) provides access to the ramus for condylar/ramus component fixation, with identification and protection of the marginal mandibular branch of the facial nerve.

Key Surgical Steps

The procedure begins with preauricular exposure of the TMJ, removing residual disc, fibrous tissue, and scar from the fossa. The condyle (or condylar stump) is removed with a reciprocating saw, using a cutting guide for custom devices. The articular surface of the glenoid fossa is smoothed, and osteophytes and irregularities are removed. In ankylosis cases, all heterotopic bone is aggressively removed to create a gap. The fossa component is seated and fixed with typically 4-6 self-tapping screws into the zygomatic arch and root. Through the submandibular approach, the lateral ramus is exposed and the ramus component is adapted to the lateral surface of the mandible, secured with 6-8 bicortical screws along the ramus plate. An abdominal or periumbilical fat graft is harvested and packed around the prosthesis to fill dead space and act as an interpositional barrier to heterotopic bone formation. Layered closure of both incisions is performed with consideration for drain placement.

Fat Grafting

A dermal fat graft or free fat graft is harvested from the abdomen and placed around the prosthetic joint, especially in the gap between fossa and condylar components. The primary purpose is to prevent heterotopic bone formation (re-ankylosis). Fat grafting also provides tissue bulk in the surgical site and reduces dead space. Evidence supports decreased re-ankylosis rates with fat grafting (Wolford 2003).

<image>Intraoperative photographs demonstrating the key steps of alloplastic TMJ reconstruction: preauricular exposure of the glenoid fossa with the diseased condyle, condylectomy specimen, seating of the fossa component with screw fixation, and the final condylar-ramus component fixated to the lateral ramus with the fat graft packed around the prosthetic articulation</image>

Post-Operative Management

Immediate jaw function is encouraged with no prolonged immobilization, unlike autogenous reconstruction. A soft diet is maintained for 6-8 weeks with progressive advancement to a regular diet. Aggressive jaw physiotherapy begins within 1 week, including active and passive range of motion exercises targeting maximum interincisal opening of 35-40 mm, with a Therabite or similar mechanical opening device. Pain management uses a multimodal approach. Follow-up imaging includes a panoramic radiograph at 6 weeks and CT at 6-12 months. Long-term follow-up consists of annual clinical and radiographic evaluation.

Outcomes

Pain reduction is reported by 80-90% of patients, with VAS reduction of 50-70%. Maximum interincisal opening improves from an average of 20-25 mm to 35-40 mm. Most patients return to a soft to regular diet, and quality of life improves significantly on validated measures. Long-term device survival exceeds 90% at 10 years in recent series, with a revision rate of 5-10% for loosening, heterotopic bone, or infection.

Complications

Facial nerve injury may involve the temporal branch (preauricular approach) or the marginal mandibular branch (submandibular approach) and is usually neuropraxia (temporary). Infection occurs in 1-3% and may require prosthesis removal if deep infection cannot be controlled. Heterotopic bone formation occurs in 5-15%, and fat grafting reduces this risk. Component loosening (screw loosening or plate fracture) may require revision. Malocclusion may develop as an open bite if the condylar component is seated too high, or as overclosure. Wear debris and foreign body reaction are rare with modern materials. Hematoma or seroma may occur at the surgical site or fat graft donor site. Recurrent ankylosis is a particular risk in patients with prior ankylosis, emphasizing the need for fat grafting and aggressive physiotherapy.

Controversies

Custom vs. Stock Devices

Custom devices offer better fit, reduced intraoperative adjustment, and are ideal for complex anatomy. Stock devices are immediately available, lower in cost, and adequate for straightforward cases. Limited head-to-head comparative studies exist, and most surgeons have a preference based on training and experience. The trend favors custom devices for most cases given improving technology and reasonable cost differences.

Fat Grafting

Strong advocacy exists for routine fat grafting to prevent heterotopic bone (Wolford, Mercuri). Some surgeons omit fat grafting in non-ankylosis cases. Donor site morbidity is low but not negligible. The growing consensus favors routine use, especially in ankylosis and multiply operated joints.

Bilateral vs. Unilateral Replacement

Bilateral replacement is performed when both joints are severely affected. Some surgeons advocate bilateral replacement even when one side is less symptomatic to balance the system, while others prefer staged procedures, replacing the worse side first.

Clinical Pearls

Alloplastic TMJ reconstruction is a salvage procedure, and conservative and minimally invasive options should be exhausted first. Fat grafting is essential in ankylosis cases to prevent re-ankylosis and should not be omitted. Immediate postoperative jaw physiotherapy is critical, as delayed or inadequate physical therapy leads to poor outcomes. Custom devices are preferred for multiply operated patients with significant anatomic distortion. The facial nerve must be protected meticulously during both approaches -- neuropraxia is common but permanent injury is devastating. Patients should be counseled that the goal is pain reduction and improved function, not a normal joint, to manage expectations. In condylar resorption cases, especially in young females, autoimmune conditions should be ruled out and medical management of the underlying disease considered. Alloplastic replacement should be avoided in growing patients -- costochondral graft remains the standard for pediatric and adolescent condylar reconstruction.

<image>Postoperative 3D CT reconstruction showing bilateral alloplastic TMJ prostheses in situ with the fossa components seated on the zygomatic root and the condylar-ramus components fixated along the lateral ramus, demonstrating appropriate prosthetic positioning and screw placement</image>

References

• Wolford LM, et al. Custom-made total joint prostheses for TMJ reconstruction. J Oral Maxillofac Surg. 2003.
• Mercuri LG. Alloplastic temporomandibular joint replacement: rationale for the use of custom devices. Int J Oral Maxillofac Surg. 2012.
• Leandro LF, et al. Alloplastic TMJ replacement with the Zimmer Biomet system: a retrospective study. Int J Oral Maxillofac Surg. 2013.
• Idle MR, et al. Current UK practice in the management of end-stage TMJ disease. Br J Oral Maxillofac Surg. 2014.
• Wolford LM, Movahed R, Teschke M. Results of total TMJ replacement using custom versus stock devices. J Oral Maxillofac Surg. 2016.
• Mercuri LG, Giobbie-Hurder A. Long-term outcomes of total alloplastic TMJ replacement: a prospective study. J Oral Maxillofac Surg. 2004.

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