Residency · Residency · Oral Maxillofacial Surgery

TMJ Ankylosis: Etiology and Surgical Management

Overview

TMJ ankylosis is the fusion of the mandibular condyle to the glenoid fossa, resulting in restricted or absent mandibular movement. It is classified as fibrous or bony and as intra-articular or extra-articular. The condition causes significant functional (inability to open the mouth), nutritional, airway, and psychosocial consequences. Pediatric ankylosis produces additional growth disturbances including micrognathia, facial asymmetry, and obstructive sleep apnea. Surgical management is challenging with significant recurrence rates.

Classification

By Tissue Type

Fibrous ankylosis involves dense fibrous adhesions between articular surfaces with some residual movement present. Bony ankylosis involves complete osseous fusion of the condyle to the temporal bone with no movement. Mixed forms exist on a spectrum between these two entities.

By Location

Intra-articular (true ankylosis) involves fusion within the joint space and is the most common form. Extra-articular (false ankylosis) involves mechanical obstruction to mandibular movement outside the joint, including coronoid hyperplasia (impingement on the zygomatic arch), zygomatic arch fracture malunion, myositis ossificans of the masticatory muscles, radiation fibrosis, and submucous fibrosis.

Sawhney Classification (Bony Ankylosis)

Type I features fibrous adhesions around the condylar head with preserved condyle morphology. Type II shows bony fusion at the outer edges with an identifiable condyle and fibrous tissue centrally. Type III has a bony bridge between the ramus and zygomatic arch with an unidentifiable condyle. Type IV represents a complete bony mass replacing the joint -- a true bony block from the ramus to the temporal bone.

Etiology

Trauma is the most common cause worldwide, particularly condylar fractures in children. Intracapsular condylar fractures cause hemarthrosis that undergoes organization, fibrosis, and eventually ossification. The risk is higher in pediatric patients due to their thin condylar cortex and greater osteogenic potential. Infection, from the spread of otitis media, mastoiditis, or odontogenic infection to the TMJ, is another cause. Previous surgery may lead to post-surgical adhesions or heterotopic bone formation. Systemic diseases including rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis can cause ankylosis. Post-radiation fibrosis and idiopathic cases with no identifiable cause account for the remaining etiologies.

Clinical Presentation

Limited or absent mouth opening is the hallmark, with maximum interincisal opening often less than 10 mm and potentially 0 mm in complete bony ankylosis. Facial asymmetry presents as deviation of the chin to the affected side in unilateral cases. Micrognathia and retrognathia develop especially with childhood-onset ankylosis due to growth center involvement. The bird-face deformity occurs in bilateral ankylosis in children, producing severe retrognathia, short ramus, steep mandibular plane, and anterior open bite. Obstructive sleep apnea results from retrognathia causing airway compromise. Additional problems include poor oral hygiene from inability to open for dental care, nutritional deficiency from a liquid or pureed diet, speech difficulties, and coronoid process elongation from compensatory hyperplasia on the affected side, which may further limit opening.

<image>Clinical photographs and 3D CT reconstructions comparing unilateral TMJ ankylosis (showing chin deviation, facial asymmetry, and the bony mass at the TMJ) with bilateral ankylosis in a pediatric patient demonstrating the classic bird-face deformity with severe retrognathia and anterior open bite</image>

Diagnostic Imaging

CT scan is the gold standard for evaluating bony ankylosis, with axial and coronal views and 3D reconstruction demonstrating the extent of bony fusion, medial extension, and relationship to the skull base. CT also assesses the coronoid process (which may need coronoidectomy) and measures ramus height and condylar morphology. Panoramic radiograph serves as a screening tool that may show a fused condyle-fossa complex. MRI is useful for fibrous ankylosis, showing absence of the disc and a fibrous mass. 3D printing of preoperative models is invaluable for planning osteotomy lines and reconstruction.

Surgical Management

Goals of Treatment

The goals are resection of the ankylotic mass and creation of a new joint space, restoration of mandibular function (mouth opening), prevention of re-ankylosis, reconstruction of the ramus-condyle unit when indicated, and correction of associated deformities including micrognathia and asymmetry.

Surgical Approaches

The preauricular approach is standard for TMJ ankylosis release, with the Al-Kayat and Bramley extended preauricular modification providing wide exposure. The submandibular approach supplements access for ramus work and reconstruction fixation. An intraoral approach is used for coronoidectomy if performed separately.

Surgical Options

Gap Arthroplasty

Gap arthroplasty involves resection of the ankylotic mass to create a gap of at least 10-15 mm between the ramus stump and the glenoid fossa, without reconstruction of the ramus-condyle unit. Its advantages include simplicity and shorter operative time. Disadvantages include mandibular shortening, malocclusion (open bite on the affected side), and risk of re-ankylosis. It is best suited for elderly patients, those with medical comorbidities, or as an interim measure.

Interpositional Arthroplasty

Interpositional arthroplasty combines gap arthroplasty with placement of interpositional material to prevent re-ankylosis. Materials include a temporalis muscle or fascia flap (the most commonly used autogenous option), dermis graft, auricular cartilage, abdominal fat graft (increasingly popular), and alloplastic materials such as silicone or acrylic (largely abandoned due to complications). This approach maintains a tissue barrier in the gap and reduces re-ankylosis, though the graft may resorb and there is donor site morbidity.

Costochondral Graft Reconstruction

Costochondral graft (CCG) reconstruction involves resection of the ankylotic mass followed by reconstruction with a graft harvested from the 5th, 6th, or 7th rib with 2-3 mm of cartilage cap. The CCG provides a biological condylar replacement, offers growth potential in children (the cartilage cap acts as a growth center), and restores ramus height. However, growth is unpredictable (overgrowth or undergrowth in pediatric patients), donor site morbidity includes pneumothorax, chest wall deformity, and pain, and there is risk of graft fracture, resorption, or ankylosis of the graft itself. CCG remains the standard for pediatric TMJ ankylosis reconstruction.

Distraction Osteogenesis

Distraction osteogenesis is used as an adjunct to ankylosis release, primarily in pediatric patients. Mandibular distraction (ramus or body) addresses the micrognathia and airway and can be performed simultaneously with ankylosis release or as a staged procedure. Transport distraction of the ramus segment can reconstruct the condyle. Advantages include gradual correction, simultaneous soft tissue expansion, and airway improvement. Disadvantages include device management, pin-site infections, and the need for a second surgery for device removal.

Alloplastic Total Joint Replacement

Alloplastic total joint replacement is considered for adult patients with recurrent ankylosis (failed previous autogenous reconstruction), severe anatomic distortion, or bilateral ankylosis. Custom devices (TMJ Concepts) are preferred for ankylosis cases due to distorted anatomy. This approach is always combined with fat grafting to prevent re-ankylosis and is not recommended for growing patients.

<image>Surgical illustrations showing the different approaches to TMJ ankylosis management: gap arthroplasty with the resection specimen and resulting gap, interpositional arthroplasty with a temporalis fascia flap rotated into the gap, and costochondral graft reconstruction with the graft seated in the glenoid fossa and fixated to the ramus stump</image>

Kaban Protocol for TMJ Ankylosis (Modified)

The Kaban protocol consists of aggressive excision of the ankylotic or fibrotic mass, ipsilateral coronoidectomy, contralateral coronoidectomy if MIO remains less than 35 mm after step 2, lining of the joint with temporalis fascia flap or fat graft, reconstruction of the ramus-condyle unit (CCG, alloplastic prosthesis, or distraction), rigid fixation if reconstruction is performed, and early mobilization with aggressive physiotherapy.

Coronoidectomy

Coronoidectomy is often necessary to achieve adequate mouth opening. The elongated coronoid process (compensatory hyperplasia) may impinge on the zygomatic arch or temporal fossa. Ipsilateral coronoidectomy is performed first; if MIO remains less than 35 mm, contralateral coronoidectomy is performed via an intraoral approach. This is a critical step, as failure to address coronoid hyperplasia is a common reason for inadequate postoperative opening.

Post-Operative Management

Aggressive jaw physiotherapy is the most important factor in preventing re-ankylosis. Exercises begin within 24-48 hours (or as soon as pain allows), including active and passive range of motion exercises and use of mechanical opening devices (Therabite, stacked tongue depressors). The target MIO is greater than 35 mm by 6 weeks, and exercises should continue for at least 6-12 months. Intermaxillary fixation is avoided or minimized as it promotes re-ankylosis. Diet progresses from liquid to soft over 4-6 weeks. Regular clinical and radiographic monitoring continues for 2-5 years.

Re-Ankylosis Prevention

Key measures include adequate gap creation (greater than 10 mm), interpositional material (temporalis flap or fat graft), coronoidectomy when indicated, aggressive early physiotherapy (the single most important factor), fat grafting around alloplastic prostheses, and avoidance of prolonged immobilization. The re-ankylosis rate is 5-30% depending on technique and compliance with physiotherapy.

Clinical Pearls

TMJ ankylosis in children is a surgical urgency because delayed treatment worsens facial growth disturbance, airway compromise, and psychosocial impact. Coronoidectomy should always be performed, as failure to do so is the most common reason for persistent limited opening after ankylosis release. Aggressive physiotherapy is non-negotiable and must begin early; patients require education, motivation, and regular follow-up to maintain compliance. Costochondral graft overgrowth in children can cause contralateral facial asymmetry and crossbite, necessitating careful growth monitoring. Alloplastic reconstruction should be considered in adults with recurrent ankylosis, as autogenous reconstructions have a higher re-ankylosis rate in multiply operated joints. Airway management for induction is a major challenge, and awake fiberoptic intubation or awake tracheostomy may be required for severe trismus. Fat grafting around the reconstructed joint has become a key adjunct in preventing heterotopic bone formation. Correction of associated deformities (micrognathia, asymmetry) should be planned, as staged orthognathic surgery or distraction after ankylosis release may be required.

<image>Postoperative CT 3D reconstruction showing bilateral TMJ ankylosis release with costochondral graft reconstruction, demonstrating the position of the grafts in the glenoid fossae and the improved ramus height and mandibular form compared with the preoperative images</image>

References

• Kaban LB, Perrott DH, Fisher K. A protocol for management of temporomandibular joint ankylosis. J Oral Maxillofac Surg. 1990.
• Sawhney CP. Bony ankylosis of the temporomandibular joint: follow-up of 70 patients treated with arthroplasty and acrylic spacer interposition. Plast Reconstr Surg. 1986.
• Loveless TP, et al. Efficacy of temporomandibular joint ankylosis surgical treatment. J Oral Maxillofac Surg. 2010.
• Elgazzar RF, et al. Treatment of TMJ ankylosis: a review of 14 cases. Int J Oral Maxillofac Surg. 2010.
• Ma J, et al. New evidence of the mechanism of TMJ ankylosis. J Dent Res. 2014.
• Wolford LM, et al. Outcomes of treatment for TMJ ankylosis with alloplastic total joint replacement. Proc Bayl Univ Med Cent. 2016.

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