Traumatic temporomandibular joint ankylosis: our classification and treatment experience

This article studies the classification of traumatic temporomandibular joint (TMJ) ankylosis based on coronal computed tomographic (CT) scan and presents our treatment experience in the TMJ division of Shanghai Ninth People's Hospital.

From 2001 to 2009, 130 patients diagnosed with TMJ ankylosis were treated in the TMJ division. Among them, 84 patients with 124 joint injuries caused by trauma were treated first by our group of surgeons and were included in this study. All of them had CT scans, especially coronal reconstruction through the TMJ area before and after surgery. A new classification based on the coronal CT scan was proposed: type A1 is fibrous ankylosis without bony fusion of the joint; type A2 is ankylosis with bony fusion on the lateral side of the joint, while the residual condyle fragment is bigger than 0.5 of the condylar head in the medial side; type A3 is similar to A2 but the residual condylar fragment is smaller than 0.5 of the condylar head; type A4 is ankylosis with complete bony fusion of the joint. Our treatment protocol for type A1 ankylosis is fibrous tissue release or condylar head resection with costochondral graft (CCG) and temporalis myofascial flap (TMF). For type A2 and A3 ankylosis, the lateral bony fusion is resected, while the intact residual condylar fragment, displaced medially, is retained. We call it "lateral arthroplasty" (LAP). TMF or masseter muscle flap (MMF) is used as a barrier in the lateral gap between the TMJ fossa and the stump of the mandibular ramus. If the medial condylar fragment in type A3 ankylosis is too small to bear the load, it is resected with the bony mass. The joint is then reconstructed with CCG and TMF or MMF. For type A4 ankylosis, the bony fusion is completely removed and the joint is reconstructed with CCG and TMF or MMF. The result of the treatment was evaluated by CT scan and clinical follow-up.

Among the 124 ankylotic joints, there were 14 type A1 ankylosis (11.3%); 43 type A2 ankylosis (34.7%); 46 type A3 ankylosis (37.1%); and 21 type A4 ankylosis (16.9%). Part of type A1, and all of type A2 and A3 ankylosis had the residual condylar head displaced medially, which accounted for 75% (93/124) of the TMJ ankylosis. Eighty-two joints (66.1%) had LAP treatment; 33 joints (26.6%) had CCG joint reconstruction; and 3 joints (2.4%) had TMJ fibrous tissue release. In our case, 1 joint (0.8%) had condylectomy and TMF; 3 joints (2.4%) with fibrous ankylosis had mouth opening treatment; and 2 joints had gap arthroplasty (1.6%). Forty-eight patients with 68 joints had long follow-ups from 10 months to 4 years. Among them, 4 of 17 joints reconstructed with CCG had reankylosis (23.5%), and 7 of 48 joints treated with LAP had reankylosis (14.6%).

The new classification of TMJ ankylosis based on coronal CT scan is valuable in guiding clinical treatment. LAP with TMF is a good way to treat traumatic TMJ ankylosis when the medially displaced condylar head and disc are intact. CCG with TMF has a good result for type A4 ankylosis.