Bony ankylosis of the temporomandibular joint: a computed tomography study

Bony ankylosis of the temporomandibular joint is a disabling disease that almost invariably manifests itself in the first two decades of life. CT of the temporomandibular joints was performed in 50 patients--axial CT in 2 and coronal CT in 48--of whom 43 (86%) had received trauma to the joints. New bone of variable form and thickness was observed in 64 joints (the involvement was bilateral in 14 patients). These joints were classified into one of two categories: type I, medially angulated condyle with deformed articular fossa and a mild-to-moderate amount of new bone formation; and type II, no recognizable condyle or fossa but instead a large mass of new bone. Type I was etiology-specific and seen only when trauma was the antecedent, whereas type II was a sequelae of either insult. A pseudofracture in the new bone was seen in 49 (77%) joints. Six joints showed subtle deformities but no new bone. Since coronal CT fully characterizes the lesion at acceptable radiation exposure levels, it appears to be valuable in the preoperative workup of these patients.