Anterior displacement of temporomandibular joint disk evaluated by MRI

Anterior displacement of the temporomandibular joint disk was evaluated in relation to the disk morphology and the osseous change using the magnetic resonance imaging (MRI). Twenty-six joints of 16 volunteers without symptoms and 123 joints of 63 patients with symptoms were examined. The joint was divided into three parts; a lateral, a central, and a medial part. In each part, the disk displacement and its degree, disk morphology, reduction of the disk, and osseous change were determined. The results showed that 12-15% of anterior displacement and 4-15% of 'even thickness' shape of the disks were present in the asymptomatic group. Meanwhile, 90% of disk displacement was present in the symptomatic group. Furthermore, the lateral part of the joint had a more significant tendency to displace anteriorly than the central or medial part. The disk was biconcave in the normal case. With advancement of displacement, however, it became even-thick, and eventually convex. As displacement was advanced, the disk was irreducible and its osseous change was increased. The results indicate that the disk displacement could be related to disk deformity and osseous change. (author) 54 refs