Anterior disc displacement of the temporomandibular joint suggested by CT imaging

Computed tomography (CT) has been increasingly used to examine the temporomandibular joint (TMJ). Some of the literature has dealt with internal derangement of the TMJ, including "arthrosis". Internal derangement is considered to be, in principle, anterior disc displacement. In our patient, anterior disc displacement was strongly suggested, by the CT images. A 66-year-old woman was admitted to Kyushu University Dental Hospital, the First Department of Prosthodontics complaining of pain of the TMJ and difficulty in opening her mouth, the maximum was 15mm. There was little condylar movement, laterally or anteriorly, without clicking. Radiographic findings of the lateral oblique transcranial projection (Fig. 1) revealed little movement of the bilateral condylar heads, with mouth opening. Although the anterior surface of the right condylar head showed a slight erosion, there were no bone changes of the left condylar head, bilateral articular tubercles and bilateral articular surfaces of the glenoid fossa. CT examination was performed using a Siemens SOMATOM DR scanner. Both temporomandibular joints were scanned in parallel to the Reid's line (Frankfurt plane). Each lmm section through the whole joints was obtained. Transverse images reviewed an irregular outline at the medial pole of the left condylar head (Fig. 2). Eburnation or sclerosis were not evident. Bone imaging of the right condylar head revealed no abnormality. Soft tissues, including muscles were normal and symmetric. The sagittal image, reformed at the center of the condyler head from the transverse images, revealed a partial loss of cortical bone and deformity of the right condylar head (Fig. 3). The left side (Fig. 4) showed no remarkable change, except for narrowing of the joint space. The "highlighting images" with a particular density in white, the densities being between 60 and 100 HI U. was present anterior to the right condylar head (Fig. 5). Not only the disc itself, but also the soft tissues in the TMJ