Disc position and morphology in patients with nonreducing disc displacement treated by injection of sodium hyaluronate.

Disc position and morphology were examined in 21 patients (22 joints) with nonreducing disc displacement of the temporomandibular joint (TMJ) at more than 12 months after undergoing injection of sodium hyaluronate into the superior joint space. The patients' clinical signs and symptoms improved during the follow-up period. In all patients, the disc was displaced anteriorly on mouth closure and did not reduce into the normal position during mouth opening at follow-up, whereas a normal disc position was found in all the controls. In the patients, the disc deviated from the normal biconcave configuration found in all of the controls on the follow-up magnetic resonance imaging (MRI). Disc displacement apparently is persistent and continued disc deformity common in patients, although the clinical signs and symptoms improved.