TMJ articular disc position and configuration 30 years after initial diagnosis of internal derangement

Purpose: This study evaluates disc position and configuration on magnetic resonance imaging (MRI) in temporomandibular joints (TMJs) with a long history of internal derangement. Patients and Methods: Sagittal T1-weighted MRIs of 55 TMJs that were diagnosed with internal derangement approximately 30 years ago were made with the mouth closed and open, and the position and configuration of the articular disc were determined. For comparison, a control group consisting of 15 asymptomatic TMJs without clinical signs of internal derangement or of other TMJ disorders were studied in the same way. Results: Anterior disc position was found in 90% of the TMJs with a history of internal derangement. Reducing disc displacement was found in one third of these TMJs, whereas permanent displacement was found in two thirds. In four joints, no disc was discernible. In one of the joints of the control group, a permanent disc displacement was found; normal disc position was found in all other joints of the control group. A biconcave disc configuration, which was considered normal, was found only in TMJs with normal disc position or with reducing discs. Conclusion: It was concluded that, after 30 years of displacement, the TMJ disc can be clearly identified on MRI in most cases. If the disc becomes permanently displaced, its configuration deviates from the normal biconcave configuration, and its anteroposterior length decreases. Convex and folded appearances of the disc are common in this situation. However, the disc usually maintains its biconcave configuration as long as it resumes its position on top of the condyle during mouth opening, even if this condition lasts for several decades.