Is the morphology of the articular eminence of the temporomandibular joint a predisposing factor for disc displacement?

Objectives: To test the hypothesis that the morphology of the articular eminence of the TMJ is a predisposing factor for disc displacement. Methods: MR images of 220 TM joints in 151 patients were studied: 47 joints had no disk displacement (NDD), 81 joints disc displacement with reduction (DDWR) and 92 joints disc displacement without reduction (DDWOR). The shape of the articular eminence of the TMJ was classified into four types, box, sigmoid, flattened and deformed. The prevalence of the box and flattened forms in the three groups of joints was compared. Results: There was no statistically significant difference in the prevalence of the box form between the joints with NDD, DDWR, and DDWOR. On the other hand, the prevalence of the flattened-type was statistically lower in the joints with DDWR (goodness test of fit for chi(2), P<0.05). Conclusions: It appears that disc displacement is less likely to be found in joints with a shallow articular eminence.