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

Objectives: To test the hypothesis that the morphology of the articular emi nence 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 shap e of the articular eminence of the TMJ was classified into four types, box, sigmoid, flattened and deformed. The prevalence of the box and flattened f orms in the three groups of joints was compared. Results: There was no statistically significant difference in the prevalenc e of the box form between the joints with NDD, DDWR, and DDWOR. On the othe r 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 i n joints with a shallow articular eminence.