A steep articular eminence has been proposed as one etiologic factor for the development of TMJ disk displacement. The purpose of this study was to determine the steepness of the articular eminence in asymptomatic volunteers with superior disk position and to compare it with the articular eminence in patients with internal derangement.
We investigated 34 asymptomatic volunteers and 71 patients. The steepness of the articular eminence was determined on sagittally corrected tomograms, and disk position was diagnosed by dual space arthrotomography.
The results showed that the articular eminence was on the average steeper in the asymptomatic volunteers in the lateral (64.9 degrees), central (64.4 degrees), and medial (65.4 degrees) sections of the joint than in the patients (56.1 degrees, 60.2 degrees, 58.9 degrees, respectively). When the comparison of the steepness of the eminence was based on the presence or absence of osseous changes in the form of remodeling or osteoarthrosis, no difference was found between the asymptomatic volunteers and the patients with disk displacement but without such changes. The largest difference in the steepness of the eminence was found between the persons with osseous changes and those without.
These findings contradict earlier studies that have indicated a steep articular eminence to be one etiologic factor for the development of disk displacement. The results of this study showed that the steepness of the articular eminence is decreased in the patients as a result of remodeling or degenerative changes of the bone that are a result of the internal derangement.