Dynamic intra-articular space variation in clicking TMJs

During mandibular movement, the geometric relationships of the articular surfaces in the temporomandibular joint (TMJ) change, so that the disc undergoes different stress concentrations with respect to time and position. In this study, we compared the intra-articular space variations of 13 clicking and 15 asymptomatic TMJs for jaw opening/closing. Magnetic resonance imaging and jaw tracking were combined to display the motion of the whole condyle within the fossa. In clicking TMJs, the mediolateral spread s of the stress-field trajectories was 2.4 +/- 1.0 mm (s(max) = 4.9 +/- 2.1 mm) with an aspect ratio a/h of 2.5 +/- 1.6, both significantly greater than in controls (p < 0.05). The stress-field trajectories of the controls coincided during opening/closing (s = 0.9 +/- 0.2 mm, s(max) = 1.8 +/- 0.8 mm, a/h = 1.6 +/- 0.3). Clicking TMJs showed much less coincident stress-field paths and much "flatter" stress-fields than controls during jaw opening/closing.