Reconsideration of the TMJ condylar position during internal derangement: Comparison between condylar position on tomogram and degree of disk displacement on MRI

The objective of this study was to investigate condylar position during dif ferent degrees of disk displacement. The degree of disk displacement was ev aluated on 1.5 Tesla high-field sagittal MR images of 76 joints (48 patient s; mean age 19.4 years) and was classified into three grades (1 to 3), To e stablish condylar position, the anterior, superior and posterior joint spac es were measured on corrected tomograms. The possible relationship between condylar position, indicated by the width of joint space and successive deg ree of disk displacement, was compared by a one-way factorial ANOVA (p < 0. 05). The anterior joint space was significantly larger in grades 1, 2, and 3 disk displacements than in grade 0 pointing to a dorsal condylar position , The posterior joint space was significantly smaller in grades 1 and 2 com pared with grade 0, When the degree of the disk displacement becomes severe (i.e., grade 3 disk displacement), the posterior joint space tends to incr ease to a similar distance as in a normal healthy joint pointing to a more normal condylar position.