Thirty one patients with internal derangement of the TMJ and 12 subjects with normal TMJ were selected and their MR imaging and border movements of the mandible were recorded. Inaddition, the relationship between them was examined.
In this study, the disk position and configuration in MR findings were classified as follows. Diskposition: superior, anterior and anterolateral (medial and lateral were omitted), grade of anteriordisk displacement (with and without reduction): slight, moderate and severe, disk configuration: biconcave, enlargement of posterior band, even thickness and biconvex.
The results were as follows:
1. Border movements of the mandible were influenced not only by unilateral or bilateralinternal derangement but also by with or without reduction of the disk.
2. Border movements in patients with anterolateral disk displacement were more severelyrestricted than those with anterior disk displacement.
3. Border movements were remarkably limited in patients with slight disk displacement, especially in unilateral cases with reduction of the disk.
4. Border movements in patients with even thickness and biconvex types of disk configurationwere a little restricted and rather similar to those of normal subjects.
5. There was significant correlation between border movements and disk position and configu-ration. It means that measurement of the mandibular movements is very significant to diagnose thecondition of internal derangements of the TMJ.