Analysis of the Correlation between Morphology and Kinematics of Anteriorly Displaced TMJ Discs Using Cine-MRI and ARCUSdigma Systems

Studies of mandibular movement trajectories have provided a good understanding of the motion of the condyle but little information on the geometric relationships of the disc because they have not related the movements to anatomic structures.

This study investigated the morphology and kinematic characteristics of the Temporomandibular Joint (TMJ) using Cine-MRI and ARCUSdigma systems.

For this study population, preliminary clinical diagnoses were asymptomatic in 15 cases, unilateral anterior disc displacement with reduction (ADDWR) in 17 cases, and unilateral Anterior Disc Displacement Without Reduction (ADDWoR) in 14 cases. Patients were investigated with Cine-MRI and ARCUSdigma systems during physiological opening and closing of the mouth.

In these groups, there were 13 healthy subjects, 19 patients with unilateral ADDWR and 14 patients with unilateral ADDWoR classified by Cine-MRI. (1) To assess morphology by MRI, disc deformities were evaluated as follows: biplanar, rounded, thickening in the posterior band, lengthened and folded. (2) The opening trajectory for healthy subjects was close to the closing trajectory. Conversely, the incisal and condylar trajectories during opening and closing were obviously bounced, deviated or shortened in the ADDWR and ADDWoR groups. The pathway of the kinematic axis was not parallel, and the condylar trajectory had an inflexion. (3) The mean values of the incisal and condylar paths of the ADDWoR group were significantly different from those in the healthy group (P<0.05), whereas there were no significant differences between the ADDWR and the healthy group (P>0.05).

This study combined analysis of the condylar pathways and disc-condylar relationship to provide good visualization of morphology and kinematics during jaw movement. This process helps improve our understanding of the complexity of disk-condylar movements in subjects with TMJ internal derangement and may also contribute to our knowledge of the etiology of TMJ internal derangement.