CREATION OF DISK DISPLACEMENT IN HUMAN TEMPOROMANDIBULAR-JOINT AUTOPSY SPECIMENS

The purpose of this study was to investigate the possibility of iatrogenically creating disc displacement in the human temporomandibular joint (TMJ). Fourteen fresh TMJ autopsy specimens with superior disc position were selected for the study. The upper and lower joint spaces were exposed via a preauricular incision and two to three superficial mediolateral incisions were made in the inferior surface of the posterior disc attachment (ie, retrodiscal tissue). After these incisions were made it was possible to manually displace the disc anteriorly. To maintain the disc in the anterior position the condyle was positioned against the posterior disc attachment in a manner corresponding to the closed mouth position. The joints were then fixed in this relationship and magnetic resonance imaging (MRI) was repeated using the same scanning plane and scanning parameters as before intervention. After imaging, the joints were cryosectioned to show the degree of disc displacement. Histologic analysis was made of the posterior disc attachment. Postoperative MR images and cryosections showed the disc to be displaced anteriorly in 12 of the 14 joints. Displacement of the disc was complete in eight joints (the entire mediolateral dimension of the joint) and partial (only in the lateral part of the joint) in four joints. The disc remained in a superior position in two joints. Cryosections and histologic analysis showed the incisions in the inferior aspect of the posterior disc attachment to be superficial. The results of this study suggest that the integrity of the inferior aspect of the posterior attachment of the disc to the condyle is essential for keeping the disc in its position superior to the condyle. Minor damage to this tissue layer could be one event that leads to disc displacement and internal derangement. © 1992.