HISTOPATHOLOGICAL CHANGES IN RABBIT CRANIOMANDIBULAR JOINT ASSOCIATEDWITH EXPERIMENTALLY-INDUCED ANTERIOR DISK DISPLACEMENT (ADD)

Several studies have shown that anterior disk displacement (ADD) of hu man temporomandibular joint (TMJ) can lead to cellular and extracellul ar alterations in the disk proper, bilaminar zone (BZ), condyle, artic ular eminence and synovial membrane. Due to lack of an animal model fo r this disease, it is not known whether the mechanical displacement of the disk could lead to the observed histopathological changes. The pu rpose of this experiment was to investigate the histopathological chan ges that occur in the rabbit craniomandibular joint (CMJ) following su rgical induction of ADD. The right CMJ was exposed surgically and the discal attachments were severed except for the BZ attachments. Then th e disk was displaced anteriorly and sutured to the zygomatic arch. The left joint served as surgical control. The CMJs were removed after 24 h, 1 week, 2 weeks or 6 weeks and stained with H&E or modified Masson stain. The results showed neovascularization, cell clustering and fib rillation of the displaced disk. The BZ showed marked fibrosis. The co ndyle showed subchondral hemorrhage and fibrosis followed by osteoarth ritic changes in the articular cartilage. The articular eminence showe d chondrocytic clustering and an increase in the amount of chondroid b one. Synovial membrane exhibited marked hyperplasia. We concluded that surgical induction of ADD in the rabbit CMJ leads to cellular and ext racellular alterations in the disk proper, BZ, condyle, articular emin ence and synovial membrane similar to those described previously in hu man ADD. It appears that the mechanical trauma resulting from ADD coul d lead to a cascade of reparative and degenerative changes of the affe cted joints similar to those described for osteoarthritis.