Histopathological changes in rabbit craniomandibular joint associated with experimentally induced anterior disk displacement (ADD)

Several studies have shown that anterior disk displacement (ADD) of human temporomandibular joint (TMJ) can lead to cellular and extracellular alterations in the disk proper, bilaminar zone (BZ), condyle, articular eminence and synovial membrane. Due to lack of an animal model for this disease, it is not known whether the mechanical displacement of the disk could lead to the observed histopathological changes. The purpose of this experiment was to investigate the histopathological changes that occur in the rabbit craniomandibular joint (CMJ) following surgical induction of ADD. The right CMJ was exposed surgically and the discal attachments were severed except for the BZ attachments. Then the 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 fibrillation of the displaced disk. The BZ showed marked fibrosis. The condyle showed subchondral hemorrhage and fibrosis followed by osteoarthritic changes in the articular cartilage. The articular eminence showed chondrocytic clustering and an increase in the amount of chon‐droid bone. Synovial membrane exhibited marked hyperplasia. We concluded that surgical induction of ADD in the rabbit CMJ leads to cellular and extracellular alterations in the disk proper, BZ, condyle, articular eminence and synovial membrane similar to those described previously in human ADD. It appears that the mechanical trauma resulting from ADD could lead to a cascade of reparative and degenerative changes of the affected joints similar to those described for osteoarthritis.