Ultrastructural characterization of the rabbit mandibular condyle following experimental induction of anterior disk displacement

Previous studies in our laboratory have shown that surgical induction of an terior disk displacement (ADD) in the rabbit craniomandibular joint (CMJ) l eads to cellular and extracellular alterations consistent with osteoarthrit is. Similar findings were also reported in human ADD as well as osteoarthri tis of other joints. The purpose of this study was to further characterize these histopathological findings at the ultrastructural level. The right jo int of 15 rabbits was exposed surgically and ail discal attachments were se vered except for the posterior attachment. The disk was then repositioned a nteriorly and sutured to the zygomatic arch. The left joint served as a sha m-operated control. Ten additional joints were used as nonoperated controls . Mandibular condyles were excised 2 weeks following surgery and processed for transmission electron microscopy. Experimental condyles showed neovascu larization, fibrillation and vacuolation of the extracellular matrix and an increase in the number of apoptotic cells compared to controls. in additio n, chondrocytes in osteoarthritic cartilage showed an increase in the amoun ts of rough endoplasmic reticulum and Golgi complex suggesting an increase in protein synthesis. The presence of thick collagen fibers in osteoarthrit ic cartilage supports our previous immunohistochemical results of the prese nce of type I collagen instead of normally existing type II collagen. It wa s concluded that surgical induction of ADD in the rabbit CMJ leads to ultra structural changes in the mandibular condylar cartilage consistent with deg enerative alterations known to occur in osteoarthritis. Copyright(C)2000S.K argerAG,Basel.