Study of Regeneration of Experimentally Induced Perforation of Monkey Temporomandibular Joint

Abstract

The regenerative response of the va~ious components of the TMJ to injury have not been fully elucidated. The main purpose of the present study was to develop a non-human primate model system for the study of the regenerative response of TMJ to injury such as discal perforation. Eight adult Macaca fascicularis monkeys were used in this study. Four monkeys were use.d as a control group. Each TMJ of the four experimental monkeys was .surgically exposed and 4-6mm perforation in the posterolateral part of the disc was produced by electrosurgery. Control and experimental monkeys were fed their routine diets. All the monkeys were anesthetized and then perfused with Karnovsky's fixative. The Jour control monkeys were sacrificed prior to the experimental animals. The latter were sacrificed 11 weeks (two monkeys)and 12.weeks (two monkeys) following disc perforation. The TMJ' s were excised, decalcified and then saggital sections were studied under a stereomicroscope. They were then photographed before they were processed for light microscopic studies using H & E, resorcin-fuchsin and Alcian blue stains. The stereoscopic and microscopic observations· of the control joints revealed a marked similarity to human TMJ' s. The stereoscopic study of the experimental joints revealed that the perforations had increased markedly in size in five joints, complete loss of the disc in two jqints, and healing of the perforation in one joint. Thickening of the synovial membrane and uneven roughened thickening of the fibrous covering of the articular surfaces were seen in five joints. Denudation of articular surfaces and bone to bone contact was seen in two joints. Histologically the following changes were observed: fibrillation of the articular surf aces with diminished proteoglycans; moderate to severe thickening of the synovial membrane; synovial cells migrating on the surface of the , disc; thi~kening of the fibroelastic coverings of the condyle and the temporal articular surfaces; marked cellularity and vascularization of the disc close to the perforation; and chondrocytic clustering in both the disc and the fibrous covering of the articular surfaces. Loose synovial enchondromatosis were also seen in four joints. The body of the disc degenerated completely in two joints. Most of these changes are consistent with the diagnosis of osteoarthrosis. In conclusion, (1) disc perforations can lead to osteoarthrosis of .the TMJ, (2) disc perforations can heal spontaneously, (3) synovial membrane has the greatest regeneration response in TMJ, (4) this model system for osteoarthrosis should be used in the future to study the mechanism of development and the reversibility of the pathological changes.