ARTICULAR DISC AND EMINENCE MODELING AFTER EXPERIMENTAL RELOCATION OFTHE GLENOID FOSSA IN GROWING RABBITS

The articular surface of the glenoid fossa shows some analogy to the m andibular condyle, since the surface is covered by secondary cartilage , which makes the process more elastic than purely bony structures. Th e condylar cartilage has been shown to be responsive to alterations in load pressures, and this secondary type of cartilage is also able to increase its proliferative activity to a limited extent when the load pressure is altered. The aim here was to measure changes in proliferat ive activity and type II collagen secretion in the articular surface o f the glenoid fossa after steady experimental posterior relocation of the fossa in the rabbit without actively interfering with normal masti catory action. The shape of the articular disc and interrelations of t he joint components were measured macroscopically. Twenty-four five-da y-old rabbits underwent gluing of the interparietal, temporoparietal, and lambdoidal sutures. Three experimental and 3 control rabbits were injected with tritiated thymidine at 10, 15, 20, and 30 days and were killed after 2 h for histological, autoradiographic, and immunohistoch emical examination. The total number of labeled cells in the prolifera tive layer near the articular eminence was higher in the experimental group, the difference being greatest in the 15- and 20-day-old rabbits . Immunohistochemical examination revealed less staining for type II c ollagen on the postero-inferior side of the eminence in the experiment al group. The articular disc was flattened in the experimental group, and the elastic tissue bundle connecting the articular eminence and th e anterior border of the disc was significantly narrower and longer.