Masayoshi Narinobou

Histologic evaluation of auricular cartilage grafts after discectomy in the rabbit craniomandibular joint

PURPOSE The clinical use of auricular cartilage grafting after discectomy has been reported as a treatment in the terminal stage of internal derangement of the temporomandibular joint (TMJ). Although the occurrence of fibrous adhesions has been observed in such grafted joints, the exact tissue reaction to the graft is still not understood. The purpose of this study was to evaluate the histologic changes after discectomy and auricular cartilage grafting in the rabbit craniomandibular joint (CMJ). MATERIALS AND METHODS Unilateral discectomy of the left CMJ was performed in 28 Japanese white rabbits. Auricular cartilage harvested from the ipsilateral ear was grafted as a disc replacement in 14 animals (Group C), and the other 14 underwent wound closure immediately after discectomy (Group B). Two other rabbits (Group A) served as nonsurgically treated controls. Two rabbits from each experimental group were killed at 2, 4, 6, 8, 10, 12, and 24 weeks postoperatively. Microscopic observation of the specimens was performed in the parasaggital plane. RESULTS Complete resorption of the cartilage layer on the articular surface was observed within 4 weeks postoperatively in group B. Regeneration of a fibrous cartilage layer was observed in this group after 6 weeks, but the postoperative degenerative changes were so severe that the surface of the condyle and eminence was flattened. In contrast, the degenerative changes were milder in group C, although the grafted cartilage showed perforation and fragmentation from the sixth postoperative week onward. The condylar shape and cartilage layer were well preserved at all times. CONCLUSIONS These results suggest that the structure and function of the condyle may be preserved by auricular cartilage grafting after discectomy. However, the problems of adhesion and fragmentation need to be addressed.