OSTEOCHONDRAL DOWEL TRANSPLANTATION FOR REPAIR OF FOCAL DEFECTS IN THE KNEE - AN OUTCOME STUDY USING AN OVINE MODEL

Objective-A model system was developed to objectively assess the quali ty of articular cartilage after surgical reconstruction of focal defec ts in the medial femoral condyle using osteochondral dowel grafts. Stu dy Design-The surgical technique was developed and customized to repro ducibly minimize surgical trauma and graft instability in order to imp rove the survival of the transplanted cartilage and the long-term inte grity of the joint surfaces. Animals or Sample Population-24 adult fem ale Suffolk-Romanoff crossbred sheep.Methods-Biomechanical creep testi ng, paravital staining for chondrocyte viability, histological analysi s, and gross morphological analysis were performed at 3, 6, and 12 mon ths postoperatively to compare fresh autografted osteochondral dowels with allografts that had been subject to a freezing protocol known to kill chondrocytes. The latter was used to investigate the time course of cartilage degeneration after injury. These two groups were also com pared with normal unoperated control tissue. Results-Biomechanical beh avior, chondrocyte survival, and cartilage histology differed signific antly between fresh grafts and those that had been frozen. Conclusions -Indentation testing and paravital staining were able to identify dege nerative changes earlier than other methods of assessment. The techniq ue developed here reproducibly and reliably transplanted osteochondral dowel grafts while minimizing the confounding effects of surgical tra uma and graft instability. Clinical Relevance-The technique provides b oth a promising surgical technique for the repair of focal defects of the medial femoral condyle and a sensitive model for the future study of cryopreservation strategies for articular cartilage. (C) Copyright 1998 by The American College of Veterinary Surgeons.