Osteochondral dowel transplantation for repair of focal defects in the knee: an outcome study using an ovine model.

Abstract

A model system was developed to objectively assess the quality of articular cartilage after surgical reconstruction of focal defects in the median femoral condyle using osteochondral dowel grafts. The surgical technique was developed and customized to reproducibly minimize surgical trauma and graft instability in order to improve the survival of the transplanted cartilage and the long-term integrity of the joint surfaces. 24 adult female Suffolk-Romanoff crossbred sheep. Biomechanical creep testing, paravital staining for chondrocyte viability, histological analysis, and gross morphological analysis were performed at 3, 6, and 12 months 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 compared with normal unoperated control tissue. Biomechanical behavior, chondrocyte survival, and cartilage histology differed significantly between fresh grafts and those that had been frozen. Indentation testing and paravital staining were able to identify degenerative changes earlier than other methods of assessment. The technique developed here reproducibly and reliably transplanted osteochondral dowel grafts while minimizing the confounding effects of surgical trauma and graft instability. The technique provides both 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.