Effective repair of a fresh osteochondral defect in the rabbit knee joint by articulated joint distraction following subchondral drilling

Abstract

Purpose: Joint distraction has been used to treat osteoarthritis and was found to delay the need for arthrodesis or joint replacement. However, there has been little basic research on articulated joint distraction for the repair of osteochondral defects. We investigated the effects of joint distraction with motion after drilling on a fresh osteochondral defect in the weight bearing area of the rabbit knee joint. Methods: A full thickness osteochondral defect was created in the weight bearing area of both medial femoral condyles of an adult Japanese white rabbit. After drilling of the defect, the experimental knee joint was distracted for 1.5 mm using a pair of external fixators to decrease compression force. The contralateral knee joint was used as a control with no apparatus. Gross findings and histological evaluation were assessed to study morphology of the repaired cartilage. Results: A partial repair with cartilage-like tissue was observed in the joints of the experimental group at 4 weeks. While cartilage-like tissue stained with Safranin O was found in the experimental group at 8 and 12 weeks, destructive changes were observed in the control joints. Morphological changes were evaluated using the histological grading scale [Wakitani S, Goto T, Pineda SJ, et al. Mesenchymal cell-based repair of large, full-thickness defect of articular cartilage. J Bone Joint Surg Am 1994;76(4):579–92]. There was no significant difference between experimental and control groups at 4 weeks (mean 11.2 and 13.8 points, respectively). However, the mean scores of the experimental groups at 8 and 12 weeks (mean 6.8 and 7.5, respectively) were significantly better than those of the control groups at the same time points (mean 14 points each). Between the experimental groups, the scores at 8 and 12 weeks were both significantly better than those at 4 weeks. Conclusion: A combination of subchondral drilling, joint motion and distraction by an articulated external fixator promoted repair of a fresh osteochondral defect in the weight bearing area. Although distraction for 4 weeks was not a long enough period to repair the defect, distraction for 8 and 12 weeks resulted in a good outcome.