A morphologic, biochemical, and biomechanical assessment of short-term effects of osteochondral autograft plug transfer in an animal model

Purpose: The objective of this study was to assess the short-term. changes that occur after an osteochondral autograft plug transfer from the femoral trochlea to the media femoral condyle in a goat model. Type of Study: Artic ular cartilage repair animal study. Methods: Six adult male goats were used in this study. Two 4.5-mm osteochondral plugs were transferred from the su perolateral femoral trochlea to 2 recipient sites in the central portion of the medial femoral condyle for a survival period of 12 weeks. Postmortem, the global effects of the procedure were assessed by gross morphologic insp ection and by analyzing the synovial DNA for inflammatory response. The rec ipient sites were also evaluated histologically and biomechanically. Metabo lic activity was determined by (SO4)-S-35 uptake, and viability assessed us ing a live/dead stain and by confocal laser microscopy. Results: There was no evidence of significant gross morphologic or histologic changes in the o perative knee as a result of the osteochondral donor or recipient sites. Th e patella, tibial plateau, and medial meniscus did not show any increased d egenerative changes as a result of articulating against the donor or recipi ent sites of the osteochondral autografts. Analysis of synovial DNA reveale d no inflammatory response, Biomechanically, 6- to 7-fold greater stiffness was noted in the cartilage of the transferred plugs compared with the cont rol medial femoral condyle. Furthermore, on histologic examination, the hea ling subchondral bone interface at the recipient site had increased density . Glycosaminoglycan synthesis as determined by (SO4)-S-35 uptake was upregu lated in the transplanted cartilage plug relative to the contralateral cont rol, showing a repair response at the site of implantation. And finally, co nfocal microscopy showed 95% viability of the transferred plugs in the medi al femoral condyle region. Conclusions: Our findings demonstrate the abilit y to successfully transfer an osteochondral autograft plug with maintenance of chondrocyte cellular viability. The transferred cartilage is stiffer th an the control media] femoral condyle cartilage, and there is concern regar ding the increased trabecular mass in the healing subchondral plate, but th ese do not result in increased degenerative chancres of the opposing articu lar surfaces in the short term.