Follow-up of osteochondral plug transfers in a goat model - A 6-month study

Background: Osteochondral transfer procedures are increasingly used to resurface full-thickness articular cartilage defects. There has not been long-term assessment/description of autogenous donor and recipient sites. Hypothesis: The healing process occurs at the donor/host cartilage and bone interfaces. Study Design: Histologic, biochemical, and biomechanical changes were assessed 6 months after an osteochondral transfer in a goat model. Methods: Eight adult goats were studied. In the 6 osteochondral transfer goats, 2 autogenous plugs were transferred from the femoral trochlea to defects in the weightbearing portion of the medial femoral condyle. The goats were allowed free range for 6 months. Randomly assigned plugs were assessed. Results: Knees of the sacrificed animals had preservation of the joint space with mild chondromalacic changes in both transfer and contralateral control groups. Histologically, no evidence of cartilage (host/donor) healing was seen. Subchondral bone of the plug was contiguous with the surrounding recipient bone. Cellular viability in the autogenous osteochondral plug was seen, and (SO4)-S-35 uptake of the articular cartilage was not statistically different from the contralateral control condyle. The indentation stiffness of the transfer plug (mosaicplasty) and the contralateral donor site were similar- much stiffer than normal cartilage including surrounding condylar cartilage. Large structural stiffness of transferred cores and donor sites appeared to be related to their thinner cartilage layer. Conclusions: At 6-month follow-up, a cleft between host and transferred articular regions remained, with no integration between the two. Clinical Relevance: Autogenous transplantation of osteochondral plugs is possible with integration of subchondral bone and preservation of chondral viability.