Repeated platelet concentrate injections enhance reparative response of microfractures in the treatment of chondral defects of the knee: an experimental study in an animal model.

PURPOSE To assess the histology and biomechanics of repair cartilage after microfractures with and without repeated local injections of platelet concentrate for the treatment of full-thickness focal chondral defects of the knee. METHODS A full-thickness chondral lesion on the medial femoral condyle was created in 30 sheep and treated with microfractures. Animals were divided into 2 groups, according to postoperative treatment: in group 1 we performed 5 weekly injections of autologous conditioned plasma, whereas group 2 did not undergo further treatments. Animals were killed at 3, 6, and 12 months after treatment. Macroscopic, histologic, and biomechanical evaluations were performed. Differences between groups at each time interval and differences over time within groups were analyzed for each outcome. Significance was set at P < .05. RESULTS Group 1 showed significantly better macroscopic, histologic, and biomechanical results than group 2 at each time interval. Analysis of time effect within groups showed that in group 1, quality of repair tissue significantly improved from 3 to 6 months after treatment and remained stable over time for all the outcomes; in group 2 a significant histologic and mechanical deterioration was observed between 6 and 12 months' follow-up. CONCLUSIONS Five repeated local injections of autologous conditioned plasma after microfractures in the treatment of full-thickness cartilage injuries promoted a better and more durable reparative response than isolated microfractures, although they did not produce hyaline cartilage. CLINICAL RELEVANCE Periodical intra-articular injections of platelet concentrate after microfractures may improve cartilage repair and prevent further degenerative changes.