No effect of platelet-rich plasma as adjuvant to bone marrow stimulation for the treatment of chondral defects in a large animal model

Background Bone marrow stimulation (BMS) remains a dominant treatment strategy for symptomatic full thickness articular cartilage defects. Autologous platelet-rich plasma (PRP), may improve biological cartilage repair as an adjunct to BMS. Objectives To assess the histological quality of cartilage repair after BMS with and without repeated local injections of PRP for the treatment of full-thickness focal chondral defects of the knee. Methods Two full-thickness chondral defects (Ø = 6 mm) were surgically performed in the medial and lateral trochlea of each knee in skeletally mature Göttingen minipigs. The two treatment groups with 12 defect for each groups were (1) BMS with one weekly PRP injection for 4 weeks, and (2) BMS alone. The animals were euthanized after 6 months. Samples of both whole blood and PRP were analysed with an automated hematology analyzer to determine the concentrations of platelets and nucleated cells. The composition of cartilage repair tissue was assessed using gross appearance assessment, histomorphometry and semi-quantitative scoring (ICRS II). Results The average fold increase in platelets was 10.2 ± 2.2. Leukocyte concentration increased in PRP samples by an average fold change of 7.2 ± 1.3. Our macroscopic findings showed that the defects in the BMS + PRP-treated group, were filled with an irregular, partially rough tissue similar to the BMS-treated group. No significant difference in amount of hyalin cartilage, fibrocartilage or fibrous tissue content and ICRS II scores was found between the groups. Conclusions Four repeated local injections of leukocyte-rich PRP after BMS in the treatment of full-thickness cartilage injuries demonstrated no beneficial effects in terms of macroscopic and histological cartilage repair tissue quality.