The effect of platelet rich plasma on bone healing after opening-wedge high tibial osteotomy. An animal study.

Purpose: To evaluate the effect of Platelet Rich Plasma (PRP) in increasing and accelerating bone healing and integration of bone graft after high tibial osteotomy. Methods: Twenty adult sheep underwent a medial opening-wedge high tibial osteotomy. Fixation was achieved using a purposely modified Puddu’s plate. Animals were divided into 2 groups. In group 1 the bone defect at the site of osteotomy was filled with cancellous bone harvested from iliac crest; in group 2 the defect was filled with autogenous bone graft and PRP derived from autologous blood. No immobilization was used after surgery. Animals were sacrificed at 4 and 8 weeks. Contralateral knees were used as controls. Biomechanical and radiographic evaluation were performed on each sample. On biomechanical compression test, we recorded ultimate load, yield load, axial stiffness in the elastic region, displacement at 250, 500, 750, 1000 N, and mode of failure. Radiographic appearance was scored according to An’s classification. Comparisons between different time intervals within each group were carried out with Wilocoxon rank sum test; comparisons between groups at each time interval were carried out with Mann-Whitney U-test; analysis of variance between groups at each time interval was carried out with Kruskal-Wallis test; post-hoc analysis for multiple paired comparisons was carried out with Tukey’s test. Significance was set at p<0.05. Results: Radiographic score at 8 weeks was significantly greater than that at 4 weeks in both groups. Group 2 showed mean score significantly greater than group 1 at each time interval. At mechanical testing, mean ultimate load and yield load of group 1 were significantly lower than those of group 2 and control group at each time interval. At 8 weeks, group 2 showed mean ultimate load and yield load significantly greater than control group. Mean axial stiffness of group 2 was significantly greater than group 1 and control group at each time interval. Mean displacement of group 2 was significantly lower than group 1, but significantly greater than control group at each time interval. At 4 weeks, failure always occurred mainly in the area surrounding osteotomy in both groups. At8 weeks, failure mostly occurred in the diaphysis in both groups. Conclusions: PRP had a significant accelerating effect on early healing of autogenous bone graft used for filling the defect in opening-wedge HTO. Autogenous bone graft was significantly stronger and stiffer when used in combination with PRP.