Temporal and spatial expression of BMP-2 in sub-chondral bone of necrotic femoral heads in rabbits by use of extracorporeal shock waves

Background and purpose Extracorporeal shock wave treatment has been used successfully for the treatment of avascular necrosis of the femoral head. The pathway of biological events by which this is accomplished has not been fully elucidated. BMP-2 is a key mediator of bone development and repair, and is uniquely required for bone formation. We therefore examined the effect of extracorporeal shock waves on induction of BMP-2 in necrotic femoral heads. Methods Femoral head necrosis was induced in rabbits by treatment with methylprednisolone and lipopolysaccharide. BMP-2 expression was assessed by immunohistochemistry, quantitative real-time PCR, and western blot analysis. Histomorphometric analysis was performed to evaluate the rate of bone formation in femoral heads treated with extracorporeal shock waves. Results Extracorporeal shock wave treatment was associated with a significant increase in expression of BMP-2 protein and mRNA in the subchondral bone of the necrotic femoral heads. Moreover, the most intensive immunostaining of BMP-2 was observed in the prolifer-ative zone above the necrotic zone. Histomorphometric analysis showed that extracorporeal shock wave treatment significantly increased the rate of bone formation in the subchondral bone. Interpretation We conclude that extracorporeal shock wave treatment significantly upregulates the expression of BMP-2 in necrotic femoral heads. The process of repair of femoral head necrosis is accelerated by the use of extracorporeal shock waves.