Experimental Study With Biodegradable Strontium-doped Calcium Polyphosphate To Repair The Defect Of Osteonecrosis Of The Femoral Head In Steroid-treated Rabbits

Objective To explore a new method and the expression of vascular endothelial growth factor using biodegradable strontium-doped calcium polyphosphate to repair the defect of osteonecrosis of the femoral head in steroid-treated rabbits. Methodes Twenty-one adult male Japanese white rabbits were given three the right gluteus medius muscle injections of 20 mg/kg methylprednisolone at intervals of 24 hours. Three rabbits were killed randomly at 2 weeks after the methylpednisolone injection, both the femora and humeri were histologically examined for the presence of osteonecrosis. The remaining 18 animals with a total of 36 cylindrical 2.5×5mm femoral head defects were created following the trapdoor procedure. Eighteen animals with femoral head bone defects were randomly divided into three groups. Group A: the defects were filled with strontium-doped calcium polyphosphate. Group B:the defects were filled with calcium polyphosphate. Group C:the defects were filled with autologous cancellous bone alone. Roentgenographic and histological examinations were performed postoperatively at various time. Finally, immunohistochemical analysis using monoclonal antibodies anti-VEGF and RT-PCR were carried out.Results No hip joint dislocation occurred. In the group A,most of the biodegradable strontium-doped calcium polyphosphate was resorbed and was largely replaced by newly formed trabecular bone at 12 weeks. While in the group B, a major part of defect were repaired. New formed trabecular bone in the defect were very thin. In the group C:morsellized cancellous bone were completely surrounded by fibrous and newly formed trabecular bone. In the group A the results of VEGF mRNA expression had a significantly difference from those in other groups 12 weeks after operation. Conlusion Biodegradable strontium-doped calcium polyphosphate noy only can enhance the repairing proceduce of femoral head defects but alse can deduce the angiogenesis during the bone repair. Therefore, SCPP may serve as a promising bone tissue engineering materials.