Treatment Of Femoral Head Defects By BFGF/BMP/Antigen-extracted Bone: An Experimental Study

[Objective] To mimic the clinical situation with trapdoor bone-grafting in the treatment of avascular necrosis of the femoral head ,and to evaluate the effect of bFGF (basic fibroblast growth factor) BMP(Bone morphogenetic protein) composed of xenogeneic or allogeneic antigen-extracted bone on the repair of the femoral head defects in angiogenesis and osteogenesis.[Methods] The current study was conducted in two parts. In part one, we combined an effective angiogenic growth factor bFGF with natural derived scaffold material XPDPB(xenogeneic partially deproteinised bone) that possesses proper mechanical strength and biocompatibility. We developed a rabbit femoral head defect(5mm in diameter) model. Forty eight femoral head defects in twenty four rabbits were randomly divided into three groups, which implanted with bFGF/XPDPB(group A), XPDPB(group B) and without implantation of XPDPB(group C). The rabbits were killed after injection through blood vessels with prepared Chinese ink in the 2nd, 4th, 8th weeks after operation, and then the femoral heads of each rabbit were taken off at each interval. The specimens were investigated by histology and image analysis. In part two, using PVP(Polyvinylpyrrolidone) as a carrier of bFGF, and then mixed with BMP and allogeneic antigen-extracted cancellous bone (AACB), and the bFGF/BMP/AACB composite' s morphological features and constitute were examined. We developed a canine femoral head defect(1.2cm in diameter) using liquid nitrogen to establish the necrosis model of the femoral head. Sixty femoral head defects of thirty canines were randomly divided into five groups. Group A without implantation; Group B were implanted with AACB; Group c implanted with BMP/AACB; Group D were implanted with bFGF/BMP/AACB; Group E were implanted with bone autograft. The specimenswere harvested separately at the end of 3, 6ahd 12 weeks after operation. A series of examinations were carried out including of gross observation, X-ray, radiography, histology, immuhistochemical staining, image pattern analysis, scanning electron microscope(SEM) and energy dispersion analysis X-ray(EDAX), inorganic substance detection and the ratio of calcium and phosphorus, mechanical measurement.[ Results ] In part one, the experiments suggest that bFGF/XPDPB was much superior than XPDPB both in angiogenesis and Osteogenesis at all intervals, and only partly repair effect was observed in the untreated defects. In part two, the experiments suggest that we successfully reconstituted bFGF , PVP, BMP and AACB together. Liquid nitrogen freezing could lead to completely necrosis of the femoral head around the defect in the early stage, and spontaneous repair could not heal the defect. Liquid nitrogen freezing did not interfere the femoral head' s physics and chemistry environment and the implanted growth factors. All results show that bFGF/BMP/AACB (group D) was much superior than group A, GroupB, and Group C in angiogenesis and osteogenesis at all intervals, and even better than bone autograft(Group E) by the end of 3 weeks and 6 weeks. By the end of 12 weeks, bone repairing and remodeling in bFGF/BMP/AACB group was comparable with that in bone autograft group.[Conclusions] (1) bFGF has the effect of enhacing revascularization and osteogenesis for repairing femoral head defect; (2) We successfully reconstituted BMP, bFGF and PVP with AACB, and obtained an effective bone graft material bFGF/BMP/AACB; (3) bFGF accelerated the blood vessels'entering into implanting materials and enhanced strongly osteogenesis induced by BMP; (4)The bFGF/BMP/ AACB composite has satisfied effects of repairing femoral head defect and necrosis model and even much superior repair effect was seen than the bone autograft group by the end of 3 weeks and 6 weeks. By the end of 12 weeks, bone repairing and remodeling in bFGF/BMP/AACB group was comparable with that in bone autograft group; (5) Defect and necrosis of the femoral head produced by our experiment is a good animal model in the treatment study of avascular necrosis of the femoral head using growth factors.