Experimental study on repair of large segmental bone defects of goat femur by nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer membrane tubes

Abstract

Objective The purpose of this study was to observe feasibility of nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer (n-CDHA-MAC) membrane tubes in repairing goat femurs’ large defects. Methods Twelve goats were divided into two groups, whose femurs were created 30 mm segmental bone defects and then implants were performed. In experimental group, the bone defect of right femur was reconstructed by n-CDHA-MAC membrane tube, while left side was reconstructed by allogenic bone tube in control group. Every three goats were sacrificed at 4, 8, 16, 24 weeks after operation respectively. General observation, X-ray analysis, histology, Scanning electron microscope (SEM) examination and protein level comparison of BMP-2 were conducted to evaluate the effects of repairing segmental bone defects. Results All goats recovered well from anesthesia and surgical interventions. The radiographic evaluations showed that periosteal reaction outside of the membrane tubes and allogenic bone tubes were observed 4 weeks after surgery. At 16 weeks, callus was continuously increased in experimental group, which was more obvious than control group. At 24 weeks, callus outside of the membrane tubes connected together. Histologic evaluation showed fibro-cartilage callus was evolved into bony callus in experimental group, which was more obvious than control group at 8 and 16 weeks. The protein expression level of BMP-2 increased at 4, 8 weeks and peaked at 16 weeks in experimental groups. There were statistical differences at 8 and 16 weeks ( P < 0.05). At each time point in 8, 16, 24 weeks after surgery, the bending stiffness, torsional stiffness and compressive strength of the two groups were similar, and there was no significant difference ( P > 0.05). Conclusions This novel surface degradation n-CDHA-MAC membrane tube has good ability to maintain enough membrane space, which can provide long-term and stable biomechanical support for large bone defects and integrate well with the surrounding bone.