脱脂对异体皮质骨生物力学的影响

Effect of defatting on the biomechanics of cortical bone

背景:脱脂的目的在于通过清除脂肪和脂蛋白,减少特殊细胞表面抗原,以降低免疫排斥反应,改善异体骨的生物相容性,提高异体骨移植的成骨能力,但目前有关脱脂对骨生物力学性能的影响尚无统一观点。目的:探讨脱脂对异体皮质骨生物力学性能的影响。设计、时间及地点:随机分组自身对照观察实验,于2006/2008在广东医学院附属福田人民医院完成。材料:新鲜宰杀的成年健康牛股骨8对。从每一对牛股骨相应位置中挑取约50mm长,10mm宽的骨块,将骨块打磨成7mm×7mm×40mm长方体牛皮质骨试件24对。方法:将24对试件随机抽签法分成2组(n=12),每对中随机抽取一个试件为实验组,另一个试件为对照组。实验组试件在1∶1的三氯甲烷:甲醇混合液500mL中脱脂24h;对照组标本按同样流程在去离子水中浸泡24h。两组分别选取6个试件进行抗压缩试验及三点弯试验。主要观察指标:力学试验中每一试件所能承受的载荷、挠度。结果:压缩试验显示,与对照组比较,实验组的试件所能承受的最大压力明显减小,且脱脂后每个试件间所受最大应力的差别明显缩小,试件的脆性增加,最大应变减小,弹性模量增大(P均<0.05);三点弯试验显示,与对照组比较,实验组的试件所能承受的最大载荷明显减小,所受最大应力的差别明显缩小,最大挠度减小,弹性模量增大(P均<0.05)。结论:脱脂后皮质骨的力学强度下降,脆性增加。

BACKGROUND： Defatting is to reduce the special cell surface antigens by clearing fat and Iipoprotein, so as to decrease immunological rejection, improve the biocompatibility of allograft bone, and increase osteogenic potential. However, the effect of defatting on biomechanical performance of bone remains controversial. OBJECTIVE： To explore the influence of defatting on the biomechanics of bovine cortical bone samples. DESIGN, TIME AND SETTING： Randomized, self-controlled observation was performed in Futian People＇s Hospital of Guangdong Medical College between 2006 and 2008. MATERIALS： Eight pairs of healthy adult bovine femora were used. Bone blocks, 50 mm long and 10 mm wide, were selected from each pair of femora, and burnished into 24 pairs of 7 mm×7 mm×40 mm rectangular bovine cortical bone samples. METHODS： The 24 pairs of cortical bone samples were randomly divided into two groups （n=12）. One of each pair was selected as test group sample, and the other as control group sample. The samples of test group were defatted in 500 mL chloroform and methanol mixture （1：1 ） for 24 hours, while control samples were immerged in deionized water for 24 hours. Six samples from each group were selected for axial compressive test and three-point bending test. MAIN OUTCOME MEASURES： Load and deflection of every sample. RESULTS： Axial compressive test showed that the maximum load and the maximum strain of defatted samples were significantly decreased compared with control group, but the fragility and elastic modulus were increased （P 〈 0.05）. In three-point bending test, the maximum load and the maximum stress of defatted sampled were significantly decreased, the maximum deflection was decreased, and the elastic modulus was increased （P 〈 0.05）. CONCLUSION： The mechanical strength of cortical bone decreased but the fragility increased after defatting.