BONE REMODELING IN THE CALLUS FORMED DURING -DISTRACTION OSTEOGENESIS

本研究旨在探讨牵张成骨过程中骨痂的骨重建机制。实验研究在30只体重约2.0 kg的日本白色家兔上进行。将单侧外固定器应用于右侧胫骨，并在骨干中段进行截骨。等待7天后，以0.7 mm/天的速度进行缓慢牵张，持续3周。牵引间隙自发地填充有具有三个不同区域的愈伤组织。延伸发生在一个中央的放射性同位素带，这是由两个scrubbers带为界。新形成的骨痂被吸收并迅速重塑，留下新的皮质。为了研究双膦酸盐对骨愈合和骨痂重建的影响，以高剂量（0.4mg/Kg/周）或低剂量（0.004mg/Kg/周）静脉给予米诺膦酸盐。术后7周（完成牵张后3周）处死动物，通过软X线分析测量骨密度。实验结果表明，大剂量米诺膦酸盐能明显促进骨愈合。双膦酸盐给药动物的延长节段骨密度远高于对照动物。三点弯曲试验显示双磷酸盐给药组延长段的机械稳定性高于对照组。延长段的组织形态计量学研究表明，双膦酸盐不改变破骨细胞的数量，但干扰破骨细胞的功能，从而抑制骨吸收和骨痂的改建

The purpose of this study is to elucidate the mechanism of bone remodeling in the callus formed during distraction osteogenesis. The experimental study was carried out on 30 Japanese white rabbits weighing about 2.0 kg. A unilateral external fixator was applied to the right tibia and osteotomy was achieved in the mid-diaphysis. After 7 days of waiting period, slow distraction was carried out at a rate of 0.7 mm/day for three weeks. Distraction gap was spontaneously filled with the callus having three distinct zones. Elongation occurred in a central radiolucent zone, which was bounded by two sclerotic zones. Newly formed callus was resorbed and remodeled quickly, leaving a new cortex. In order to examine the effects of bisphosphonate on bone healing and remodeling of the callus, minodronate was administrated intravenously at high dose (0.4mg/Kg/week) or at low dose(0.004mg/Kg/week). The animal was killed 7 weeks after operation (3 weeks after completion of distraction), and bone mineral density was measured by soft X-ray analysis. Experimental results showed that bone healing was definitely accelerated by administration of high dose of minodronate. The bone mineral density of the lengthened segments was much higher in the bisphosphonate-administrated animals than in control animals. Three point bending test showed higher mechanical stability of the lengthened segment in bisphosphonate-administrated group than in control group. Histomorphometric study of the lengthened segments demonstrated that bisphosphonate did not change the number of osteoclasts but disturbe the function of osteoclasts and consequently suppressed bone resorption and remodeling of the callus during distraction osteogenesis