决定胸腰椎骨折椎体内植骨组织爬行替代的因素

Factors critical for creeping substitution of intracorporeal grafting following thoracolumbar fractures

背景:胸腰椎骨折椎弓根螺钉固定复位后常常出现椎体内"蛋壳样"改变,内固定取出后出现矫正丢失甚至后凸畸形。椎体内植骨理论上可以有效恢复前柱支撑提高矫正效果,但临床报道效果差异很大,具体的原因尚不清楚。目的:了解不同椎体内空腔大小和植骨量对植骨疗效的影响,探讨胸腰椎骨折椎体内植骨疗效的组织学因素。方法:将12只绵羊制造骨折复位后两组不同大小的椎体内空腔:1 cm3空腔组和2 cm3空腔组的骨缺损模型,每组6只。每只绵羊L1,3,5椎体制造模型,并随机植入植骨/空腔体积比为0.5,0.75,1.0的自体髂骨,植骨后4个月处死动物并取出植骨区域,行影像学和组织学分析,了解植骨的演变过程。结果与结论:植骨/缺损体积比大于0.75的两组椎体均显示良好的小梁骨爬行替代,低于该比例的植骨为纤维组织所替代;两组骨小梁数目,骨小梁面积百分数和平均骨小梁板厚度均显示随着植骨/空腔比例的增加而增加,而骨小梁分离度则减少,植骨/空腔体积比0.75,1.0与植骨比例0.5相比差异有显著性意义(P<0.01)。结果说明,胸腰椎骨折椎体内植骨的骨量需丰富,植骨/空腔体积比>0.75可达到满意的组织爬行替代效果,植骨疗效较好。

BACKGROUND： The occurrence of “eggshell” change after the pedicular screw reduction is the main cause of reduction lose and kyphosis. Theoretically intracorporeal grafting in the juried vertebra could enhance the anterior supporting, but the clinical effects vary obviously and the specific cause is unclear.OBJECTIVE： To understand the effect of defect size and the amount of bone grafting on the osteogenesis and to explore the histological factors concerning osteogenesis of intracorporeal grafting following thoracolumbar fractures.METHODS： The two-different sizes bone defect models （1 cm3 and 2 cm3 defect groups） in the lumbar vertebras of 12 sheep were made, and each group included six sheep. Different amount of autologous iliac bone was randomly grafted into the L1, 3, 5 vertebral segments according to grafting/bone defect ratios of 0.5, 0.75, 1.0, respectively. The grafting area of operated vertebra was separated for the imaging and histological analysis to understand the osteogenesis process.RESULTS AND CONCLUSION： The bone histomorphometry and histological results of different grafting ratio in different size defects demonstrated excellent creeping substitution and osteogenesis in the grafting/cavity ratio larger than 0.75, and the grafting bone was substituted by fibrous tissue if the ratio was less than 0.75. Trabecular number, percent of trabecular area and mean trabecular plate height increased and trabecular separation decreased with the increment of grafting/cavity ratio. There was no significant difference between the grafting ratio 0.75 and 1.0, but they had obvious difference from ratio 0.5 subgroup. The sufficient grafting amount is critical for intracorpereal grafting, and the ratio of grafting/bone defect larger than 0.75 could produce satisfactory osteogenesis.