生物力学因素诱导股骨颈骨折后股骨头坏死:单侧股骨颈骨折内固定犬模型验证

Osteonecrosis of the femoral head after femoral neck fractures induced by biomechanical factors: testified by dog models of internal fixation for unilateral femoral neck fracture

背景:生物力学因素在股骨颈骨折术后股骨头坏死的发生和病理演变过程中起着重要作用,但是目前尚缺乏与之相关的实验证据。目的:探讨生物力学因素在股骨颈骨折后股骨头坏死发生发展过程中的作用。方法:12只健康成年田园犬均行股骨颈中部垂直截骨和螺钉内固定,制作单侧股骨颈骨折内固定模型。造模后6周照射X射线片,确认所有动物模型骨折愈合,将其随机分为空白组、取钉联合植骨组和取钉组,每组4只。取钉联合植骨组取出螺钉联合植骨,取钉组进行取出螺钉处理,空白组不做处理。6周后一次性处死所有田园犬,对各组田园犬股骨颈Ward三角区骨组织进行组织学观察和骨组织形态计量学评估。结果与结论:(1)组织学观察示,空白组的骨小梁较为宽大,分布较为密集,结构连续;取钉联合植骨组的骨小梁宽大,呈板状,分布密集,结构连续;取钉组的骨小梁纤细,分布稀疏,结构紊乱,部分骨小梁断裂;(2)骨组织形态计量学参数示,取钉联合植骨组和空白组的骨小梁面积百分数、骨小梁厚度显著高于取钉组(P<0.05),而骨小梁分离度显著低于取钉组(P<0.05);取钉联合植骨组的骨小梁面积百分数、骨小梁厚度显著高于空白组(P<0.05);取钉联合植骨组的骨小梁分离度显著低于空白组(P<0.05);取钉联合植骨组的骨小梁数量显著高于取钉组(P<0.05);空白组的骨小梁数量与取钉组比较,差异无显著性意义(P>0.05);取钉联合植骨组的骨小梁数量与空白组比较,差异无显著性意义(P>0.05);(3)结果提示,股骨颈骨折愈合后股骨头生物力学性能的降低会造成骨小梁出现吸收、微骨折等骨微观结构变化,最终导致股骨头塌陷、坏死。

METHODS： Twelve healthy adult rural dogs received the vertical osteotomy at the middle femoral neck and screw fixation to establish the internal fixation model of unilateral femoral neck fracture. At 6 weeks after modeling, X-ray was performed to confirm the fracture healing of all animal models. The model dogs were randomized into blank control, combination （screw removal and bone grafting） and experimental （screw removal） groups （n=4 per group）. Six weeks later, all dogs were executed, and the histological observation and the evaluation of bone histomorphometry were performed on the osseous tissue of the femoral neck Ward triangle. RESULTE AND CONCLUSION： （1） Histological observation showed that the bone trabecula in the blank control group was large and dense with continuous structure. In the combination group, the trabeculae were tremendous and tabular with dense distribution and continuous structure. In the experimental group, the bone trabecula was thin, sparse, disorganized and partially fractured. （2） The percent trabecular area and trabecular thickness were highest in the combination group, followed by blank control group, and lowest in the experimental group （P 〈 0.05）. The order of trabecular separation was as follows： combination group 〈 blank control group 〈 experimental group （P 〈 0.05）. The trabecular number in the combination group was significantly more than that in the experimental group （P 〈 0.05）. Compared with the blank control group, the trabecular number in the combination and experimental groups showed no significant difference （both P 〉 0.05）. （3） These results indicate that the decrease in biomechanical properties of femoral head after the femoral neck fracture healing can result in the changes of absorption and microfracture of the bone trabeculae, further induces collapse and necrosis of the femoral head.