中文摘要：

目的研究股骨头坏死病程各阶段的生物力学改变,探讨其生物力学发生作用的机制。方法取杂种犬24只,固定一侧前肢建立三足负重犬模型。随机取三足负重犬一侧后肢为实验侧,在股骨头内注射无水酒精,致股骨头坏死;对侧为对照侧,在股骨头内注入等量生理盐水。造模后1、3、6及12周处死动物,每组6只,分别对两组股骨头行大体观察以及放射学、组织学、生物力学检测。结果术后3周股骨头坏死侧点压硬度及中部松质骨弹性模量相对对照侧分别下降29%和32.9%,此时仅MRI可见股骨头出现低密度坏死区,组织学主要表现为骨坏死。术后6、12周股骨头坏死侧点压硬度相对对照侧分别下降了45.5%和48.7%,中部松质骨弹性模量相对对照侧分别下降了34.1%和32.4%。6周时坏死侧X线可见股骨头内密度不均,组织学表现为坏死和修复反应并存,坏死区向软骨下骨区进展。12周时坏死侧X线可见股骨头负重区下出现局部骨密度减低区,组织学出现关节软骨面塌陷和关节间隙狭窄。结论生物力学是股骨头病程进展的重要影响因素;病程进展中,特别是修复期力学性能的显著下降可能是后期塌陷的最直接原因。治疗股骨头坏死不仅应促进骨修复,更应提供病变区一个有利、稳定的生物力学环境。

英文摘要：

Objective To study changes in biomechanical characteristics of the femoral head during the progression of avascular osteonecrosis and investigate the mechanism of these biomechanical changes.Methods Twenty-four three-foot weight bearing canine models with osteonecrosis of the femoral head（ONFH） were established by fixing one fore limb of the canine.Osteonecrosis was induced in all experimental animals by randomly injecting 5 mL pure ethanol into one side of the femoral head,and the contralateral femoral head was injected with an equal amount of normal saline as the control group.The canines were killed at 1st,3rd,6th,and 12th week after the injection of ethanol,with six canines in each group.The radiographic,histological changes and biomechanical characteristics of the femoral head were observed and analyzed.Results At 3rd week,29% reduction of indentation stiffness and 32.9% reduction of elastic modulus in the cancellous bone were found in the infected femoral heads compared to the control heads,and a low density area was detected only in MRI and osteonecrosis was the main histological characteristics.At 6th and 12th week,the indentation stiffness in the infected femoral heads was reduced by 45.5% and 48.7%,respectively,and the elastic modulus of the cancellous bone in the infected femoral heads was reduced by 34.1% and 32.4%,respectively,compared to the control heads.At 6th week,uneven bone density of the femoral head was detected in radiographs,and the progression of osteonecrosis and bone healing was found at the same time.At 12th week,areas of reduced bone mineral density beneath the load bearing position of the femoral head were observed on radiographs.Collapse of the articular cartilage surface and narrowing of the joint space were the main histological findings.Conclusions Biomechanics is an important factor in the progression of ONFH.The decreased mechanical properties may be a direct reason leading to the late collapse of the femoral head.The treatment of ONFH should focus not only on acceleration o