站立负重位足跖骨的应变分析

Strain Analysis of Weight-bearing Metatarsal Bone

目的探讨完整状态下站立负重时足跖骨的应变。方法6具正常成人新鲜尸体足标本,解剖并有限显露5根跖骨的背侧骨表面,粘贴应变片。应用电子万能试验机以2mm/min的速度从胫骨远端施加轴向压载,从0N直至1200N(间隔为200N)。通过电阻应变片法检测跖骨表面的应变变化。结果各测点的应变均为压应变,随轴向载荷的增加,跖骨表面的应变逐步增大。同一载荷下跖骨表面各测点的应变有显著性差异(P<0.05),由大到小依次是:第二跖骨、第三跖骨、第四跖骨、第一跖骨、第五跖骨。第二跖骨的应变由大到小依次是:中部、颈部、基底部。结论站立负重时第二、三跖骨的应变较大,提示第二、三跖骨为应力性骨折的好发部位,特别是第二跖骨中部。

Objective To evaluate the strain of the weight-bearing metatarsal bone. Methods 6 fresh-frozen cadaveric lower extremities were dissected to expose the dorsal aspect of metatarsal. Bone segments were clarified for adherence of strain-gauges while feet kept intact. Then vertical downward axial load was exerted to distal tibia at a 2 ram/min velocity, from 0 N to 1200 N with one minute interval of 200 N leveled loading augment each for sampling. Superficial strain of the metatarsal was measured by resistance strainmeter methods. Results The strain increased gradually with axial loading, and compress force was always found at every marked bone. The strain of every marked bone was significantly different at the same loading （P〈0.05）. As to the strain of the middle of the metatarsal, the sequence was the second metatarsal〉the third metatarsal〉the fourth metatarsal〉the first metatarsal 〉the fifth metatarsal. As to the strain of the second metatarsal, the sequence was the middle, the neck〉the base. Conclusion The peak strain was found at the middle of the second and third metatarsal with axial loading, which prompts the stress fractures of the second and third metatarsal are most common, esoeciallv the middle of the second metatarsal.