足前掌在不同着地角度下跖骨应力状态的有限元研究
A Finite Element Study of the Stress on Metatarsals during Forefoot Strike at Different Angles
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摘要: 目的:旨在研究不同矢状面角度下前掌落地过程中脚内部各跖骨上应力的分布。方法:建立足部有限元模型并用生物力学测试对模型的有效性进行了验证。使用三维红外影像捕捉系统的运动学数据作为边界条件的幅值曲线, 采用显示求解器模拟了前掌在3种不同触地角度下的落地过程。结果:前掌落地各阶段外侧跖骨的应力显著高于内侧。当载荷超过体重后, 跖骨应力集中的区域在不同角度下具有重复性。第4跖骨在1倍2倍体重的载荷过程中, 应力的增长幅度能超过100%。模拟结果显示, 前掌落地角度太小 (<5°) 会使各跖骨应力分布不均衡, 第1跖骨应力未达到其他跖骨的1/3。前掌触地角度过大 (>15°) 时, 即使是低载荷 (0.5倍) 情况下各跖骨也会出现明显的应力集中。结论:采用前掌落地时应该采用合理的触地角度, 尤其是对于刚开始采用这种落地方式的跑步者来说, 要注意运动量的控制, 避免高应力区域长时间重复载荷超过骨骼自身的功能适应性, 而发生应力性骨折。Abstract: Objective: This paper studied the stress distribution on metatarsals during different forefoot strike angles on sagittal plane. Method: finite element model of human foot was built by hex elements and validated bybiomechanical test. The amplitude of boundary condition applied on foot FE model was from kinematic data of 3 D motion capture system. Result: lateral metatarsals had significant higher stress than medial at each loading stage. Same stress concentration was observed during different loading angles when the load is over body weight. The stress increasing rate on the 4 th metatarsal was more than 100% when the load increased from one bodyweight to two bodyweights. Unevenly distributed stress on metatarsals would be seen while forefoot strike angle at 5°or less, in which the average stress on 1 st metatarsal was lower than one third of the average value on the other four metatarsals. Stress concentration could happen at high forefoot strike angle (15°) even the loading was lower than half bodyweight. Conclusion: Forefoot strike angle should be controlled in a reasonable range in order to avoidstress fracture due to repetitive loading on the same high stress area which is beyond the functional adaptation of foot bones.