跟骨内翻畸形对踝关节应力变化三维有限元分析

目的通过踝关节三维有限元模型的建立,模拟正常负重应力状态下随着跟骨内翻角度的增大,对踝关节的损伤模式的变化。方法取一名28岁男性志愿者,基于踝关节CT的数据建立包括骨骼、软组织和关节囊,考虑材料的非线性和关节接触的踝关节的三维有限元模型。采用统一的模型和方法,志愿者人体重量为60 kg,单腿站立,总加力600 N,垂直朝下,跟踪跟骨内翻角度从4~°、8~°、11~°、14~°的变化共四种情况力学表征形式,关注对踝关节应力分布的影响进行对比分析。应用有限元分析软件(Abaqus6 v6.14,DS System公司,法国)。结果踝关节应力集中区域在内踝与对应距骨关节面的凹陷区域,其次是外侧。距骨应力集中区域在距骨顶与内踝接触位置的区域,其次是外侧。我们发现4种情况下分析结果显示趋势一致,符合线性力学分析基本规律。结论跟骨内翻畸形负重应力集中固定在内踝、距骨接触位置,随着跟骨内翻畸形角度的增大,局部所承载的应力负荷增大,成正相关。跟骨手术治疗时跟骨内翻角变异应控制在患者跟骨生理内翻角+2°内。

A three-dimensional finite element analysis of ankle joint stress with calcaneal varus angle change

Objective To investigate the impact of various calcaneal varus angle on ankle joint stress under normal load with three-dimensional finite element analysis. Methods CT radiographs of ankle joint from a 28-year healthy volunteers were obtained while having the subject stand on one foot. A three-dimensional ankle model with different calcaneal varus angle changes (including +4°, +8°, +11°, and +14°), non-linear surrounding structure, and interfaces was established using Abaqus6 v 6.14 software. Stress of ankle joint under a load of 600 N at different calcaneal varus angles were measured. Results The stress concentering regions in ankle are medial malleolus and its corresponding concave surface of talus. The point of talus in contacting with medial malleolar facet is the area where stress is the most significant, followed by lateral surface. The findings are consistent across alterations of calcaneal varus angle. Conclusion Calcaneal varus induced stress is located at area where medial malleolus and talus meet. It is positively correlated with the calcaneal varus angle. The calcaneal varus angle following operative treatment of calcaneal fractures should be controlled within +2°.