基于前外侧保留角预测股骨头坏死塌陷的有限元分析

Finite element analysis for predicting osteonecrosis of the femoral head collapse based on the preserved angles

目的建立股骨头坏死(osteonecrosis of the femoral head,ONFH)不同保留角有限元模型进行生物力学分析,为以股骨头前侧保留角(anterior preserved angle,APA)和外侧保留角(lateral preserved angle,LPA)预测ONFH塌陷风险提供力学依据。方法选择1名健康成人左侧股骨头为研究对象,获取CT数据导入Mimics21.0软件,重建完整股骨近端模型以及构建3个体积相等、形态不同的ONFH模型,导入Solidworks 2022软件中分别构建APA为60°且LPA分别为45°、50°、55°、60°、65°、70°、75°的21个ONFH有限元模型,以及LPA为60°且APA分别为45°、50°、55°、60°、65°、70°、75°的21个ONFH有限元模型。根据生理状态下股骨头负荷情况,股骨远端设置完全固定,在股骨头表面负重区施加与股骨干成25°夹角、方向向下且大小为受试者3.5倍体质量的合力,利用有限元分析软件Abaqus 2021计算并观察股骨头表面、坏死区最大应力及股骨头负重区最大位移情况。结果研究建立的ONFH模型基本符合ONFH力学情况。在相同载荷条件下,3个不同形态相同体积的坏死区构成的42个ONFH不同保留角模型中,坏死区周围均有应力集中现象。APA为60°时,LPA<60°模型的股骨头表面、坏死区最大应力和股骨头负重区最大位移明显高于LPA≥60°模型(P<0.05);LPA≥60°模型间的各指标差异无统计学意义(P>0.05)。LPA为60°时,APA<60°模型的各指标明显高于APA≥60°模型(P<0.05);APA≥60°模型间的各指标差异无统计学意义(P>0.05)。结论从生物力学角度来看,当ONFH保留角小于临界值时,股骨头应力集中现象更为明显,提示此种状态下坏死股骨头发生塌陷风险更高。

Objective To establish finite element models of different preserved angles of osteonecrosis of the femoral head(ONFH)for the biomechanical analysis,and to provide mechanical evidence for predicting the risk of ONFH collapse with anterior preserved angle(APA)and lateral preserved angle(LPA).Methods A healthy adult was selected as the study object,and the CT data of the left femoral head was acquired and imported into Mimics 21.0 software to reconstruct a complete proximal femur model and construct 3 models of necrotic area with equal volume and different morphology,all models were imported into Solidworks 2022 software to construct 21 finite element models of ONFH with LPA of 45°,50°,55°,60°,65°,70°,and 75°when APA was 45°,respectively,and 21 finite element models of ONFH with APA of 45°,50°,55°,60°,65°,70°,75°when LPA was 45°,respectively.According to the physiological load condition of the femoral head,the distal femur was completely fixed,and a force with an angle of 25°,downward direction,and a magnitude of 3.5 times the subject’s body mass was applied to the weight-bearing area of the femoral head surface.The maximum Von Mises stress of the surface of the femoral head and the necrotic area and the maximum displacement of the weight-bearing area of the femoral head were calculated and observed by Abaqus 2021 software.Results The finite element models of ONFH were basically consistent with biomechanics of ONFH.Under the same loading condition,there was stress concentration around the necrotic area in the 42 ONFH models with different preserved angles composed of 3 necrotic areas with equal volume and different morphology.When APA was 60°,the maximum Von Mises stress of the surface of the femoral head and the necrotic area and the maximum displacement of the weight-bearing area of the femoral head of the ONFH models with LPA<60°were significantly higher than those of the models with LPA≥60°(P<0.05);there was no significant difference in each index among the ONFH models with LPA≥60°(P>0.05).When LPA was 60°,each index of the ONFH models with APA<60°were significantly higher than those of the models with APA≥60°(P<0.05);there was no significant difference in each index among the ONFH models with APA≥60°(P>0.05).Conclusion From the perspective of biomechanics,when a preserved angle of ONFH is less than its critical value,the stress concentration phenomenon in the femoral head is more pronounced,suggesting that the necrotic femoral head may have a higher risk of collapse in this state.