座椅高度对老年人坐立转换时股骨近端应力分布影响的有限元分析

Finite Element Analysis of the Effect of Seat Height on Stress Distribution in the Proximal Femur during Sit-to-stand Transitions among the Elderly

目的:通过建立股骨近端有限元模型,分析在坐立转换站立阶段初期,老年人的股骨近端在不同座椅高度起立的应力特征和应变数据,探讨其损伤的风险。方法:将老年人股骨近端CT影像进行三维重建、逆向建模完成实体模型。通过材料赋值和网格划分建立有限元模型,基于有限元分析软件ANSYS,进行边界条件约束,并加载1445 N、1579 N、1767 N、1916 N的载荷,得到不同座椅高度下,坐立转换站立阶段初期时老年人股骨近端的应力分布和应变数据。结果:股骨颈和大转子内侧边缘在各个座椅高度的仿真结果中均为应力集中区,在65%座椅高度时,股骨干处也为应力集中区。115%、100%、80%、65%标准座高的应力峰值,男性为23.25 MPa、26.27 MPa、27.69 MPa、33.47 MPa,女性为24.00 MPa、26.62MPa、27.09 MPa、33.90 MPa,微应变峰值男性为1968、2226、2341、2740,女性为1604、1782、2149、2724。结论:股骨近端的股骨颈和大转子内侧边缘在老年人坐立转换中有较高损伤风险,在座椅较低时,股骨干也有较高的损伤风险;坐立转换中座椅高度的降低会增加股骨近端的损伤风险;性别差异不会影响坐立转换中股骨近端的损伤风险。

Objective To develop a finite element model of the proximal femur and analyse the stress characteristics and strain data of the proximal femur of elderly people rising from different seat heights,so as to explore the risk of injury.Methods The CT images of the proximal femur of the elderly were reconstructed three-demensionally and further transformed into the solid model.The finite element model was established by material assignment and meshing,and based on the finite element analysis software ANSYS,the boundary condition constraints were applied,and the 1445 N,1579 N,1767 N and 1916 N were loaded to obtain the stress distribution and strain data in the early stage of the stting-to-standing conversion from seats with different heights.Results The femoral neck and the medial edge of the greater trochanter were stress-concentrated areas in the simulation of all seat heights,and at 65%seat height,the femoral stem was also a stress-concentrated area.Moreover,115%,100%,80%,and 65%of the standard seat heights had stress peaks of 23.25 MPa,26.27 MPa,27.69 MPa,and 33.47 MPa in males,and 24.00 MPa,26.62 MPa,27.09 MPa,and 33.90 MPa for females,with peak microstrain of 1968,2226,2341,and 2740 for males,as well as 1604,1782,2149,and 2724 for females.Conclusions The proximal femoral neck and medial margin of greater trochanter have higher risk of injury for the elderly during sit-stand transition.Moreover,when the seat is low,the femoral shaft also has higher risk of injury.However,the reduction of seat height can further increase the risk of proximal femur injury,while no significant differences were observed in such injury between different genders.