3种不同弹性模量钛合金股骨假体在羊股骨置换模型中应力分布的三维有限元分析

A Three-dimensional Finite Element Analysis of 3 Different Elastic Modulus Titanium Alloy Femoral Prostheses in the Sheep Femur Replacement Model in the Stress Distributions

目的:通过三维有限元分析方法来观察并比较3种不同弹性模量钛合金股骨假体在羊股骨置换模型中von-Mises应力分布的情况。方法:采用64排螺旋CT对一健康成年羊的下肢股骨进行全长的CT扫描,扫描层厚为0.5 mm,扫描所得的数据存储为DICOM文件。将得到的DICOM文件导入到CT图像分析软件Mimics 10.0,然后利用Mimics 10.0软件来生成股骨的骨质点云数据,再将生成的骨质点云数据导入到Simpleware分析软件,通过机械加工反求中的复杂曲面造型技术建立起精确的三维实体模型。对三维实体模型进行网格划分,确定了髓腔的形状,并根据羊下肢股骨髓腔的形状设计了作者实验用的羊股骨假体模型,然后在ANSYS 12.1软件中进行网格划分。给予加载缓慢行走载荷以及扭转载荷,分析并比较羊股骨以及3种不同弹性模量钛合金股骨假体在股骨置换模型中von-Mises应力分布的情况。结果:在缓慢行走载荷以及扭转载荷条件下,3种不同弹性模量钛合金股骨假体von-Mises应力分布变化趋势一致,假体的柄颈结合部以及假体柄上1/3为应力集中区域。3种不同弹性模量的最大应力集中点均位于柄颈结合部,60 GPa弹性模量的股骨假体植入后假体的最大应力最小(37.8 MPa、29.1 MPa),股骨的最大应力最大(12.6 MPa、24.5 MPa);80 GPa的次之,假体的最大应力(38.4 MPa、33.4 MPa),股骨的最大应力(12.5 MPa、24.5 MPa);110 GPa的股骨假体植入后假体的最大应力最大(38.9 MPa、38.1 MPa),股骨的最大应力最小(12.3 MPa、24.5 MPa)。60 GPa弹性模量的股骨假体植入后的假体最大位移和相对位移均最小(缓慢行走载荷下假体最大位移为0.551 mm、相对位移为0.008 mm,扭转载荷下假体最大位移为0.730 mm、相对位移为0.011 mm)。结论:较低弹性模量的钛合金股骨假体(60 GPa)由于其弹性模量更接近于骨组织的弹性模量,股骨假体与股骨间的"应力遮挡"效应较小,更有利于应力在股骨假体及股骨间的传递,增加了股骨假体的早期稳定性,延长了其临床寿命。

Objeetive： To observe and compare the von-Mises stress distributions of 3 different elastic modulus titanium alloy femoral prostheses in the sheep femur replacement model by three-dimensional finite element analysis （FEA） and calculation. Methods： The femur of a healthy adult sheep received full-length CT scanning with a slice thickness of 0.5 ram. The scanning data were stored as DICOM files. The DICOM files were imported to CT image analysis software Mimics 10.0 and to generate the femur bone point cloud data with Mimics 10.0 software. Then, the resulting point cloud data were input into simple ware software to establish a precise three-dimensional solid model with reverse the complex surface modeling technology by machining. Meshing three-dimensional solid model to determine the canal shape and meanwhile design femoral prosthesis models according to the shape of the femoral canal. Femoral prosthesis model was meshed with ANSYS 12.1 software. Loads were applied on 3 different elastic modulus titanium alloy femoral prostheses when a sheep slowly walking and torsion were simulated. The von-Mises stress distributions in the 3 different elastic modulus titanium alloy femoral prostheses and the sheep femur were analyzed and compared. Results： Under the slowly walking and torsion loads, the 3 different elastic modulus titanium alloy femoral prostheses led to similar change tendency in the von-Mises stress distributions. The stress centered around the prostheses neck and the upper 1/3 of the prostheses. The maximum stress on the femur of 3 different elastic modulus titanium alloy femoral prostheses was the largest in 60 GPa （12.6 MPa, 24.5 MPa） and the maximum stress on the femoral prostheses was the smallest in 60 GPa （37,8 MPa, 29.1 MPa）, the second in 80 GPa （12.5 MPa, 24.5 MPa） on the femur and （38.4 MPa, 33.4 MPa） on the femoral prostheses. The maximum stress on the femur was the smallest in 110 GPa （12.3 MPa, 24.5 MPa） and the maximum stress on the femoral prostheses was the largest in 110 GPa （38.9 MPa, 38.1 MPa）. The maximum displacement and relative displacement of the femoral prosthesis after implantation were the smallest in 60 GPa modulus of elasticity （the maximum displacement was 0.551 mm, the relative displacement was 0.008 mm under slowly walking load; 0.730 mm ＆ 0.011 mm under torsion load）. Conclusions： Lower elastic modulus titanium alloy femoral prosthesis （60 GPa） due to its elastic modulus is closer to the elastic modulus of the bone and accordingly the ＂stress shielding＂ effect is smaller, is more convenient to the pass of force between femoral prosthesis and the femur, meanwhile it can increase the early stability of the femoral prosthesis and prolong its service life in clinic.