基于CT图像的股骨上段有限元建模及单元尺寸分析

目的 基于CT图像构建5个不同的股骨上段有限元模型，并分析模型单元尺寸对股骨模型材料属性分布以及生物力学性能的影响。方法 利用螺旋CT扫描股骨上段并以DICOM格式输出图像文件，利用Mimics软件提取三维几何文件，分别使用Mimics、3-Matica、ICEM软件生成体素网格模型、四面体网格模型和3个六面体网格模型（单元尺寸分别为2、1 和0.5 mm），在Mimics中对网格文件进行材料赋值，将最终的有限元模型导入ABAQUS中进行力学行为分析。结果 单元尺寸对5个模型总质量影响较小，5个模型沿相同路径上节点处Von Mises应力和节点位移整体变化趋势一致，但是各个节点处Von Mises应力误差较大，单元尺寸为0.5 mm的六面体网格模型与体素网格模型各节点处Von Mises应力值接近。结论 基于CT灰度值进行材料赋值时，单元尺寸对模型的总质量和节点位移影响较小，但是单元尺寸的减小将导致模型中各材料含量和分布的改变，引起应力分布的变化。当模型单元尺寸与体素尺寸接近时，能较好反映股骨的质量分布和力学行为。
Objective To establish 5 different finite element models of the proximal femur based on CT images, and analyze the influences of element size on materials distribution and biomechanical behavior of the proximal femur model. Methods The proximal femur was scanned by spiral CT. The images, stored as DICOM format, were extracted by Mimics to obtain 3D geometric data, and then meshed separately by Mimics, 3-Matic and ICEM software to establa voxel element model, a tetrahedral element model and 3 hexahedral element model (with element size of 2, 1, 0.5 mm). These meshed models were assigned materials by Mimics, and their mechanical behavior was analyzed by Abaqus eventually. Results For the proximal femur model with material assignment based on CT images, the influence of element size on the total mass of all the 5 models was not significant. The nodal Mises stress and nodal displacement along the same path in 5 models showed a similar tendency, while the Mises stress at each node displayed an obvious deviation. The nodal Mises stress in the hexahedral element model with the element size of 0.5 mm showed accordance with the voxel element model. Conclusions The element size has a small influence on the total mass and nodal displacement when the material assignment is attributed to the model based on CT gray values, while decrease in the element size will affect the materials distributions and stress distributions of the model. When the element size of the proximal femur model is close to its voxel size, the mass distributions and mechanical behavior of the femur can be preferably reflected.