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Title:: Biomechanical study of femoral stem prosthesis based on topology optimization

Author(s):: ZHANG Tingting; CHENG Yunzhang; School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China

Keywords:: Implant; Finite element; Hip joint; Stress constraint; Stress shielding; Lattice optimization

摘要:: 本研究利用拓扑优化的方法对股骨柄假体进行结构优化，研究不同保留阈值下假体体积对力学性能的影响，并探索优化假体对股骨的影响。利用股骨假体三维模型建立有限元模型，拓扑优化后保存5个不同保留阈值的模型，对其进行力学性能分析，并对比初始假体与一例优化假体置入对股骨的内固定效果。优化前假体的柔度为123.06 mJ，应力为179.96 MPa；优化后假体的柔度和应力均大于优化前，其中柔度最小值为142.31 mJ，应力最小值为182.23 MPa。置入初始假体的股骨A区应力平均值为23.083 MPa；置入优化假体的为25.246 MPa。拓扑优化方法下假体柔度随着体积的减小而增加；应力受构型和体积的双重影响，且构型的影响占据了主导因素。保留阈值为0.5的优化假体相较于通用假体能减小股骨的应力遮挡。

Abstract:: We used topology optimization method to optimize the structure of femoral stem prosthesis, studied the effect of prosthesis volume on mechanical properties under different retained thresholds, and explored the effect of optimized prosthesis on femur. The finite element model was established by using the three-dimensional model of femoral prosthesis. After topology optimization, five models with different retained thresholds were saved, their mechanical properties were analyzed, and the internal fixation effects of initial prosthesis and an optimized prosthesis were compared. The compliance of prosthesis before optimization was 123.06 mJ and the stress was 179.96 MPa; the compliance and stress of the prosthesis after optimization were greater than those before optimization, in which the minimum compliance was 142.31 mJ and the minimum stress was 182.23 MPa. The average stress in zone A of femur with initial prosthesis was 23.083 MPa; and of the optimal prosthesis was 25.246 MPa. Under the topology optimization method, the compliance of prosthesis increased with the decrease of volume; the stress was affected by both configuration and volume, and the influence of configuration was the dominant factor. Compared with the generic prosthesis, the optimized prosthesis with a retained threshold of 0.5 can reduce the stress shielding of the femur.