面向个性化椎间融合器生物力学评价的有限元建模因素影响分析

目的有限元分析已广泛应用于个性化椎间融合器生物力学的评价和优化。针对有限元建模过程中存在的耗时长、计算要求高、参数选择依赖主观经验的问题,本文研究有限元建模因素对仿真结果的影响,为提高个性化椎间融合器生物力学评价中有限元建模效率提供科学依据。方法以L3、L4节段腰椎融合器设计与优化为例,选择韧带模拟方式、模型网格大小、椎体皮质骨厚度、椎体松质骨材料赋值、椎体小关节摩擦系数、融合器与椎体连接方式六种不同建模因素作为分析对象,根据相关文献中对不同因素的处理方法,采用正交实验设计建立18个有限元模型,比较不同因素对计算结果影响。结果采用融合器上的最大von Mises应力为分析指标时,韧带模拟方法、椎体小关节摩擦系数、融合器与椎体连接方式对计算结果有显著影响;采用椎间融合器最大沉降位移为分析指标时,韧带模拟方式、融合器与椎体连接方式对计算结果有显著影响;在满足一定条件下,网格大小、皮质骨厚度、松质骨材料属性对上述两种指标的影响不显著。结论在本文所研究的腰椎融合器有限元建模的6个因素中,韧带的模拟类型、椎体小关节间摩擦系数、融合器与椎体连接方式是需要重点考虑的因素。本文提出的基于正交实验设计的评价建模因素影响的方法,可以为个性化植入介入器械有限元建模过程的参数优化选择提供参考。

Effect of finite element modeling parameters on simulation results for evaluating biomechanical performance of patient-specific interbody fusion cage

Objective Finite element modeling was commonly used in biomechanical evaluating and optimizing of the patient-specific interbody fusion cages.However,it was a time-and labor-intensive process and relied on the researcher's experience.The purpose of this study was to investigate the effects of the modeling parameters on the simulation results in evaluating and optimizing the patient-specific interbody fusion cages with the finite element(FE)models.Methods Biomechanical assessment of L3-L4 spinal cage was used as an example. Six modeling parameters were taken into consideration:the element type of ligament,the size of mesh,the thickness of cortical outer shell,the definition of the cancellous bone material,the friction coefficient of the facet joint,and the connection style between the vertebral bone and the cage.According to orthogonal experimental design,18 FE models were built to analyze the influence of these parameters on the simulation results.Results The element type of ligament,the friction coefficient of the facet joint,and the connection style between the facet bone and the cage affected the simulation results significantly when the maximum von Mises stress on the cage was taken as the evaluating indicator;the element type of ligament,the connection style between the vertebral bone and the cage affected the simulation results significantly when the maximum deposition distance of the cage was taken as the evaluating indicator.The size of mesh,the thickness of cortical outer shell, and the definition of cancellous bone material did not affect the simulation results significantly.Conclusions The method proposed in this study finds out 3 parameters(the element type of ligament,the friction coefficient of the facet joint,and the connection style between the facet bone and the cage) affect the simulation results significantly during evaluating biomechanical performance of interbody cage with the finite element analysis.This method can also be used for optimizing the finite element modeling process during evaluating other patient-specific implants.