以三维非线性有限元法分析融合腰椎的生物力学变化

Biomechanical changes of lumbar segment after fusion analyzed with three-dimensional nonlinear finite element

背景:MATLAB具有大型数值计算、数学绘图和简单有限元分析的能力,建模速度快,能够识别BMP和JPG格式的灰度图,并可将识别的数据直接转换为ANSYS三维有限元软件可识别的格式,避免了常规在Autocad软件中图像的重新定位和二次处理而产生的人为误差。目的:寻求一种简便、快捷、准确的方法建立各种腰椎融合模型,对腰椎融合后腰椎活动节段的生物力学进行分析。方法:利用薄层CT技术,结合Matlab(MatrixLaboratory即矩阵实验室)科学计算软件,辅助Ansys有限元分析软件建立各种腰椎融合模型。对所建立的模型施加各种载荷,分析其生物力学变化。结果与结论:对所建立的融合模型施加轴向、屈曲及伸展载荷后,生物力学分析得出所有的融合模型中椎体间融合稳定性最好。和关节间融合相结合,椎体间,侧后方,后方融合模型的轴向位移较单独的椎体间,侧后方和后方融合模型分别减少5%、1%和4%。在伸展-屈曲载荷条件下旋转角度分别减少23%、11%和45%。应力向融合部位集中的现象表明融合块可增加载荷的转移。说明薄层CT和Matlab软件的辅助使得Ansys有限元软件建立腰椎融合模型的速度和精度提高。小关节融合和椎体间,侧后方,后方融合相结合,可使腰椎获得更好的稳定性,这种稳定性的增加在后方融合中更为显著。后方融合模型的应力分布更加合理。

BACKGROUND： MATLAB has capabilities of large numerical calculation, mathematical drawing and simple finite element analysis. It can establish models rapidly and can be able to identify the grayscale with BMP and JPG format, and it can directly transform the identified data into ANSYS finite element software-readable format, thus avoiding personal error produced by the repositioning and secondary treatment in the Autocad software. OBJECTIVE： To find a simple, convenient and accurate method to construct the model of lumber fusion and to analyze the biomechanics of lumbar motion segment after lumbar fusion. METHODS： Lamellar CT and Matlab （Matrix Laboratory） scientific computing software combining Ansys finite element software was used to construct the models of lumber fusion. Then the models were loaded to analyze the biomechanical change of the fusion model. RESULTS AND CONCLUSION： The established models were loaded with axial, bending and stretching loads, and the biomechanical analysis showed that interbody fusion had the best stability among all the fusion models. Combined with joint fusion, the axial displacements of interbody, rear side and rear fusion models were decreased by 5%, 1% and 4% than that of simple interbody fusion, posterolateral fusion and Posterior fusion models. Under the stretch-buckling load conditions, the rotation angles were reduced by 23%, 11% and 45%. Stress concentration to the fusion parts showed fusion block could increase the load displacement. The technology of lamellar CT, Matlab software and Ansys finite element software can accelerate the construction of lumber fusion model and make the model more accurate. Facet joint fusion combined with interbody fusion, posterolateral fusion and posterior fusion can get better lumbar stability, and this increased stability is moresignificant in the rear fusion. Stress distribution of posterior fusion is more reasonable.