终板凹陷角变化对腰椎运动节段生物力学影响的有限元分析

The influence of endplate concave angle on the mechanical response of lumbar motion segment:a finite element analysis

目的:研究终板凹陷程度变化对腰椎运动节段生物力学影响。方法:在以往建立的腰椎L4～5运动节段三维非线性有限元模型基础上,采用CAD方法精确构建三种不同终板凹陷角改变的有限元模型,有限元模型的椎间盘前凸角、小关节间隙等其余形态学参数及网格划分均保持一致。垂直压缩、屈曲、伸直、前后剪力5种载荷条件下,分别对三种有限元模型生物力学参数进行测试。结果:负载条件下,终板凹陷角增加、终板凹陷程度减小可导致终板-椎间盘界面应变减小,椎间盘刚度及髓核内压增加,椎间盘膨出、纤维环纤维张应力、纤维环基质应力、腰椎后部结构应力以及关节突接触力减小。结论:终板凹陷程度的减小增强了椎间盘对椎体的保护作用;同时可通过影响终板的形变减少对椎间盘的营养传递。

Objective： To investigate the effects of variations in vertebral endplate concavity on the mechanical behaviors of the lumbar motion segment. Mothods： A three-dimensional nonlinear geometrical and mechanical accurate finite element model of lumbar L4-L5 segment was developed. CAD methods were used to establish three finite element models with different endplate concave angle, where disc lordosis angle, the gap of facet joint and all other geometrical parameters and finite element mesh partition were kept constant. The effects of endplate concavity on the mechanical properties of the lumbar segment was studied for two moment loads （flexion and extension） and for three different direct forces （compression, anterior and posterior shear forces）. Results： The decrease in the endplate concavity, simulated by an increasing endplate concave angle would result in decreased strains of the endplate and vertebral body, increased disc stiffness and nucleus pressure, decreased annular fiber stress, radial disc bulge and stress in the annulus ground substance,and simultaneously produce decreased facet contact force and stresses in posterior structure. Conclusions： The decrease of endplate concavity enhances the protective effect of the disc on the breakage of the vertebral body. Smaller endplate deformations resulted from the decreasing endplate concavity would contribute to reduction of the nutritional diffusion to the diso.