三维有限元法人工椎间盘力学分析

Biomechanical analysis of artificial intervertebral disc in a 3-dimensional finite-element model

目的:建立人工腰椎间盘的三维实体模型,应用有限元方法模拟人工椎间盘置换术后的受力状态,分析人工椎间盘的生物力学特性,建立以计算机辅助分析技术为基础的技术平台,为优化设计提供力学基础。方法:根据人工椎间盘在人体脊柱不同体位的受力特点施加不同载荷,采用梯度斜坡面力加载的方法,用三维有限元法分析各组件在不同载荷下的力学数据。结果:成功构建了人工椎间盘三维实体模型,并完成高阶实体单元分网。获得各组件力学特征值;获得结构内位移、应力、应变及能量分布。假体核内应力-应变-能量分布具有非均匀性。结论:建立了以三维有限元计算机辅助分析技术为基础的人工椎间盘逆向工程技术平台;梯度斜坡面力加载方法是高效可行的加载方法;指明假体核及盖板的设计使顶面保持更高的承载及分散载荷的能力,不易发生假体圆弧变形而导致应力集中和结构塌陷。采用均一材料制作的现有假体核在内部不均匀应力-应变分布的长期作用下,会发生非均匀的内部损害,需要设计优化;人工椎间盘置换术中,合适范围内尽量选择较大规格的假体核将获得更好缓冲和抗磨损能力。

Objective To evaluate the mechanical properties of artificial lumbar intervertebral disc by finite-element （ FE ） analysis, to predict the mechanical influence of loading on the prosthesis after placement, especially after the long-term employment, and to offer the mechanical basis and technological means for the design optimization. Methods A 3-dimensional solid model was built according to the geometry of the prosthesis; finite-element analysis was applied to determine the effect of the implanted artificial disc prosthesis on the biomechanical behavior; and the data of its mechanical responses were calculated in 3 compression modes which simulated its different load conditions in vivo. Simulations were conducted in a new specially designed manner, preferably simulated load con- ditions in vivo. Results A finite-element model was established by generating mesh out of the prosthesis geometry. The analysis was conducted in employing models of the disc prosthesis under 3 types of emulational realism loading conditions, obtaining the distributing characteristics and data of displacement-stress-strain-energy in the structure, which are difficult to measure exactly by conventional methods. Conclusion Implanted loading strongly influences prosthesis in its internal distribution of displacement-stress-strain-energy in the structure, suggesting that the disc prosthesis allows correctly reproducing a profitable motion and cushion at the implanted level. Predictive wear may occur in special parts according to the designed prosthesis mechanical structure. When implanting an artificial disc, proper size should be taken in choosing disc and the higher core could provide better mechanical characteristics. The results may assist in optimizing artificial lumbar disc replacement primarily from a biomechanical point of view.