Nikkhoo Mohammad, Hsu Yu-Chun, Haghpanahi Mohammad, Parnianpour Mohamad, Wang Jaw-Lin
School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran.
Proc Inst Mech Eng H. 2013 Jun;227(6):672-82. doi: 10.1177/0954411913480668. Epub 2013 Mar 26.
Finite element analysis is an effective tool to evaluate the material properties of living tissue. For an interactive optimization procedure, the finite element analysis usually needs many simulations to reach a reasonable solution. The meta-model analysis of finite element simulation can be used to reduce the computation of a structure with complex geometry or a material with composite constitutive equations. The intervertebral disc is a complex, heterogeneous, and hydrated porous structure. A poroelastic finite element model can be used to observe the fluid transferring, pressure deviation, and other properties within the disc. Defining reasonable poroelastic material properties of the anulus fibrosus and nucleus pulposus is critical for the quality of the simulation. We developed a material property updating protocol, which is basically a fitting algorithm consisted of finite element simulations and a quadratic response surface regression. This protocol was used to find the material properties, such as the hydraulic permeability, elastic modulus, and Poisson's ratio, of intact and degenerated porcine discs. The results showed that the in vitro disc experimental deformations were well fitted with limited finite element simulations and a quadratic response surface regression. The comparison of material properties of intact and degenerated discs showed that the hydraulic permeability significantly decreased but Poisson's ratio significantly increased for the degenerated discs. This study shows that the developed protocol is efficient and effective in defining material properties of a complex structure such as the intervertebral disc.
有限元分析是评估活体组织材料特性的有效工具。对于交互式优化过程，有限元分析通常需要进行多次模拟才能得到合理的解决方案。有限元模拟的元模型分析可用于减少具有复杂几何形状的结构或具有复合本构方程的材料的计算量。椎间盘是一种复杂、非均质且含水的多孔结构。多孔弹性有限元模型可用于观察椎间盘内的流体传输、压力偏差及其他特性。定义纤维环和髓核合理的多孔弹性材料特性对于模拟的质量至关重要。我们开发了一种材料特性更新协议，它本质上是一种由有限元模拟和二次响应面回归组成的拟合算法。该协议用于确定完整和退变猪椎间盘的材料特性，如水力渗透率、弹性模量和泊松比。结果表明，体外椎间盘实验变形与有限的有限元模拟和二次响应面回归拟合良好。完整椎间盘和退变椎间盘材料特性的比较表明，退变椎间盘的水力渗透率显著降低，而泊松比显著增加。本研究表明，所开发的协议在定义诸如椎间盘这样的复杂结构的材料特性方面是高效且有效的。
