Martinez J B, Oloyede V O, Broom N D
Department of Mechanical Engineering, University of Auckland, New Zealand.
Med Eng Phys. 1997 Mar;19(2):145-56. doi: 10.1016/s1350-4533(96)00056-2.
This paper presents an experimental and finite element study of the biomechanical response of the intervertebral disc to static-axial loading in which classical consolidation theory was used to analyse its time-dependent response. A newly developed experimental technique was employed to load the disc in compression and measure simultaneously the matrix internal pressure and creep strain for the full consolidation process. It is shown that, upon loading, the disc develops a maximum hydrostatic excess pore pressure which gradually decays as water is exuded from the matrix. During this decay process, the applied load is progressively transferred to the solid components of the matrix until the load is borne in full by the solid at the end of consolidation. Material properties for the tissue were then obtained from the experimental stress-strain data and used in the finite element study in the development of a finite element solution based on Biot's theory of coupled solid-fluid interaction. An axisymmetric formulation was employed and the disc modelled as an anisotropic, non-linear poroelastic solid. A sensitivity analysis of the material properties for the structural components of the disc was carried out and the biomechanical response to compressive loading evaluated and compared to experimental data. The results show that the matrix permeability plays a significant role in determining the transient response of the tissue. Annular disruptions of the disc were shown to result in an increase in the nuclear principal stresses suggesting that disrupted regions of the annulus fibrosus play a reduced role in load bearing.
本文介绍了一项关于椎间盘对静态轴向载荷生物力学响应的实验和有限元研究，其中使用经典固结理论分析其随时间变化的响应。采用一种新开发的实验技术对椎间盘进行压缩加载，并在整个固结过程中同时测量基质内压和蠕变应变。结果表明，加载时，椎间盘会产生最大静水超孔隙压力，随着水从基质中渗出，该压力会逐渐衰减。在这个衰减过程中，施加的载荷逐渐转移到基质的固体成分上，直到固结结束时载荷完全由固体承担。然后从实验应力 - 应变数据中获得组织的材料特性，并将其用于有限元研究，以基于比奥固 - 流耦合相互作用理论开发有限元解。采用轴对称公式，将椎间盘建模为各向异性、非线性多孔弹性固体。对椎间盘结构成分的材料特性进行了敏感性分析，并评估了其对压缩载荷的生物力学响应，并与实验数据进行了比较。结果表明，基质渗透率在决定组织的瞬态响应中起重要作用。椎间盘的环形破裂会导致髓核主应力增加，这表明纤维环的破裂区域在承载方面的作用减弱。
