Périé Delphine, Korda David, Iatridis James C
Department of Mechanical Engineering, University of Vermont, Burlington, VT, USA.
J Biomech. 2005 Nov;38(11):2164-71. doi: 10.1016/j.jbiomech.2004.10.002. Epub 2004 Dec 13.
The biphasic material properties for nucleus pulposus tissue in confined compression have not been reported previously, and are required for a better understanding of intervertebral disc function and to provide material properties for use in finite-element models. The aims of this study were to determine linear and non-linear material properties for nucleus pulposus and annulus fibrosus tissues in confined compression, to define the influence of swelling conditions on these properties, and to determine the changes in the compressive modulus and hydraulic permeability induced by the repetition of the stress-relaxation experiment after a return to swelling pressure equilibrium. Specimens from caudal bovine nucleus and annulus were tested in confined compression stress-relaxation experiments and analyzed to quantify the compressive modulus and hydraulic permeability using linear and non-linear biphasic models. Our results suggested the use of confined swelling pre-test condition and non-linear biphasic model, which provided the material parameters with lowest relative variance and water content most representative of physiological conditions. Smaller compressive modulus and higher hydraulic permeability were obtained for the nucleus (H(A0)=0.31+/-0.04 MPa, k(0)=0.67+/-0.09 x 10(-15)m(4)/Ns) than for the annulus (H(A0)=0.74+/-0.13 MPa, k(0)=0.23+/-0.19 x 10(-15)m(4)/Ns), with relatively weak non-linearities. Strains up to 20% resulted in material properties that were significantly altered upon retesting. These altered material properties are an effort to quantify non-recoverable damage that occurs in disc tissue and suggest that in vivo exposure of disc tissues to low strain-rate and high-deformation loading conditions which outpace biological repair may result in altered mechanical behaviors.
此前尚未报道过髓核组织在受限压缩下的双相材料特性，而了解椎间盘功能以及为有限元模型提供材料特性都需要这些信息。本研究的目的是确定髓核和纤维环组织在受限压缩下的线性和非线性材料特性，确定肿胀条件对这些特性的影响，并确定在恢复到肿胀压力平衡后重复应力松弛实验所引起的压缩模量和水力渗透率的变化。对来自牛尾髓核和纤维环的样本进行受限压缩应力松弛实验，并使用线性和非线性双相模型进行分析，以量化压缩模量和水力渗透率。我们的结果表明，使用受限肿胀预测试条件和非线性双相模型，能提供相对方差最低且水分含量最具生理代表性的材料参数。与纤维环（H(A0)=0.74±0.13 MPa，k(0)=0.23±0.19×10(-15)m(4)/Ns）相比，髓核的压缩模量较小，水力渗透率较高（H(A0)=0.31±0.04 MPa，k(0)=0.67±0.09×10(-15)m(4)/Ns），且非线性相对较弱。高达20%的应变会导致再次测试时材料特性发生显著变化。这些改变的材料特性旨在量化椎间盘组织中发生的不可恢复损伤，并表明椎间盘组织在体内暴露于低应变率和高变形加载条件下，若超过生物修复能力，可能会导致力学行为改变。
