The mechanical response of the ovine lumbar anulus fibrosus to uniaxial, biaxial and shear loads
The mechanical response of the ovine lumbar anulus fibrosus to uniaxial, biaxial and shear loads
复制标题
DOI：
10.1016/j.jmbbm.2009.09.002
复制
发表时间：
2010-02-01
影响因子：
3.9
通讯作者：
Adam, C. J.
中科院分区：
文献类型：
--
作者：
Little, J. P.;Pearcy, M. J.;Adam, C. J.
椎间盘（IVD）的分析和计算模型通常用于增强对人类脊柱和脊柱运动节段生物力学的理解。这些模型在预测脊柱生理行为方面的准确性本质上依赖于用于表示脊柱组织的材料本构表征的准确性。目前缺乏详细的力学数据来描述IVD纤维环中增强基质的材料响应。在本研究中，“增强基质”被定义为嵌入胶原纤维但不主动承受轴向载荷的基质，因此包含了纤维-纤维和纤维-基质相互作用的贡献。为确定环空基质的力学参数，对绵羊环空试件进行了无侧限单轴压缩、单轴剪切和双轴压缩的力学试验。绵羊纤维环的测试标本在标本的上下表面有相邻的椎骨/软骨层。标本的几何形状是这样的，没有连续的胶原纤维耦合两个终板。根据椎间盘区域（前、外侧和后）对样本进行细分，以确定环力学反应的区域不均匀性。试样以足够的应变速率加载，以避免流体从组织中流出，并确定了三种加载类型中每种加载类型在初始加载应用和重复加载下的典型应力-应变响应。除了前环的双轴压缩外，环组织对初始和重复载荷循环的响应在所有载荷类型中都有显著差异。由于最大外加应变超过组织的损伤应变，因此反复加载的实验结果反映了组织在损伤开始后的承载能力。据我们所知，这是第一个提供描述“加固地基矩阵”对双轴压缩响应的实验数据的研究。此外，在定义研究目标以确定“加固地基基质”在适合组织力学特征的广泛加载条件下的区域非均匀响应方面是新颖的。所提出的结果有助于对环空地基大应变非线性弹性或超弹性响应进行更详细和全面的本构描述。2009爱思唯尔有限公司版权所有。
Analytical and computational models of the intervertebral disc (IVD) are commonly employed to enhance understanding of the biomechanics of the human spine and spinal motion segments. The accuracy of these models in predicting physiological behaviour of the spine is intrinsically reliant on the accuracy of the material constitutive representations employed to represent the spinal tissues. There is a paucity of detailed mechanical data describing the material response of the reinforced-ground matrix in the anulus fibrosus of the IVD. In the present study, the 'reinforced-ground matrix' was defined as the matrix with the Collagen fibres embedded but not actively bearing axial load, thus incorporating the contribution of the fibre-fibre and fibre-matrix interactions. To determine mechanical parameters for the anulus ground matrix, mechanical tests were carried out on specimens of ovine anulus, under unconfined uniaxial compression, simple shear and biaxial compression.Test specimens of ovine anulus fibrosus were obtained with an adjacent layer of vertebral bone/cartilage on the superior and inferior specimen surface. Specimen geometry was such that there were no continuous Collagen fibres coupling the two endplates. Samples were subdivided according to disc region - anterior, lateral and posterior - to determine the regional inhomogeneity in the anulus mechanical response. Specimens were loaded at a strain rate sufficient to avoid fluid outflow from the tissue and typical stress-strain responses under the initial load application and under repeated loading were determined for each of the three loading types.The response of the anulus tissue to the initial and repeated load cycles was significantly different for all load types, except biaxial compression in the anterior anulus. Since the maximum applied strain exceeded the damage strain for the tissue, experimental results for repeated loading reflected the mechanical ability of the tissue to carry load, subsequent to the initiation of damage.To our knowledge, this is the first study to provide experimental data describing the response of the 'reinforced-ground matrix' to biaxial compression. Additionally, it is novel in defining a study objective to determine the regionally inhomogeneous response of the 'reinforced-ground matrix' under an extensive range of loading conditions suitable for mechanical characterisation of the tissue. The results presented facilitate the development of more detailed and comprehensive constitutive descriptions for the large strain nonlinear elastic or hyperelastic response of the anulus ground matrix. (C) 2009 Elsevier Ltd. All rights reserved.