Theoretical and Uniaxial Experimental Evaluation of Human Annulus Fibrosus Degeneration
Theoretical and Uniaxial Experimental Evaluation of Human Annulus Fibrosus Degeneration
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DOI：
10.1115/1.3212104
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发表时间：
2009-11-01
影响因子：
1.7
通讯作者：
Elliott, Dawn M.
中科院分区：
文献类型：
--
作者：
O'Connell, Grace D.;Guerin, Heather L.;Elliott, Dawn M.
纤维环高度组织化的结构和组成为组织提供了包括各向异性和非线性在内的力学行为。数学模型对于解释和阐明直接测量的力学性能的意义以及理解组织成分（即纤维和纤维外基质）的结构-连接关系是必要的。本研究将纤维环建模为描述纤维、基质及其相互作用的应变能函数的组合。目的是利用单轴拉伸实验数据量化非变性和变性纤维环组织的行为。力学测试是沿着圆周、轴向和径向方向进行的。对于沿径向取向的样品，脚趾区域的模量随着退化增加了2倍。然而，在退化过程中没有观察到其他测量力学性能的差异。本构模型适用于沿径向和周向取向的试样。（r-2 >= 0.97）。纤维在周向载荷下承受的应力比例最高，为60%。基质对应力的贡献减少了70%，从脚趾区域到线性区域的非退行性和退行性组织。随着线性区域的退化，纤维-基体相互作用（FMI）的贡献增加了80%。沿径向和轴向取向的试样在单轴拉伸下表现相似（模量分别为0.32 MPa和0.37 MPa），表明轴向单轴试验不适用于量化环空纤维增强材料的力学特性。综上所述，结构驱动的非线性各向异性超弹性本构模型有助于进一步理解变性过程中微观结构变化的影响，表明子组分（即胶原纤维基质和FMI）的重塑可能会将变性过程中对体材力学功能的总体影响降至最低。(DOI: 10.1115/1.3212104)
The highly organized structure and composition of the annulus fibrosus provides the tissue with mechanical behaviors that include anisotropy and nonlinearity. Mathematical models are necessary to interpret and elucidate the meaning of directly measured mechanical properties and to understand the structure-Junction relationships of the tissue components, namely, the fibers and extrafibrillar matrix. This study models the annulus fibrosus as a combination of strain energy functions describing the fibers, matrix, and their interactions. The objective was to quantify the behavior of both nondegenerate and degenerate annulus fibrosus tissue using uniaxial tensile experimental data. Mechanical testing was performed with samples oriented along the circumferential, axial, and radial directions. For samples oriented along the radial direction, the toe-region modulus was 2X stiffer with degeneration. However, no other differences in measured mechanical properties were observed with degeneration. The constitutive model fit well to samples oriented along the radial and circumferential directions.(R-2 >= 0.97). The fibers supported the highest proportion of stress for circumferential loading at 60%. There was a 70% decrease in the matrix contribution to stress from the toe-region to the linear-region of both the nondegenerate and degenerate tissue. The shear fiber-matrix interaction (FMI) contribution increased by 80% with degeneration in the linear-region. Samples oriented along the radial and axial direction behaved similarly under uniaxial tension (modulus = 0.32 MPa versus 0.37 MPa), suggesting that uniaxial testing in the axial direction is not appropriate for quantifying the mechanics of a fiber reinforcement in the annulus. In conclusion, the structurally motivated nonlinear anisotropic hyperelastic constitutive model helps to further understand the effect of microstructural changes with degeneration, suggesting that remodeling in the subcomponents (i.e., the collagen fiber matrix and FMI) may minimize the overall effects on mechanical function of the bulk material with degeneration. [DOI: 10.1115/1.3212104]