Guerin Heather Anne L, Elliott Dawn M
Department of Mechanical Engineering and Applied Mechanics, McKay Orthopaedic Research Laboratory, University of Pennsylvania, 424 Stemmler Hall, Philadelphia, PA 19104-6081, USA.
J Biomech. 2006;39(8):1410-8. doi: 10.1016/j.jbiomech.2005.04.007. Epub 2005 Jun 13.
The angled, lamellar structure of the annulus fibrosus is integral to its load-bearing function. Reorientation of this fiber structure with applied load may contribute to nonlinear mechanical behavior and to large increases in tensile modulus. Fiber reorientation has not yet been quantified for loaded non-degenerated and degenerated annulus fibrosus tissue. The objective of this study was to measure fiber reorientation and mechanical properties (toe- and linear-region modulus, transition strain, and Poisson's ratio) of loaded outer annulus fibrosus tissue using a new application of FFT image processing techniques. This method was validated for quantification of annulus fiber reorientation during loading in this study. We hypothesized that annulus fibrosus fibers would reorient under circumferential tensile load, and that fiber reorientation would be affine. Additionally, we hypothesized that degeneration would affect fiber reorientation, toe-region modulus and Poisson's ratio. Annulus fibrosus fibers were found to reorient toward the loading direction, and degeneration significantly decreased fiber reorientation (the fiber reorientation parameter, m(FFT)=-1.70 degrees /% strain for non-degenerated and -0.95 degrees /% strain for degenerated tissue). Toe-region modulus was significantly correlated with age (r=0.6). Paired t-tests showed no significant difference in the fiber reorientation parameter calculated experimentally with that calculated using an affine prediction. Thus, an affine prediction is a good approximation of fiber reorientation. The findings of this study add to the understanding of overall disc mechanical behavior and degeneration.
纤维环的倾斜板层结构对于其承重功能至关重要。这种纤维结构在施加负荷时的重新定向可能导致非线性力学行为以及拉伸模量的大幅增加。对于加载的未退变和退变纤维环组织，纤维重新定向尚未得到量化。本研究的目的是使用一种新的快速傅里叶变换（FFT）图像处理技术应用，来测量加载的外层纤维环组织的纤维重新定向和力学性能（趾部和线性区域模量、转变应变和泊松比）。在本研究中，该方法被验证可用于量化加载过程中环纤维的重新定向。我们假设纤维环纤维会在周向拉伸负荷下重新定向，并且纤维重新定向将是仿射的。此外，我们假设退变会影响纤维重新定向、趾部区域模量和泊松比。发现纤维环纤维会朝着加载方向重新定向，并且退变显著降低了纤维重新定向（纤维重新定向参数，非退变组织的m(FFT)= -1.70度/%应变，退变组织的为-0.95度/%应变）。趾部区域模量与年龄显著相关（r = 0.6）。配对t检验显示，实验计算得到的纤维重新定向参数与使用仿射预测计算得到的参数之间没有显著差异。因此，仿射预测是纤维重新定向的良好近似。本研究的结果有助于增进对椎间盘整体力学行为和退变的理解。
