Mengoni Marlène, Luxmoore Bethany J, Wijayathunga Vithanage N, Jones Alison C, Broom Neil D, Wilcox Ruth K
Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK.
University of Leeds, UK.
J Mech Behav Biomed Mater. 2015 Aug;48:164-172. doi: 10.1016/j.jmbbm.2015.03.028. Epub 2015 Apr 13.
The inter-lamellar connectivity of the annulus fibrosus in the intervertebral disc has been shown to affect the prediction of the overall disc behaviour in computational models. Using a combined experimental and computational approach, the inter-lamellar mechanical behaviour of the disc annulus was investigated under conditions of radial loading. Twenty-seven specimens of anterior annulus fibrosus were dissected from 12 discs taken from four frozen ovine thoracolumbar spines. Specimens were grouped depending on their radial provenance within the annulus fibrosus. Standard tensile tests were performed. In addition, micro-tensile tests under microscopy were used to observe the displacement of the lamellae and inter-lamellar connections. Finite elements models matching the experimental protocols were developed with specimen-specific geometries and boundary conditions assuming a known lamellar behaviour. An optimisation process was used to derive the interface stiffness values for each group. The assumption of a linear cohesive interface was used to model the behaviour of the inter-lamellar connectivity. The interface stiffness values derived from the optimisation process were consistently higher than the corresponding lamellar values. The interface stiffness values of the outer annulus were from 43% to 75% higher than those of the inner annulus. Tangential stiffness values for the interface were from 6% to 39% higher than normal stiffness values within each group and similar to values reported by other investigators. These results reflect the intricate fibrous nature of the inter-lamellar connectivity and provide values for the representation of the inter-lamellar behaviour at a continuum level.
椎间盘纤维环的层间连接已被证明会影响计算模型中对整个椎间盘行为的预测。采用实验与计算相结合的方法，研究了在径向加载条件下椎间盘纤维环的层间力学行为。从取自四只冷冻绵羊胸腰椎的12个椎间盘中解剖出27个前纤维环标本。标本根据其在纤维环内的径向来源进行分组。进行了标准拉伸试验。此外，还采用显微镜下的微拉伸试验来观察薄片和层间连接的位移。开发了与实验方案相匹配的有限元模型，其具有特定于标本的几何形状和边界条件，并假设薄片行为已知。使用优化过程来推导每组的界面刚度值。采用线性粘结界面的假设来模拟层间连接的行为。从优化过程中得出的界面刚度值始终高于相应的薄片值。外环的界面刚度值比内环高43%至75%。每组中界面的切向刚度值比法向刚度值高6%至39%，与其他研究者报告的值相似。这些结果反映了层间连接复杂的纤维性质，并为在连续水平上表示层间行为提供了数值。
