5122 Etcheverry Hall, Mechanical Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.
Biomech Model Mechanobiol. 2017 Dec;16(6):2005-2015. doi: 10.1007/s10237-017-0934-2. Epub 2017 Jul 21.
The intervertebral disc is a complex fibro-cartilaginous material, consisting of a pressurized nucleus pulposus surrounded by the annulus fibrosus, which has an angle-ply structure. Disc injury and degeneration are noted by significant changes in tissue structure and function, which significantly alters stress distribution and disc joint stiffness. Differences in fibre orientation are thought to contribute to changes in disc torsion mechanics. Therefore, the objective of this study was to evaluate the effect of collagen fibre orientation on internal disc mechanics under compression combined with axial rotation. We developed and validated a finite element model (FEM) to delineate changes in disc mechanics due to fibre orientation from differences in material properties. FEM simulations were performed with fibres oriented at [Formula: see text] throughout the disc (uniform by region and fibre layer). The initial model was validated by published experimental results for two load conditions, including [Formula: see text] axial compression and [Formula: see text] axial rotation. Once validated, fibre orientation was rotated by [Formula: see text] or [Formula: see text] towards the horizontal plane, resulting in a decrease in disc joint torsional stiffness. Furthermore, we observed that axial rotation caused a sinusoidal change in disc height and radial bulge, which may be beneficial for nutrient transport. In conclusion, including anatomically relevant fibre angles in disc joint FEMs is important for understanding stress distribution throughout the disc and will be important for understanding potential causes for disc injury. Future models will include regional differences in fibre orientation to better represent the fibre architecture of the native disc.
椎间盘是一种复杂的纤维软骨材料，由受压的髓核和纤维环组成，纤维环具有角向层结构。组织结构和功能的显著变化表明椎间盘损伤和退变，这显著改变了应力分布和椎间盘关节的刚度。纤维方向的差异被认为导致了椎间盘扭转力学的变化。因此，本研究的目的是评估在压缩和轴向旋转结合下，胶原纤维方向对椎间盘内部力学的影响。我们开发并验证了一个有限元模型（FEM），以从材料特性的差异中阐明纤维方向对椎间盘力学的影响。对纤维在整个椎间盘上以[Formula: see text]方向排列（区域和纤维层均匀）的模型进行了 FEM 模拟。初始模型通过两种载荷条件下的实验结果进行了验证，包括[Formula: see text]轴向压缩和[Formula: see text]轴向旋转。模型验证后，纤维方向以[Formula: see text]或[Formula: see text]旋转至水平平面，导致椎间盘关节扭转刚度降低。此外，我们观察到轴向旋转导致椎间盘高度和径向膨出呈正弦变化，这可能有利于营养物质的运输。总之，在椎间盘关节的 FEM 中包含解剖学上相关的纤维角度对于理解整个椎间盘的应力分布很重要，并且对于理解椎间盘损伤的潜在原因也很重要。未来的模型将包括纤维方向的区域差异，以更好地代表天然椎间盘的纤维结构。
