Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China; Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China; Biomechanics and Biotechnology Lab, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057, China.
China United Engineering Corporation, China.
Clin Biomech (Bristol). 2022 Aug;98:105738. doi: 10.1016/j.clinbiomech.2022.105738. Epub 2022 Aug 12.
Recently, more and more people suffer from low back pain triggered by lumbar degenerative disc disease. The mechanical factor is one of the most significant causes of disc degeneration. This study aims to explore the biomechanical responses of the intervertebral disc, and investigate the process of disc injury by the theory of continuum damage mechanics.
A finite element model of the L4-L5 lumbar spine was developed and validated. The model not only considered changes in permeability coefficient with strain, but also included physiological factors such as osmotic pressure. Three loading conditions were simulated: (A) static loads, (B) vibration loads, (C) injury process.
The simulation results revealed that the facet joints shared massive stresses of the intervertebral discs, and prevented excessive lumbar spine movement. However, their asymmetrical position may have led to degeneration. The von Mises stress and pore pressure of annulus fibrosus showed significantly different trends under static loads and vibration loads. The von Mises stress of nucleus pulposus was not sensitive to vibration loads, but its pore pressure was conspicuously influenced by vibration loads. The injury first appeared at the posterior centre, and then, it gradually expanded along the edge of the intervertebral disc. With an increase in the loading steps, the damage rate of the intervertebral disc increased logarithmically.
The variation in the biomechanical performance of the intervertebral disc could be attributed to the periodic movement of internal fluids. This study might be helpful for understanding the mechanism of intervertebral disc degeneration.
近来，越来越多的人因腰椎退行性椎间盘疾病引发腰痛。力学因素是椎间盘退变的最重要原因之一。本研究旨在通过连续介质损伤力学理论探索椎间盘的生物力学响应，并研究椎间盘损伤的过程。
建立并验证了 L4-L5 腰椎的有限元模型。该模型不仅考虑了渗透系数随应变的变化，还包括渗透压等生理因素。模拟了三种加载条件：（A）静态载荷，（B）振动载荷，（C）损伤过程。
模拟结果表明关节突关节分担了椎间盘的大部分应力，防止了腰椎过度运动。然而，它们不对称的位置可能导致了退化。在静态载荷和振动载荷下，纤维环的 von Mises 应力和孔隙压力表现出明显不同的趋势。核髓的 von Mises 应力对振动载荷不敏感，但孔隙压力受振动载荷的显著影响。损伤首先出现在后中心，然后逐渐沿椎间盘边缘扩展。随着加载步骤的增加，椎间盘的损伤率呈对数增加。
椎间盘生物力学性能的变化可能归因于内部流体的周期性运动。本研究可能有助于理解椎间盘退变的机制。
