Gao Yongchang, Fu Yantao, Cui Qingfeng, Chen Shibin, Liu Peng, Liu Xifang
National Engineering Laboratory for Highway Maintenance Equipment, Chang'an University, Xi'an 710064, P. R. China.
Honghui Hospital, Xi'an Jiaotong University, Xi'an 710054, P. R. China.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2025 Aug 25;42(4):799-807. doi: 10.7507/1001-5515.202310021.
The lumbar intervertebral disc exhibits a complex physiological structure with interactions between various segments, and its components are extremely complex. The material properties of different components in the lumbar intervertebral disc, especially the water content (undergoing dynamic change as influenced by age, degeneration, mechanical loading, and proteoglycan content) - critically determine its mechanical properties. When the lumbar intervertebral disc is under continuous pressure, water seeps out, and after the pressure is removed, water re-infiltrates. This dynamic fluid exchange process directly affects the mechanical properties of the lumbar intervertebral disc, while previous isotropic modeling methods have been unable to accurately reflect such solid-liquid phase behaviors. To explore the load-bearing mechanism of the lumbar intervertebral disc and establish a more realistic mechanical model of the lumbar intervertebral disc, this study developed a solid-liquid biphasic, fiber-reinforced finite element model. This model was used to simulate the four movements of the human lumbar spine in daily life, namely flexion, extension, axial rotation, and lateral bending. The fluid pressure, effective solid stress, and liquid pressure-bearing ratio of the annulus fibrosus and nucleus pulposus of different lumbar intervertebral discs were compared and analyzed under the movements. Under all the movements, the fluid pressure distribution was closer to the nucleus pulposus, while the effective solid stress distribution was more concentrated in the outer annulus fibrosus. In terms of fluid pressure, the maximum fluid pressure of the lumbar intervertebral disc during lateral bending was 1.95 MPa, significantly higher than the maximum fluid pressure under other movements. Meanwhile, the maximum effective solid stress of the lumbar intervertebral disc during flexion was 2.43 MPa, markedly higher than the maximum effective solid stress under other movements. Overall, the liquid pressure-bearing ratio under axial rotation was smaller than that under other movements. Based on the solid-liquid biphasic modeling method, this study more accurately revealed the dominant role of the liquid phase in the daily load-bearing process of the lumbar intervertebral disc and the solid-phase mechanical mechanism of the annulus fibrosus load-bearing, and more effectively predicted the solid-liquid phase co-load-bearing mechanism of the lumbar intervertebral disc in daily life.
腰椎间盘呈现出一种复杂的生理结构，各节段之间存在相互作用，其组成部分极其复杂。腰椎间盘不同组成部分的材料特性，尤其是含水量（受年龄、退变、机械负荷和蛋白聚糖含量影响而发生动态变化）—— 关键地决定了其力学性能。当腰椎间盘受到持续压力时，水分渗出，压力去除后，水分重新渗入。这种动态的流体交换过程直接影响腰椎间盘的力学性能，而以往的各向同性建模方法无法准确反映这种固液相行为。为了探究腰椎间盘的承载机制并建立更符合实际的腰椎间盘力学模型，本研究建立了一种固液双相、纤维增强有限元模型。该模型用于模拟人体腰椎在日常生活中的四种运动，即前屈、后伸、轴向旋转和侧屈。比较并分析了不同腰椎间盘在这些运动下纤维环和髓核的流体压力、有效固体应力以及液体承载率。在所有运动中，流体压力分布更靠近髓核，而有效固体应力分布更集中在纤维环外层。在流体压力方面，腰椎间盘在侧屈时的最大流体压力为1.95MPa，显著高于其他运动下的最大流体压力。同时，腰椎间盘在前屈时的最大有效固体应力为2.43MPa，明显高于其他运动下的最大有效固体应力。总体而言，轴向旋转时的液体承载率小于其他运动时的液体承载率。基于固液双相建模方法，本研究更准确地揭示了液相在腰椎间盘日常承载过程中的主导作用以及纤维环承载的固相力学机制，并更有效地预测了腰椎间盘在日常生活中的固液相共同承载机制。
