Nikkhoo Mohammad, Wang Jaw-Lin, Parnianpour Mohamad, El-Rich Marwan, Khalaf Kinda
Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
Institute of Biomedical Engineering, College of Medicine and Engineering, National Taiwan University, Taipei, Taiwan, ROC.
J Biomech. 2018 Mar 21;70:26-32. doi: 10.1016/j.jbiomech.2018.01.026. Epub 2018 Jan 31.
Understanding the effect of impact loading on the mechanical response of the intervertebral disc (IVD) is valuable for investigating injury mechanisms and devising effective therapeutic modalities. This study used 24 porcine thoracic motion segments to characterize the mechanical response of intact (N = 8), degenerated (Trypsin-denatured, N = 8), and repaired (Genepin-treated, N = 8) IVDs subject to impact loading. A meta-model analysis of poroelastic finite element simulations was used in combination with ex-vivo creep and impact tests to extract the material properties. Forward analyses using updated specimen-specific FE models were performed to evaluate the effect of impact duration. The maximum axial stress in the IVDs, Von-Mises stress in the endplates, and intradiscal pore pressure (IDP) were calculated, under a 400 N preload, subject to a sequence of impact loads for 10 impact durations (10-100 ms). The results were in good agreement with both creep and impact experiments (error < 10%). A significant difference was found in the maximum axial stress between the intact and degenerated disc groups. The IDP was also significantly lower in the degenerated disc group. The Von Mises stress in the adjacent endplates significantly increased with degeneration. It is concluded that the disc time-dependent response significantly changes with disc degeneration. Cross-linker Genipin has the potential to recover the hydraulic permeability and can potentially change the time dependent response, particularly in the IDP. This is the first study, to our best knowledge, which explores the effect of impact loading on the healthy, degenerated and repaired IVD using both creep and impact validation tests.
了解冲击载荷对椎间盘（IVD）力学响应的影响，对于研究损伤机制和设计有效的治疗方法具有重要价值。本研究使用24个猪胸椎运动节段，来表征完整（N = 8）、退变（胰蛋白酶变性，N = 8）和修复（京尼平处理，N = 8）的IVD在冲击载荷作用下的力学响应。将多孔弹性有限元模拟的元模型分析与体外蠕变和冲击试验相结合，以提取材料特性。使用更新后的特定标本有限元模型进行正向分析，以评估冲击持续时间的影响。在400 N预载荷下，对IVD施加一系列冲击载荷，持续10个冲击持续时间（10 - 100 ms），计算IVD中的最大轴向应力、终板中的冯·米塞斯应力和椎间盘内孔隙压力（IDP）。结果与蠕变和冲击实验结果吻合良好（误差<10%）。完整椎间盘组和退变椎间盘组的最大轴向应力存在显著差异。退变椎间盘组的IDP也显著较低。相邻终板中的冯·米塞斯应力随退变显著增加。得出的结论是，椎间盘的时间依赖性响应随椎间盘退变而显著变化。交联剂京尼平有可能恢复水力渗透率，并有可能改变时间依赖性响应，特别是在IDP方面。据我们所知，这是第一项同时使用蠕变和冲击验证试验来探究冲击载荷对健康、退变和修复的IVD影响的研究。
