Tianjin Key Laboratory of Film Electronic and Communication Device, Tianjin University of Technology, Tianjin, China.
Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, Tianjin University of Technology, Tianjin, China.
Orthop Surg. 2020 Dec;12(6):1980-1989. doi: 10.1111/os.12847. Epub 2020 Nov 16.
To evaluate the strain-rate-dependent viscoelastic properties of the intervertebral disc by in vitro experiments.
The biomechanical experiments were conducted from September 2019 to December 2019. The lumbar spines of sheep were purchased within 4-6 hours from the local slaughterhouse, and the intervertebral disc samples were divided into three groups. In rupture group, the samples were used to test the mechanical behavior of the intervertebral disc rupture at different strain rates. In fatigue injury group, the samples were used to test the mechanical behavior of fatigue injury on the intervertebral disc under different strain rates. In internal displacement group, the samples were used to test the internal displacement distribution of the intervertebral disc at different strain rates by applying an optimized digital image correlation (DIC) technique.
Both the yielding and cracking phenomenon occurs at fast and medium loading rates, while only the yielding phenomenon occurs at a slow loading rate. The yield stress, compressive strength, and elastic modulus all increase with the increase of the strain rate, while the yield strain decreases with the increase of the strain rate. The logarithm of the elastic modulus in the intervertebral disc is approximately linear with the logarithm of the strain rate under different strain rates. Both before and after fatigue loading, the stiffness in the loading and unloading curves of the intervertebral disc is inconsistent, forming a hysteresis loop, which is caused by the viscoelastic effect. The strain rate has no significant effect on the internal displacement distribution of the intervertebral disc. Based on the experimental data, the constitutive relationship of the intervertebral disc at different strain rates is obtained. The fitting curves are well coupled with the experimental data, while the fitting parameters are approximately linear with the logarithm of the strain rate.
These experiments indicate that the strain rate has a significant effect on the mechanical behavior of the intervertebral disc rupture and fatigue injury, while the constitutive equation can predict the rate-dependent mechanical behavior of lumbar intervertebral disc under flexion very well. These results have important theoretical guiding significance for preventing lumbar disc herniation in daily life.
通过体外实验评估椎间盘的应变率相关粘弹性特性。
生物力学实验于 2019 年 9 月至 12 月进行。从当地屠宰场购买绵羊的腰椎，在 4-6 小时内将椎间盘样本分为三组。在破裂组中，样本用于测试不同应变速率下椎间盘破裂的力学行为。在疲劳损伤组中，样本用于测试不同应变速率下椎间盘疲劳损伤的力学行为。在内部位移组中，通过应用优化的数字图像相关（DIC）技术，样本用于测试不同应变速率下椎间盘的内部位移分布。
在快速和中速加载率下都会发生屈服和开裂现象，而在慢速加载率下只会发生屈服现象。屈服应力、压缩强度和弹性模量都随着应变率的增加而增加，而屈服应变则随着应变率的增加而减小。在不同应变率下，椎间盘的弹性模量的对数与应变率的对数大致呈线性关系。在疲劳加载前后，椎间盘在加载和卸载曲线上的刚度不一致，形成滞后环，这是由粘弹性效应引起的。应变率对椎间盘的内部位移分布没有显著影响。基于实验数据，获得了不同应变率下椎间盘的本构关系。拟合曲线与实验数据耦合良好，而拟合参数与应变率的对数大致呈线性关系。
这些实验表明，应变率对椎间盘破裂和疲劳损伤的力学行为有显著影响，而本构方程可以很好地预测弯曲状态下腰椎间盘的率相关力学行为。这些结果对日常生活中预防腰椎间盘突出症具有重要的理论指导意义。
