Fewster Kayla M, Barrett Jeff M, Callaghan Jack P
Department of Kinesiology, University of Waterloo, Waterloo, ON N2 L 3G1, Canada.
Faculty of Applied Health Science, Department of Kinesiology, University of Waterloo, Waterloo, ON N2 L 3G1, Canada.
J Biomech Eng. 2022 May 1;144(5). doi: 10.1115/1.4054022.
The facet capsule ligament (FCL) is a structure in the lumbar spine that constrains motions of the vertebrae. Subfailure loads can produce microdamage resulting in increased laxity, decreased stiffness, and altered viscoelastic responses. Therefore, the purpose of this investigation was to determine the mechanical and viscoelastic properties of the FCL under various magnitudes of strain from control samples and samples that had been through an impact protocol. Two hundred FCL tissue samples were tested (20 control and 180 impacted). Impacted FCL tissue samples were obtained from functional spinal units that had been exposed to one of nine subfailure impact conditions. All specimens underwent the following loading protocol: preconditioning with five cycles of 5% strain, followed by a 30 s rest period, five cycles of 10% strain, and 1 cycle of 10% strain with a hold duration at 10% strain for 240 s (4 min). The same protocol was followed for 30% and 50% strain. Measures of stiffness, hysteresis, and force-relaxation were computed. No significant differences in stiffness were observed for impacted specimens in comparison to control. Impacted specimens from the 8 g flexed and 11 g flexed and neutral conditions exhibited greater hysteresis during the cyclic-30% and cyclic-50% portion of the protocol in comparison to controls. In addition, specimens from the 8 g and 11 g flexed conditions resulted in greater stress decay for the 50%-hold conditions. Results from this study demonstrate viscoelastic changes in FCL samples exposed to moderate and highspeed single impacts in a flexed posture.
小关节囊韧带（FCL）是腰椎中的一种结构，可限制椎体的运动。亚失效负荷会产生微损伤，导致松弛度增加、刚度降低和粘弹性反应改变。因此，本研究的目的是确定来自对照样本和经过冲击试验的样本在不同应变幅度下FCL的力学和粘弹性特性。对200个FCL组织样本进行了测试（20个对照样本和180个受冲击样本）。受冲击的FCL组织样本取自暴露于九种亚失效冲击条件之一的功能性脊柱单元。所有样本均接受以下加载方案：先以5%应变进行五个循环的预加载，随后休息30秒，再以10%应变进行五个循环，然后以10%应变进行一个循环，并在10%应变下保持240秒（4分钟）。对30%和50%应变采用相同方案。计算了刚度、滞后和力松弛的测量值。与对照相比，受冲击样本的刚度未观察到显著差异。与对照相比，来自8g屈曲、11g屈曲和中立条件的受冲击样本在方案的30%循环和50%循环部分表现出更大的滞后。此外，来自8g和11g屈曲条件的样本在50%保持条件下导致更大的应力衰减。本研究结果表明，处于屈曲姿势的FCL样本在受到中高速单次冲击后会发生粘弹性变化。
