While few studies have improved our understanding of composition and organization of elastic fibres in the inter-lamellar matrix (ILM), its clinical relevance is not fully understood. Moreover, no studies have measured the direct tensile and shear failure and viscoelastic properties of the ILM. Therefore, the aim of this study was, for the first time, to measure the viscoelastic and failure properties of the ILM in both the tension and shear directions of loading. Using an ovine model, isolated ILM samples were stretched to 40% of their initial length at three strain rates of 0.1%s^-1 (slow), 1%s^-1 (medium) and 10%s^-1 (fast) and a ramp test to failure was performed at a strain rate of 10%s^-1. The findings from this study identified that the stiffness of the ILM was significantly larger at faster strain rates, and energy absorption significantly smaller, compared to slower strain rates, and the viscoelastic and failure properties were not significantly different under tension and shear loading. We found a strain rate dependent response of the ILM during dynamic loading, particularly at the fastest rate. The ILM demonstrated a significantly higher capability for energy absorption at slow strain rates compared to medium and fast strain rates. A significant increase in modulus was found in both loading directions and all strain rates, having a trend of larger modulus in tension and at faster strain rates. The finding of no significant difference in failure properties in both loading directions, was consistent with our previous ultra-structural studies that revealed a well-organized (±45°) elastic fibre orientation in the ILM. The results from this study can be used to develop and validate finite element models of the AF at the tissue scale, as well as providing new strategies for fabricating tissue engineered scaffolds.

Statement of significance

While few studies have improved our understanding of composition and organization of elastic fibres in the inter-lamellar matrix (ILM) of the annulus in the disc no studies have measured the direct mechanical failure and viscoelastic properties of the ILM. The findings from this study identified that the stiffness of the ILM was significantly larger at faster strain rates, and energy absorption significantly smaller, compared to slower strain rates. The failure properties of the ILM were not significantly different under tension and shear.

中文翻译：

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新发现证实了椎间盘纤维环的层间基质在径向和周向载荷方向上的粘弹性行为

尽管很少有研究改善我们对层间基质（ILM）中弹性纤维的组成和组织的了解，但其临床相关性尚未得到充分了解。此外，还没有研究测量ILM的直接拉伸和剪切破坏以及粘弹性。因此，这项研究的目的是第一次在载荷的拉伸和剪切方向上测量ILM的粘弹性和破坏特性。使用绵羊模型，将分离的ILM样品以0.1％s ^-1（慢），1％s ^-1（中）和10％s ^-1（快）的三种应变率拉伸至初始长度的40％。以10％s ^-1的应变速率进行失效的斜坡测试。这项研究的发现表明，与较慢的应变速率相比，ILM的刚度在较快的应变速率下显着较大，并且能量吸收显着较小，并且在拉伸和剪切载荷作用下，粘弹性和破坏特性没有显着差异。我们发现了动态加载过程中ILM的应变速率相关响应，尤其是在最快速率下。与中等应变速率和快速应变速率相比，ILM在慢应变速率下表现出明显更高的能量吸收能力。发现在加载方向和所有应变率下模量均显着增加，具有在拉伸模量较大且应变速率较快的趋势。发现在两个加载方向上的失效特性没有显着差异，与我们先前的超结构研究一致，该研究揭示了ILM中组织良好的（±45°）弹性纤维取向。这项研究的结果可用于在组织规模上开发和验证房颤的有限元模型，以及为制造组织工程支架提供新的策略。

重要声明

尽管很少有研究改善了我们对椎间盘瓣环片层间基质（ILM）中弹性纤维的组成和组织的了解，但尚无研究测量ILM的直接机械破坏和粘弹性质。这项研究的发现表明，与较慢的应变速率相比，ILM的刚度在较快的应变速率下明显更大，而能量吸收则明显较小。在拉伸和剪切作用下，ILM的破坏特性没有显着差异。