Compared to the outer dura mater, the mechanical behavior of spinal pia and arachnoid meningeal layers has received very little attention in the literature. This is despite experimental evidence of their importance with respect to the overall spinal cord stiffness and recovery following compression. Accordingly, inclusion of the mechanical contribution of the pia and arachnoid maters would improve the predictive accuracy of finite element models of the spine, especially in the distribution of stresses and strain through the cord’s cross-section. However, to-date, only linearly elastic moduli for what has been previously identified as spinal pia mater is available in the literature. This study is the first to quantitatively compare the viscoelastic behavior of isolated spinal pia-arachnoid-complex, neural tissue of the spinal cord parenchyma, and intact construct of the two. The results show that while it only makes up 5.5% of the overall cross-sectional area, the thin membranes of the innermost meninges significantly affect both the elastic and viscous response of the intact construct. Without the contribution of the pia and arachnoid maters, the spinal cord has very little inherent stiffness and experiences significant relaxation when strained. The ability of the fitted non-linear viscoelastic material models of each condition to predict independent data within experimental variability supports their implementation into future finite element computational studies of the spine.

Statement of Significance

The neural tissue of the spinal cord is surrounded by three fibrous layers called meninges which are important in the behavior of the overall spinal-cord-meningeal construct. While the mechanical properties of the outermost layer have been reported, the pia mater and arachnoid mater have received considerably less attention. This study is the first to directly compare the behavior of the isolated neural tissue of the cord, the isolated pia-arachnoid complex, and the construct of these individual components. The results show that, despite being very thin, the inner meninges significantly affect the elastic and time-dependent response of the spinal cord, which may have important implications for studies of spinal cord injury.

中文翻译：

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脊髓和脑膜组织的粘弹性

与硬脑膜外层相比，脊椎小梁和蛛网膜脑膜层的力学行为在文献中很少受到关注。尽管有实验证据表明它们在总体脊髓刚度和压迫后恢复方面具有重要意义。因此，包括pia和蛛网膜的机械作用将改善脊柱有限元模型的预测准确性，尤其是在通过脊髓横断面的应力和应变分布方面。然而，迄今为止，文献中仅可获得对于先前已被确定为脊柱侧凸的线性弹性模量。这项研究是第一个定量比较孤立的脊髓pia-蛛网膜复合体，脊髓实质的神经组织的粘弹性行为的研究，和完整的两者的构造。结果表明，虽然它仅占总横截面面积的5.5％，但最里面的脑膜的薄膜会显着影响完整结构的弹性和粘性响应。没有脊椎和蛛网膜的作用，脊髓几乎没有固有的刚度，并且在拉紧时会出现明显的松弛。每个条件的拟合非线性粘弹性材料模型预测实验变异性内的独立数据的能力支持将其应用于未来的脊柱有限元计算研究中。最里面的脑膜的薄膜会显着影响完整结构的弹性和粘性响应。没有脊椎和蛛网膜的作用，脊髓几乎没有固有的刚度，并且在拉紧时会出现明显的松弛。每个条件的拟合非线性粘弹性材料模型预测实验变异性内的独立数据的能力支持将其应用于未来的脊柱有限元计算研究中。最里面的脑膜的薄膜会显着影响完整结构的弹性和粘性响应。没有脊椎和蛛网膜的作用，脊髓几乎没有固有的刚度，并且在拉紧时会出现明显的松弛。每个条件的拟合非线性粘弹性材料模型预测实验变异性内的独立数据的能力支持将其应用于未来的脊柱有限元计算研究中。

重要声明

脊髓的神经组织被三层称为脑膜的纤维层包围，这对整个脊髓-脑膜-脑膜结构的行为很重要。尽管已经报道了最外层的机械性能，但皮亚瘤和蛛网膜基质的关注度却大大降低。这项研究是第一个直接比较脐带的孤立神经组织，孤立的pia-蛛网膜复合物以及这些单个组件的结构的行为。结果表明，尽管内部脑膜非常薄，但仍会严重影响脊髓的弹性和时间依赖性反应，这可能对研究脊髓损伤具有重要意义。