MacManus David B, Pierrat Baptiste, Murphy Jeremiah G, Gilchrist Michael D
School of Mechanical & Materials Engineering, University College Dublin, Dublin, Ireland.
Department of Mechanical & Manufacturing Engineering, Dublin City University, Dublin, Ireland.
Acta Biomater. 2017 Jul 15;57:384-394. doi: 10.1016/j.actbio.2017.05.022. Epub 2017 May 10.
Traumatic brain injury (TBI) has become a recent focus of biomedical research with a growing international effort targeting material characterization of brain tissue and simulations of trauma using computer models of the head and brain to try to elucidate the mechanisms and pathogenesis of TBI. The meninges, a collagenous protective tri-layer, which encloses the entire brain and spinal cord has been largely overlooked in these material characterization studies. This has resulted in a lack of accurate constitutive data for the cranial meninges, particularly under dynamic conditions such as those experienced during head impacts. The work presented here addresses this lack of data by providing for the first time, in situ large deformation material properties of the porcine dura-arachnoid mater composite under dynamic indentation. It is demonstrated that this tissue is substantially stiffer (shear modulus, μ=19.10±8.55kPa) and relaxes at a slower rate (τ=0.034±0.008s, τ=0.336±0.077s) than the underlying brain tissue (μ=6.97±2.26kPa, τ=0.021±0.007s, τ=0.199±0.036s), reducing the magnitudes of stress by 250% and 65% for strains that arise during indentation-type deformations in adolescent brains.
We present the first mechanical analysis of the protective capacity of the cranial meninges using in situ micro-indentation techniques. Force-relaxation tests are performed on in situ meninges and cortex tissue, under large strain dynamic micro-indentation. A quasi-linear viscoelastic model is used subsequently, providing time-dependent mechanical properties of these neural tissues under loading conditions comparable to what is experienced in TBI. The reported data highlights the large differences in mechanical properties between these two tissues. Finite element simulations of the indentation experiments are also performed to investigate the protective capacity of the meninges. These simulations show that the meninges protect the underlying brain tissue by reducing the overall magnitude of stress by 250% and up to 65% for strains.
创伤性脑损伤（TBI）已成为生物医学研究的一个近期焦点，国际上越来越多的努力旨在对脑组织进行材料特性表征，并使用头部和大脑的计算机模型模拟创伤，以试图阐明TBI的机制和发病原理。脑膜是一层包裹整个大脑和脊髓的胶原质保护三层膜，在这些材料特性研究中很大程度上被忽视了。这导致缺乏关于颅脑膜的准确本构数据，尤其是在诸如头部撞击时所经历的动态条件下。本文所展示的工作通过首次提供猪硬脑膜 - 蛛网膜复合体在动态压痕下的原位大变形材料特性，解决了这一数据缺失问题。结果表明，与下层脑组织（剪切模量，μ = 6.97±2.26kPa，τ = 0.021±0.007s，τ = 0.199±0.036s）相比，该组织明显更硬（μ = 19.10±8.55kPa）且松弛速率更慢（τ = 0.034±0.008s，τ = 0.336±0.077s），在青少年大脑压痕型变形过程中产生的应变下，应力大小分别降低了250%和65%。
我们使用原位微压痕技术首次对颅脑膜的保护能力进行了力学分析。在大应变动态微压痕下对原位脑膜和皮质组织进行了力松弛测试。随后使用准线性粘弹性模型，提供了这些神经组织在与TBI中所经历的加载条件相当的情况下的时间相关力学特性。所报告的数据突出了这两种组织在力学特性上的巨大差异。还进行了压痕实验的有限元模拟，以研究脑膜的保护能力。这些模拟表明，脑膜通过将应变下的应力总体大小降低250%以及高达65%来保护下层脑组织。
