Micromechanics of diffuse axonal injury: influence of axonal orientation and anisotropy
Micromechanics of diffuse axonal injury: influence of axonal orientation and anisotropy
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DOI：
10.1007/s10237-010-0243-5
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发表时间：
2011-06-01
影响因子：
3.5
通讯作者：
Geers, M. G. D.
中科院分区：
文献类型：
--
作者：
Cloots, R. J. H.;van Dommelen, J. A. W.;Geers, M. G. D.
创伤性脑损伤的发展涉及多个长度尺度，其中头部水平的整体力学是脑细胞局部生理损伤的原因。在这项研究中，在组织水平和细胞水平的力学状态之间的关系建立。已经开发了基于局部轴突损伤的病理学观察的模型。该模型包含围绕障碍物的轴突（例如，血管或脑索马）。轴突，这是由各向异性纤维增强材料模型描述，有几个物理上不同的方向。模拟的结果显示轴突应变高于所施加的最大主组织应变。对于具有相对刚性夹杂物的各向异性脑组织，相对对数应变增加超过60%。此外，可以得出结论，在特定位点处远离主要轴突方向取向的单个轴突可以在应力驱动过程中经受甚至更高的轴突应变，例如，由大脑中的惯性力引起。这些轴突可以具有在加载方向的整个范围上在主轴突方向上的轴突的最大对数应变的约2.5倍的对数应变。结果表明，细胞水平的异质性有一个重要的影响轴突应变，导致方向和位置依赖的敏感性的组织机械负荷。因此，在依赖有限元股骨头模型的损伤评估中应考虑这些影响。
Multiple length scales are involved in the development of traumatic brain injury, where the global mechanics of the head level are responsible for local physiological impairment of brain cells. In this study, a relation between the mechanical state at the tissue level and the cellular level is established. A model has been developed that is based on pathological observations of local axonal injury. The model contains axons surrounding an obstacle (e.g., a blood vessel or a brain soma). The axons, which are described by an anisotropic fiber-reinforced material model, have several physically different orientations. The results of the simulations reveal axonal strains being higher than the applied maximum principal tissue strain. For anisotropic brain tissue with a relatively stiff inclusion, the relative logarithmic strain increase is above 60%. Furthermore, it is concluded that individual axons oriented away from the main axonal direction at a specific site can be subjected to even higher axonal strains in a stress-driven process, e.g., invoked by inertial forces in the brain. These axons can have a logarithmic strain of about 2.5 times the maximum logarithmic strain of the axons in the main axonal direction over the complete range of loading directions. The results indicate that cellular level heterogeneities have an important influence on the axonal strain, leading to an orientation and location-dependent sensitivity of the tissue to mechanical loads. Therefore, these effects should be accounted for in injury assessments relying on finite element head models.