Material characterization of the brainstem from oscillatory shear tests
Material characterization of the brainstem from oscillatory shear tests
复制标题
DOI：
10.1016/s0021-9290(98)00068-2
复制
发表时间：
1998-09-01
影响因子：
2.4
通讯作者：
Margulies, SS
中科院分区：
文献类型：
--
作者：
Arbogast, KB;Margulies, SS
当脑-颅复合体经历损伤性负荷时，特别是在产生弥漫性轴索损伤（DAI）的创伤情况下，经常发生脑干的创伤性损伤。DAI已被证明是依赖于负载方向和相关的区域组织变形响应旋转惯性负载。脑干的选择性脆弱性的可能机制是（1）中枢神经系统的几何形状负责在这些区域产生高组织应变，（2）整体材料刚度的区域差异导致这些部位的较大变形，以及（3）这些区域的各向异性机械特性导致对旋转载荷方向和幅度的敏感性。本文通过对成年猪脑干进行三个相互垂直方向的振荡剪切实验，计算了三个峰值应变水平（2.5%，5.0%，7.5%）下频率范围（20-200 Hz）内的复合剪切模量。方向数据表明，脑干表现出显着的横观各向同性的行为。这两个组件的复杂的模量，其中轴突纤维的方向平行于剪切平面，但横向剪切方向显着高于其他两个，相互不可区分的测试情况下，在整个测试的应变范围。通过与对脑组织的类似测试进行比较，这些数据表明脑干显示出更僵硬的生物力学反应。这些差异存在于复合剪切模量的两个分量中，并且随着施加的应变的大小增加而增大。脑干的区域刚度和各向异性反应与其作为CNS区域之间的狭窄桥梁的位置相互作用，导致该区域在旋转负载中的选择性脆弱性。(C)1998爱思唯尔科技有限公司版权所有。
Traumatic damage to the brainstem occurs frequently when the brain-skull complex experiences injurious loading especially during those traumatic situations that produce diffuse axonal injury (DAI). DAI has been shown to be dependent on load direction and correlated with regional tissue deformation in response to rotational inertial loads. Possible mechanisms for the selective vulnerability of the brainstem are (1) the geometry of the central nervous system is responsible for producing high tissue strains in these regions, (2) regional differences in overall material stiffness result in larger deformations at these sites, and (3) the anisotropic mechanical properties of these regions lead to a sensitivity to the rotational load direction and magnitude. This paper investigates the latter two hypotheses by performing oscillatory shear tests on adult porcine brainstem in three mutually perpendicular directions.The complex shear moduli were calculated over a range of frequencies (20-200 Hz), for three levels of peak engineering strain (2.5%, 5.0%, and 7.5%). The directional data demonstrated that the brainstem exhibits significant transversely isotropic behavior. Both components of the complex modulus in which the axonal fibers are oriented parallel to the plane of shear but transverse to the shear direction were significantly higher than those of the other two, mutually indistinguishable test cases across the range of strains tested. By comparison with similar tests on cerebral tissue, these data demonstrated that the brainstem displays a stiffer biomechanical response. These differences were present for both components of the complex shear modulus and were greater as the magnitude of the applied strain increased. The regional stiffness and anisotropic response of the brainstem coupled with its location as a narrow bridge between CNS regions interact to result in the selective vulnerability of this region in rotational loading. (C) 1998 Elsevier Science Ltd. All rights reserved.