Arbogast K B, Margulies S S
Department of Bioengineering, University of Pennsylvania, Philadelphia, USA.
J Biomech. 1999 Aug;32(8):865-70. doi: 10.1016/s0021-9290(99)00042-1.
Brainstem trauma occurs frequently in severe head injury, often resulting in fatal lesions due to importance of brainstem in crucial neural functions. Structurally, the brainstem is composed of bundles of axonal fibers distinctly oriented in a longitudinal direction surrounded by an extracellular matrix. We hypothesize that the oriented structure and architecture of the brainstem dictates this mechanical response and results in its selective vulnerability in rotational loading. In order to understand the relationship between the biologic architecture and the mechanical response and provide further insight into the high vulnerability of this region, a structural and mathematical model was created. A fiber-reinforced composite model composed of viscoelastic fibers surrounded by a viscoelastic matrix was used to relate the biological architecture of the brainstem to its anisotropic mechanical response. Relevant model parameters measured include the brainstem's composite complex moduli and relative fraction of matrix and fiber. The model predicted that the fiber component is three times stiffer and more viscous than the matrix. The fiber modulus predictions were compared with experimental tissue measurements. The optic nerve, a bundle of tightly packed longitudinally arranged myelinated fibers with little matrix, served as a surrogate for the brainstem fiber component. Model predictions agreed with experimental measures, offering a validation of the model. This approach provided an understanding of the relationship between the specific biologic architecture of the brainstem and the anisotropic mechanical response and allowed insight into reasons for the selective vulnerability of this region in rotational head injury.
脑干创伤在严重颅脑损伤中经常发生，由于脑干在关键神经功能中的重要性，往往会导致致命性损伤。在结构上，脑干由沿纵向明显排列的轴突纤维束组成，周围环绕着细胞外基质。我们假设脑干的定向结构和构造决定了这种力学反应，并导致其在旋转负荷下具有选择性易损性。为了理解生物构造与力学反应之间的关系，并进一步深入了解该区域的高易损性，创建了一个结构和数学模型。使用由粘弹性纤维包围在粘弹性基质中的纤维增强复合材料模型，将脑干的生物构造与其各向异性力学反应联系起来。测量的相关模型参数包括脑干的复合复数模量以及基质和纤维的相对比例。该模型预测，纤维成分的硬度和粘性是基质的三倍。将纤维模量预测结果与实验组织测量结果进行了比较。视神经是一束紧密排列的纵向排列的有髓纤维，几乎没有基质，用作脑干纤维成分的替代物。模型预测与实验测量结果一致，为模型提供了验证。这种方法有助于理解脑干特定生物构造与各向异性力学反应之间的关系，并能够深入了解该区域在旋转性头部损伤中具有选择性易损性的原因。
