额、枕部直接冲击导致脑挫裂伤的力学机制研究

目的 分析额、枕部直接冲击时脑组织的应力响应，探讨颅脑直接冲击导致脑挫裂伤的力学机制。方法 利用头颅三维有限元模型，模拟计算8个不同方向额、枕部冲击载荷下脑组织应力应变响应，图形输出脑表面应力计算结果，分析不同载荷下，脑组织应力改变范围及大小，总结脑挫裂伤致伤机制。结果 直接冲击作用于顶颅时，其造成冲击方向上脑表面von Mises应力升高，这包括冲击对侧脑的表面。上述计算结果与临床额、枕部冲击伤的影像学发现相一致。背向前、中颅底或枕部后颅窝骨壁的冲击可造成相应区域脑表面应力显著升高。结论 由于颅骨、脑组织材料特性不同，在冲击中的两者变形不一致，即颅骨先变形先停止，脑组织后变形后停止，这造成颅骨与脑组织在冲击方向上发生显著相对位移，导致脑表面应力改变，当应力改变超过脑组织耐受时出现脑挫裂伤。这是脑挫裂伤的一种致伤机制。

Mechanics study of brain contusion and laceration by direct head impact on the frontal or occipital region

Objective To analysis the stress response of brain at the moment of direct frontal or occipital impact and discuss the mechanics mechanism of causing the brain contusion and laceration by the direct impact. Methods Using a three-dimensional finite element model, the stress response of brain tissue at the moment of frontal and occipital direct impacts from 8 different directions was studied. The results were exhibited in diagrams so as to analyze the stress limits and investigate the mechanics mechanism of leading to brain contusion and laceration. Results The areas of von Mises stress change of brain surface compared favorably with clinical imaging findings in frontal or occipital impact: In vertex , they agree with impact direction , or they are in contralateral brain surface. If the impact direction were perpendicular to anterior or middle skull base or occipital squama, the brain surfaces in those areas also suffer great stress. Conclusion Under a direct head impact, the distortion of skull and brain are not isochronous, that is, skull distortion happened earlier and stopped earlier than that of brain, which is remarkable in the impact direction. That may be the cause of brain surface stress change and can be used to explain the mechanisms of brain contusion and laceration.