Matsui Yasuhiro, Nishimoto Tetsuya
National Traffic Safety and Environment Laboratory, Japan.
Stapp Car Crash J. 2010 Nov;54:197-210. doi: 10.4271/2010-22-0010.
The number of traffic deaths in Japan was 4,914 in 2009. Since the head was the most common site of injury in traffic accidents (2,302, 47%), traumatic brain injury causes the fatalities in these accidents. The aim of the present study was to quantify micro injuries in the animal brain for gaining insight and understanding of the human brain injury tolerance. Using porcine brain matter, in vitro stress relaxation experiments and in vivo impact experiments were conducted. In both experiments, the distribution of the damage ratio of the transverse to longitudinal length of cells, hereafter, referred to as an aspect ratio, in the brain matter under loading was examined. In the in vitro stress relaxation experiments, specimens were compressed vertically with a compression velocity of 1 mm/s, and the displacement was held for 140 sec when the compression strain reached the target strain. In the experiments, there were five categories of compression strain: 10, 20, 30, 40, and 50 percent. Regarding the aspect ratio of the cell body, it was 1.5 or less in a no-load condition. On the other hand, it was observed to be greater than 1.5 in the results from the experiments if the compression strain was 30% or more. The results from the experiments show that a compression strain between 20% and 30% corresponds to the threshold for the extremely deformed cell at the micro level. In the in vivo impact experiments, pigs in an unconscious state were exposed through craniotomy, and their exposed brains were hit with a ram at a low speed of 3.3 m/s and a high speed of 7.2 m/s, respectively. It was revealed that the number of cells in which the aspect ratio was greater than 1.5 increased if the impact is provided under the high speed. At the same time, the results indicated that cell deformation was dependent on the ram velocity in the brain matter. Thus, the compression strain on the entire brain from the direction of the force applied to the brain may be one criterion for assessment of brain damage.
2009年日本交通事故死亡人数为4914人。由于头部是交通事故中最常见的受伤部位（2302人，占47%），创伤性脑损伤导致了这些事故中的死亡。本研究的目的是量化动物大脑中的微观损伤，以深入了解和认识人类大脑的损伤耐受性。使用猪脑组织进行了体外应力松弛实验和体内冲击实验。在这两个实验中，均检测了加载状态下脑组织中细胞横向与纵向长度的损伤率分布，以下简称纵横比。在体外应力松弛实验中，以1mm/s的压缩速度垂直压缩标本，当压缩应变达到目标应变时，位移保持140秒。实验中有五类压缩应变：10%、20%、30%、40%和50%。关于细胞体的纵横比，在无负载条件下为1.5或更小。另一方面，实验结果表明，如果压缩应变达到30%或更高，则纵横比大于1.5。实验结果表明，20%至30%的压缩应变对应于微观层面细胞极度变形的阈值。在体内冲击实验中，对处于无意识状态的猪进行开颅手术，然后分别以3.3m/s的低速和7.2m/s的高速用撞锤撞击其暴露的大脑。结果显示，如果在高速冲击下，纵横比大于1.5的细胞数量会增加。同时，结果表明细胞变形取决于脑组织中的撞锤速度。因此，从施加于大脑的力的方向对整个大脑产生的压缩应变可能是评估脑损伤的一个标准。
