張 月琳

屋内での転倒により頭部外傷が引き起こされる事故が数多く報告されている。本研究は数値シミュレーションを用いて、転倒により引き起こされる頭部外傷に対して絨毯の保護効果を定量的に明確にすることを目的とした。本研究では、4 つの転倒姿勢を想定しヒト全身数値モデルを用いて頭部が床面に衝突した時の全身挙動を再現した。次に、頭 部に作用した外力を頭部有限要素モデルに入力し、力学的応答を計算し、骨折、脳挫傷、脳震盪の発症リスクを算出し比較した。床面は、フローリングのみ、絨毯とフローリング、アンダーフェルトと絨毯の3 種類とした。頭部外傷発症リスクは、フローリングのみが最も高く、アンダーフェルトと絨毯の組み合わせを使用した場合が最も低かった。よって、 クッション性の高い絨毯は保護性能が高く、絨毯は頭部外傷の発症率を低減させる効果のあることが判明した。

屋内での転倒により引き起こされる頭部外傷事故が数多く報告されている。本研究は数値シミュレーションを用いて、転倒により引き起こされる頭部外傷に対してヘッドバンドの防護効果を定量的に評価した。まずヒト全身数値モデルを用いて転倒動作を再現し、その内の衝突部位が前頭部、側頭部、頭頂部、後頭部になるケースよりそれぞれ1 ケースを選定した。選定された4 つのケースにおいて、頭部有限要素モデルを用いてタイルと木製フローリングの2 種類の床面を想定して、ヘッドバンドなしとヘッドバンドありの2つの場合での頭部と地面の衝突時の挙動を再現し、頭部の力学的応答を計算した。これらの値を基に、骨折、脳挫傷、脳震盪の発症リスクを算出し比較した。その結果、転倒姿勢や床の種類により防護効果に差があるが、総じて、各種の頭部外傷発症リスクは低くなり、ヘッドバンドは防護効果があることが示された。

<p> The aim of this study is to visualize Judo accident using the reconstruction analysis for the medical field, and propose an injury risk assessment system based on detailed statistical analysis of the past cases for calling medical field's attention. In the assessment system, the mechanical input caused by the accident is obtained from replication of the motion called as Waza in Judo based on game video by using whole body numerical simulation, then the obtained acceleration response of the head was input to a human head finite element model to evaluate the injury risk by using the calculated mechanical parameter inside the skull. In this study, the replicated motion based on the video was verified by comparing the movement loci of the player's head analyzed by a three-dimensional motion analysis system experimentally. In this paper, two concussion suspected accident cases were analyzed by using the purposed evaluation system, and the concussion was evaluated by seven mechanical parameters generated inside the skull caused by the collision. The injury risk evaluated by the parameters belonged to the dangerous range that may cause concussion. The brain injury risk can be successfully estimated by the reconstructed simulation of the game video and FE analysis.</p>

Diffuse axonal injury (DAI), a major component of traumatic brain injury, has been suggested to result from inertial forces applied on the head. DAI is a manifestation of microstructural cellular trauma and is accompanied by distinct morphological changes. Focal axonal swellings are the morphological hallmarks of DAI pathology and lead to the disconnection of neurons from target tissues resulting in neuronal death. Our goal is the understanding of the quantitative relation between strain acting on the axons and generation of axonal swellings. In present study, we developed an in vitro two dimensional stretch device that reproduced axonal swellings of in vivo DAI, and verified the input-output relation of the device. Then using this device, we exposed PC12 cells, which extend structurally axon-like cylindrical protrusions in culture, to 10% or 20% strains and measured the length of neurites and number of swellings in PC12 cells until 48 hours after the exposure to stretch by microscope observation. As a result, the length of neurites transiently shortened at 5 minutes and 1 hour after exposure to strain compared to those before exposure to strain. On the other hand, swellings were generated at 5minutes after exposure to strain and were the most in number at 1 hour after exposure to strain compared to swellings in normal neurites. Moreover, the number of swellings in neurites exposed to 20% strain was significantly larger than that exposed to 10% strain at 5 minutes after exposure to strain. These results suggest that production of axonal swellings correlate with strain magnitude acting on the axons.

Human umbilical veinendothelial cells (HUVECs) were exposed to an impact pressure of -100 kPa and changes in morphology of HUVECs and expression of vascular entodhelial (VE)-cadherin were examined in order to investigate effect of exposure to impact pressure on endothelial permeability. In the results, HUVECs exposed to impact pressure were absent locally. VE-cadherin in control were continuously expressed along peripheral region of cells. However, VE-cadherin in HUVECs exposed to impact pressure were sparsely expressed along peripheral region of cells and partly distributed in cells. These findings suggest that the exposure to impact pressure may change the expression and the distribution of VE-cadherin, influencing endothelial permeability.

When the human head is loaded by the rotational impact, a diffuse axonal injury (DAI) is caused in human brain. DAI is caused by the shear strain and shear strain rate that arises at the brain stem when the head does the rotation movement by the angular acceleration. However, the influences on the shear strain and shear strain rate by the change in parameters of the angular acceleration were not described. In this study, various accelerations that differs parameters were given to a human head finite element model, the influence on the shear strain and shear strain rate caused on the brain stem was considered. In this report, rise time of angular acceleration was focused on. As the result, the change in rise time did not influence the shear strain so much. But the change in the rise time greatly influenced the shear strain rate.

頭部が外部衝撃を受けた際には局在性脳損傷,或は脳震盪やびまん性軸索損傷(DAI)等が発症する。局在性脳損傷は脳表面の局部的なひずみや急激な圧力変動により引き起こされ,DAI等は脳の広範囲に発生するせん断応力により引き起こされる。局在性脳損傷は出血など明白な損傷形態を有することが多いのに対し,特にDAIでは死に至ることもあるが,受傷痕跡は病理解剖においても発見が極めて困難である。現状,もし局在性脳損傷とDAIが併発しても,明白な損傷形態を有する局在性脳損傷の陰に隠れ,見過ごされている可能性がある。本研究では,頭蓋内の力学的挙動をコンピュータにより計算することができる頭部有限要素モデルを構築し様々な衝撃を与え,局在性脳損傷とDAIの発症条件を統一した力学的指標である頭部重心に発生した平均加速度とその持続時間を用いて評価し,両損傷の併発の可能性を検証した。司法解剖例をコンピュータシミュレーションにより再現した結果,局在性脳損傷が死因と判断された場合でもDAIが併発している可能性が高いことを示した。

The mechanism of coup contusion and contrecoup contusion was studied by impact experiment and finite element analysis. The finite element analysis of the cerebral contusion was carried out by taking skull fracture into consideration to show the relationship of the force duration, pressure fluctuation inside the human head model and the coup contusion, contrecoup contusion. The threshold of the skull fracture was evaluated by using Japan Head Tolerance Curve as -10MPa. The result showed coup contusion would occur when impacted by light weight impactor with high velocity which yields short force duration, and contrecoup contusion would occur when impacted by heavy weight impactor with low velocity which yields long force duration. The result showed on 5 second or less of the force duration, coup contusion occurs dominantly, and contrecoup contusion occurs dominantly over 5 second.