張 月琳

Following head trauma caused by traffic accidents, many patients are unable to completely recover their social functions due to higher brain dysfunction although they are able to return home. To predict the onset and severity of post-traumatic higher brain dysfunction, the visualization of responsible injury is considered urgent. In this study, we focused on five patients with higher brain dysfunction following head trauma caused by traffic accidents to establish a method for quantitatively evaluating higher brain dysfunction. The injury conditions were reproduced on the basis of multibody dynamic and collision analyses using finite element (FE) modeling of the human head to determine mechanical responses inside the cranium of these patients. The strain on the frontal lobe generated by an injury condition was suggested to contribute to the onset of attention disturbance during the chronic phase of medical treatment. Reproduction analysis of the injury conditions using FE modeling of the head could predict the onset and severity of traumatic higher brain dysfunction.

Severe head injuries can occur in cyclists involved in traffic accidents. In Japan, head injuries accounted for 62% of cyclist fatalities in 2015 (ITARDA, 2016). The purpose of this study is to estimate head injuries for cyclists and quantify the effectiveness of a bicycle helmet by performing finite element (FE) simulations of head impacts against roads. Impacts with and without a helmet over a range of relative head velocities and head impact angles were simulated. A number of possible head injuries were assessed skull fracture by skull strain, traumatic intracerebral hematoma (ICH) by brain pressure, brain contusion by brain negative-pressure and von Mises stress, and moderate and severe diffuse axonal injuries (DAIs) by von Mises stress. Results showed that without a helmet, the peak values of all metrics exceeded the 50% probability point for head injury in all impacts. The 50% probability points of moderate and severe DAIs were exceeded under impacts of 8.22 m/s at 26.5 degrees and 10.33 m/s at 15.0 degrees for moderate DAI, and 10.33 m/s at 15.0 degrees for severe DAI, without a helmet. All the peak values were reduced when a bicycle helmet was worn, and the largest reduction was found in the skull strain. These results predict that the risks of head injuries due to road impacts may be considerably decreased by helmet use.

<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>

The collision accident in collegiate football game was simulated based on the game video and the concussive impact on the head was analyzed. First, the collision motion of players was reproduced based on the video by using motion analysis, and the translational and rotational velocities, relative position and contact location of the struck and the striking players' heads just before the collision were calculated. Then the data obtained were input to two helmeted finite element (FE) human head models as the initial condition, and the brain injury risk was evaluated by using the impact analysis. The FE helmet model was validated by a drop test of the helmet in which the head impactor was embedded. In the present study, two concussion suspected accident cases were analyzed then the concussion was evaluated by ten mechanical parameters generated inside the skull caused by the collision. The injury risk evaluated by multi parameters belonged to the dangerous range that may cause concussion and was consistent with the diagnosis of the medical team doctor. The brain injury risk can be successfully estimated by the reconstructed simulation of the game video and FE analysis. To our knowledge, this study is the first attempt in Japan to estimate the brain injury risk systematically by a combination of game video analysis which is originally introduced for the players' health care and FE analysis by helmeted human head model. In the future, brain injury risk caused by an accident can be evaluated with higher accuracy by analyzing more accident cases.

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.

In this study, the mechanism of cerebral contusion was investigated using finite element analysis. A finite element human head model was constructed and used to simulate of 9 real-world fatal cerebral contusion accident cases. In these simulations, the impact velocities of the impact objects were estimated on the basis of the available information such as the regions of skull fracture and cerebral contusion. The pressure fluctuations inside the skull and the input force durations in each case were obtained using these simulations. These results show that in case of coup contusion, a negative pressure occurs on the impact side and is directly correlated with short force durations. In contrast, in case of contrecoup contusion, negative pressure occurs on the opposite side of impact and is directly correlated with long force durations. As the result, coup contusions are caused when the input force durations are short, contrecoup contusions are caused when the input force durations are long. © 2011 by JSME.

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.

In this study, the effects of a dynamic strain in the cytotoxicity and mortality of the PC12 cell line were evaluated by using impact experiment with huge acceleration. In order to consider the influence of axonal damage on nerve cells, 2 types of nerve cells were used for the impact experiments, i.e. with and without axons. The cytotoxicity and mortality of cells were evaluated by the input acceleration, strain and strain rate and the strain rate seemed to be the most appropriate to evaluate the cytotoxicity and mortality of cells. Cells with axons showed higher cytotoxicity and mortality than cells without axons, when the strain rate was larger than 13.11 (1/s). Damage to axons was confirmed by terminal swellings and beadings of the axons. These data indicated that the presence of axons increased the cytotoxicity and mortality of cells. Copyright © 2010 by JSME.

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.

The mechanism of cerebral contusion was studied by using finite element analysis. Prior to numerical analysis of a finite element human head model, experimental study of an impact loading for a water-filled acrylic cylindrical container was carried out. The frequency of fluctuation of internal pressure was close to the natural frequency of the acrylic container. The human head model was analyzed by finite element analysis and the numerical result was compared with the result of the experimental study reported by Nahum and good agreement was obtained. In impact analysis, mass and velocity of the impactor were changed so as to keep the energy constant and intracranial pressure fluctuations of the impact side and the opposite side were obtained. When the input force duration was short, the thumping pressure fluctuation between the positive and negative pressure with higher frequencies were observed both at the impact side and the opposite side. As the input force duration became longer, the pressure fluctuation was suppressed and the positive pressure became dominant at the impact side and the negative pressure became dominant at the opposite side, and lower frequencies became dominant. © 2008, The Japan Society of Mechanical Engineers. All rights reserved.