颌面部高速投射伤时颅脑响应的生物力学研究

实验采用瑞典模型方法，选用重１．０３ｇ，射速８００ｍ／ｓ和１４００ｍ／ｓ的钢珠致伤犬（１０只）和猪头（２０只），建立重型颌面部损伤动物模型，记录致伤瞬间脑内压力、头颅冲击加速度和下颌骨、颞骨骨应变值，研究颌面部投射伤伴发颅脑损伤机理。实验结果证实，颌面部高速投射伤时，瞬时空腔效应、冲击波效应、冲击加速度效应骨间应力传导作用均参与颅脑的致伤过程。文中还对本研究相关的临床意义进行了讨论。     

利用有限元研究非贯穿弹道冲击防弹衣后人体躯干的力学响应

目的通过建立人体躯干有限元计算模型,对弹头非贯穿性弹道冲击下人体躯干主要脏器的力学响应进行数值模拟。方法利用正常成年男性的CT扫描数据,应用医学图像重建软件Mimics和有限元前处理工具Hy-perMesh进行人体躯干有限元建模,在显式动力有限元分析软件LS-DYNA中对速度为360 m/s的9 mm手枪弹弹头撞击装配有软质防弹衣人体躯干的压力、加速度响应进行数值计算。结果建立了包括胸廓骨骼结构、脏器、纵膈和肌肉/皮肤的人体躯干有限元模型,通过数值计算获得了心脏、肺脏、肝脏、胃的压力响应以及胸骨的加速度响应,发现不同脏器之间或同一脏器的不同位置,离弹头撞击点位置的远近决定了压力峰值的大小和出现压力峰值的时间。结论装配有软质防弹衣的人体躯干有限元计算模型可作为非贯穿弹道冲击下人体力学响应的仿真分析工具,仿真结果可为防弹衣后钝性损伤机制和防护研究提供依据。     

头部钝器损伤实验与仿真分析

目的　为了研究头部在钝器作用下的生物力学响应及损伤机理。 方法　利用CT图像数据和MRI图像数据对头部骨骼与内部软组织进行几何重建,然后画分网格,构建颅脑有限元模型。另一方面,对连于躯干的头部标本进行10 m/s的低速冲击,测试冲击部位接触力、顶部应变及冲击的对侧（枕部）加速度。把构建的有限元模型导入MADYMO软件进行相同条件下模拟仿真,从输出模块里输出相应部位的结果。 结果　仿真结果表明模型的头部接触力、顶部应变、对撞侧加速度与头部标本冲击实验测得值能较好吻合。 结论　建立的头部有限元模型及采用的仿真方法可满足头部钝器损伤的仿真研究需要。     

舰员抗冲击鞋性能试验及评估方法研究

水下爆炸在极短的时间内产生巨大的冲击加速度,引起舰船结构设备破坏和人员损伤。在自下而上的垂向冲击加速度作用下,甲板上的立姿舰员下肢首先承受强大的冲击载荷,人体的跟骨和脚踝是最易损伤的薄弱部位。研究舰员的抗冲击鞋,目的是通过缓冲脚底部载荷并降低到耐受限值以下。利用双波冲击机模拟3种典型冲击强度,采用国际标准假人代替真人作为试验载体,开展舰员抗冲击鞋的防护性能试验及评估方法研究。结果表明,舰员抗冲击鞋具有较强的冲击防护作用,可以衰减约60%的冲击载荷,从而达到有效避免或减轻舰员冲击损伤的作用。     

舰船人员冲击损伤标准及耐受性研究

水下爆炸在极短的时间内产生强大的冲击加速度,引起人员严重损伤.在评估舰船的作业能力时,人员对冲击的耐受性足一个极其重要的因素.根据人体的冲击损伤特点,本文提出人体主要组织器官对舰船冲击运动的耐受程度和损伤阈值,为舰船冲击环境下人员的损伤评估、预测及防护等提供重要的参考依据.     

1.5岁儿童头部有限元模型的建立及验证

利用1.5岁儿童头部MRI和CT扫描数据,通过医学扫描断层图像三维重构和有限元前处理,建立一个具有高度解剖学细节的1.5岁儿童头部有限元模型并赋予其最新公布的儿童颅骨材料参数。利用这个头部模型重构Loyd开展的儿童尸体头部跌落试验(17个样本),将仿真输出的加速度历程曲线和尸体试验曲线的加速度峰值、脉冲持续时间等进行对比。结果表明,该模型能够反映跌落工况中儿童头部的受载情况,具有良好的生物逼真度。30 cm跌落高度下,枕部撞击时得到最大HIC值357;不同跌落工况的头部颅内压力分析显示,儿童头部遭受撞击时,颅内压的分布满足经典的撞击压-对撞压产生理论;相比前额撞击和枕部撞击,颅顶撞击和侧向顶骨撞击的撞击侧正压力峰值较大,最大值分别为241.6 和157.3 kPa,遭受同侧脑挫裂伤的风险较高;枕部撞击工况下,撞击对侧的负压力峰值大于其他撞击工况,最大值为-74.4 kPa,遭受对侧脑挫裂伤的风险较高。跌落高度增加时,HIC和颅内压力峰值增大,损伤风险随之增加。     

钝性胸部损伤诊断和治疗进展

钝性胸部伤是由于挤压、撞击暴力所致的一类胸部损伤,与胸部穿透伤相区别的是,这类损伤的胸壁还保持完整性.随着现代交通业的发展,这类损伤有逐年增多的趋势.钝性胸部外伤占全部外伤的10％,死亡率4％～20％[1],钝性胸部伤的损伤程度轻重不一,可以是轻微的胸壁擦伤,也可能是危及生命的重要脏器损伤.一些钝性胸部伤早期的临床表现并不能反应损伤的严重程度,部分早期没有生命威胁的胸部伤病人,往往在伤后2～3d内出现病情恶化,因此,这类损伤值得大家关注,现就胸部钝性伤的诊断和治疗进展综述如下.     

化学和机械损伤对大鼠血管内皮细胞的影响

本文采用循环内皮细胞计数和扫描电镜观察等技术，研究了在化学性和机械性致伤条件下，大鼠（ｎ＝４０）血管内皮细胞脱落的程度和形态学改变。实验结果表明上述两种致伤因素均可导致循环内皮细胞显著增多和形态学变化。提示以酸性枸橼酸钠液致和钝性机械损伤大鼠尾静脉均可作为活体内研究血管内皮细胞损伤的实验模型。     

基于汽车碰撞损伤的人体胸部有限元模型构建与验证

目的利用胸部有限元模型预测与评估碰撞载荷下胸部生物力响应与损伤机理。方法利用CT和MRI图像数据对胸部骨骼与内部软组织进行几何重建,并划分网格。模型的生物组织材料参数与材料本构模型基于文献尸体实验与组织材料实验。结果对模型进行前碰撞与侧碰撞仿真实验验证,结果表明胸部接触力、胸部位移量、力与位移曲线与尸体实验吻合较好,并利用胸部位移量、黏性准则对仿真过程进行损伤评估。结论模型可满足汽车碰撞安全中胸部损伤机理与防护及医学胸部钝器损伤的仿真研究需要。     

人头部力锤冲击试验的生物力学研究

目的：探讨人头部受主动冲击的钝力作用时的力响应特点,同时测试头部各部位承受最大冲击力的限度,从冲击动力学角度去探讨颅脑损伤的生物力学机理。方法：使用配备大量程力传感器的力锤对人尸体头部各部位进行冲击试验,记录接触力响应曲线,并手工记录锤头的质地、质量、初速度、冲击面大小,以及被冲击的头部是否有破坏性反应(头皮挫裂及颅骨骨折)。结果：人头部对主动冲击的钝物的接触力响应曲线为类似正弦波的脉冲波形,其波形宽度及峰值因冲击物的质地、有无头皮等发生变化;人头部在小面积钝物的冲击作用下,造成头皮挫裂的冲击力最大值平均为5100N;使颞部、顶部、额部、枕部骨折的冲击力最大值的平均值分别为6200、8100、8300、11000N;利用试验得到的数据,验证了作用于头部的钝物与头部组成的系统相当于带有强阻尼的弹簧振子。结论：头部在受到主动冲击时,典型的接触力一时间曲线为类似正弦波的脉冲波形;大面积的钝器作用于头部造成的颅骨骨折,更多发生延伸至远处的线形骨折;本试验还得出了人头部能耐受的冲击力大小等参数,这些对于建立有限元模型进行分析和验证是必须的。     

Intracranial Pressure Response to Non-Penetrating Ballistic Impact: An Experimental Study Using a Pig Physical Head Model and Live Pigs

This study was conducted to characterize the intracranial pressure response to non-penetrating ballistic impact using a "scalp-skull-brain" pig physical head model and live pigs. Forty-eight ballistic tests targeting the physical head model and anesthetized pigs protected by aramid plates were conducted with standard 9 mm bullets at low (279-297 m/s), moderate (350-372 m/s), and high (409-436 m/s) velocities. Intracranial pressure responses were recorded with pressure sensors embedded in similar brain locations in the physical head model and the anesthetized pigs. Three parameters of intracranial pressure were determined from the measured data: intracranial maximum pressure (P_max), intracranial maximum pressure impulse (PI_max), and the duration of the first positive phase (PPD). The intracranial pressure waves exhibited blast-like characteristics for both the physical model and l live pigs. Of all three parameters, P_max is most sensitive to impact velocity, with means of 126 kPa (219 kPa), 178 kPa (474 kPa), and 241 kPa (751 kPa) for the physical model (live pigs) for low, moderate, and high impact velocities, respectively. The mean PPD becomes increasingly short as the impact velocity increases, whereas PI_max shows the opposite trend. Although the pressure parameters of the physical model were much lower than those of the live pigs, good correlations between the physical model and the live pigs for the three pressure parameters, especially P_max, were found using linear regression. This investigation suggests that P_max is a preferred parameter for predicting the severity of the brain injury resulting from behind armor blunt trauma (BABT).     

A thoracic mechanism of mild traumatic brain injury due to blast pressure waves

The mechanisms by which blast pressure waves cause mild-to-moderate traumatic brain injury (mTBI) are an open question. Possibilities include acceleration of the head, direct passage of the blast wave via the cranium, and propagation of the blast wave to the brain via a thoracic mechanism. The hypothesis that the blast pressure wave reaches the brain via a thoracic mechanism is considered in light of ballistic and blast pressure wave research. Ballistic pressure waves, caused by penetrating ballistic projectiles or ballistic impacts to body armor, can only reach the brain via an internal mechanism and have been shown to cause cerebral effects. Similar effects have been documented when a blast pressure wave has been applied to the whole body or focused on the thorax in animal models. While vagotomy reduces apnea and bradycardia due to ballistic or blast pressure waves, it does not eliminate neural damage in the brain, suggesting that the pressure wave directly affects the brain cells via a thoracic mechanism. An experiment is proposed which isolates the thoracic mechanism from cranial mechanisms of mTBI due to blast wave exposure. Results have implications for evaluating risk of mTBI due to blast exposure and for developing effective protection.     

Factors affecting mortality of critical care trauma patients

Background

Critically-ill trauma patients have a high mortality.

Objective

To study the factors affecting the mortality of ICU trauma patients treated at Al-Ain Hospital, United Arab Emirates (UAE).

Methods

All trauma patients who were admitted to the ICU were prospectively collected over three years (2003–2006). Univariate and multivariate analysis were used to compare patients who died and who did not. Gender, age, nationality, mechanism of injury, systolic blood pressure and GCS on arrival, the need for ventilation, presence of head or chest injuries, AIS for the chest and head injuries and the ISS were studied.

Results

There were 202 patients (181 males). The most common mechanism of injury was road traffic collisions (72.3 %). The overall mortality was 13.9%. A direct logistic regression model has shown that factors that affected mortality were decreased GCS (p < 0.0001), mechanism of injury (p = 0.004) with burns having the highest mortality, increased age (p = 0.004), and increased ISS (p = 0.02). The best GCS that predicted mortality was 5.5 while the best ISS that predicted mortality was 13.5.

Conclusion

Road traffic collision is the most common cause of serious trauma in UAE followed by falls. Decreased GCS was the most significant factor that predicted mortality in the ICU trauma patients.     

川芎嗪干预钝性肺挫伤急性期大鼠肺组织细胞的凋亡

背景：急性胸部撞击后所致的肺挫伤(钝性肺挫伤)常引起呼吸功能异常和继发性炎性反应,并参与全身炎性反应综合征和多器官功能障碍综合征,其发病原因及致病机制亟待明确。 目的：观察胸部撞击所致钝性肺挫伤急性期细胞凋亡的变化及其川芎嗪对其的影响。 方法：健康雄性SD大鼠随机分为正常对照组、模型组、川芎嗪治疗组,后两组制备胸部撞击伤模型,川芎嗪治疗组建模后立即腹腔注射川芎嗪80 mg/kg 1次。在创伤发生后1,2,3 h观察肺组织病理形态学及细胞凋亡的改变、检测肺水肿程度和肺血管通透性改变,免疫组织化学检测肺组织Bcl-2、Bax和Caspase-3的表达及血液中肿瘤坏死因子α水平变化。 结果与结论：模型组肿瘤坏死因子α水平在创伤后1 h即显著增加,创伤后2 h及3 h间急剧增加(P < 0.05);创伤后2 h及3 h肺组织细胞凋亡指数及肺组织损伤程度显著增高(均P < 0.05);肺血管通透性及肺水肿程度增加(P < 0.05);Caspase-3表达显著增高(P < 0.05),Bcl-2/Bax比值显著降低(P < 0.05)。川芎嗪治疗组在相应时间点相对于模型组肿瘤坏死因子α水平显著降低(P < 0.05),肺组织内细胞凋亡指数及肺组织损伤程度降低(P < 0.05),肺血管通透性及肺水肿程度减轻(P < 0.05);Caspase-3表达下降(P < 0.05),Bcl-2/Bax比值增加(P < 0.01)。结果提示,川芎嗪可通过抑制肿瘤坏死因子α表达,下调Caspase-3的表达并提高Bcl-2/Bax的比值,以降低胸部撞击所致肺组织急性期的异常凋亡并减轻胸部撞击所致急性期肺挫伤。     

The frequency domain versus time domain methods for processing of intracranial pressure (ICP) signals

Two methods for analyzing intracranial pressure (ICP) waveforms were compared. The frequency domain (FD) method converts the signal from the time domain to the frequency domain by a fast Fourier transform (FFT), while the time domain (TD) method calculates peak-to-peak value of the pulse waveform directly from the time samples. First, the ICP signal was regenerated from the first harmonic of the FFT and compared against the time domain raw ICP signal. We found that the FD method may underestimate pulse amplitude if there is heart rate variability or a high harmonic distortion. Second, to explore the significance in a larger data set, differences between FD- and TD-derived pulse amplitudes were determined for a total of 50,978 6-s time windows of 79 head injury patients. The mean difference in pulse pressure amplitude was 2.9 mmHg for the 50,978 6-s time windows. Differences between TD- and FD-derived pulse amplitudes were >or= 2.0 mmHg in 58.8% of the 50,978 time windows. In about 33% of time windows FD amplitudes were <2 mmHg when TD amplitudes were >or= 4 mmHg, and vice versa. Hence, the TD method is superior to the FD method for calculation of pulse amplitudes. Nevertheless, in this material both the TD and FD methods revealed significantly elevated pulse amplitudes in head injury patients with bad outcome (i.e. Glasgow Outcome Score 1-3).     

Skeletal histology of the dermal armor of Placodontia: the occurrence of 'postcranial fibro-cartilaginous bone' and its developmental implications

Placodontia (Reptilia: Sauropterygia) is a group of enigmatic armored marine reptiles restricted to the Triassic time period. Only a single row of osteoderms dorsal to the spine is present in the basal placodontoid Placodus gigas, whereas derived cyamodontoids superficially resemble turtles in enclosing their body in an armor shell. Despite the extensive occurrence of the dermal armor in the derived cyamodontoid group, little research has focused on its bone histology and development. Here, I present an overview of the bone microstructures that reveals the unique presence of cartilaginous tissue in the postcranial armor plates. Placodont armor plates stand in contrast to osteoderms of other tetrapods that develop intramembraneously or through metaplastic ossification without cartilaginous preformation. The different developmental pathways leading to this 'postcranial fibro-cartilaginous bone' tissue found in placodont plates compared to the dermal bone tissues of most other tetrapod osteoderms indicate the non-homology of these structures. A resulting morphogenetic model of histogenesis is given to exemplify how the derived armor morphologies (i.e. spiked, flat polygonal and hexagonal, and rhomboidal shapes) together with the peculiar bone histologies could have developed through differential growth. In accordance with the pachyostotic limb bones of placodonts, the presence of the compact 'postcranial fibro-cartilaginous bone' is interpreted as an osteosclerotic trend in the armor plates which aids in buoyancy control and affects maneuverability and swimming speed.     

Finite element analysis of brain contusion: An indirect impact study

The mechanism of brain contusion has been investigated using a series of three-dimensional (3D) finite element analyses. A head injury model was used to simulate forward and backward rotation around the upper cervical vertebra. Intracranial pressure and shear stress responses were calculated and compared. The results obtained with this model support the predictions of cavitation theory that a pressure gradient develops in the brain during indirect impact. Contrecoup pressure-time histories in the parasagittal plane demonstrated that an indirect impact induced a smaller intracranial pressure (−53.7 kPa for backward rotation, and −65.5 kPa for forward rotation) than that caused by a direct impact. In addition, negative pressures induced by indirect impact to the head were not high enough to form cavitation bubbles, which can damage the brain tissue. Simulations predicted that a decrease in skull deformation had a large effect in reducing the intracranial pressure. However, the areas of high shear stress concentration were consistent with those of clinical observations. The findings of this study suggest that shear strain theory appears to better account for the clinical findings in head injury when the head is subjected to an indirect impact.     

Up-regulation of reactivity and survival genes in astrocytes after exposure to short duration overpressure

Gurdjian et al. proposed decades ago that pressure gradients played a major factor in neuronal injury due to impact. In the late 1950s, their experiments on concussion demonstrated that the principal factor in the production of concussion in animals was the sudden increase of intracranial pressure accompanying head injury. They reported the increase in pressure severity correlated with an increase in 'altered cells' resulting in animal death. More recently, Hardy et al. (2006) demonstrated the presence of transient pressure pulses with impact conditions. These studies indicate that short duration overpressure should be further examined as a mechanism of traumatic brain injury (TBI). In the present study, we designed and fabricated a barochamber that simulated overpressure noted in various head injury studies. We tested the effect of overpressure on astrocytes. Expressions of apoptotic, reactivity and survival genes were examined at 24, 48 and 72 h post-overpressure exposure. At 24 h, we found elevated levels of reactivity and survival gene expression. By 48 h, a decreased expression of apoptotic genes was demonstrated. This study reinforces the hypothesis that transient pressure acts to instigate the cellular response displayed following TBI.     

Eye and head coupled and dissociated movements during orientation to a double step visual target displacement

Summary Tight coupling between eye and head movements has been observed in response to a single visual target offset. On this basis, when the visual stimulus consists of two successive steps in the same (horizontal) direction, either increasing in eccentricity (staircase) or decreasing in eccentricity (pulse-step) gaze should be due to concomitant eye and head angular displacement. That is, the eyes and head should aim at each target displacement so that their combined movement matches target offset. We have tested this hypothesis in five healthy subjects. The measured variables were head and gaze offset, the interval between two consecutive saccades from onset to onset (I) and the response delay between onset of the second step and onset of the first gaze saccade (D). With both staircase and pulse-step stimuli, the eye saccade preceded the head movement, and the gaze response either had the stimulus profile pattern or consisted of one gaze saccade to the final target offset. In response to staircase stimuli, I decreased concomitantly with an increase in D; with pulse-step stimuli, as D increased, I decreased slightly in three subjects and decreased markedly in two subjects. Dissociation between the eye and head movements could clearly be demonstrated with pulse-step stimuli: the first gaze saccade to the target pulse displacement was accompanied by a head movement to the target step offset. We also observed cases in which the gaze saccade to the target step displacement was made simultaneously with the head movement to the target pulse offset. Our study extends previous observations in head fixed condition and illustrates that in the majority of cases, when the head is free and a visual pulse step stimulus is presented, both the saccadic and head systems have the ability to modify or cancel the initial neural command to move to the first target displacement. When this modification takes place in only one system, eye and head movements are dissociated.On leave from the Occupational Health and Rehabilitation Institute at Loewenstein Hospital, P.O. Box 3, Raanana 43 100, Israel     

10岁儿童头部有限元模型的建立及验证

运用ANSYS ICEM CFD以及HYPERMESH软件对10岁儿童头部几何模型进行合理的网格划分,获得具有高度解剖学细节的10岁儿童头部有限元模型。利用MADYMO软件自带的假人,模拟一起典型跌落事故中,受伤儿童从3个不同高度跌落时人体的动力学响应过程,并计算头部与地面碰撞接触瞬间的方位和速度等运动学参数。然后将这些参数输入到10岁儿童头部有限元模型中,模拟头部与地面的碰撞过程,并分析与损伤相关的生物力学参数。结果表明,颅骨的最大应力和最大应变分布在枕骨右侧,与碰撞点的位置较为吻合,但均未超过颅骨的耐受极限。利用颅内压力可较好地预测脑组织的损伤程度,而利用脑组织的von mises应力可较好地判断脑组织的损伤位置。事故重建的结果表明,该模型具有较好的生物逼真度,可以用于儿童头部损伤生物力学的研究。