安全气囊点爆展开时儿童颈部约束对颅脑损伤的影响

目的探讨在交通事故中安全气囊点爆展开时儿童颈部约束对颅脑损伤的影响。方法基于已构建并经过有效性验证的3岁儿童头部有限元(finite element, FE)模型,采用FE方法模拟气囊点爆展开对离位(out-of-position, OOP)状态儿童乘员头部的冲击过程,研究颈部约束对交通事故中儿童颅脑响应及其损伤机制的影响。结果颈部约束的头部在受到安全气囊点爆展开的冲击之后,其运动状态与无颈部约束有很大差异,会导致儿童脑组织最大Von Mises应力明显减小,儿童颅脑损伤程度减弱。儿童头部与安全气囊距离为20、25 cm时,有颈部约束的头部脑组织最大颅内压小于没有颈部约束的头部。结论颈部约束对儿童颅脑损伤响应有较大的影响,用FE方法预测儿童颅脑损伤时应考虑颈部约束的影响。     

拦阻着舰过程中飞行员头颈部的动力学响应

目的分析航母舰载机拦阻着舰过程中飞行员在佩戴和不佩戴头盔时的头颈部动力学响应以及主要肌肉应变量。方法建立包括头部、7个颈椎和2个胸椎共10个刚体的人体头颈部的多体动力学模型;采用集总参数法描述韧带、椎间盘等软组织的力学特性;应用非线性应力-应变关系描述人体头颈部15组肌肉的力学特性。采用多组汽车碰撞过程人体头颈部动力学响应实验数据对模型进行验证。结果获取了拦阻着舰过程飞行员头部的过载曲线和15组肌肉的应变,结果表明颈夹肌拉伸程度最大,在不佩戴头盔时其应变可达50%,佩戴2.7 kg头盔时其应变可达56%。结论佩戴防护头盔会增加飞行员在拦阻着舰过程的颈部肌肉拉伸,仿真结果可用于进一步的损伤评估。     

气囊上液引流对重症颅脑损伤患者呼吸机相关肺炎的预防作用

目的探讨气管插管气囊上液引流对重症颅脑损伤患者呼吸机相关肺炎的预防作用。方法应用机械通气辅助呼吸重症颅脑损伤患者72例,随机分为实验组及对照组各36例。实验组患者采用Hi-LoTM高容量/低压气囊可冲洗式气管插管,EvacTM冲洗管连接负压引流器行持续引流,每隔6h应用生理盐水冲洗气囊上声门下间隙2~3次,每次注入生理盐水4~5ml;对照组采用普通气管插管。结果实验组呼吸机相关肺炎发生率、机械通气时间、住ICU时间均低于对照组,差异具有显著性。结论气囊上液持续引流及生理盐水间断灌洗,对重症颅脑损伤患者VAP具有预防作用,继而缩短了机械通气时间和住ICU时间,减轻了患者及家属的心理和经济负担。     

6岁儿童行人-汽车碰撞中碰撞角度对头部损伤的影响

目的应用符合欧洲新车安全评鉴协会(the European New Car Assessment Programme,Euro NCAP)要求的6岁儿童行人有限元模型,探究不同碰撞角度对儿童头部损伤的影响。方法应用符合Euro NCAP技术公告(TB024)并且具有详细解剖学结构的6岁儿童行人有限元模型,设置4组行人-汽车碰撞仿真试验,探究不同碰撞角度下儿童头部损伤情况。人体头部质心初始位置在车的纵向中心线上,轿车初速度为40 km/h,轿车分别与人体右侧、前侧、左侧、后侧碰撞(即0°、90°、180°、270°)。比较不同碰撞角度下运动学差异和头部碰撞响应,同时分析面骨和颅骨的损伤情况。结果通过分析儿童行人头部接触力、头部质心合加速度、头部质心相对于车的合速度、头部损伤标准(head injury criterion,HIC_(15))、面骨骨折情况以及颅骨应力分布发现,背面、正面碰撞下儿童头部骨折及发生脑组织损伤的风险大于侧面碰撞,其中背面碰撞下儿童行人头部损伤风险最高,侧面碰撞下儿童行人头部损伤风险最低。结论背面碰撞下儿童行人头部损伤风险最大,研究结果对行人-汽车碰撞评估和防护装置研发具有重要的应用价值。     

自动紧急制动对公交车内儿童乘员颅脑损伤影响

目的 研究自动紧急制动(autonomous emergency braking,AEB)对公交车内儿童乘员的颅脑损伤影响。 方法 使用 Prescan 软件搭建公交车 AEB 测试场景,通过仿真得到 60 km/ h 初速度下公交车 AEB 制动工况下的减速度曲线。 基于已经验证的公交车模型和具有详细解剖学头部结构的 6 岁儿童混合有限元模型,选取车内儿童乘员典型的 4 个乘坐位置,使用 LS-DYNA 软件对公交车有、无 AEB 制动工况下儿童乘员头部损伤进行仿真。 以儿童乘员头部损伤指标 HIC15 、大脑灰质处压力、脑组织 von Mises 应力及剪切应力等生物力学响应为损伤评价指标,对儿童乘员的颅脑损伤进行分析。 结果 各组仿真试验中,位置 1 和 2 前方设置挡板时,儿童乘员大脑灰质处压力超过其损伤阈值,其余各位置儿童乘员的各项损伤指标均远小于对应的损伤阈值。 结论 AEB 能有效降低公交车内儿童乘员头部碰撞损伤,公交车内位置 3 处的儿童容易发生碰撞损伤风险,位置 1、2 处设置广告牌挡板会增加儿童乘员的颅脑损伤风险。     

手枪子弹冲击下有防护生物靶标多参数测量与分析

目的 研究枪弹对有防护生物靶标的致伤情况与原因,为揭示人体在防护条件下的致伤机理和医学治疗提供参考。方法 选择体重60 kg的活猪作为生物靶标,参照防护条件下单兵头部和胸部的易损情况确定生物靶标内的测试物理量和具体位置。在25 m射距下分别对防护条件下生物靶标的头部和胸部射击3发9 mm巴拉贝鲁姆手枪弹,综合测量手枪弹冲击对有防护生物靶标钝性损伤起重要作用的加速度、压力、载荷力等多个力学量。结果 （1） 手枪弹对生物靶标头部的钝性损伤使颅内产生负压脉冲并伴随产生远达效应,在其脊柱和颈动脉内出现脉冲压力;（2） 手枪弹对生物靶标胸部的钝性损伤使心脏承受高加速度冲击,肺部承受高压力波作用。结论 测量结果为定量认识手枪弹对防护条件下有生目标致伤机理提供依据。     

颅脑损伤并发脑性盐耗综合征的临床分析

目的探讨颅脑损伤并发脑性盐耗综合征的临床表现特点与治疗方法。方法回顾性分析我科近15年收治的932例颅脑损伤病人影像与血生化资料。结果932例颅脑损伤中9例合并脑性盐耗综合征。9例入院时格拉斯（GCS）评分均在8分以下。伤后7-11 d开始出现低钠血症症状。6例病人出现精神症状和意识状态改变。其中7例病人意识障碍加深,并出现再次昏迷。9例病人血钠均低于130 mmol/L,其中3例病人低于120 mmol/L,所有病人血浆抗利尿激素（ADH）值小于15 pg/mL,血浆渗透压高于270 mOsm/L,尿钠均大于80 mmol/d,其中2例高于200 mmol/d。治愈7例,死亡2例。结论颅脑损伤并发的脑性耗盐综合征的发病机制与治疗措施不同于抗利尿激素分泌异常综合征,早期诊治能降低颅脑损伤病人的病残率和病死率。     

重型颅脑损伤患者甲状腺激素水平及其与预后的关系

目的 探讨颅脑损伤患者甲状腺激素水平与颅脑外伤程度和预后的关系。方法 用放免法测定395例颅脑损伤患者的甲状腺激素水平并与疾病严重程度进行比较。结果 GCS评分越低，TT3、TT4含量下降越明显；GCS评分与TT3、FT3含量均呈正相关（r1=-0．506，r2=-0．434，P均〈0．05）；重型颅脑损伤组TT3和FT3含量均低于对照组（P〈0．05）；死亡组TT3和FT3的含量明显低于存活组（P〈0．05）。结论重型颅脑损伤患者病情越重，甲状腺激素水平下降幅度越大；TT3和FT3含量可作为评价颅脑损伤患者预后的指标。     

枪弹冲击下新型防弹头盔质量对颈椎损伤影响

目的建立有效的头颈部及防弹头盔有限元模型,研究枪弹冲击不同质量防弹头盔时颈部的生物力学响应。方法通过在头盔本体(1.24 kg)增加附件均布质量2 kg,并加载手枪弹以450 m/s速度从正面、侧面、顶部冲击防弹头盔,获得人体颈椎的力学响应。结果受到冲击时,颈椎应力远大于颅骨应力。枪弹冲击防弹头盔时,相比头部,颈椎为易受伤部位,其中椎骨C3所受应力最大。不考虑增加附件质量时,子弹从正面、侧面、顶部方向冲击头盔时,侧面冲击对颈椎伤害最大,相比其他方向冲击最大应力约增加2.58%;同时正面冲击对头部损伤最大,应力约增加59.4%。考虑附件质量时,头盔质量越大对颈椎的损伤越严重。头盔质量从1.24 kg增加到3.24 kg,顶部冲击对颈椎的损伤最大,其应力相比其他方向冲击增加12.98%。结论在设计防弹头盔时应考虑其轻量化,研究结果为防弹头盔设计提供科学参考。     

不同载荷作用下头部生物力学响应仿真分析

目的建立符合解剖结构的人颅骨三维有限元模型,研究多种载荷作用下头部生物力学响应。方法通过建立具有解剖结构的高精度头部有限元模型,颅骨采用能模拟骨折的弹塑性材料本构模型,结合已发表的正面冲击颅内压实验、动态颅骨骨折实验、头部跌落实验结果,仿真再现实验过程中头部受冲击载荷作用下的生物力学响应、颅骨骨折及头部不同速度下的跌落响应。结果前碰撞表现出冲击与对冲侧正-负颅内压分布,相近载荷下枕骨变形比前额、顶骨严重,跌落中速度越快损伤越大。结论建立精确解剖结构的头部有限元模型可以较好模拟头部在冲击、跌落等载荷下的生物力学响应。通过量化接触力、颅内压力等参数来评价头部损伤风险,为防护系统的设计提供科学依据。     

Methodology to determine skull bone and brain responses from ballistic helmet-to-head contact loading using experiments and finite element analysis

The objective of the study was to obtain helmet-to-head contact forces from experiments, use a human head finite element model to determine regional responses, and compare outputs to skull fracture and brain injury thresholds. Tests were conducted using two types of helmets (A and B) fitted to a head-form. Seven load cells were used on the head-form back face to measure helmet-to-head contact forces. Projectiles were fired in frontal, left, right, and rear directions. Three tests were conducted with each helmet in each direction. Individual and summated force- and impulse-histories were obtained. Force-histories were inputted to the human head–helmet finite element model. Pulse durations were approximately 4 ms. One-third force and impulse were from the central load cell. 0.2% strain and 40 MPa stress limits were not exceeded for helmet-A. For helmet-B, strains exceeded in left, right, and rear; pressures exceeded in bilateral directions; volume of elements exceeding 0.2% strains correlated with the central load cell forces. For helmet-A, volumes exceeding brain pressure threshold were: 5–93%. All elements crossed the pressure limit for helmet-B. For both helmets, no brain elements exceeded peak principal strain limit. These findings advance our understanding of skull and brain biomechanics from helmet–head contact forces.     

Progressive cognitive decline in an adult patient with cleidocranial dysplasia

Cleidocranial dysplasia is a skeletal disorder characterized by a defective skull and defective clavicles caused by RUNX2, an activator of osteoblast differentiation. Consistent with the expression pattern of RUNX2, this disorder typically affects the skeletal system, but not the central nervous system. A 56-year-old man with the prototypic skeletal defects of cleidocranial dysplasia and a RUNX2 deletion presented with a progressive cognitive decline after the age of 40 years. After a failed cranioplasty during childhood, he had worn a protective helmet until young adulthood. His current neuroimaging studies revealed extensive cystic encephalomalacia beneath the defective skull, suggesting that his cognitive decline could likely be attributed to repetitive cerebral contusions. Late-onset progressive cognitive decline in the context of a defective skull accompanied by extensive cystic encephalomalacia illustrates the importance of natural calvarial protection against head injury. Since the majority of patients with cleidocranial dysplasia do not wear protective helmets beyond childhood, mainly for cosmetic reasons, a discussion of whether the social disadvantage outweighs the potential risk of brain parenchymal injury may be necessary.     

Comparison of Ice Hockey Goaltender Helmets for Concussion Type Impacts

Concussions are among the most common injuries sustained by ice hockey goaltenders and can result from collisions, falls and puck impacts. However, ice hockey goaltender helmet certification standards solely involve drop tests to a rigid surface. This study examined how the design characteristics of different ice hockey goaltender helmets affect head kinematics and brain strain for the three most common impact events associated with concussion for goaltenders. A NOCSAE headform was impacted under conditions representing falls, puck impacts and shoulder collisions while wearing three different types of ice hockey goaltender helmet models. Resulting linear and rotational acceleration as well as maximum principal strain were measured for each impact condition. The results indicate that a thick liner and stiff shell material are desirable design characteristics for falls and puck impacts to reduce head kinematic and brain tissue responses. However for collisions, the shoulder being more compliant than the materials of the helmet causes insufficient compression of the helmet materials and minimizing any potential performance differences. This suggests that current ice hockey goaltender helmets can be optimized for protection against falls and puck impacts. However, given collisions are the leading cause of concussion for ice hockey goaltenders and the tested helmets provided little to no protection, a clear opportunity exists to design new goaltender helmets which can better protect ice hockey goaltenders from collisions.     

Effect of helmet liner systems and impact directions on severity of head injuries sustained in ballistic impacts: a finite element (FE) study

The current study aims to investigate the effectiveness of two different designs of helmet interior cushion, (Helmet 1: strap-netting; Helmet 2: Oregon Aero foam-padding), and the effect of the impact directions on the helmeted head during ballistic impact. Series of ballistic impact simulations (frontal, lateral, rear, and top) of a full-metal-jacketed bullet were performed on a validated finite element head model equipped with the two helmets, to assess the severity of head injuries sustained in ballistic impacts using both head kinematics and biomechanical metrics. Benchmarking with experimental ventricular and intracranial pressures showed that there is good agreement between the simulations and experiments. In terms of extracranial injuries, top impact had the highest skull stress, still without fracturing the skull. In regard to intracranial injuries, both the lateral and rear impacts generally gave the highest principal strains as well as highest shear strains, which exceed the injury thresholds. Off-cushion impacts were found to be at higher risk of intracranial injuries. The study also showed that the Oregon Aero foam pads helped to reduce impact forces. It also suggested that more padding inserts of smaller size may offer better protection. This provides some insights on future’s helmet design against ballistic threats.     

Readiness for community-based bicycle helmet use programs: a study using community-and individual-level readiness models

Understanding community context is as important to develop effective community-based injury prevention programs as assessing attitudes and behaviors among individuals. Readiness of a community toward community efforts to promote bicycle helmet use and of individuals to use bicycle helmets were examined in a northern Colorado town in the United States, using a semi-qualitative approach. Community readiness and individual readiness to prevent injuries through use of bicycle helmets differed across groups. The findings provide a better understanding of interactions between community perceptions and individual attitudes and behaviors. Further, target groups for improving bicycle helmet use were identified.     

Dynamic Response Due to Behind Helmet Blunt Trauma Measured with a Human Head Surrogate

A Human Head Surrogate has been developed for use in behind helmet blunt trauma experiments. This human head surrogate fills the void between Post-Mortem Human Subject testing (with biofidelity but handling restrictions) and commercial ballistic head forms (with no biofidelity but ease of use). This unique human head surrogate is based on refreshed human craniums and surrogate materials representing human head soft tissues such as the skin, dura, and brain. A methodology for refreshing the craniums is developed and verified through material testing. A test methodology utilizing these unique human head surrogates is also developed and then demonstrated in a series of experiments in which non-perforating ballistic impact of combat helmets is performed with and without supplemental ceramic appliques for protecting against larger caliber threats. Sensors embedded in the human head surrogates allow for direct measurement of intracranial pressure, cranial strain, and head and helmet acceleration. Over seventy (70) fully instrumented experiments have been executed using this unique surrogate. Examples of the data collected are presented. Based on these series of tests, the Southwest Research Institute (SwRI) Human Head Surrogate has demonstrated great potential for providing insights in to injury mechanics resulting from non-perforating ballistic impact on combat helmets, and directly supports behind helmet blunt trauma studies.     

Bicycle helmet ventilation and comfort angle dependence

Five modern bicycle helmets were studied to elucidate some of the variations in ventilation performance, using both a heated manikin headform and human subjects (n=7). Wind speed and head angle were varied to test their influence on the measured steady-state heat exchange (cooling power) in the skull section of the headform. The cooling power transmitted by the helmets varied from about 60% to over 90% of that of the nude headform, illustrating the range of present manufacturer designs. Angling the head forward by 30° was found to provide better cooling power to the skull (up to 25%) for three of the helmets and almost equal cooling power in the remaining two cases. Comparisons of skull ventilation at these angles with human subjects strongly supported the headform results.     

A case-control study of the effectiveness of bicycle safety helmets

Bicycling accidents cause many serious injuries and, in the United States, about 1300 deaths per year, mainly from head injuries. Safety helmets are widely recommended for cyclists, but convincing evidence of their effectiveness is lacking. Over one year we conducted a case-control study in which the case patients were 235 persons with head injuries received while bicycling, who sought emergency care at one of five hospitals. One control group consisted of 433 persons who received emergency care at the same hospitals for bicycling injuries not involving the head. A second control group consisted of 558 members of a large health maintenance organization who had had bicycling accidents during the previous year. Seven percent of the case patients were wearing helmets at the time of their head injuries, as compared with 24 percent of the emergency room controls and 23 percent of the second control group. Of the 99 cyclists with serious brain injury only 4 percent wore helmets. In regression analyses to control for age, sex, income, education, cycling experience, and the severity of the accident, we found that riders with helmets had an 85 percent reduction in their risk of head injury (odds ratio, 0.15; 95 percent confidence interval, 0.07 to 0.29) and an 88 percent reduction in their risk of brain injury (odds ratio, 0.12; 95 percent confidence interval, 0.04 to 0.40). We conclude that bicycle safety helmets are highly effective in preventing head injury. Helmets are particularly important for children, since they suffer the majority of serious head injuries from bicycling accidents.