穿盖弹射对人体头、肩、膝部的损伤程度

目的 探讨穿盖弹射对人体头、肩、膝部的损伤程度,以提出适宜的生理参数,供工程部门使用。方法 用17具颅骨在摆锤式冲击台上进行动态冲击实验,在材料实验机上进行准静态压力实验,观察颅骨骨折情况。用假人进行地面弹射、火箭滑车实验,测试假人与舱盖碰撞的外力值。结果 外力峰值不超过3.5 kN或作用时间不超过30 ms时颅骨没有发生骨折。颅盖骨可承受6.9 kN以下的缓慢均匀加压,颅底骨只可承受1.5 kN。膝部承受8.0 kN冲击力时无损伤发生。结论 穿盖弹射时对人体主要的威胁是头部碰撞伤,损伤程度不仅取决于作用力的大小,而且与作用时间有关。颅盖骨承受的破坏力值比颅底骨大得多。破盖器工作时人体与舱盖碰撞的机率很小,且不易发生损伤,膝部承受较大的穿盖力也不致发生损伤。     

穿盖弹射时人体头、膝部的冲击限值

目的探讨穿盖弹射对人体头部、膝部的损伤程度，以提出适宜的生理参数，供工程部门使用。方法用１７具头颅骨在摆锤式冲击台上进行动态冲击试验，在材料试验机上进行准静态压力试验，观察试验后颅骨骨折情况。在落锤式冲击台上进行８具膝部冲击实验。用假人进行地面弹射、火箭滑车实验，测试假人与舱盖碰撞的外力值。结果外力峰值不超过３．５ｋＮ或作用时间不超过３０ｍｓ时颅骨没有发生骨折。颅盖骨可承受６．９ｋＮ以下的缓慢均匀加压，颅底骨只可承受１．５ｋＮ。膝部承受８．０ｋＮ冲击力时无损伤发生。结论穿盖弹射时对人体主要的威胁是头部碰撞伤，颅盖骨承受的破坏力值比颅底骨大得多。破盖器工作时人体与舱盖碰撞的机率很小，且不易发生损伤。膝部可承受较大的穿盖力，不致发生损伤     

模拟气动载荷对猴头颈部损伤的研究

本实验使用动态加载机模拟了应急弹射时气流吹袭对人体的作用曲线。对24只猴的头部进行了冲击,通过多项医学指标的综合判断,获得了猴头颈部对模拟气动载荷的耐受限度。实验表明:冲击载荷在2.3kN 以下不会对猴产生任何损伤。在2.5kN 会使猴发生脑振荡,2.8kN 以上对猴生命威胁较大,此结果为人体头颈部对气流吹袭耐限的确定提供了依据。实验还表明动态加载机对气流吹袭作用曲线模拟效果较好,是目前国内进行冲击创伤研究比较理想的实验设备。     

人体脊柱对开伞冲击力的耐受强度

在Schenck材料试验机上,对人体脊柱的每节椎骨进行了慢速与快速加载,分析提出了人体脊柱骨强度,较长时间内耐受开伞冲击力在21G以下。利用人体脊柱自然频率动态特性,设制了人体脊柱开伞冲击电子模型,分析了人体脊柱系统强度特性,提出几十毫秒以内冲击允许值为25G50ms。以此为设计、生产部门提供生理数值。     

弹射座椅座垫的人体工程学要求

本文根据人体动态响应特性提出座垫应在弹射开始后10ms 以内压缩至最薄,以避免增加人体超调。相应地要求在坐人后坐骨结节处的座垫厚度不要超过15mm。由于人体工程学研究的动态指标与描述座垫材料的参数不同,使得模型研究与材料之间没有直接联系,因此在采用新材料制作座垫时需要用人体冲击试验进行动态检验。     

弹射椅试验时的颈部载荷

前言 只能从火箭滑车或飞行实验室的弹射椅试验中测量人体模型的颈部载荷,才可能通过试验来确定综合惯性和气流吹袭的载荷影响。这些载荷要保持在人体耐受水平以下,以防止发生损伤。方法 在各种空速、横滚、坡度、侧滑条件下测试了俄罗斯K-36D弹射椅、带有小身材的和大身材的男性ADAM人体模     

不同内固定器固定股骨颈骨折的生物力学比较研究

目的 对治疗股骨颈骨折的几种常用内固定器进行生物力学对比,为临床选择理想的内固定器提供理论依据.方法 利用聚甲基丙烯酸甲酯(poly methylmethacrylate,PMMA)制作人工股骨模型12个,按照人体股骨颈骨折时最常见的Pauwels 70.角用电锯锯断,造成内收型股骨颈骨折模型.将骨折标本解剖复位后,按手术操作方法用动力髋螺钉(dynamic hip screw,DHS)、3枚空心螺钉、股骨近端髓内钉(proximal femoral nail,PFN)和动态套筒式三翼钉不同置人物加以内固定.标本模拟人体单足站立位固定于Instron - 8874液压伺服力学实验测试机上,选择股骨近端15个点作为应变测试点,以10 mm/min加载速度、线性载荷0～1200 N分级加载,测定各组于1200N载荷下各点的应变值、不同载荷下头下沉位移和主压力侧8点的应变值.结果 1200N载荷下各组均在8点处出现峰值,DHS组、3枚空心螺钉组、PFN组和动态套筒式三翼钉组应变值分别为(-700±35)με、(-756±14)με、(-1362±136)με和(3024±127) με,两两比较差异均有统计学意义(P＜0.01).同一载荷下,动态套筒式三翼钉组股骨头下沉位移大于空心螺钉组和PFN组(P＜0.01),但小于DHS组(P＜0.01).同一载荷下,动态套筒式三翼钉组在主压力侧8点处的应变值均比其他三组的应变值大,其差异均有统计学意义(P＜0.01);同一固定组,随着载荷的增大,应变值也逐渐增大.结论动态套筒式三翼钉固定股骨颈骨折稳定可靠,从生物力学角度可以推广使用.     

飞行员弹射跳伞致剑突损伤一例

一、临床资料患者,男性,37岁,高性能战斗机飞行员,飞行时间2000 h.甲类身体.2009年7月因机械故障,飞行员在距地面97 m的高度穿盖弹射跳伞.当时飞机呈迎角20°俯冲状态,速度290 km/h.飞行员俯身拉中央拉环后,被肩带惯性机构迅速拉回.     

自由体操落地冲击的下肢动力学仿真研究

目的:约70%的自由体操损伤由落地冲击引发,本文旨在量化运动员下肢内、外负荷,为减少下肢损伤风险提供理论依据。方法:利用高速摄像机采集男子自由操团身后空翻一周落地站稳动作,以SIMI motion三维运动分析系统对人体主要关节进行三维运动学解析,用ADAMS/Lifemod创建个性化人体14环节刚体模型和自由体操落地垫模型,然后对采集的动作进行计算机仿真。结果:选择冲击前期、冲击后期、缓冲期3个阶段量化冲击负荷。外部负荷:冲击前期,人体承受最大冲击力约5倍体重,冲量和峰值负荷率最大。内部负荷:冲击前期,左踝关节的峰值负荷率最大(168W/kg),髋、膝、踝关节承受的冲击能量百分比分别为21%、21%、58%;冲击后期,矢状面,膝关节伸肌力矩峰值最大(161 N·m),冠状面,髋关节外展力矩峰值最大(154N·m)。结论:该方法可有效开展自由操落地冲击的动力学研究;对比髋、膝关节,踝关节肌肉承受着绝大部分的冲击能量,运动损伤风险最高。     

弹射加速度测试系统性能要求的研究

高速飞机和航天常采用弹射座椅应急救生。准确地测量弹射加速度对判断弹射座椅的人体工程学性能和人体安全关系密切。在我国,对该测试系统性能要求尚无统一规定。本文旨在研究的基础上提出建议。加速度测试系统的性能指标很多,其中特异性最强的是频响特性,它直接影响加速度信息的内涵,与波形畸变密切相关,是制定测试规范的核心指标。本研究根据弹射加速度的频率成分和人体频响特性确定了测试系统的性能要求。其方法是通过不同通频带滤波器所记录的加速度-时间曲线,分析弹射加速度的频率成分,以及曲线中的波峰、波谷与弹射机构的时相关系,从而确定弹射加速度的主要频率成分。根据人体弹射用数学模型的动态响应特点,并用人体振动试验检验,表明人体对作用时间为5、6.25、10、20ms 的脉冲(相当于基频为200、160、100、50Hz 的输入),其响应分别为原信息的25%、30%、50%、和70%。即人体频响特性与80Hz低通滤波器相近。由于弹射加速度过程以低频为主并包含有某些瞬间作用于人体的高频成分,若测试系统的频响范围过低,将滤掉某些作用于人体的激励成分,不利于人体安全。为此,测试系统的频率范围应不低于0～160Hz,用于研究人体工程学问题时,采用0～80Hz 的低通滤波器。本研究还在座椅的不同部位测量了加速度值,表明以在座椅框架上测试最合理。根据我国《向上弹射人体耐限军用标准》,人体耐力限度将由人体模型的运动方程计算得到。式中主要变量是输入加速度(?)(t)。由于我国的假人只模拟人体的外形、尺寸、重量,并不考虑人体的动力学特征,在假人胸腔测定加速度数据,仅仅是假人对输入的响应,而不能看作是对人体输入的加速度过程,所以也不能反映人体的动态响应。关于测试系统的灵敏度、线性、频响特性与阻尼特性等指标,应对整个系统进行动态标定,如翻转传感器只能获得静态重力状况下±1G 之间的数据。挂法码的标定只能在研制中检查系统的静态灵敏度、线性等。离心机给出的加速度是静态过载,不能代表动态过程。动态较准可用振动或冲击的方式进行。     

人头颈部耐受高速气流吹袭限值

研究了人头颈部的气动特性的生物力学特性，提出人头颈部受到高速气流吹袭时，对气动阻力的耐受限值为２．４５２ｋＮ，对气劝和的耐受限值为１．３５８ｋＮ，对气动侧力的耐受限值为０．１６９ｋＮ，并给出了人头颈部高速气流吹袭的耐限曲线，不论乘员在何种姿势下弹射，作用在头颈部的气动力不超过以上数值才可免遭高速气流吹所的损伤。     

Estimation of vertical ground reaction force parameters during athletic tasks using 2D video

BackgroundGiven that elevated vertical ground reaction forces (vGRF) have been reported to contribute to various lower-extremity injuries, there is a need for a practical method to characterize movement behavior that is representative of elevated impact forces.Research questionCan images obtained from 2D video be used to predict vGRF parameters during athletic tasks? Specifically, we sought to determine whether the 2D thigh angle obtained at peak knee flexion could be used to predict the peak vGRF and vGRF impulse during single limb and double limb landings and movements that involve a change of direction.Methods2D sagittal plane video and vGRFs were obtained simultaneously from 39 participants (15 males and 24 females) during 5 athletic tasks (drop jump, lateral shuffle, deceleration, triple hop, side-step-cut). Linear regression analysis was performed to determine if the 2D thigh angle at peak knee flexion predicted the first peak of the vGRF and vGRF impulse during the deceleration phase of each task.ResultsThe 2D thigh angle predicted the peak vGRF for all tasks except cutting (R² = 0.17 to 0.47, all p < 0.01). However, the 2D thigh angle predicted the vGRF impulse for all 5 tasks (R² = 0.13 to 0.39, all p < 0.025).SignificanceAn increased 2D thigh angle (which is representative of increased hip and knee flexion) was able to predict lower peak vGRFs and vGRF impulse during athletic tasks. The 2D thigh angle is a potential clinical method to characterize movement behavior that may expose individuals to high impact forces.     

Muscle, ligament, and joint-contact forces at the knee during walking

PURPOSE: In vivo measurement of the forces and strains in human tissues is currently impracticable. Computer modeling and simulation allows estimates of these quantities to be obtained noninvasively. This paper reviews our recent work on muscle, ligament, and joint loading at the knee during gait. METHODS: Muscle and ground-reaction forces obtained from a sophisticated computer simulation of walking were input into a detailed model of the lower limb to obtain ligament and joint-contact loading at the knee for one full cycle of gait. RESULTS: Peak anterior cruciate ligament (ACL) force occurred in early stance and was mainly determined by the anterior pull of the patellar tendon on the tibia. The medial collateral ligament was the primary restraint to anterior tibial translation (ATT) in the ACL-deficient knee. ATT in the ACL-deficient knee can be reduced to the level calculated for the intact knee by increasing hamstrings muscle force. Reducing quadriceps force was insufficient to restore ATT to the level calculated for the intact knee. For both normal and ACL-deficient walking, the resultant force acting between the femur and tibia remained mainly on the medial side of the knee. The knee adductor moment was resisted by a combination of muscle and ligament forces. CONCLUSION: Knee-ligament loading during the stance phase of gait is explained by the pattern of anterior shear force applied to the leg. The distribution of force at the tibiofemoral joint is determined by the variation in the external adductor moment applied at the knee. The forces acting at the tibiofemoral and patellofemoral joints are similar during normal and ACL-deficient gait. Hamstrings facilitation is more effective than quadriceps avoidance in reducing ATT during ACL-deficient gait.     

Effects of a functional knee brace on the biomechanics of running.

The purpose of the study was to assess the biomechanical effects of a functional knee brace on joint moments of force and joint powers in the lower extremity during the stance phase of running in subjects with a previous ACL injury. Sagittal-plane film records and ground reaction force data were obtained from five previously injured subjects running with and without a functional knee brace and from five healthy subjects running without the brace. Inverse dynamics were performed on these data to obtain the moments of force and joint powers. The angular impulse in the extensor direction was assessed from each moment of force curve, and the work performed during selected portions of the stance phase was assessed from the joint power curves. ANOVA techniques on these variables indicated no significant differences between the brace and no-brace conditions in the previously injured subjects. In comparison with the healthy runners, the previously injured subjects had, on average, 49% and 32% greater extensor angular impulse about the hip and ankle (both P less than 0.05). In contrast, the healthy runners had, on average, 233% greater (P less than 0.05) extensor angular impulse about the knee. The corresponding negative and positive work performed at the knee were 321% and 191% larger (both P less than 0.05) in the healthy runners. The reduction in the extensor moment of force about the knee and the increase in the moments of force about the hip and ankle in the previously injured subjects reduced the stresses on the ACL and tibia while at the same time enabling them to run at the required speed.     

人尸体头颅在撞击载荷下的动态响应研究

目的探讨撞击参数与影响损伤严重程度的撞击力之间的相互关系,以期为致伤机制和医学防护提供理论依据.方法将甲醛浸泡的成年男性尸体头颅(颌面骨骼、软组织完整)用石膏包裹固定于撞击台面.采用不同撞击参数对下颌骨不同部位进行撞击.将力传感器固定于撞击杆和撞击砣之间,记录不同撞击参数时的响应曲线.对实验所得计量资料进行均数t检验比较.结果撞击力的响应曲线为半个正弦波形式,力值和响应时间随撞击参数而异.随着撞击速度增高,撞击力量显著上升,而响应时间缩短(P<0.01).下颌骨颏部斜向撞击作用力大小显著高于水平撞击(P<0.01);用橡胶垫覆盖撞击头可使撞击力显著下降(P<0.01).下颌骨不同部位在承受相同撞击载荷时下颌角受力最大,其次为体部和颏部(P<0.01).结论下颌骨在撞击载荷作用下的响应与撞击参数有一定的相关关系.撞击的速度、方向、部位以及撞击头材料可以作为损伤限量的参考值.     

Rapid force generation is impaired in cerebral palsy and is related to decreased muscle size and functional mobility

Limb movements involving contraction times of 50-200 ms occur in many everyday activities, such as gait, which is faster than the time required to generate maximal force. Therefore, the ability to rapidly produce force may be even more important for the performance of functional activities. In this study rate of force development (RFD) and impulse of the knee extensors were examined in 12 ambulatory children with cerebral palsy (CP) (age: 11.9 ± 2.9 years) and 11 with typical development (TD) (Age: 11.3 ± 3.0 years). The relationship with muscle architecture and functional mobility was also determined. RFD and impulse were calculated during a maximal isometric knee extension contraction. Rectus femoris (RF) cross-sectional area and RF and vastus lateralis (VL) muscle thickness (MT), fascicle length (FL), and fascicle angle (FA) were measured using ultrasound imaging. Gait temporal-spatial parameters, Pediatric Outcomes Data Collection Instrument (PODCI), and Activities Scale for Kids performance version (ASKp) were collected. Although VL MT was the primary determinant of RFD and impulse in CP, FA and FL were also significant predictors in the TD group. RFD and impulse were significantly lower in CP compared to TD (70% decrease) in addition to maximal strength (50% decrease). RFD and impulse were predictive of measures of functional mobility, including gait, transfers, and sports and higher level activities but not temporal-spatial gait measures. Results suggest that the ability to rapidly generate torque may be of greater importance than maximal strength during certain tasks, such as transfers and sports and higher level activities.     

Predicting driver from front passenger using only the postmortem pattern of injury following a motor vehicle collision

This study aimed to establish whether post-mortem injury patterns can assist in distinguishing drivers from front seat passengers among victims of motor vehicle collisions without regard to collision type, vehicle type or if safety equipment had been used. Injuries sustained by 206 drivers and 91 front seat passengers were catalogued from post-mortem reports. Injuries were coded for the body region, depth and location of the injury. Statistical analysis was used to detect injuries capable of discriminating between driver and passenger. Drivers were more likely to sustain the following injuries: brain injury; fractures to the right femur, right posterior ribs, base of skull, right humerus and right shoulder; and superficial wounds at the right lateral and posterior thigh, right face, right and left anterior knee, right anterior shoulder, lateral right arm and forearm and left anterior thigh. Front passengers were more vulnerable to splenic injury; fractures to the left posterior and anterior ribs, left shoulder and left femur; and superficial wounds at the left anterior shoulder region and left lateral neck. Linear discriminant analysis generated a model for predicting seating position based on the presence of injury to certain regions of the body; the overall predictive accuracy of the model was 69.3%. It was found that driver and front passenger fatalities receive different injury patterns from motor vehicle collisions, regardless of collision type. A larger study is required to improve the predictive accuracy of this model and to ascertain its value to forensic medicine.     

Thigh compartment syndrome in a football athlete: a case report and review of the literature.

Although contusions of the thigh are common in all sports, a compartment syndrome from closed blunt trauma without a femur fracture is rare. Thigh compartment syndrome is unusual due to increased compliance of the thigh to accommodate increased expansion from hematoma or third space fluid. Compartment syndrome of the thigh is characterized by unrelenting pain, swelling, and limited knee range of motion. A single case of a thigh compartment syndrome caused by a direct blow to the anterior aspect of the thigh from a football helmet during kickoff occurred. Immediate thigh fasciotomy was performed. Early diagnosis with appropriate emergency treatment can avoid serious and permanent complications.