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Head injuries are the most common injuries sustained by children in motor vehicle crashes regardless of age, restraint and crash direction. Previous research identified the front seat back as relevant contact point associated with head injuries sustained by restrained rear seated child occupants. The objective of this study was to conduct a test series of headform impacts to seat backs to evaluate the energy management characteristics of relevant contact points for pediatric head injury. A total of eight seats were tested: two each of 2007 Ford Focus, Toyota Corolla, 2006 Volvo S40, and 2008 Volkswagen Golf. Five to six contact points were chosen for each unique seat model guided by contact locations determined from real world crashes. Each vehicle seat was rigidly mounted in the center track position with the seatback angle adjusted to 70 degrees above the horizontal.

Computational modeling is a potentially powerful tool to provide information about the mechanisms of traumatic brain injury. In order to ensure that the estimates calculated by these computer models provide the most useful information, it is essential that these models contain accurate central nervous system (CNS) tissue properties. Previous material property measurements lack strict control over crucial experimental parameters that may influence material properties and tail to examine any regional variation in the measured response. To address these issues, we measured the material response of two regions of the CNS, the brainstem and the cerebrum. Specifically, adult porcine tissue was subjected to high loading rate mechanical deformation using a custom designed oscillatory shear device. Complex shear moduli were calculated over a range of frequencies (20-200 Hz) at two engineering strain amplitudes (2.5%, and 5.0%).

Pediatric Anthropomorphic Test Devices (ATDs) are valuable tools for assessing the injury mitigation capability of automotive safety systems. The neck pendulum test is widely used in biofidelity assessment and calibration of the ATD neck, and neck moment vs. angle response requirements are the metrics typically derived from the test. Herein, we describe the basis and methods for modifying the neck pendulum such that it more closely reflects base of the neck accelerations observed by a restrained three-year old ATD in a frontal crash. As a measure of base of the neck acceleration, the x-direction chest acceleration from thirty-one restrained Hybrid III three-year-old ATDs in vehicle frontal crash tests were analyzed. The standard neck pendulum yielded a mean peak acceleration that is 1.2x the peak of vehicle base of the neck accelerations, 1.6x the average, and 0.24x the duration.

The present study describes the development of a refined finite element model of the human pelvis. The objectives of this research work were to: Statistically study the human pelvis geometry, and develop a parameterized model. Mechanically validate the model with regard to the available in-house experimental data. Model the injury mechanisms observed in the experimental studies. The significant dimensions of the pelvis were identified by statistical analysis of the pelvis geometry based on the Reynolds et al. data [1]. Those dimensions were used to classify the in-house tested pelves. An interpolation technique (Kriging [2, 3, 4, 5, 6, 7 and 8]) was then used in order to distort a reference mesh and adapt its geometry to the measured geometry of the tested pelvis. The mechanical validation of the model was carried out by comparing numerical and experimental results, and the influence of the geometrical variations on the behavior of the pelvis was thus assessed.

This study presents a detailed comparison of internally and externally measured chest deflections resulting from eight tests conducted on three male post mortem human subjects. A hydraulically driven shoulder belt loaded the anterior thorax under a fixed spine condition while displacement data were obtained via a high-speed 16-camera motion capture system (VICON MX™). Comparison of belt displacement and sternal displacement measured at the bone surface provided a method for quantifying effective change in superficial soft tissue depth at the mid sternum under belt loading. The relationship between the external displacement and the decrease in the effective superficial tissue depth was found to be monotonic and nonlinear. At 65 mm of mid-sternal posterior displacement measured externally, the effective thickness of the superficial tissues and air gap between the belt and the skin had decreased by 14 mm relative to the unloaded state.

A finite element human model has been developed to simulate occupant behavior and to estimate injuries in real-world car crashes. The model represents an average adult male of the US population in a driving posture. Physical geometry, mechanical characteristics and joint structures were replicated as precise as possible. The total number of nodes and materials is around 67,000 and 1,000 respectively. Each part of the model was not only validated against human test data in the literature but also for realistic loading conditions. Additional tests were newly conducted to reproduce realistic loading to human subjects. A data set obtained in human volunteer tests was used for validating the neck part. The head-neck kinematics and responses in low-speed rear impacts were compared between the measured and calculated results. The validity of the lower extremity part was examined by comparing the tibia force in a foot impact between the test data and simulation results.

This paper discusses struck-side occupant thoracic response to side-impact loading and the requirements of a sled system capable of reproducing the relevant motions of a laterally impacted vehicle. A simplified viscoelastic representation of a thorax is used to evaluate the effect of the door velocity-time profile on injury criteria and on the internal stress state of the thorax. Simulations using a prescribed door velocity-time profile (punch impact) are contrasted against simulations using a constant-velocity impact (Heidelberg-type impact). It is found that the stress distribution and magnitude within the thorax, in addition to the maximum thorax compression and viscous response, depend not only on the door-occupant closing velocity, but also on the shape of the door velocity-time profile throughout the time of contact with the occupant. A sled system capable of properly reproducing side-impact door and seat motion is described.

On-site, in-depth investigations were conducted on 14 crashes involving 15 children who sustained facial fractures. Of the 23 facial fractures documented, the most frequent were the nose (n=8), orbit (n=6), zygoma/maxilla (n=6), and mandible (n=3). The most frequent contact point of those seated in the rear was the rear of the front seat; of those seated in the front, the instrument panel. 11/15 had sub-optimal torso restraint resulting from placing the shoulder belt behind their back or sitting in a position only equipped with a lap belt. The data suggest that these injuries resulted from high-energy impact with interior vehicle components. Revision to FMVSS 201 to account for vehicle interior structures typically contacted by child occupants and enhancement of pediatric dummies to measure facial impact forces should be considered.

Restrained children between the ages of 3 to 15 years in crashes were identified in an on-going crash surveillance system (1998-2002) which links insurance claims data to telephone survey and crash investigation data. The risk of upper extremity injury associated with airbag deployment was estimated and a series of cases was examined using in-depth crash investigation to identify the mechanisms of these injuries. This study found that 3.5% of children who were exposed to a passenger airbag (PAB) received an upper extremity fracture, making them 2.5 times as likely to sustain an upper extremity fracture than children in similar crashes who were not exposed to a PAB. Female children were 2.2 times as likely to receive an isolated upper extremity fracture when exposed to a PAB than male children. The incidence rate, gender difference, and injury mechanism in children all appear to be similar to those of adults.

This paper compares restrained Hybrid III and THOR thoracic kinematics and cadaver injury outcome in 30° oblique frontal and in full frontal sled tests. Peak shoulder belt tension, the primary source of chest loading, changed by less than four percent and peak chest resultant acceleration changed by less than 10% over the 30° range tested. Thoracic kinematics were likewise insensitive to the direction of the collision vector, though they were markedly different between the two dummies. Mid-sternal Hybrid III chest deflection, measured by the standard sternal potentiometer and by supplemental internal string potentiometers, was slightly lower (∼10%) in the oblique tests, but the oblique tests produced a negligible increase in lateral movement of the sternum. In an attempt to understand the biofidelity of these dummy responses, a series of 30-km/h human cadaver tests having several collision vectors (0°, 15°, 30°, 45°) was analyzed.

Current crash dummy biofidelity standards include the estimated effects of tensing the muscles of the thorax. This study reviewed the decision to incorporate muscle tensing by examining relevant past studies and by using an existing mathematical model of thoracic impacts. The study finds evidence that muscle tensing effects are less pronounced than implied by the biofidelity standard response corridors, that the response corridors were improperly modified to include tensing effects, and that tensing of other body regions, such as extremity bracing, may have a much greater effect on the response and injury potential than tensing of only the thoracic musculature. Based on these findings, it is recommended that muscle tensing should be eliminated from thoracic biofidelity requirements until there is sufficient information regarding multi-region muscle tensing response and the capability to incorporate this new data into a crash dummy.

Rupture of the thoracic aorta is a leading cause of rapid fatality in automobile crashes, but the mechanism of this injury remains unknown. One commonly postulated mechanism is a differential motion of the aortic arch relative to the heart and its neighboring vessels caused by high-magnitude acceleration of the thorax. Recent Indy car crash data show, however, that humans can withstand accelerations exceeding 100 g with no injury to the thoracic vasculature. This paper presents a method to investigate the efficacy of acceleration as an aortic injury mechanism using high-acceleration, low chest deflection sled tests. The repeatability and predictability of the test method was evaluated using two Hybrid III tests and two tests with cadaver subjects. The cadaver tests resulted in sustained mid-spine accelerations of up to 80 g for 20 ms with peak mid-spine accelerations of up to 175 g, and maximum chest deflections lower than 11% of the total chest depth.

Data presented in this paper demonstrated that the landscape for child occupant protection - the children and their restraints, vehicles, and crashes - is changing rapidly. Children are not small adults but are rather rapidly growing, developing, and changing and so too are their restraint needs. The past several years witnessed a growing awareness of these biomechanical challenges with the emergence of increased use of size-appropriate restraints for children under age 9 years and differences in patterns of injury by age. Vehicles involved in crashes with children reflect the trend overall: less passenger vans and cars and more light trucks, the majority of which are equipped with second generation air bags. The majority of crashes occurred on roads with posted speed limits below 45 miles per hour. The age group of particular concern is the newly driving teenage years (16-19) in which the crash and fatality rates are the highest among all age groups.

This paper presents thoracic response corridors developed using fifteen post-mortem human subjects (PMHS) subjected to single and double diagonal belt, distributed, and hub loading on the anterior thorax. We believe this is the first study to quantify the force-deflection response of the same thorax to different loading conditions using dynamic, non-impact, restraint-like loading. Subjects were positioned supine on a table and a hydraulic master-slave cylinder arrangement was used with a high-speed materials testing machine to provide controlled chest deflection at a rate similar to that experienced by restrained PMHS in a 48-km/h sled test. All loading conditions were tested at a nominally non-injurious level initially. When the battery of non-injurious tests was completed, a single loading condition was used for a final, injurious test (nominal 40% chest deflection).

This study evaluated the response of restrained post-mortem human subjects (PMHS) in 40 km/h frontal sled tests. Eight male PMHS were restrained on a rigid planar seat by a custom 3-point shoulder and lap belt. A video motion tracking system measured three-dimensional trajectories of multiple skeletal sites on the torso allowing quantification of ribcage deformation. Anterior and superior displacement of the lower ribcage may have contributed to sternal fractures occurring early in the event, at displacement levels below those typically considered injurious, suggesting that fracture risk is not fully described by traditional definitions of chest deformation. The methodology presented here produced novel kinematic data that will be useful in developing biofidelic human models.

The Acoustic Startling Pre-stimulus (ASPS, i.e. a loud sound preceding a physical perturbation) was previously found to accelerate action execution in simple flexion exercises. Therefore in this study we examined if ASPS can accelerate take-over reaction times in restrained teen and adult drivers who were asked to reach for the steering wheel while experiencing sled lateral perturbations simulating a vehicle swerve. Results showed that adult drivers lift their hands toward the steering wheel faster with the ASPS versus without (161 ± 23 ms vs 216 ± 27 ms, p<0.003). However this effect was not found in teens or in trials where the drivers were engaged in a secondary task. Adults also showed reduced lateral trunk displacement out of the seat belt with the ASPS. The ASPS could represent a novel warning that reduces take over time and out-of-position movements in critical autonomous driving scenarios.

Although previous research has linked poor seat belt fit to abdominal organ injury for children, few have studied the pattern of pediatric abdominal injuries and its relationship to key characteristics beyond this primary association. In this study, data were obtained from a probability sample of 19,125 children, representing 243,540 children, under age 16 years who were enrolled in an on-going crash surveillance system which links insurance claims data to validated telephone survey and crash investigation data. The risk of AIS2+ abdominal injury was estimated for various crash, restraint, vehicle and child correlates and multivariate logistic regression was used to identify the relative importance of these predictors. Children 4–8 years of age were at the highest risk of abdominal injury: they were 24.5 times and 2.6 times more likely to sustain an AIS2+ abdominal injury than those 0–3 years and 9–15 years, respectively.

The human body undergoes a variety of changes as it ages through adulthood. These include both morphological (structural) changes (e.g., increased thoracic kyphosis) and material changes (e.g., osteoporosis). The purpose of this study is to evaluate structural changes that occur in the aging bony thorax and to assess the importance of these changes relative to the well-established material changes. The study involved two primary components. First, full-thorax computed tomography (CT) scans of 161 patients, age 18 to 89 years, were analyzed to quantify the angle of the ribs in the sagittal plane. A significant association between the angle of the ribs and age was identified, with the ribs becoming more perpendicular to the spine as age increased (0.08 degrees/year, p=0.012). Next, a finite element model of the thorax was used to evaluate the importance of this rib angle change relative to other factors associated with aging.

Accurate pediatric thoracic force and deflection data are critical to develop biofidelic pediatric anthropomorphic test devices (ATDs) used in designing motor vehicle safety systems for child occupants. Typically, postmortem human subject (PMHS) experiments are conducted to gather such data. However, there are few pediatric PMHS available for impact research; therefore, novel methods are required to determine pediatric biomechanical data from children. In this study, we have leveraged the application of chest compressions provided in the clinical environment during pediatric cardiopulmonary resuscitation (CPR) to collect this fundamental data. The maximum deflection of the chest during CPR is in the range of chest deflections in PMHS impact experiments and therefore CPR exercises the chest in ways that are meaningful for biofidelity assessment. Thus, the goal of this study was to measure the force-deflection characteristics of the thorax of children and young adults during CPR.

This paper describes the injuries generated during dynamic belt loading to a porcine model of the 6-year-old human abdomen, and correlates injury outcomes with measurable parameters. The test fixture produced transverse, dynamic belt loading on the abdomen of 47 immediately post-mortem juvenile swine at two locations (upper/lower), with penetration magnitudes ranging from 23% – 65% of the undeformed abdominal depth, with and without muscle tensing, and over a belt penetration rate range of 2.9 m/s – 7.8 m/s. All thoracoabdominal injuries were documented in detail and then coded according to the Abbreviated Injury Scale (AIS). Observed injuries ranged from AIS 1 to AIS 4. The injury distribution matched well the pattern of injuries observed in a large sample of children exposed to seatbelt loading in the field, with most of the injuries in the lower abdomen.