Epidemiology of injury patterns for 4- to 10-year-olds in side and oblique impacts

OBJECTIVES

With regard to the pediatric population involved in vehicle side impact collisions, epidemiologic data can be used to identify specific injury-producing conditions and offer possible safety technology effectiveness through population-based estimates. The objective of the current study was to perform a field data analysis to investigate injury patterns and sources of injury to 4- to 10-year-olds in side and oblique impacts to determine the potential effect of updated side impact regulations and airbag safety countermeasures.

METHODS

The NASS-CDS, years 1991 to 2014, was analyzed in the current study. The Abbreviated Injury Scale (AIS) 2005-Update 2008 was used to determine specific injuries and injury severities. Injury distributions were examined by body region as specified in the AIS dictionary and the Maximum AIS (MAIS). Children ages 4 to 10 were examined in this study. All occupant seating locations were investigated. Seating positions were designated by row and as either near side, middle, or far side. Side impacts with a principal direction of force (PDOF) between 2:00 and 4:00 as well as between 8:00 and 10:00 were included. Restraint use was documented only as restrained or unrestrained and not whether the restraint was being used properly. Injury distribution by MAIS, body region, and source of injury were documented. Analysis regarding occupant injury severity, body region injured, and injury source was performed by vehicle model year to determine the effect of updated side impact testing regulation and safety countermeasures. Because the aim of the study was to identify the most common injury patterns and sources, only unweighted data were analyzed.

RESULTS

Main results obtained from the current study with respect to 4- to 10-year-old child occupants in side impact were that a decrease was observed in frequency of MAIS 1-3 injuries; injuries to the head, face, and extremities; as well as injuries caused by child occupant interaction with the vehicle interior and seatback support structures in 1998 model year passenger cars and newer.

CONCLUSIONS

Results from this study could be useful in design advances of pediatric anthropomorphic test devices, child restraints, as well as vehicles and their safety countermeasure systems.

Biofidelity assessment of the 6-year-old ATDs in lateral impact

OBJECTIVES

The objective of this study was to assess and compare the current lateral impact biofidelity of the shoulder, thorax, abdomen, and pelvis of the Q6, Q6s, and Hybrid III (HIII) 6-year-old anthropomorphic test devices (ATDs) through lateral impact testing.

METHODS

A series of lateral impact pendulum tests, vertical drop tests, and Wayne State University (WSU) sled tests was performed, based on the procedures detailed in ISO/TR 9790 (1999) and scaling to the 6-year-old using Irwin et al. ( 2002 ). The HIII used in this study was tested with the Ford-designed abdomen described in Rouhana ( 2006 ) and Elhagediab et al. ( 2006 ). The data collected from the 3 different ATDs were filtered using SAE J211 (SAE International 2003 ), aligned using the methodology described by Donnelly and Moorhouse ( 2012 ), and compared for each body region tested (shoulder, thorax, abdomen, and pelvis). The biofidelity performance in lateral impact for the 3 ATDs was assessed against the scaled biofidelity targets published in Irwin et al. ( 2002 ), the abdominal biofidelity target suggested in van Ratingen et al. ( 1997 ), and the biofidelity targets published in Rhule et al. ( 2013 ). Regional and overall biofidelity rankings for each of the 3 ATDs were performed using both the ISO 9790 biofidelity rating system (ISO/TR 9790 1999) and the NHTSA's external biofidelity ranking system (BRS; Rhule et al. 2013 ).

RESULTS

All 3 6-year-old ATD's pelvises were rated as least biofidelic of the 4 body regions tested, based on both the ISO and BRS biofidelity rating systems, followed by the shoulder and abdomen, respectively. The thorax of all 3 ATDs was rated as the most biofidelic body region using the aforementioned biofidelity rating systems. The HIII 6-year-old ATD was rated last in overall biofidelity of the 3 tested ATDs, based on both rating systems. The Q6s ATD was rated as having the best overall biofidelity using both rating systems.

CONCLUSIONS

All 3 ATDs are more biofidelic in the thorax and abdomen than the shoulder and pelvis, with the pelvis being the least biofidelic of all 4 tested body regions. None of the 3 tested 6-year-old ATDs had an overall ranking of 2.0 or less, based on the BRS ranking. Therefore, it is expected that none of the 3 ATDs would mechanically respond like a postmortem human subject (PMHS) in a lateral impact crash test based on this ranking system. With respect to the ISO biofidelity rating, the HIII dummy would be considered unsuitable and the Q-series dummies would be considered marginal for assessing side impact occupant protection.

Lower extremity injuries in lateral impact: a retrospective study

ABSTRACT A retrospective analysis of the NASS/CDS database from 1993 to 2000 was used to investigate lower extremity injury in lateral impact. The analysis includes the study of the injury patterns, crash characteristics and the interactions between the occupant and the vehicle interior, including injuries to the farside occupants. The findings include significantly different injury patterns for the nearside and farside impacts. In particular, while the proportion of pelvis/hip injuries, with respect to AIS2 and AIS3 lower extremity skeletal injuries and 2-4 and 10-8 o'clock side impacts, was higher in nearside (70.4%) than farside (38.3%), the opposite trend was observed for the thigh (2.8% vs 4.5%), knee (6.2% vs 16.7%), leg (10.1% vs 19.5%) and foot/ankle (5.6% vs 14.7) injuries. Analysis of the PDOF suggested that a large proportion the impacts occurred obliquely, at approximately 10 and 2 o'clock, with a rearward component of force. It is hoped that the findings of the current study can help to investigate injury mechanisms.

Investigation into the noise associated with airbag deployment: part III - sound pressure level and auditory risk as a function of inflatable device

Several criteria for assessing noise-induced hearing loss from automotive inflatable devices, such as airbags, were proposed in the past. However, their development was based on epidemiological studies of steady state noise and not impulsive noise. More recently, the US Army Research Laboratory (ARL) developed and validated a mathematical model of the ear, which may be used to assess noise induced hearing loss from impulsive noise sources. Previous studies have contributed to understanding the effects of impulse noise on occupants, but were performed on first generation frontal airbags and did not provide information on airbag and occupant safety systems in today's fleet of vehicles. This study presents the results of a parametric investigation of current inflatable devices across a variety of vehicles and considers the size and seating location of the occupant in vehicles of varying volume. In addition, the study considers advanced airbag technologies such as dual stage frontal airbags, side airbags, inflatable curtains, and seat belt pretensioners.

Prediction of airbag-induced forearm fractures and airbag aggressivity

This study continued the biomechanical investigations of forearm fractures caused by direct loading of steering-wheel airbags during the early stages of deployment. Twenty-four static deployments of driver airbags were conducted into the forearms of unembalmed whole cadavers using a range of airbags, including airbags that are depowered as allowed by the new federal requirements for frontal impact testing. In general, the depowered airbags showed a reduction in incidence and severity of forearm fractures compared to the pre-depowered airbags tested. Data from these twenty-four tests were combined with results from previous studies to develop a refined empirical model for fracture occurrence based on Average Distal Forearm Speed (ADFS), and a revised value for fifty-percent probability of forearm-bone fracture of 10.5 m/s. Bone mineral content, which is directly related to forearm tolerance, was found to be linearly related to arm mass. The ADFS criterion was found to be effective in predicting forearm fracture, regardless of the airbag system, subject size, and age. Additional testing was conducted to examine the principles underlying the ADFS criterion. Specifically, static airbag-deployments were conducted into cylinders of different mass to study the relationships between forearm mass and forearm-to-airbag module distance relative to ADFS. ADFS was found to be linearly but inversely related to cylinder mass, and to the distance between the forearm and airbag module. The suitability of using existing surrogate arms to assess airbag aggressivity relative to forearm fractures using ADFS was explored as well.

Development of a Reusable, Rate-Sensitive Abdomen for the Hybrid III Family of Dummies

The objective of this work was to develop a reusable, rate-sensitive dummy abdomen with abdominal injury assessment capability. The primary goal for the abdomen developed was to have good biofidelity in a variety of loading situations that might be encountered in an automotive collision. This paper presents a review of previous designs for crash dummy abdomens, a description of the development of the new abdomen, results of testing with the new abdomen and instrumentation, and suggestions for future work. The biomechanical response targets for the new abdomen were determined from tests of the mid abdomen done in a companion biomechanical study. The response of the abdominal insert is an aggregate response of the dummy's entire abdominal area and does not address differences in upper versus lower abdominal response, solid versus hollow organs, or organ position or mobility. While the abdomen developed has demonstrated good biofidelity in rigid bar, seat belt and airbag loading situations, some work remains to be done before it can be used in crash testing.

Abdominal impact response to rigid-bar, seatbelt, and airbag loading

This study was conducted to resolve discrepancies and fill in gaps in the biomechanical impact response of the human abdomen to frontal impact loading. Three types of abdominal loading were studied: rigid-bar impacts, seatbelt loading, and close-proximity (out-of-position) airbag deployments. Eleven rigid-bar free-back tests were performed into the mid and upper abdomens of unembalmed instrumented human cadavers using nominal impact speeds of 6 and 9 m/s. Seven fixed-back rigid-bar tests were also conducted at 3, 6, and 9 m/s using one cadaver to examine the effects of body mass, spinal flexion, and repeated testing. Load-penetration corridors were developed and compared to those previously established by other researchers. Six seatbelt tests were conducted using three cadavers and a peak-loading rate of 3 m/s. The seatbelt loading tests were designed to maximize belt/abdomen interaction and were not necessarily representative of real-world crashes. The results were compared to data previously obtained by other researchers using swine and were used to establish a new abdominal load-penetration corridor for belt loading. Passenger frontal airbags were deployed into the closely positioned abdomen of three unembalmed cadavers. The penetration-time histories were used to guide the development of a repeatable high-speed surrogate airbag-loading device that uses a low-mass cylinder to simulate the initial breakout phase of close-proximity passenger airbag loading of the abdomen. This device was used to conduct simulated out-of-position airbag tests into three cadaver abdomens. The abdomen response data from these standardized tests were used to develop a load-penetration corridor for abdomen response to out-of-position airbag deployments.

Hearing loss and automobile airbag deployments

In an on-going research program, on the causation of injuries in motor vehicle accidents, at the University of Michigan Transportation Research Institute, crashes with airbags have been, and are continuing to be, investigated. In order to determine the occurrence, if any, of 'hearing problems' associated with airbag deployments, drivers and passengers who had been involved in 'airbag' automobile crashes were interviewed by telephone. From the crashes investigated, 225 attempts were made to contact drivers who were exposed to airbag deployments. From these telephone interviews, contacts were made with 177 car occupants. Only three reported that they had experienced any type of hearing-related problems subsequent to their crash. One other case is reported of a driver who had pre-crash hearing loss. It appears that permanent hearing deficit due to airbag deployment, both in cars with the steering wheel airbag alone, and in those with a passenger side airbag, is an infrequent event (1.7%) from the data of this study.

Physical and chemical characterization of airbag effluents

OBJECTIVE

This paper describes a study aimed at characterizing the exposure to physical and chemical by-products from the deployment of airbag restraint systems.

DESIGN, MATERIALS AND METHODS

Specifically, the levels of particulates and the composition of gases and bag fabric speed were measured in the passenger compartment following deployment of either a driver's side or driver's side/passenger's side airbag system.

MEASUREMENTS

A Fourier transform infrared analyzer (FTIR) and chemiluminescence analyzers were used for gas analysis, a cascade impactor and gravimetric filter measurements for aerosol determination and high-speed films to determine fabric speed.

MAIN RESULTS AND CONCLUSIONS

The measured gases were found to be within the recommended guidelines for human exposures, but no guidelines exist for particle exposures of this magnitude (150-220 mg/m3) but short duration. High-speed films were also taken of the deployments to obtain an estimate of the fabric speed as it leaves the module. The maximum average speed for both types of airbag was approximately 100 mph and in both cases average speeds ranged from lows near 50 mph to highs of over 200 mph.

Blunt rupture of the diaphragm: mechanism, diagnosis, and treatment

In the absence of respiratory distress and massive visceral herniation, the diagnosis of blunt diaphragmatic disruption can be difficult. This is particularly true for diaphragmatic injuries confined to the right hemidiaphragm. Because diagnostic delay and strangulation are associated with notable increases in mortality and morbidity, it is important to identify the injury as early as possible. Victims of lateral impact motor vehicle collisions are more likely to experience rupture of the diaphragm than victims of frontal collisions. Occupants exposed to left lateral impacts are at greatest risk. The side of diaphragmatic rupture correlates with the direction of impact. The right hemidiaphragm is more resistant to rupture. Deformation shear is a more plausible mechanism for diaphragmatic rupture after lateral impacts. Knowledge of the mechanisms that produce this injury combined with information regarding the victim's seat position and direction of the impacting force should lead to a high index of clinical suspicion for diaphragmatic rupture. Chest radiography and diagnostic peritoneal lavage will establish the correct diagnosis in almost 90% of the patients with acute diaphragmatic disruption. Additional diagnostic studies are reserved for the remaining 10% of patients. Due to the pressure differential between abdomen and thorax, the natural history of these injuries is one of enlargement, and none can be expected to heal spontaneously. Once the diagnosis has been established, the treatment of every diaphragmatic disruption is surgical repair.

Influence of velocity and forced compression on the severity of abdominal injury in blunt, nonpenetrating lateral impact

Lateral impacts of automobiles frequently result in abdominal injury to the occupants. While there have been important advances in the clinical management of this lateral impact trauma, the abdominal tolerance to injury from lateral impacts remains uncertain. The present report describes a series of 117 experiments in which the effect of changing the impact velocity and the forced abdominal compression upon the abdominal injuries sustained was monitored. The impact velocity was varied from 3 to 15 m/s, and the abdominal compression was varied from 10 to 50%. Serious injuries (AIS greater than or equal to 3) occurred in the following proportions of the total number of serious injuries: renal (54%), hepatic (44%), and splenic (1%). Impact side was a significant factor in hepatic and splenic tolerance, but not in renal tolerance. An abdominal injury criterion (AIC) is proposed which is a function of the impact velocity times the forced abdominal compression, but more work is necessary before it can be applied to human beings.

Fluid flow in bone in vitro

Recent dielectric measurements suggest that the electromechanical effect in wet (fluid saturated) bone is not due to a piezoelectric effect. This would imply that the electromechanical effect observed in wet bone is due to a streaming potential and is therefore dependent on fluid flow in stressed bone. A model for fluid flow in bone in vitro is presented. This model predicts a rapid decay (of the order of a millisecond or less) for the fluid flow in Haversian systems. The implications of this result for the interpretation of the electromechanical effect in wet bone are discussed.