Rib and sternum fracture risks for restrained occupants in frontal car crashes

OBJECTIVE

Most car occupant fatalities occur in frontal crashes and the thorax is the most frequently injured body region. The objectives of the study were, firstly, to quantify the relation between risk factors (such as speed and occupant age) and rib and sternum fracture injury probability in frontal car crashes, and, secondly, to evaluate whether rib fracture occurrence can predict sternum fractures.

METHODS

Weighted German data from 1999-2021 were used to create the injury risk curves to predict both, at least moderate and at least serious, rib and sternum fracture risks. A contingency table for rib and sternum fractures allowed the calculation of sensitivity, specificity, and precision, as well as testing for the association.

RESULTS

Elderly occupants (≥65 years old) had increased rib and sternum fracture risk compared to mid aged occupants (18-64 years old). Besides occupant age, delta-V was always and sex sometimes a significant predictor for skeletal thoracic injury. Sternum fractures were more common than rib fractures and more likely to occur at any given delta-V. Sternum fractures occurred often in isolation. Female occupants were at higher risk than males to sustain at least moderate rib and sternum fractures together and sternum fractures in isolation. Rib and sternum fractures were associated, but low sensitivity and precision show that rib fractures do not predict sternum fractures well.

CONCLUSIONS

Elderly and female occupants were at the highest risk and should be targeted by thoracic injury criteria and thresholds for frontal crash occupant protection. Rib and sternum fractures were not associated. Therefore, sternum fractures need to be predicted and evaluated separately from rib fractures.

Preventive Effectiveness of Thoracic Side Airbags in Side-Impact Crashes Based on Korea In-Depth Accident Study (KIDAS) Database

Studies on the effectiveness of thoracic side airbags (tSABs) in preventing thoracic injuries is limited and conflicting. This retrospective observational study aims to evaluate the effectiveness of tSABs in side-impact crashes based on data for motor vehicle occupants (MVOs) who visited an emergency department in Korea. The data were obtained from the Korean In-Depth Accident Study (KIDAS) database for patients treated at Wonju Severance Christian Hospital between January 2011 and April 2020. Of the 3899 patients with road traffic injuries, data for 490 patients were used. The overall frequency of tSAB deployment in side-impact crashes was found to be 8.1%. In the multivariate analysis, elderly age, near-side impact, colliding with fixed objects, non-oblique force, and higher crush extent were found to be factors associated with higher thoracic injuries (Abbreviated Injury Scale ≥ 2). MVOs in crashes with tSAB deployment were at an increased risk of injury compared with MVOs in crashes with no deployment, but no statistical difference was observed [adjusted odds ratios (AORs): 1.65 (0.73-3.73)]. Further, the incidence of lung injury and rib fractures increased with tSAB activation (p < 0.05). These results demonstrate the limited capability of tSABs in preventing thoracic injuries in motor vehicle crashes.

The association between vehicle rim type and risk of occupant injury

OBJECTIVES

Modern vehicles generally use steel fabricated or alloy blended rims. The manufacturing process and atomic structure of the rim both yield different responses under destructive loading. The aim of this research was to investigate to what extend the type of vehicle rim may influence occupant injury risk.

METHODS

A matched cohort study of frontal German In-Depth Accident Study collisions was devised. The risk of injury to various body regions was compared between vehicles with steel and alloy rims.

RESULTS

Occupants in vehicles with alloy rims were at a greater risk of thoracic injury (relative risk [RR] = 1.57; 95% confidence interval [CI], 1.01-2.42) and thoracic abdomen injury (RR = 1.62; 95% CI, 1.10-2.39) at the Maximum Abbreviations Injury Scale (MAIS) 2+ severity. Risk of thoracic injury was greatest for the cluster of occupants seated on the nonimpacted side in frontal collisions (RR = 2.21; 95% CI, 1.01-4.86). MAIS 2+ injury to the head/face/neck yielded no association (RR = 0.98; 95% CI, 0.66-1.47).

CONCLUSION

Alloy rims are more brittle and, as a result, destructive loading is realized with less severe impact. The critical failure increases the amount of loading that needs to be distributed by the restraint system and results in injury.

Fatal side impact crash scenarios for rear seat and seat belt-restrained occupants from vulnerable populations

Objective: Previous studies have revealed vulnerability of school-age children and older adults in rear seats in motor vehicle crashes. Detailed information about crashes in which these fatalities occur could help improve vehicle and restraint design.Methods: Police accident reports were obtained for crashes from the Fatality Analysis Reporting System data set. Inclusion criteria were crashes in which there was at least one fatally injured restrained rear seat occupant between the ages of 6 and 12 or 55 and older in a passenger vehicle no older than 10 years at the time of the crash. Reports were reviewed for key crash data. Side impacts were selected for analysis.Results: Thirty-nine side impact crashes met the inclusion criteria, resulting in 46 fatalities of interest. Far-side or nondirect impact cases outnumbered near-side cases by 15-11 for juvenile occupants. Sixty-one percent of occupants were in vehicles with side airbags (SABs), all of which deployed for their position, although torso SABs were only present in 3 cases. Head injuries were present in all juvenile cases with injury data available and older occupants suffered equally from head and torso injuries. Impacts with pickup trucks and heavy trucks made up 31 and 22% of all cases, respectively. Three-quarters of cases were judged as survivable for the fatally injured occupant(s), and 5 of 7 cases deemed unsurvivable involved juvenile decedents. Further, of those deemed survivable, two-thirds had damage comparable in magnitude with the same vehicles in consumer information crash tests, evaluated by photo comparison.Conclusions: Older adults suffered thoracic injuries at a higher rate than older children-who suffered predominately head injuries-and most vehicles did not have torso SABs installed, which could have mitigated thoracic injuries. Side impacts in which younger occupants were killed were more severe than impacts that resulted in the death of an older occupant; however, vehicle damage and intrusion in many fatal impacts for both age cohorts appeared similar to that of consumer information testing. Large pickups and heavy vehicles were the striking vehicle in over half of all fatalities; vehicle designs and crash tests should continue to take this into consideration. This research highlights the need for continued work as the automotive safety community seeks to eliminate fatalities in motor vehicle crashes.

Cross-correlation between the controlled collision environment and real-world motor vehicle collisions: Evaluating the protection of the thoracic side airbag

OBJECTIVE

Thoracic side airbags (tSABs) were integrated into the vehicle fleet to attenuate and distribute forces on the occupant's chest and abdomen, dissipate the impact energy, and move the occupant away from the intruding structure, all of which reduce the risk of injury. This research piece investigates and evaluates the safety performance of the airbag unit by cross-correlating data from a controlled collision environment with field data.

METHOD

We focus exclusively on vehicle-vehicle lateral impacts from the NHTSA's Vehicle Crash Test Database and NASS-CDS database, which are replicated in the controlled environment by the (crabbed) barrier impact. Similar collisions with and without seat-embedded tSABs are matched to each other and the injury risks are compared.

RESULTS

Results indicated that dummy-based thoracic injury metrics were significantly lower with tSAB exposure (P <.001). Yet, when the controlled collision environment data were cross-correlated with NASS-CDS collisions, deployment of the tSAB indicated no association with thoracic injury (tho. MAIS 2+ unadjusted relative risk [RR] = 1.14; 90% confidence interval [CI], 0.80-1.62; tho. MAIS 3+ unadjusted RR = 1.12; 90% CI, 0.76-1.65).

CONCLUSION

The data from the controlled collision environment indicated an unequivocal benefit provided by the thoracic side airbag for the crash dummy; however, the real-world collisions demonstrate that no benefit is provided to the occupant. This has resulted from a noncorrelation between the crash test/dummy-based design taking the abstracting process too far to represent the real-world collision scenario.

The influence of child restraint lower attachment method on protection offered by forward facing child restraint systems in oblique loading conditions

OBJECTIVE

The research objective was to quantify the influence of child restraint lower attachment method on head kinematics, head impact potential, and head, neck, and thorax injury metrics for a child occupant secured in a forward-facing child restraint system (FFCRS) in oblique side impacts.

METHODS

Fifteen sled tests were conducted with a Q3s seated in an FFCRS secured to the center position on a production small SUV bench seat. Three lower attachment methods were evaluated: rigid ISOFIX, a flexible single loop lower anchors and tethers for children (LATCH) webbing routed through the vehicle belt path of the FFCRS, and dual flexible LATCH webbing attachments on either side of the FFCRS. All were tested with and without a tether with one repeat test in each test condition. The same model FFCRS was used for all tests; only the attachment method varied. The vehicle bench seat was fixed on the sled carriage at 80° (from full frontal). The input pulse was the proposed FMVSS 213 side impact pulse scaled to a 35 km/h delta-v. Two-way analysis of variance (ANOVA) was used to evaluate the effect of lower attachment and tether use on 3 outcome metrics: lateral head excursion, neck tension, and neck lateral bending. Data included anthropomorphic test dummy (ATD) head excursions, head linear accelerations and angular velocities, neck loads and moments, thoracic accelerations, lateral chest deflections, lower anchor loads, and tether webbing loads. ATD head kinematics were collected from 3-dimensional motion capture cameras.

RESULTS

Results demonstrated a reduction in injury measures with the rigid ISOFIX and dual webbing attachment compared to the single webbing attachment with decreased lateral head excursions (331, 356, and 441 mm for the rigid ISOFIX, dual webbing, and single webbing systems, respectively, P <.0001), neck tension (1.4, 1.6, and 2.2 kN, P <.01), and neck lateral bending (31.8, 38.7, and 38.0 Nm, P =.002). The tether had a greater influence on lateral head excursion for the FFCRS with flexible webbing attachments than those with the rigid attachment, with the tether forces being highest with the single webbing attachment. Lateral head excursions were significantly lower and lateral neck bending moments were significantly higher with tether use (P <.0001) across all lower attachments. The effect of tether on neck tension was mixed, only showing an increased effect with the rigid ISOFIX system.

CONCLUSION

The CRS lower attachment system influenced occupant kinetics. The results indicate that CRS attached to the vehicle via rigid and dual webbing systems exhibit improved kinematics by reducing the rotation and tipping seen with the single webbing attachment. This leads to reduced lateral head excursions and neck tension values. The advantages of the tether in reducing lateral head excursion in side impacts are most pronounced with the flexible webbing attachments. With tether use low in the United States, a dual webbing type FFCRS attachment system may be a better attachment method than single webbing and provide a simpler engineering solution than rigid ISOFIX attachment.

CPR-related thoracic injuries: comparison of CPR guidelines between 2010 and 2015

Background/aim: This study aimed to evaluate traumatic thorax complications in post-CPR patients and to investigate whether or not there has been a decrease in these complications since the adoption of current chest compression recommendations. Materials and methods: Post-CPR patients with return of spontaneous circulation (ROSC) were admitted between January 2014 and January 2016 were analyzed retrospectively. Patients admitted to the ED in 2014 were resuscitated according to 2010 AHA CPR guidelines, while those admitted to the ED in 2015 were resuscitated according to current ERC CPR guidelines. Results: The study population comprised 48 male and 35 female patients. Of the 2010 AHA guideline patients, 39.21% experienced pulmonary contusion, while 54.83% of 2015 ERC guideline patients had pulmonary contusion. It was found that 11.76% of 2010 AHA guideline patients and 3.22% of 2015 ERC guideline patients had pneumothorax, while 9.8% of 2010 AHA guideline patients and 12.9% of 2015 ERC guideline patients experienced hemothorax. Incidence rates of lung contusion, pneumothorax, and hemothorax were higher in patients with rib fractures. Conclusion: In this study, traumatic thoracic complications were investigated in patients with ROSC after CPR. The incidence of CRP-related injuries did not decrease on application of the new 2015 ERC CPR guideline recommendations. The most common injury in this study was rib fracture, followed by sternal fracture, lung contusion, hemothorax, and pneumothorax. Statistically, rib fracture had a positive relationship with lung contusion, hemothorax, and pneumothorax.

Efficacy of seat-mounted thoracic side airbags in the German vehicle fleet

OBJECTIVE

Thoracic side airbags (tSABs) deploy within close proximity to the occupant. Their primary purpose is to provide a protective cushion between the occupant and the intruding door. To date, various field studies investigating their injury mitigation has been limited and contradicting. The research develops efficacy estimations associated for seat-mounted tSABs in their ability to mitigate injury risk from the German collision environment.

METHODS

A matched cohort study using German In-Depth Accident Study (GIDAS) data was implemented and aims to investigate the efficacy of seat-mounted tSAB units in preventing thoracic injury. Inclusion in the study required a nearside occupant involved in a lateral collision where the target vehicle exhibited a design year succeeding 1990. Collisions whereby a tSAB deployed were matched on a 1:n basis to collisions of similar severity where no airbag was available in the target vehicle. The outcome of interest was an incurred bodily or thoracic regional injury. Through conditional logistic regression, an estimated efficacy value for the deployed tSAB was determined.

RESULTS

A total of 255 collisions with the deployed tSAB matched with 414 collisions where no tSAB was present. For the given sample, results indicated that the deployed tSAB was not able to provide an unequivocal benefit to the occupant thoracic region, because individuals exposed to the deployed tSAB were at equal risk of injury (Thorax Maximum Abbreviated Injury Scale (Tho.MAIS)2+ odds ratio [OR] = 1.04, 95% confidence interval [CI], 0.41-2.62; Tho.MAIS3+ OR = 1.15, 95% CI, 0.41-3.18). When attempting to isolate an effect for skeletal injuries, a similar result was obtained. Yet, when the tSAB was coupled with a head curtain airbag, a protective effect became apparent, most noticeable for head/face/neck (HFN) injuries (OR = 0.59, 95% CI, 0.21-1.65).

CONCLUSION

The reduction in occupant HFN injury risk associated with the coupled tSAB and curtain airbag may be attributable to its ability to provide coverage over previous mechanisms of injury. Yet, the sole presence of the tSAB showed no ability to provide additional benefit for the occupant's thoracic region. Future work should identify mechanisms of injury in tSAB cases and attempt to quantify improvements in the vehicle's ability to resist intrusion.

Development of thoracic injury risk functions for the THOR ATD

The Test Device for Human Occupant Restraint (THOR) 50th percentile male anthropomorphic test device (ATD) aims to improve the ability to predict the risk of chest injury to restrained automobile occupants by measuring dynamic chest deflection at multiple locations. This research aimed to describe the methods for developing a thoracic injury risk function (IRF) using the multi-point chest deflection metrics from the 50th percentile male THOR Metric ATD with the SD-3 shoulder and associating to post-mortem human subjects (PMHS) outcomes that were matched on identical frontal and frontal-oblique impact sled testing conditions. Several deflection metrics were assessed as potential predictor variables for AIS 3+ injury risk, including a combined metric, called PC Score, which was generated from a principal component analysis. A parametric survival analysis (specifically, accelerated failure time (AFT) with Weibull distribution) was assessed in the development of the IRF. Model fit was assessed using various modeling diagnostics, including the area under the receiver operating characteristic curve (AUC). Models based on resultant deflection consistently exhibited improved fit compared to models based on x-axis deflection or chord deflection. Risk functions for the THOR PC Score and C_max (maximum resultant deflection) were qualitatively equivalent, producing AUCs of 0.857 and 0.861, respectively. Adjusting for the potential confounding effects of age, AFT survival models with C_max or PC Score as the primary deflection metric resulted in the THOR injury risk models with the best combination of biomechanical appropriateness, potential utility and model fit, and may be recommended as injury predictors.

Assessment of an innovative seat belt with independent control of the shoulder and lap portions using THOR tests, the THUMS model, and PMHS tests

OBJECTIVES

The objective of this study was to determine the potential chest injury benefits and influence on occupant kinematics of a belt system with independent control of the shoulder and lap portions.

METHODS

This article investigates the kinematics and dynamics of human surrogates in 35 km/h impacts with 2 different restraints: a pretensioning (PT), force-limiting (FL) seat belt, a reference belt system, and a concept design with a split buckle consisting (SB) of 2 separate shoulder and lap belt bands. The study combines mathematical simulations with the THOR dummy and THUMS human body model, and mechanical tests with the THOR dummy and 2 postmortem human surrogate (PMHS) tests of similar age (39 and 42 years) and anthropometry (62 kg, 181 cm vs. 60 kg, 171.5 cm). The test setup consisted of a rigid metallic frame representing a standard seating position of a right front passenger. The THOR dummy model predictions were compared to the mechanical THOR dummy test results. The THUMS-predicted number of fractured ribs were compared to the number of fractured ribs in the PMHS.

RESULTS

THOR sled tests showed that the SB seat belt system decreased chest deflection significantly without increasing the forward displacement of the head. The THOR model and the THOR physical dummy predicted a 13- and 7-mm reduction in peak chest deflection, respectively. Peak diagonal belt force in the mechanical test with the reference belt was 5,582 N and the predicted force was 4,770 N. The THOR model also predicted lower belt forces with the SB system than observed in the tests (5,606 vs. 6,085 N). THUMS predicted somewhat increased head displacement for the SB system compared to the reference system. Peak diagonal force with the reference belt was 4,000 N and for the SB system it was 5,200 N. The PMHS test with the SB belt resulted in improved kinematics and a smaller number of rib fractures (2 vs. 5 fractures) compared to the reference belt.

CONCLUSION

Concepts for a belt system that can reduce the load on the chest of the occupant in a crash and thereby reduce the number of injured occupants, in particular the elderly, was proposed.

Expanding pedestrian injury risk to the body region level: how to model passive safety systems in pedestrian injury risk functions

OBJECTIVE

Assessment of the effectiveness of advanced driver assistance systems (ADAS) plays a crucial role in accident research. A common way to evaluate the effectiveness of new systems is to determine the potentials for injury severity reduction. Because injury risk functions describe the probability of an injury of a given severity conditional on a technical accident severity (closing speed, delta V, barrier equivalent speed, etc.), they are predestined for such evaluations.

METHODS

Recent work has stated an approach on how to model the pedestrian injury risk in pedestrian-to-passenger car accidents as a family of functions. This approach gave explicit and easily interpretable formulae for the injury risk conditional on the closing speed of the car. These results are extended to injury risk functions for pedestrian body regions. Starting with a double-checked German In-depth Accident Study (GIDAS) pedestrian-to-car accident data set (N = 444) and a functional-anatomical definition of the body regions, investigations on the influence of specific body regions on the overall injury severity will be presented. As the measure of injury severity, the ISSx, a rescaled version of the well-known Injury Severity Score (ISS), was used. Though traditional ISS is computed by summation of the squares of the 3 most severe injured body regions, ISSx is computed by the summation of the exponentials of the Abbreviated Injury Scale (AIS) severities of the 3 most severely injured body regions. The exponentials used are scaled to fit the ISS range of values between 0 and 75.

RESULTS

Three body regions (head/face/neck, thorax, hip/legs) clearly dominated abdominal and upper extremity injuries; that is, the latter 2 body regions had no influence at all on the overall injury risk over the range of technical accident severities. Thus, the ISSx is well described by use of the injury codes from the same body regions for any pedestrian injury severity. As a mathematical consequence, the ISSx becomes explicitly decomposable into the 3 body regions and so are the risk functions as body region-specific risk functions. The risk functions for each body region are stated explicitly for different injury severity levels and compared to the real-world accident data.

CONCLUSIONS

The body region-specific risk functions can then be used to model the effect of improved passive safety systems. These modified body region-specific injury risk functions are aggregated to a new pedestrian injury risk function. Passive safety systems can therefore be modeled in injury risk functions for the first time. A short example on how the results can be used for assessing the effectiveness of new driver assistance systems concludes the article.

Improving the Chest Protection of Elderly Occupants in Frontal Crashes Using SMART Load Limiters

OBJECTIVE

To determine whether varying the seat belt load limiter (SBL) according to crash and occupant characteristics could have real-world injury reduction benefits in frontal impacts and, if so, to quantify those benefits.

METHODS

Real-world UK accident data were used to identify the target population of vehicle occupants and frontal crash scenarios where improved chest protection could be most beneficial. Generic baseline driver and front passenger numerical models using a 50th percentile dummy were developed with MADYMO software. Simulations were performed where the load limiter threshold was varied in selected frontal impact scenarios. For each SBL setting, restraint performance, dummy kinematics, and injury outcome were studied in 5 different frontal impact types. Thoracic injury predictions were converted into injury probability values using Abbreviated Injury Scale (AIS) 2+ age-dependent thoracic risk curves developed and validated based on a methodology proposed by Laituri et al. (2005). Real-world benefit was quantified using the predicted AIS 2+ risk and assuming that an appropriate adaptive system was fitted to all the cars in a real-world sample of recent frontal crashes involving European passenger cars.

RESULTS

From the accident data sample the chest was the most frequently injured body region at an AIS 2+ level in frontal impacts (7% of front seat occupants). The proportion of older vehicle front seat occupants (>64 years) with AIS 2+ injury was also greater than the proportion of younger occupants. Additionally, older occupants were more likely to sustain seat belt-induced serious chest injury in low- and moderate-speed frontal crashes. In both front seating positions, the low SBL provided the best chest injury protection, without increasing the risk to other body regions. In severe impacts, the low SBL allowed the driver to move dangerously close to the steering wheel. Compared to the driver side, greater ride-down space on the passenger side gave a higher potential for using the low SBLs. When applying the AIS 2+ risk reduction findings to the weighted accident data sample, the risk of sustaining an AIS 2+ seat belt injury changed to 0.9, 4.9, and 8.1% for young, mid, and older occupants, respectively, from their actual injury risk of 1.3, 7.6, and 13.1%.

CONCLUSIONS

These results suggest the potential for improving the safety of older occupants with the development of smarter restraint systems. This is an important finding because the number of older users is expected to increase rapidly over the next 20 years. The greatest benefits were seen at lower crash severities. This is also important because most real-world crashes occur at lower speeds.

A real-life based evaluation method of deployable vulnerable road user protection systems

OBJECTIVE

The aim of this study was to develop a real-life-based evaluation method, incorporating vulnerable road user (VRU) full-body loading to a vehicle with a deployable protection system in relevant test setups, and use this method to evaluate a prototype pedestrian and cyclist protection system.

METHODS

Based on accident data from severe crashes, the most common scenarios were selected and developed into 5 test setups, 2 for pedestrians and 3 for bicyclists. The Polar II pedestrian anthropomorphic test device was used, either standing or on a standard bicycle. These test setups could then be used to evaluate real-life performance of a prototype protection system, regarding both positioning and protection, for vulnerable road users. The protection system consisted of an active hood and a windshield airbag and was mounted on a large passenger car with a conventional hood-type front end. Injury evaluation criteria were selected for head, neck, and chest loading derived from occupant frontal and side impact test methods.

RESULTS

The protection system managed to be fully deployed, obtaining the intended position in time-that is, before VRU body contact-in all test setups, and head protection potential was not negatively influenced by the preceding thoracic impact. Head loading resulted in head injury criterion (HIC) values ranging up to 4400 for the standard car, and all HIC values were below 650 with the protection system. The risk of severe (Abbreviated Injury Scale [AIS] 3+) head injury decreased from 85% to 100% in 3 test setups (mainly to the windscreen frame), to less than a 20% risk in all setups. In general, there were larger differences between structures impacted than between the pedestrian and cyclist setup. Neck loading was maintained at an acceptable level or was slightly decreased by the protection system, and chest loading was decreased from high values in 2 test setups in which the cyclist was impacted laterally with chest impact mainly to the hood area.

CONCLUSIONS

A test method was developed to evaluate a more real-life-based test condition, as a complement to current component test methods. Being real-life based, including full-body loading, it is suggested as a complementary test method to the more simplified legal and rating component tests. Together these test methods will provide a more thorough evaluation of a protection system. The evaluated protection system performed well regarding both positioning and protection, indicating a capability to obtain the intended position in time with the potential to prevent the most common severe upper-body injuries of a pedestrian or cyclist in typical real-life accidents, without introducing negative side effects.

The rising burden of serious thoracic trauma sustained by motorcyclists in road traffic crashes

In many countries increased on-road motorcycling participation has contributed to increased motorcyclist morbidity and mortality over recent decades. Improved helmet technologies and increased helmet wearing rates have contributed to reductions in serious head injuries, to the point where in many regions thoracic injury is now the most frequently occurring serious injury. However, few advances have been made in reducing the severity of motorcyclist thoracic injury. The aim of the present study is to provide needed information regarding serious motorcyclist thoracic trauma, to assist motorcycling groups, road safety advocates and road authorities develop and prioritise counter-measures and ultimately reduce the rising trauma burden. For this purpose, a data collection of linked police-reported and hospital data was established, and considerable attention was given to establishing a weighting procedure to estimate hospital cases not reported to police and fatal cases not admitted to hospital. The resulting data collection of an estimated 19,979 hospitalised motorcyclists is used to provide detailed information on the nature, incidence and risk factors for thoracic trauma. Over the last decade the incidence of motorcyclist serious thoracic injury has more than doubled in the population considered, and by 2011 while motorcycles comprised 3.2% of the registered vehicle fleet, one quarter of road traffic-related serious thoracic trauma cases treated in hospitals were motorcyclists. Motor-vehicle collisions, fixed object collisions and non-collision crashes were fairly evenly represented amongst these cases, while older motorcyclists were over-represented. Several prevention strategies are identified and discussed.

Factors that influence chest injuries in rollovers

OBJECTIVES

The design of countermeasures to reduce serious chest injuries for belted occupants involved in rollover crashes requires an understanding of the cause of these injuries and of the test conditions to assure the effectiveness of the countermeasures. This study defines rollover environments and occupant-to-vehicle interactions that cause chest injuries for belted drivers.

METHODS

The NASS-CDS was examined to determine the frequency and crash severity for belted drivers with serious (Abbreviated Injury Scale [AIS] 3+) chest injuries in rollovers. Case studies of NASS crashes with serious chest injuries sustained by belted front occupants were undertaken and damage patterns were determined. Vehicle rollover tests with dummies were examined to determine occupant motion in crashes with damage similar to that observed in the NASS cases. Computer simulations were performed to further explore factors that could contribute to chest injury. Finite element model (FEM) vehicle models with both the FEM Hybrid III dummy and THUMS human model were used in the simulations.

RESULTS

Simulation of rollovers with 6 quarter-turns or less indicated that increases in the vehicle pitch, either positive or negative, increased the severity of dummy chest loadings. This finding was consistent with vehicle damage observations from NASS cases. For the far-side occupant, the maximum chest loadings were caused by belt and side interactions during the third quarter-turn and by the center console loading during the fourth quarter-turn. The results showed that the THUMS dummy produced more realistic kinematics and improved insights into skeletal and chest organ loadings compared to the Hybrid III dummy.

CONCLUSIONS

These results suggest that a dynamic rollover test to encourage chest injury reduction countermeasures should induce a roll of at least 4 quarter-turns and should also include initial vehicle pitch and/or yaw so that the vehicle's axis of rotation is not aligned with its inertial roll axis during the initial stage of the rollover.

Prediction of thoracic injury severity in frontal impacts by selected anatomical morphomic variables through model-averaged logistic regression approach

This study resulted in a model-averaging methodology that predicts crash injury risk using vehicle, demographic, and morphomic variables and assesses the importance of individual predictors. The effectiveness of this methodology was illustrated through analysis of occupant chest injuries in frontal vehicle crashes. The crash data were obtained from the International Center for Automotive Medicine (ICAM) database for calendar year 1996 to 2012. The morphomic data are quantitative measurements of variations in human body 3-dimensional anatomy. Morphomics are obtained from imaging records. In this study, morphomics were obtained from chest, abdomen, and spine CT using novel patented algorithms. A NASS-trained crash investigator with over thirty years of experience collected the in-depth crash data. There were 226 cases available with occupants involved in frontal crashes and morphomic measurements. Only cases with complete recorded data were retained for statistical analysis. Logistic regression models were fitted using all possible configurations of vehicle, demographic, and morphomic variables. Different models were ranked by the Akaike Information Criteria (AIC). An averaged logistic regression model approach was used due to the limited sample size relative to the number of variables. This approach is helpful when addressing variable selection, building prediction models, and assessing the importance of individual variables. The final predictive results were developed using this approach, based on the top 100 models in the AIC ranking. Model-averaging minimized model uncertainty, decreased the overall prediction variance, and provided an approach to evaluating the importance of individual variables. There were 17 variables investigated: four vehicle, four demographic, and nine morphomic. More than 130,000 logistic models were investigated in total. The models were characterized into four scenarios to assess individual variable contribution to injury risk. Scenario 1 used vehicle variables; Scenario 2, vehicle and demographic variables; Scenario 3, vehicle and morphomic variables; and Scenario 4 used all variables. AIC was used to rank the models and to address over-fitting. In each scenario, the results based on the top three models and the averages of the top 100 models were presented. The AIC and the area under the receiver operating characteristic curve (AUC) were reported in each model. The models were re-fitted after removing each variable one at a time. The increases of AIC and the decreases of AUC were then assessed to measure the contribution and importance of the individual variables in each model. The importance of the individual variables was also determined by their weighted frequencies of appearance in the top 100 selected models. Overall, the AUC was 0.58 in Scenario 1, 0.78 in Scenario 2, 0.76 in Scenario 3 and 0.82 in Scenario 4. The results showed that morphomic variables are as accurate at predicting injury risk as demographic variables. The results of this study emphasize the importance of including morphomic variables when assessing injury risk. The results also highlight the need for morphomic data in the development of human mathematical models when assessing restraint performance in frontal crashes, since morphomic variables are more "tangible" measurements compared to demographic variables such as age and gender.

Investigation of a relationship between external force to shoulder and chest injury of WorldSID and THUMS in 32 km/h oblique pole side impact

OBJECTIVE

This article describes the chest injury risk reduction effect of shoulder restraints using finite element (FE) models of the worldwide harmonized side impact dummy (WorldSID) and Total Human Model for Safety (THUMS) in an FE model 32 km/h oblique pole side impact.

METHODS

This research used an FE model of a mid-sized vehicle equipped with various combinations of curtain shield air bags, torso air bags, and shoulder restraint air bags. As occupant models, AM50 WorldSID and THUMS AM50 Version 4 were used for comparison.

RESULTS

The research investigated the effect of shoulder restraint air bag on chest injury by comparing cases with and without a shoulder side air bag. The maximum external force to the chest was reduced by shoulder restraint air bag in both WorldSID and THUMS, reducing chest injury risk as measured by the amount of rib deflection, number of the rib fractures, and rib deflection ratio. However, it was also determined that the external force to shoulder should be limited to the chest injury threshold because the external shoulder force transmits to the chest via the arm in the case of WorldSID and via the scapula in the case of THUMS. Because these results show the shoulder restraint air bag effect on chest injury risk, the vent hole size of the shoulder restraint air bag was changed for varying reaction forces to investigate the relationship between the external force to the shoulder and the risk of chest injury. In the case of THUMS, an external shoulder force of 1.8 kN and more force from the shoulder restraint air bag was necessary to help prevent rib fracture. Increasing external force applied to shoulder up to 6.2 kN (the maximum force used in this study) did not induce any rib or clavicle fractures in the THUMS. When the shoulder restraint air bag generated external force to the shoulder from 1.8 to 6.2 kN in THUMS, which were applied to the WorldSID, the shoulder deflection ranged from 35 to 68 mm, and the shoulder force ranged from 1.8 to 2.3 kN.

CONCLUSIONS

In the test configuration used, a shoulder restraint using the air bag helps reduce chest injury risk by lowering the maximum magnitude of external force to the shoulder and chest. To help reduce rib fracture risk in the THUMS, the shoulder restraint air bag was expected to generate a force of 3.7 kN with a minimum rib deflection ratio. This corresponds to a shoulder rib deflection of 60 mm and a shoulder load of 2.2 kN in WorldSID. Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

Parameter study for child injury mitigation in near-side impacts through FE simulations

OBJECTIVE

The objective of this study is to investigate the effects of crash-related car parameters on head and chest injury measures for 3- and 12-year-old children in near-side impacts.

METHODS

The evaluation was made using a model of a complete passenger car that was impacted laterally by a barrier. The car model was validated in 2 crash conditions: the Insurance Institute for Highway Safety (IIHS) and the US New Car Assessment Program (NCAP) side impact tests. The Small Side Impact Dummy (SID-IIs) and the human body model 3 (HBM3) (Total HUman Model for Safety [THUMS] 3-year-old) finite element models were used for the parametric investigation (HBM3 on a booster). The car parameters were as follows: vehicle mass, side impact structure stiffness, a head air bag, a thorax-pelvis air bag, and a seat belt with pretensioner. The studied dependent variables were as follows: resultant head linear acceleration, resultant head rotational acceleration, chest viscous criterion, rib deflection, and relative velocity at head impact. The chest measurements were only considered for the SID-IIs.

RESULTS

The head air bag had the greatest effect on the head measurements for both of the occupant models. On average, it reduced the peak head linear acceleration by 54 g for the HBM3 and 78 g for the SID-IIs. The seat belt had the second greatest effect on the head measurements; the peak head linear accelerations were reduced on average by 39 g (HBM3) and 44 g (SID-IIs). The high stiffness side structure increased the SID-IIs' head acceleration, whereas it had marginal effect on the HBM3. The vehicle mass had a marginal effect on SID-IIs' head accelerations, whereas the lower vehicle mass caused 18 g higher head acceleration for HBM3 and the greatest rotational acceleration. The thorax-pelvis air bag, vehicle mass, and seat belt pretensioner affected the chest measurements the most. The presence of a thorax-pelvis air bag, high vehicle mass, and a seat belt pretensioner all reduced the chest viscous criterion (VC) and peak rib deflection in the SID-IIs.

CONCLUSIONS

The head and thorax-pelvis air bags have the potential to reduce injury measurements for both the SID-IIs and the HBM3, provided that the air bag properties are designed to consider these occupant sizes also. The seat belt pretensioner is also effective, provided that the lateral translation of the torso is managed by other features. The importance of lateral movement management is greater the smaller the occupant is. Light vehicles require interior restraint systems of higher performance than heavy vehicles do to achieve the same level of injury measures for a given side structure.

Factors affecting mortality in patients with thorax trauma

BACKGROUND

The purpose of this study was to define the epidemiologic properties and correlation of physiological and anatomical risk factors with the mortality rate among patients with thorax trauma and to ensure early prediction of severe trauma.

METHODS

Files of 371 cases were retrospectively examined. Their initial state in the emergency department was analyzed in terms of mortality development. Age, gender, trauma mechanism, systolic blood pressure and respiration type on admission, accompanying injuries, thorax pathology, trauma scores, and treatment approaches in exitus and surviving cases were compared. Survival probabilities and unexpected mortality rates were computed using the Trauma Revised Score-Injury Severity Score (TRISS).

RESULTS

Age, hypotension, pathologic respiration, blunt injury, accompanying injury, abdominal trauma, high Injury Severity Score (ISS), and low Glasgow Coma Scale (GCS), Revised Trauma Score (RTS), and TRISS were the factors affecting mortality, and presence of blunt injuries, TRISS <85, ISS >22 and GCS <13 were found to be independent prognostic factors. The strongest factor indicating mortality was TRISS. Thirty-four of 307 cases with survival probability of over 50% died.

CONCLUSION

In the presence of factors affecting mortality, patients with thorax trauma should be evaluated as being in a high-risk group and treatment strategies must be aggressive. Case analysis based on the TRISS model would further reveal the mistakes and may improve patient care.

Door velocity and occupant distance affect lateral thoracic injury mitigation with side airbag

The relationship between thoracic injury risk and parameters of door velocity and occupant distance was delineated in blunt lateral impact with side airbag deployment. A sled impact model was exercised with the validated MADYMO fiftieth percentile facet occupant model and a generalized finite element torso side airbag. Impact velocity was incremented from 4.0 to 9.0m/s; occupant-airbag distance (at time of airbag activation) was incremented from 2.0 to 24.0 cm; simulations without airbag were also examined. Using compression, deflection rate, and the Viscous Criterion, airbag performance was characterized with respect to occupant injury risk at three points of interest: occupant distance of most protection, distance of greatest injury risk, and the newly defined critical distance. The occupant distance which demonstrated the most airbag protection, i.e., lowest injury risk, increased with increasing impact velocity. Greatest injury risk resulted when the occupant was nearest the airbag regardless of impact velocity. The critical distance was defined as the farthest distance at which airbag deployment exacerbated injury risk. This critical distance only varied considering chest compression, between 3 and 10 cm from the airbag, but did not vary when the Viscous Criterion was evaluated. At impact velocities less than or equal to 6m/s, the most protective occupant location was within 2 cm of the critical distance at which the airbag became harmful. Therefore, injury mitigation with torso airbag may be more difficult to achieve at lower ΔV.

Rib and sternum fractures in the elderly and extreme elderly following motor vehicle crashes

As the population ages, the need to protect the elderly during motor vehicle crashes becomes increasingly critical. This study focuses on causation of elderly rib and sternum fractures in seriously injured elderly occupants involved in motor vehicle crashes. We used data from the Crash Injury Research and Engineering Network (CIREN) database (1997-2009). Study case criteria included occupant (≥ 65 years old) drivers (sitting in the left outboard position of the first row) or passengers (sitting in the first row right outboard position) who were in frontal or side impacts. To avoid selection bias, only occupants with a Maximum Abbreviated Injury Scale (MAIS) 3 (serious) or greater severity injury were included in this study. Odds ratios were used as a descriptive measure of the strength of association between variables and Chi square tests were used to determine if there was a statistically significant relationship between categorical variables. Of the 211 elderly (65-79 years old) occupants with thoracic injury, 92.0% had rib fractures and 19.6% had sternum fractures. For the 76 extreme elderly (80 years or older) with thoracic injury, 90.4% had rib fractures and 27.7% had sternum fractures. Except for greater mortality and more rib fractures caused by safety belts, there were no differences between the extreme elderly and the elderly occupants. Current safety systems may need to be redesigned to prevent rib and sternum fractures in occupants 80 years and older.

Reducing chest injuries in automobile collisions: rib fracture timing and implications for thoracic injury criteria

The purpose of this study was to quantify the biomechanical response of the human thorax during dynamic shoulder belt loading representative of that seen in a severe automotive collision. Two post-mortem human surrogates (PMHSs) (one male and one female) were instrumented with 26 single-axis strain gages on the ribs, sternum, and clavicle. The thorax of each PMHS was placed on a custom spine support bracket designed to support the thorax on either side of the spinous process, thereby allowing free motion at the costovertebral joints. In addition, the support bracket raised the thorax above the flat base plate, which could otherwise constrain the deformation and motion of the posterior region of the rib cage. The thorax of each PMHS was then loaded using a custom table-top belt loading system that generated thoracic displacement rates representative of a severe automotive collision, 1.3 m/s for the male PMHS and 1.0 m/s for the female PMHS. The rib fracture timing data, determined by analyzing the strain gage time histories, showed that severe thoracic injury (AIS = 3) occurred at 16% chest compression for the male and 12% chest compression for the female. However, these values are well below the current thoracic injury criteria of 29% chest compression for the male and 23% chest compression for the female. This data illustrates that serious thoracic injury (AIS = 3) occurs at lower chest compressions than the current ATD thoracic injury criteria. Overall, this study provides critical data that can be used in the design and validation of advanced ATDs and finite element models, as well as the establishment of improved, more stringent thoracic injury criteria.

Thoracic Injury Risk as a Function of Crash Severity - Car-to-car Side Impact Tests with WorldSID Compared to Real-life Crashes

Side airbags reduce the risk of fatal injury by approximately 30%. Due to limited real-life data the risk reducing effect for serious injury has not yet been established. Since side airbags are mainly designed and validated for crash severities used in available test procedures little is known regarding the protective effect when severity increases.The objective of this study was to understand for which crash severities AIS3+ thorax occupant protection in car-to-car nearside collisions need to and can be improved. The aim was fulfilled by means of real life data, for older cars without side airbag, and a series of car-to-car tests performed with the WorldSID 50%-ile in modern and older cars at different impact speeds.The real life data showed that the risk of AIS3+ injury was highest for the thorax followed by the pelvis and head. For both non-senior and senior occupants, most thorax injuries were sustained at lateral delta-v from 20 km/h to 40 km/h. In this severity range, senior occupants were found to have approximately four times higher risk of thoracic injury than non-senior occupants. The crash tests at lateral impact speed 55 km/h (delta-v 32 km/h) confirmed the improved performance at severities represented in current legal and rating tests. The structural integrity of the modern car impacted at 70 km/h showed a potential for improved side impact protection by interior countermeasures.

The effect of obesity on the restraint of automobile occupants

As obesity rates increase, the protection of obese occupants will become increasingly important in vehicle and restraint design. As a first step in this effort, this study seeks to compare the kinematics, dynamics, and injuries of obese post mortem human surrogates (PMHS) to (approximately) 50(th) percentile adult male PMHS in frontal impact sled tests with a force-limiting, pre-tensioning restraint system. Forty-eight km/h, frontal impact sled tests were performed with a sled buck representing the rear seat occupant compartment of a 2004 mid-sized sedan. The restraint system consisted of a 3-point belt with a pretensioner and a progressive force-limiter at the retractor. The test subjects were either obese PMHS or approximately 50(th) percentile adult male PMHS. Instrumentation included accelerometer packages on the spine. Deformation of the subjects' chests were measured using chestbands placed nominally at the superior-inferior locations of the 4(th) and 8(th) ribs. Tension in the restraint system was measured at the upper shoulder belt, lower shoulder belt, and the lap belt. Motion of the head, shoulder, pelvis, and knee were recorded using high-speed video. Two obese PMHS (average mass 137 kg, average stature 186 cm) and three approximately mid-sized male PMHS (average mass 68 kg, average stature 176 cm) were tested. The obese PMHS exhibited significantly greater forward motion of the head and the pelvis compared to the mid-sized PMHS. The obese PMHS also exhibited backwards torso rotation at the time of maximum forward excursion, whereas the mid-sized PMHS did not. The obese PMHS exhibited average maximum chest compressions of approximately 44% (+/- 9% standard deviation) of their initial chest depths, and exhibited 26 g (+/- 2 g) average 3 ms clip maximum chest resultant acceleration. In comparison, the mid-sized PMHS exhibited averages of 29% (+/- 9%) maximum chest compression and 35 g (+/- 4 g) maximum 3 ms clip chest acceleration. The obese PMHS exhibited 7 and 2 rib fractures, with maximum chest AIS scores of 3 and 2. The mid-sized PMHS exhibited 12, 2, and 17 rib fractures, with maximum chest AIS scores of 4, 1, and 4, respectively. This study is the first (to the authors' knowledge) to compare the kinematic, dynamic, and injury behaviors of obese and mid-sized PMHS in frontal impact sled tests with a force-limiting, pretensioning restraint system. The unfavorable kinematics observed with the obese PMHS highlights the difficulty of designing restraint systems to adequately restrain obese occupants, even with currently available advanced restraint technologies.

Rear seat occupant thorax protection in near side impacts

Thoracic side-airbags (SAB) have proven to protect front seat occupants in side impacts. This benefit has not been evaluated for rear seat occupants who are typically small statured. The objective was to analyze field data from rear seat occupants in near side impacts, and evaluate the effect of a SAB in the rear seat, through full scale vehicle tests. A field study using the NASS-CDS database was performed to review rear seat crash characteristics, occupant injuries (Abbreviated Injury Scale 3+, AIS3+) and injury sources. Full scale tests were performed with the side impact dummy SID-IIs at two different crash severities, with and without SAB in a midsize passenger car. Field data showed that of all AIS3+ injured restrained occupants 13 years and older, 59% had AIS3+ thoracic injuries and 38% had AIS3+ head injuries. The thoracic injuries were distributed to lungs (60%), skeletal fractures (38%) and injuries to arteries (1,26%) and heart (0,1%). For AIS3+ injured children, age 4-12, 51% had AIS3+ thoracic injuries and 54% had AIS3+ head injuries. Compared to adults, children sustained less fractures and more lung injuries. The rear side interior was the main injury source regardless of age group. In the full scale tests, the thoracic side-airbag reduced the average rib deflection by 50% and resulted in an AIS3+ injury risk reduction from 36% to 3%. At the higher impact speed, SAB reduced the injury risk from 93% to 24%. The full scale crash tests showed that SAB offer a significant potential for thoracic injury reduction in the crash severities causing the majority of serious injuries in real life crashes.

Clinical implications of the seat belt sign in blunt trauma

Patients with the seat belt sign (SBS) from motor vehicle crashes (MVCs) are prone to specific regional injury patterns. Investigators at a Level 1 trauma center analyzed the incidence, clinical implications, and spectrum of regional injuries in patients injured in MVC over 2 years. SBS was seen in 11.3 per cent of patients injured in MVCs and 20.5 per cent of patients with known restraint use. Restrained patients were less severely injured with lower injury severity scores (7.62 vs 11.33) and mortality (1.1 vs 5.7%). Patients with SBS had lower mortality rates than patients without SBS (1.4 vs 3.7%). Thoraco-abdominal injuries were present in 47 per cent (34 of 72) of patients with SBS. Compared with patients without SBS, patients had a higher incidence of hollow viscous injuries (HVI) and solid organ trauma (8 and 17% vs 1 and 3%, P < 0.05); splenic trauma was 24-fold higher (9.7 vs 0.4%), liver injuries 3.1-fold higher (6 vs 3%), and rib fractures 2.4-fold higher (P < 0.05). Children had 2.8-fold higher rates of HVI (18 vs 9%, P < 0.05). SBS is associated with underlying regional injuries in nearly half of patients with a higher prevalence of HVI and solid organ trauma.

Injury reduction opportunities of far side impact countermeasures

Over 17,000 non-struck or far side occupants in side and rollover crashes are seriously or fatally injured annually in the US. Although no legal or rating tests exist for far side crashes, test methods including appropriate dummies as well as countermeasures have been recently suggested. The aim of this study was to establish the incidence and risk of injury / fatality as a function of vehicle change in velocity (Deltav) for the most frequent injuries of belted, far side occupants in side impacts. The study was based upon the NASS/CDS 1995-2006 records of 5,653 occupants exposed to a far side crash. 401 of these were seriously or fatally injured. Combining this data with new and previously published crash test results, the potential opportunities of various concepts of far side countermeasures were evaluated. Head/thorax injuries caused by interaction with the struck side interior were found to dominate. Countermeasures such as side support airbags and altered three-point belt geometry (e.g. four-point belts) are relevant for Deltav of at least 20-30 km/h. The opportunity for mitigating AIS3+ injuries in these severity ranges was found to be 19%- 57%. Countermeasures such as struck-side curtains are able to provide cushioning at Deltav 30 to 50 km/h, which would cover almost a third of all fatalities.

Effects of shoulder belt limit forces on adult thoracic protection in frontal collisions

Three-point restraint systems have been installed in vehicles since the early 1960s. However, it wasn't until the automatic protection rule became effective for 1987 Model Year vehicles that manufacturers began installing 3-point restraints with force-limiting shoulder belts and frontal airbags for the driver and right front passenger. This was the first time that all vehicle manufacturers had to certify that their cars would meet the 50th percentile, adult male protection requirements in the 48 km/h frontal, rigid-barrier test specified in FMVSS 208. To assess the effectiveness of these certified 3-point restraint systems, a search was done of the 1988-2005 NASS data for 3-point belted, front outboard-seated, adult occupants in passenger vehicles that were equipped with airbags and that were involved in frontal, towaway collisions. These data showed that i) half of the occupants with AIS > or = 3 chest injuries were in collisions with a DeltaV < or = 40 km/h; ii) for older occupants (50+ years), half experienced their chest injuries at DeltaVs < or = 34 km/h; and iii) the chest injury rate for the older occupants was more than double that of the younger occupants. An analysis was done to estimate the effectiveness of various levels of shoulder belt limit loads in reducing chest injuries to older occupants. The result of the analysis indicated that a 2.5 kN shoulder belt limit load would substantially reduce shoulder belt-induced AIS > or = 3 chest injuries in 99 percent of frontal collisions to all adult, front outboard seated occupants whose normalized bone strengths are greater than 0.4.

Handlebar injuries in children: should we raise the bar of suspicion?

Injury prevention strategies for child bicyclists have focused on helmet use to prevent head trauma. Handlebars are another source of injury. A retrospective review from 2005 identified 385 admissions to a Level 1 pediatric trauma center of which 23 (5.9%) were pedal cyclists. Four cases (<1.0%) of handlebar injuries were identified. Three children (two bicyclists, one riding a scooter) sustained handlebar impact to the neck. All children with neck injuries had subcutaneous emphysema. Two of the children had pneumomediastinum, which after work-up was managed nonoperatively. One child had a tracheal injury requiring operative intervention. Another child was struck in the upper abdomen resulting in a traumatic abdominal wall hernia requiring emergent exploration and hernia repair. Discordance exists between the apparently minor circumstances of handlebar trauma and the severity of injury sustained by bicyclists. Recognizing the mechanism of handlebar-related injuries and maintaining a high index of suspicion for visceral injuries aids in the diagnosis. The incidence of these injuries is underestimated due to insufficient documentation of the circumstances of injury events and a lack of applicable E-codes specific for handlebar injury.

Assessing Behind Armor Blunt Trauma in Accordance With the National Institute of Justice Standard for Personal Body Armor Protection Using Finite Element Modeling

BACKGROUND

To assess the possibility of injury as a result of behind armor blunt trauma (BABT), a study was undertaken to determine the conditions necessary to produce the 44-mm clay deformation as set forth in the National Institute of Justice (NIJ) Standard 0101.04. These energy levels were then applied to a three-dimensional Human Torso Finite Element Model (HTFEM) with soft armor vest. An examination will be made of tissue stresses to determine the effects of the increased kinetic energy levels on the probability of injury.

METHODS

A clay finite element model (CFEM) was created with a material model that required nonlinear properties for clay. To determine these properties empirically, the results from the CFEM were matched with experimental drop tests. A soft armor vest was modeled over the clay to create a vest over clay block finite element model (VCFEM) and empirical methods were again used to obtain material properties for the vest from experimental ballistic testing. Once the properties for the vest and clay had been obtained, the kinetic energy required to produce a 44-mm deformation in the VCFEM was determined through ballistic testing. The resulting kinetic energy was then used in the HTFEM to evaluate the probability of BABT.

RESULTS

The VCFEM, with determined clay and vest material properties, was exercised with the equivalent of a 9-mm (8-gm) projectile at various impact velocities. The 44-mm clay deformation was produced with a velocity of 785 m/s. This impact condition (9-mm projectile at 785 m/s) was used in ballistic exercises of the HTFEM, which was modeled with high-strain rate human tissue properties for the organs. The impact zones were over the sternum anterior to T6 and over the liver. The principal stresses in both soft and hard tissue at both locations exceeded the tissue tensile strength.

CONCLUSIONS

This study indicates that although NIJ standard 0101.04 may be a good guide to soft armor failure, it may not be as good a guide in BABT, especially at large projectile kinetic energies. Further studies, both numerical and experimental, are needed to assist in predicting injury using the NIJ standard.

Evaluation of chest barriers for protection against sudden death due to commotio cordis

Blunt precordial blows triggering ventricular fibrillation (commotio cordis) represent a leading cause of sudden death in young athletes. Attention has focused on the primary prevention of these tragedies with chest barriers. The U.S. Commotio Cordis Registry was accessed to determine the likelihood of sudden death in athletes exposed to precordial blows while wearing chest protectors. Of 182 cases of commotio cordis, 85 (47%) occurred during practice or competition in organized sports. In 32 of these 85 competitive athletes (38%), fatal chest blows occurred despite the presence of potentially protective equipment. Athletes wore standard, commercially available chest barriers made of polymer foam covered by fabric or hard shells, generally perceived as protective from arrhythmic consequences of the blows. These events occurred in 4 sports: hockey (n = 13; 1 goalie), football (n = 10), lacrosse (n = 6; 3 goalies), and baseball (n = 3; all catchers). Scenarios included the failure of the padding to cover the precordium so that blows circumvented the protective barrier (n = 25) or projectiles that struck the chest barrier directly (n = 7). In conclusion, a significant proportion (about 40%) of sudden deaths reported in young competitive athletes due to blunt chest blows (commotio cordis) occur despite the presence of commercially available sports equipment generally perceived as protective.

Does the frontal airbag avoid thoracic injury?

INTRODUCTION

The airbag is an established car safety device. However, recent studies pointed out that even the airbag might cause injuries. Nevertheless, most physicians do consider a lower risk in accident victims sustaining severe injury of the chest, when a deployed frontal airbag has been reported. We set out to verify the frequency and pattern of thoracic injury in car drivers protected by a frontal airbag during traffic accidents.

METHODS

This investigation was conducted as part of a prospective surveillance analyzing traffic accidents. Enrolled were car drivers included in a databank between January 2001 and December 2004 consecutively. The chance for sustaining chest injury with or without a frontal airbag was described using the relative risk.

RESULTS

A total of 188 car drivers were included in the analysis. In 54 (28.7%) cases a deployed airbag and in 134 (71.3%) the absence of an airbag has been documented. Out of those cases 16 (29.6%) drivers with airbag and 30 (22.4%) without airbag sustained a chest injury. The mean abbreviated injury scale (AIS) of chest injuries in drivers with deployed airbag was 2.3 (1-5; SD +/- 1.45; mean injury severity scale [ISS] 21.1 [SD +/- 17.18]), in drivers without airbag 1.6 (1-4; SD +/- 1.12; mean ISS 15.8 [SD +/- 20.6]). For belted drivers with an airbag the relative risk to sustain chest injury was 1.96 compared to those without an airbag.

CONCLUSIONS

The airbag does not avoid chest injury definitively. Much more, it has been demonstrated that the relative risk to sustain relevant thoracic injury seems to be almost higher in restrained drivers with a frontal airbag.

Failure of commercially available chest wall protectors to prevent sudden cardiac death induced by chest wall blows in an experimental model of commotio cordis

OBJECTIVE

Sudden cardiac death that results from chest wall blows (commotio cordis) the second leading cause of death in young athletes. Most events are caused by blows from projectiles, such as baseballs or lacrosse balls, with a substantial proportion occurring despite the use of a chest protector. In the present experiment, we tested the effectiveness of commercially available chest protectors in preventing ventricular fibrillation (VF) that results from chest wall strikes with baseballs and lacrosse balls.

METHODS

Twelve different baseball or lacrosse chest protectors were evaluated in juvenile swines that were subjected to 40-mph baseball or lacrosse ball blows to the precordium during the vulnerable period of repolarization for VF and were compared with control impacts without chest protectors. Seven baseball chest protectors were hit by regulation baseballs, and 5 lacrosse chest protectors were tested by blows with standard lacrosse balls. Each animal received 2 chest blows for each protector and 2 control impacts without a chest protector, with the sequence of impacts assigned randomly.

RESULTS

VF was elicited by 12 (32%) of 37 strikes in control animals without baseball chest protectors. None of the baseball chest wall protectors tested were shown to decrease significantly the occurrence of VF when compared with controls. VF was elicited by 11 (46%) of 24 strikes in control animals without lacrosse chest protectors. None of the lacrosse chest wall protectors tested decreased significantly the occurrence of VF when compared with controls.

CONCLUSION

In our experimental animal model of commotio cordis, commercially available baseball and lacrosse chest wall protectors were ineffective in protecting against VF that was triggered by chest blows and, by inference, sudden cardiac death. Improvements in materials and design of chest wall barriers are necessary to reduce the occurrence of these tragic events and make the athletic field safer for youths.

Improved protection for children in forward-facing restraints during side impacts

OBJECTIVE

This study aims to determine the potential for improved child occupant protection in side impacts that can be obtained using rigid and semi-rigid anchorage systems and the addition of energy-absorbing padding in the side structures of child restraints.

METHODS

This study uses a comprehensive set of simulated side impacts to evaluate the potential for improved side impact protection in forward-facing child restraints. Factors investigated included methods of anchoring the restraint to the vehicle, energy-absorbing materials in the side structure of restraints, and design features of the restraints such as side wing geometry and seat belt routing.

RESULTS

The results show clearly that completely rigid lower attachment of restraints offers the potential for great reductions in head injury risk, which anchorage systems employing a combination of a rigid anchorage bar and webbing attached to a child restraint cannot match. The addition of energy absorbing material in the side structure of restraint systems is effective when the head is fully contained within an adequately designed side wing structure. For restraints anchored by seat belts and loop style semi rigid anchorage straps, belt routing has the potential to significantly affect occupant head excursion.

CONCLUSIONS

The results suggest that current child restraint standards and consumer testing protocols do not adequately encourage best practice design of child restraints for side impact protection.

Modeling the Effect of Non-Penetrating Ballistic Impact As a Means of Detecting Behind Armor Blunt Trauma

BACKGROUND

According to the National Institute of Justice (NIJ) Standard 0101.04, the maximum deformation a soft armor vest can undergo without penetration is 44 mm. However, this does not take into account the effect of the pressure wave or energy transferred to the organs within the torso due to behind armor blunt trauma (BABT). Therefore, a study was undertaken to develop a finite element model (FEM) to study these effects.

METHODS

A finite element model (FEM) of the human thorax; complete with musculoskeletal structure and internal organs (heart, liver, lungs and stomach), intercostal muscle and skin, has been developed in LS-DYNA. A Kevlar vest was modeled on the chest to simulate non-penetrating ballistic impact.

RESULTS

Using a projectile modeled with a size and mass equivalent to a 9 mm (124 grain) bullet at 360 and 425 m/s, four impacts were simulated against NIJ Level II and Level IIIa Kevlar vests at the midsternum and right thorax. At the same velocity, the pressures decreased by a factor of 3 and the energy absorbed by the organs decreased by a factor of 6 for the NIJ Level II and Level IIIa vests, respectively. As the projectile velocity increased, the peak pressures increased by a factor of 3 while the energy absorbed by the organs increased by a factor of 4.

CONCLUSIONS

The resulting pressure profiles and kinetic energy exhibited by the respective organs indicate this model may be useful in identifying mechanisms of injury as well as organs at an elevated injury risk as a result of BABT.

Surgical repair of rib fractures in 14 neonatal foals: case selection, surgical technique and results

REASONS FOR PERFORMING STUDY

Fractured ribs are encountered quite frequently in newborn Thoroughbred foals, often with fatal outcome. Surgical repair of fractures therefore requires consideration as a means of reducing mortality.

OBJECTIVES

To evaluate the repair of rib fractures using internal fixation techniques in foals at 2 different equine hospitals following similar diagnostics and case selection.

METHODS

The records of 14 foals that underwent internal fixation of fracture ribs were reviewed. Subject details, clinical presentation, diagnosis, surgical technique, post operative care and complications were recorded. Follow-up information was obtained in 7 foals.

RESULTS

The fractured ribs were reduced and stabilised using reconstruction plate(s), self-tapping cortical screws and cerclage wire in 12 cases, Steinmann pins and cerclage wires in 1 case and both techniques in 1 case. Not every rib was reduced on each case. Surgical reduction was performed on an average of 2 ribs, range 1-3 ribs in each foal. At the time of writing, 4 foals had been sold, one age 2 years was in training and 2 others died from unrelated causes.

CONCLUSIONS

Our data support the use of surgical stabilisation utilising reconstruction plates, self-tapping cortical screws and cerclage wire for selected cases of thoracic trauma in neonatal foals. The use of Steinmann pins may be suboptimal due to cyclic failure, implant migration and the potential for iatrogenic internal thoracic trauma.

POTENTIAL RELEVANCE

Foals with existing extensive internal thoracic trauma resulting from rib fracture(s), or the potential for such trauma, previously considered to have a guarded to poor prognosis for survival, may be successfully managed with internal fixation of selected fracture sites.

Factors affecting pelvic and thoracic forces in near-side impact crashes: a study of US-NCAP, NASS, and CIREN data

The goal of this study was to identify variables related to vehicle design which are associated with pelvic and thoracic accelerations as measured by the driver's (near side) crash dummy during new car assessment program (NCAP) testing of motor vehicles. Vehicle specific parameters were analyzed using NCAP side impact test results. Data from national automotive sampling system, crashworthiness data system (NASS-CDS) and crash injury research and engineering network (CIREN) (both National Highway Traffic Safety Administration (NHTSA) injury databases) were assessed to confirm NCAP test observations. In addition, door armrest stiffness measurements were performed using a mechanical tester on a sample of 40 vehicles. NCAP data showed that of 10 variables tested using multiple linear regression, vehicle weight and door crush correlated with pelvic acceleration of the driver's crash dummy (overall, r2=0.58, p=0.002, n=165). For thoracic trauma index (TTI) vehicle weight and peak door velocity correlated, significantly (overall, r2=0.41, p=0.03, n=165). Mean TTI was 63.7 g with no side airbag (n=108) and 55.6 g with a thoracic side airbag (n=54), p=0.01. The mean vehicle weight and door crush between airbag and no airbag groups were not significantly different. NASS-CDS data demonstrated a direct relationship between increased door crush and increased abbreviated injury score (AIS). CIREN data showed that occupants who sustained pelvic injuries had a median AIS of 3 with 24.9 cm of door crush, with abdominal injuries, a median AIS of 3 and 30 cm of crush, and with thoracic injuries, a median AIS of 4 and 34 cm of door crush. In addition, the frequency of bilateral pelvic injuries was significantly higher for subjects in CIREN crashes who were in a vehicle with a center console, but only if door intrusion was greater than 15 cm. This information may be useful in design of vehicles with greater protection in side impact crashes.

Impact injuries in baseball : prevalence, aetiology and the role of equipment performance

Baseball has one of the highest impact injury rates of all sports. These injuries are primarily attributed to impact by a ball after it has been hit, pitched or thrown. This paper will review the incidence and causal factors for impact injuries in baseball. Attention is given to the design and material properties of bats, in light of evidence suggesting balls hit into the infield from metal bats can reach velocities potentially lethal to defensive players. The distribution of bat mass along the long axis of the implement appears a major factor in the greater performance potential of metal bats over wooden bats of equal length and mass. The dynamic behaviour of baseballs has also been implicated in the severity of head and chest injuries experienced by players. Balls of greatly reduced stiffness have been introduced for junior play, but debate still remains over their performance and impact characteristics. The behaviour of the ball during high-speed impact with the bat has been the subject of relatively limited research, and the effect of manipulating baseball material properties to decrease batted-ball velocity is unclear. The value of batting helmets is evident in the observed reduction of head injuries in baseball, but the use of protective vests to decrease the incidence and severity of cardio-thoracic trauma appears to be contraindicated.

The Influence of Side Airbags on the Risk of Head and Thoracic Injury after Motor Vehicle Collisions

BACKGROUND

Side airbags (SABs) were developed as an energy-absorbing barrier to protect specific occupant body regions in near side impact motor vehicle collisions.

METHODS

The National Automotive Sampling System Crashworthiness Data System was used to evaluate drivers and front-seated passengers in 1998 or newer vehicles involved in near side impact collisions. Risk ratios were calculated comparing the risk of head and thoracic injury among occupants in vehicles with and without SABs adjusting for occupant, vehicle, and collision characteristics.

RESULTS

Occupants in vehicles equipped with head protection SABs had a 75% lower risk of head injury (p = 0.008) after near side collisions. With respect to thoracic injury, SABs that provide thoracic protection are associated with a 68% reduction (p = 0.01) in thoracic injury risk.

CONCLUSION

As SAB-equipped vehicles become an increasingly larger segment of the on-road vehicle fleet, the impact of head and thoracic injury after near side impact collision is likely to be reduced.

[Thoracal injuries in adolescents]

In adolescents, the chest is frequently vulnerable to sports-related trauma due to its size and location. Fortunately, most of them are insignificant in nature. However, sports physicians should always be alert to rare serious visceral organ injuries.

Reduced risk of sudden death from chest wall blows (commotio cordis) with safety baseballs

OBJECTIVES

In an experimental model of sudden death from baseball chest wall impact (commotio cordis), we sought to determine if sudden death by baseball impact could be reduced with safety baseballs.

BACKGROUND

Sudden cardiac death can occur after chest wall impact with a baseball (commotio cordis). Whether softer-than-standard (safety) baseballs reduce the risk of sudden death is unresolved from the available human data. In a juvenile swine model, ventricular fibrillation (VF) has been shown to be induced reproducibly by precordial impact with a 30-mph baseball 10 to 30 ms before the T-wave peak, and this likelihood was reduced with the softest safety baseballs (T-balls). To further test whether safety baseballs would reduce the risk of sudden death at velocities more relevant to youth sports competition, we used our swine model of commotio cordis to test baseballs propelled at the 40-mph velocity commonly attained in that sport.

METHODS

Forty animals received up to 3 chest wall impacts at 40 mph during the vulnerable period of repolarization for VF with 1 of 3 different safety baseballs of varying hardness, and also by a standard baseball.

RESULTS

Safety baseballs propelled at 40 mph significantly reduced the risk for VF. The softest safety baseballs triggered VF in only 11% of impacts, compared with 19% and 22% with safety baseballs of intermediate hardness, and 69% with standard baseballs.

CONCLUSION

In this experimental model of low-energy chest wall impact, safety baseballs reduced (but did not abolish) the risk of sudden cardiac death. More universal use of these safety baseballs may decrease the risk of sudden death on the playing field for young athletes.

Correlation between crash severity, injury severity, and clinical course in car occupants with thoracic trauma: a technical and medical study

BACKGROUND

The crash mechanisms and clinical course of car occupants with thoracic injury were analyzed to determine prognostic factors and to create a basis for injury prophylaxis.

METHODS

A technical and medical investigation of car occupants with a thoracic injury (Abbreviated Injury Scale-thorax [AIS(THORAX)] > or = 1) at the scene of the crash and the primary admitting hospital was performed.

RESULTS

Between 1985 and 1998, 581 car occupants sustained a thoracic injury. Mean parameter values were as follows: AIS(THORAX), 2.5; Hannover Polytrauma Score (PTS), 21.4; Injury Severity Score (ISS), 24.2; Delta-v, 49.6 km/h (30.8 mph); and extent of passenger compartment deformation (DEF) (scale, 1--9), 4.0. In 19% (n = 112) of patients involved, the clinical course was evaluated: AIS(THORAX), 2.5; PTS, 20.0; ISS, 19.3; Delta-v, 50.1 km/h (31.1 mph); DEF, 3.9; intensive care unit time, 8.3 days; ventilation time, 5.7 days; and hospital stay, 15.3 days. In the groups with higher AIS(THORAX), ISS, PTS, and intensive care unit and ventilation time, higher Delta-v and DEF occurred. In patients with longer hospital stay, higher Delta-v, but no difference in DEF occurred.

CONCLUSION

The injury severity and the clinical course demonstrated a positive correlation with the crash severity. Therefore, our technical accident analysis allows prediction of the severity of injury and the clinical course. It may consequently serve as a tool for development of more sophisticated injury prevention strategies and may improve passive car safety.

Behind armour blunt trauma--an emerging problem

Behind Armour Blunt Trauma (BABT) is the non-penetrating injury resulting from the rapid deformation of armours covering the body. The deformation of the surface of an armour in contact with the body wall arises from the impact of a bullet or other projectile on its front face. The deformation is part of the retardation and energy absorbing process that captures the projectile. In extreme circumstances, the BABT may result in death, even though the projectile has not perforated the armour. An escalation of the available energy of bullets and the desire of armour designers to minimise the weight and bulk of personal armour systems will increase the risk of BABT in military and security forces personnel. In order to develop materials that can be interposed between the armour and the body wall to attenuate the transfer of energy into the body, it is essential that the mechanism of BABT is known. There is a great deal of activity within UK and NATO to unravel the interactions; the mechanism is likely to be a combination of stress (pressure) waves generated by the rapid initial motion of the rear of the armour, and shear deformation to viscera produced by gross deflection of the body wall. Physical and computer model systems are under development to characterise the biophysical processes and provide performance targets for materials to be placed between armours and the body wall in order to attenuate the injuries (trauma attenuating backings-TABs). The patho-physiological consequences of BABT are being clarified by research, but the injuries will have some of the features of blunt chest trauma observed in road traffic accidents and other forms of civilian blunt impact injury. The injuries also have characteristics of primary blast injury. An overview diagnosis and treatment is described.

Effectiveness of automatic shoulder belt systems in motor vehicle crashes

CONTEXT

Approximately 10 million cars with automatic shoulder belt systems are currently in use in the United States. However, reports on the effectiveness of such restraints have yielded conflicting results.

OBJECTIVE

To determine the effectiveness of automatic shoulder belt systems in reducing the risk of injury and death among front-seat passenger vehicle occupants.

DESIGN, SETTING, AND SUBJECTS

Analysis of data collected from the 1993-1996 National Highway Traffic Safety Administration Crashworthiness Data System on front-seat occupants involved in 25,811 tow-away crashes of passenger cars, light trucks, vans, and sport utility vehicles.

MAIN OUTCOME MEASURES

Death and serious injury to specific body areas by use of manual lap and shoulder belts, automatic shoulder belts with manual lap belts, or automatic shoulder belts without lap belts, compared with no restraint use.

RESULTS

Use of automatic shoulder belts without lap belts was associated with a decrease in the risk of death vs no restraint use but was not statistically significant for all crashes (odds ratio [OR], 0.66; 95% confidence interval [CI], 0.42-1.06) or for frontal crashes (OR, 0.71; 95% CI, 0.38-1.35) after adjustment for occupant age, sex, vehicle year, air-bag deployment, estimated change in vehicle speed during the crash, and principal direction of force. This association was significantly weaker than the 86% lower risk observed for use of automatic shoulder belts with lap belts (OR, 0.14; 95% CI, 0.07-0.26 vs no restraint; P<.05). Use of automatic shoulder belts without lap belts was associated with an increased risk of serious chest (OR, 2.66; 95% CI, 1.11-6.35) and abdominal (OR, 2.06; 95% CI, 1.004-4.22) injuries for all crashes.

CONCLUSIONS

These data indicate that improperly used automatic restraint systems may be less effective than properly used systems and are associated with an increased risk of serious chest and abdominal injuries. Given the continued widespread use of these automatic systems, educational programs may be warranted. JAMA. 2000;283:2826-2828

Sports-specific concerns in the young athlete: baseball

The sport of baseball is played by millions of children across America and around the world. Although generally considered a safe activity, it is estimated that there are over 100,000 acute baseball injuries yearly in the 5- to 14-year age range in the United States, many of which present to the emergency department. Acute injuries often involve ball impact to the face and hands; baseball is the leading cause of sport-related eye injury. Ball impact particularly to the chest results in a small but steady number of fatalities each year, many of which are widely publicized events. In addition to acute injury, many young baseball players are affected by chronic and acute conditions of the elbow. In this article, we review the history, epidemiology, and common injury patterns that are specific to baseball. Case reports are included, as well as a section on the physical examination of the elbow.

Driver and right-front passenger restraint system interaction, injury potential, and thoracic injury prediction

Restrained driver and right-front passenger kinematics and injury outcome in frontal collisions are compared using FARS data and human cadaver sled tests. The FARS data indicate that a frontal airbag may provide greater benefit for a passenger than for a driver. The thoracic injuries sustained by passenger subjects restrained by a force-limited, pretensioned belt and airbag are evaluated, and kinematics are compared to driver-side subjects. The injury-predictive ability of existing thoracic injury criteria is evaluated for passenger-side occupants. Driver and passenger kinematic differences are identified and the implications are discussed. The chest acceleration of the passenger-side subjects exhibited a bimodal profile with an initial (and global) maximum before the subject loaded the airbag. A second acceleration peak occurred as the subject loaded both the belt and the airbag. A similarly restrained driver-side subject loaded the belt and airbag concurrently at the time of peak chest acceleration and therefore did not exhibit this bimodal chest acceleration.