Upper extremity injuries related to airbag deployments

Estimation of Injury Limits at Vulnerable Impact Locations Along the Forearm Via THUMS AM50 Finite Element Model at Airbag Loading Rates

Side and frontal airbag deployment represents the main injury mechanism to the upper extremity during automotive collisions. Previous dynamic injury limit research has been limited to testing the forearm at either the assumed most vulnerable location to fracture, the distal 1/3rd, or the midpoint. Studies have varied the surface to which impacts were applied, with no clear consensus on the site of greatest vulnerability. The unpredictability of airbag impact location, especially with altered hand positioning, limits the effectiveness of existing forearm injury limits determined from impacts at only one location. The current study quantified the effect of impacts at alternative locations on injury risk along the forearm using the THUMS FE model. Airbag-level impacts were simulated along the forearm on all four anatomical surfaces. Results showed the distal 1/3rd is not the most vulnerable location (for any side), indicating forearm fracture is not solely driven by area moment of inertia (as previously assumed). The posterior forearm was the weakest, suggesting that current test standards underestimate the fracture risk of the forearm. Linear regression models showed strong correlation between forearm fracture risk and bone geometry (cross-sectional area and area moment of inertia) as well as soft-tissue depth, potentially providing the ability to predict forearm injury tolerances for any location or forearm size. This study demonstrated the forearm's vulnerability to fracture from airbag deployments, indicating the need for safety systems to better address injury mechanisms for the upper limb to effectively protect drivers.

Deploying Airbag in Motor Vehicle Collision as the Mechanism of Neurogenic Thoracic Outlet Syndrome: A Case Report

Neurogenic thoracic outlet syndrome (NTOS) is a disorder that is often misdiagnosed and challenging to treat due to the varied and complex mechanisms that precipitate common sensory symptoms associated with neurovascular dysfunction. In this report, we describe a 21-year-old male who presented with left NTOS after being involved in a motor vehicle collision the previous year. Although NTOS is a condition known to develop after motor vehicle collisions, the mechanism of NTOS in this case, the deploying airbag, has not been documented in existing literature. The patient was first treated conservatively with physical therapy, but treatment failed to relieve his symptoms. A left first rib resection using the transaxillary approach and an anterior scalenectomy was performed without any complications, and the patient's symptoms had improved 3 months postoperation.

UPPER EXTREMITY BIOMECHANICS MODELING OF AVERAGE CHINESE DRIVERS AND INJURY RESPONSES TO AIRBAG IMPACT

The upper limb of a vehicle driver is vulnerable to injury in a car collision accident. In order to study the injury mechanism and biomechanical response of the upper limb, a finite element model of upper limbs including upper limb bones, muscles, ligaments and skin was established from CT scan data, and was validated by quasi-static and dynamic three point bending tests to the long bones, as well as airbag and forearm impact tests. Further, the influence of airbag parameters and driver’s postures on the upper limb injury were simulated and analyzed. The results showed that the risk of forearm fracture increased with the increase of the forearm radial speed. When the air mass rate of airbag reduced to half of the initial, the forearm distal-end average speed was decreased by 19.1%, and the peak decreased by 9.0% accordingly. When the distance between forearm and the airbag was selected from 0 to 15, 25 and 35[Formula: see text]mm, respectively, the forearm distal-end average speed was decreased by 23.8%, 45.1% and 56.7% accordingly, and the peak decreased by 1.6%, 28.4% and 42.0%, respectively. The simulation result indicates this model has a good bio-fidelity and can accurately reflect the dynamic response of the upper limb and quantitative injury mechanism, enabling the evaluation of vehicle safety restraint system.

[Airbag-related death in a toddler. A poorly known danger?]

We report the case of an 8-month-old baby killed by the deployment of an airbag. He was correctly positioned, in a safety seat designed for his age class, on the passenger side, and rear-facing. The accident occurred at low speed, on the left front of the car, without provoking any harm to the mother who was driving the vehicle, but the impact led to airbag deployment. A CT scan showed an occipital fracture, hemorrhagic parenchymal contusions, subarachnoid hemorrhage and edema, which quickly led to fatal intracranial hypertension. Severe retinal hemorrhages were also noted. Brain death was declared 24h later. Both direct impact and violent projection of the head are involved in the severity of brain lesions. Retinal hemorrhages are similar to what is observed in shaken-baby syndrome. To our knowledge, this is the first French publication on this topic in childhood. In France, children are allowed to be positioned on the passenger side seat, but the airbag, if present, is supposed to be deactivated, which is not always possible. In recent cars, depowering the airbag is easy, with on/off switches, but these systems are not uniform between models. Moreover, it is very likely that this possibility is ignored by numerous parents. A widespread communication on this topic should be initiated in France to prevent such events. Banning infants from front passenger seats completely does not seem possible. Nevertheless, greater attention on the part of police departments and better information to drivers appear necessary.

Airbag-induced thumb avulsion: two case reports

Although airbags are designed to save lives and protect victims from serious injuries, airbag deployment can cause unwanted lesions. In this case report, two cases are presented of young women who sustained an important fracture dislocation of the first carpometacarpal joint (CMC I joint) caused by airbag deployment during a car collision.

Trigeminal Nerve Injury Following Accidental Airbag Deployment and Assessment with Quantitative Sensory Testing

High velocity motor vehicle accidents are associated with an increase in mortality rates and a significant number of facial injuries. Accidental deployment of airbags and the associated release of hot gases can result in both thermal and mechanical injuries. The more commonly reported maxillofacial injuries include temporomandibular joint fractures and dislocations, dental trauma, facial nerve paralysis, and other orofacial pain complaints. The following case report describes a patient with facial trauma from the accidental deployment of an airbag resulting in complaints consistent with a neurological injury for which quantitative sensory testing was used in confirming the diagnosis.

Determination of pre-impact occupant postures and analysis of consequences on injury outcome--part II: biomechanical study

This paper considers pre-impact vehicle maneuvers and analyzes the resulting driver motion from their comfort seating position. Part I of this work consisted of analyzing the driver behavior during a simulated crash in a car driving simulator. The configuration of the virtual accident led to an unavoidable frontal crash with a truck. The typical response to this type of emergency event was to brace rearward into the seat and to straighten the arms against the steering wheel, or, to swerve to attempt to avoid the impacting vehicle. In a turn crossover maneuvers, the forearm is directly positioned on the airbag module at time of crash. This position represents a potential injurious situation and is investigated in this Part II. Static airbag-deployment tests were realized in collaboration with Zodiac using conventional airbag (sewn cushion, pyrotechnical system and open event) and a Hybrid III 50th Male Dummy seated with the left arm positioned in the path of the deploying airbag. These experiments were numerically reproduced with Madymo and the ellipsoid Hybrid III dummy model. The dummy arm interaction with airbag was correlated with experiments. Then, a numerical simulation of a frontal collision at 56 km/h was realized. The results of the computational runs put forward injurious situations when the driver's arm was in front of the steering wheel. Indeed, in this case, the arm could hit the head under airbag deployment and induced serious neck bending and violent head launching. To mitigate head and neck trauma in this out-of-position situation, an airbag prototype (bonded cushion, two pure helium cold gas generators allowing mono- or multi-stage inflating, patented silicone membrane) was proposed by Zodiac. The results of static airbag-deployment tests with conventional and prototype airbags showed a significant reduction of the maximum linear head acceleration and neck bending with airbag prototype when a dual stage inflating was ignited, due to a reduced 'flinging' of the arm.

Determination of pre-impact occupant postures and analysis of consequences on injury outcome. Part I: a driving simulator study

This paper considers pre-impact vehicle maneuvers and analyzes the resulting driver motion from their comfort seating position. Part I of this work consists of analyzing the driver behavior during a crash. The study is conducted using the LAMIH driving simulator and involves 76 participants. The emergency situation is created by a truck emerging from behind a tractor on the opposite side of the road and tearing along the participant. The driver positioning throughout the simulation is recorded via five video cameras allowing view of the front scene, the driver face, feet and pedals, hands on the steering wheel and global lateral view. Data related to braking force, seat pressure, muscular activity for major groups of muscles and actions on the steering wheel are also collected. The typical response to this type of emergency event is to brace rearward into the seat and to straighten the arms against the steering wheel, or, to swerve to attempt to avoid the impacting vehicle. While turning the steering wheel, the forearm can be directly positioned on the airbag module at time of crash which represents a potential injurious situation. These positions are used in Part II to determine scenario of positions for numerical simulation of a frontal collision.

Injury risks in frontal crashes by delta V and body region with focus on head injuries in low-speed collisions

PURPOSE

This study investigated injury risks in frontal crashes by belt use and crash severity (delta V) with a focus on studying whether there is a pattern to the crashes causing serious head injuries in low-speed frontal collisions.

METHODS

1996-2007 National Automotive Sample System-Crashworthiness Data System (NASS-CDS) was analyzed for frontal crashes involving front-outboard occupants. Light vehicles were included with model year 1997+. Injuries of maximum severity MAIS 0-6 and fatalities were determined by crash severity and belt. Body region injury (AIS 0-6) was also determined. NASS-CDS electronic cases involving <15 mph crashes were evaluated to determine the crash circumstances causing serious head injury (AIS 3+) in occupants with overall severe injuries (MAIS 4+F).

RESULTS

More than half (51.3%) of belted occupants in 10-15 mph delta V crashes were uninjured compared with 30.2 percent for unbelted occupants. The ratio of the fraction (relative risk) of belted occupants who were uninjured to the fraction of unbelted, uninjured occupants was highest at 3.74 in the 30-35 mph delta V. For 10-15 mph crashes, 0.40 +/- 0.15 percent of unbelted occupants were severely injured (MAIS 4+F) compared to 0.033 +/- 0.009 percent for belted occupants. For 30-35 mph crashes, 8.51 +/- 2.20 percent of unbelted and 5.83 +/- 1.93 percent of belted occupants were severely injured. Overall, seat belt use was 87.4 percent effective in preventing severe injury (MAIS 4+F). The effectiveness decreased with increasing crash severity. The highest relative risk for severe injury of unbelted compared to belted occupants was 12.3 in crashes of 10-15 mph delta V. The relative risk was 8.8 in <10 mph crashes. Overall, the relative risk was 8.0 for severe injury (MAIS 4+F) in frontal crashes. 16.5 +/- 0.98 percent of unbelted occupants experienced serious (AIS 3-6) injury. This risk was 6.49 times greater than the 2.53 +/- 0.10 percent risk with belted occupants. The largest relative risk for serious injury (AIS 3-6) was to the neck (367 times), face (15.5 times) and head (10.2 times).

CONCLUSIONS

The highest relative risk for severe injury of unbelted occupants was in frontal crashes <15 mph. Most of the crashes involved multiple impacts and air bag deployment in the accident sequence. The use of long fill-time side curtains, additional curtain deployment logic, limited deflation front air bags and broader curtain coverage of the front interior may address these injuries.

Risk factors for 24-hour mortality after traumatic rib fractures owing to motor vehicle accidents: a nationwide population-based study

BACKGROUND

Accurate identification of patients at high risk of death as a result of major chest trauma is essential within a trauma system. We used 3-year population-based data in Taiwan to evaluate risk factors associated with 24-hour mortality among adults with obvious rib fractures and needing hospitalization after traffic accidents.

METHODS

Pooled data from Taiwan's National Health Insurance Research Database for the years 2002 through 2004 were used. A total of 18,856 patients hospitalized with rib fractures after traffic accidents were included. Multivariate logistic regression using generalized estimating equations was performed to explore the relationship between 24-hour mortality and patients' age, sex, and comorbid conditions, as well as hospital characteristics, adjusting for social factors and any clustering of the sampled patients by hospital.

RESULTS

Of patients in the sample, 459 (2.4%) died within 24 hours of admission. Patients who had six or more rib fractures were three times more likely to die within 24 hours of admission compared with patients with only one rib fracture (odds ratio [OR], 3.16; p < 0.001). The adjusted odds of death within 24 hours were higher for patients who had hemopneumothorax (OR, 3.15; p < 0.001), extremity fractures (OR, 1.74; p < 0.001), pelvic fractures (OR, 2.92; p < 0.001), head injuries (OR, 4.29; p < 0.001), spleen injury (OR, 1.83; p < 0.05), hepatic injury (OR, 4.39; p < 0.001), heart injury (OR, 4.48; p < 0.001), and diaphragm injury (OR, 3.16; p < 0.05) compared with patients who had none of these injuries.

CONCLUSIONS

We concluded that more than six ribs fractured, heart injuries, hepatic injuries, head injuries, and advanced age are the most important determinants of 24-hour mortality after thoracic trauma from traffic accidents.

Engineering with uncertainty: monitoring air bag performance

Modern engineering is complicated by an enormous number of uncertainties. Engineers know a great deal about the material world and how it works. But due to the inherent limits of testing and the complexities of the world outside the lab, engineers will never be able to fully predict how their creations will behave. One way the uncertainties of engineering can be dealt with is by actively monitoring technologies once they have left the development and production stage. This article uses an episode in the history of automobile air bags as an example of engineers who had the foresight and initiative to carefully track the technology on the road to discover problems as early as possible. Not only can monitoring help engineers identify problems that surface in the field, it can also assist them in their efforts to mobilize resources to resolve problem.

Air bag-associated burn

Burns due to the deployment of air bags have been occasionally described in recent years. Most reports are about injuries in the USA. However, there have been few reports of this type of injury in Australia. This case report details such an injury that took place in a road traffic accident in Melbourne, Australia.

Injury severity, vehicle safety features, and intersection crashes

OBJECTIVE

This article examines injury severity in crashes that occur within signalized intersections and identifies some factors that explain them.

METHOD

It uses a random effect ordered logit model and an unbalanced longitudinal panel data for 303 intersections for one medium-size city.

RESULTS

Among its findings are 3% and 0.29% lower probabilities of sustaining evident and disabling injuries respectively when vehicle occupants wear three-point seat belts and corresponding 1.71% and 0.16% lower probabilities when they wear only shoulder belts. Also, the probabilities of sustaining evident and disabling injuries reduce by 0.87% and 0.08% when vehicles with airbags are involved in crashes. But, when front airbags deploy the probabilities of sustaining disabling, evident, and possible injuries increase by 1.3%, 11.93%, and 26.80%, respectively. Similarly, both side airbags deploying increases disabling and evident injuries by 1.8% and 15.53%, respectively. In addition, we find that the probability of sustaining severe injuries increases in head-on crashes.

CONCLUSION

These results emphasize the effectiveness of seat belt use, especially three-point seat belts, the inclusion of airbags in all vehicles, increased awareness of possible injuries from airbags deploying, signalized intersection designs that include pedestrian crossing signals, and additional research to identify the predominant types of injuries associated with airbags deploying.

Occipital condyle fracture: An unusual airbag injury

The installation of airbags in motor vehicles, in association with the use of seat belts, has reduced the incidence of head injuries, as well as significantly decreasing morbidity and mortality in motor vehicle accidents. Nevertheless, the literature on the subject increasingly refers to lesions related to airbag deployment. These are usually minor, but in certain circumstances, severe and fatal injuries can result. This is a case report of serious injury due to airbag deployment, involving a restrained driver who suffered occipital condylar injury when his airbag deployed in a frontal collision. The range of airbag associated injuries is reported and predisposing factors, such as the probable proximity to the airbag housing, is discussed.

Upper extremity fracture patterns following motor vehicle crashes differ for drivers and passengers

PURPOSE

Injury patterns of occupants in motor vehicle crashes are changing, with upper extremity injury becoming more common in patients treated at trauma centres. Although not life threatening, upper extremity injuries may result in long-term disability, including chronic deformity, neurovascular compromise and degenerative arthritis. The purpose of this study was to compare upper extremity injury in drivers and passengers using the Crash Injury Research Engineering Network (CIREN) database.

METHODS

CIREN data were used to compare upper extremity skeletal injury patterns and sources for drivers and passengers in frontal and side impacts. Occupant variables (age, gender, co-morbidity, avoidance maneuvers and restraint use) and crash variables (direction of impact, delta V and vehicle crush) were considered in the analysis.

RESULTS

Only 24.8% of all occupants in the CIREN database had upper extremity injuries. One-half of upper extremity injuries to drivers were forearm fractures compared to one-third for passengers. Occupants in side impacts were more likely (OR=5.05) to have clavicle fractures, even while controlling for driver versus passenger status and safety belt use. Air bags were more likely to be a source of forearm fracture (OR=2.31) when controlling for driver versus passenger status, direction of force, sex and age compared to other sources. Only 10% of driver fractures with air bag deployment in frontal impacts were associated with air bag fling.

CONCLUSIONS

This study found that drivers and passengers have different upper extremity injury patterns but the direction of impact also plays an important role.

Isolated intra-articular fracture of the distal ulna: a rare injury related to airbag deployment

An isolated intra-articular and adjacent shaft fracture of the distal ulna is described. A 38-old-year woman driver sustained an automobile accident with subsequent airbag deployment injuring her left wrist. Imaging studies showed displacement of a radiovolar fragment and deformity of the ulnar articular surface. The fracture was reduced and internally fixed with 3, 3.5-mm, cannulated screws to avoid future difficulties in forearm rotation, ulnocarpal impaction, and late posttraumatic arthritis. The final outcome was excellent. Careful clinical and radiologic examination is strongly recommended for this type of fracture, which seems to be a part of the spectrum of upper limb injuries associated with airbag deployment. Such injuries can be expected to occur more frequently with the increasing use of airbags.

The association between restraint system and upper extremity injury after motor vehicle collisions

OBJECTIVES

This study was designed to investigate the relationship between upper extremity (UE) injuries and occupant restraint systems among front seat occupants who were involved in frontal motor vehicle collisions (MVCs).

DESIGN

Case-control.

SETTING

The 1995 through 2002 National Automotive Sampling System (NASS) Crashworthiness Data System (CDS).

PARTICIPANTS

Subjects were identified from the NASS-CDS. All cases sustained an UE injury with a > or = 2 Abbreviated Injury Scale Score.

OUTCOMES

Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated comparing risk of UE in 3 mutually exclusive restraint system groups (seatbelt-only, airbag-only, seatbelt-airbag-combined) to the unrestrained group. Data analysis was adjusted for significant occupant, vehicle, and collision characteristics.

RESULTS

Seatbelt-only occupants had a reduced UE injury risk (OR, 0.41; 95% CI, 0.22-0.76). Near null associations were found for airbag-only (OR, 1.1; 95% CI, 0.68-1.76) and seatbelt-airbag-combined (OR, 0.97; 95% CI, 0.56-1.69).

CONCLUSION

The results of this study suggest that UE injuries may become more common as a result of MVCs as the proportion of airbags in motor vehicles increases.

Does the Presence of an Upper Extremity Injury Affect Outcomes after Major Trauma?

BACKGROUND

There is a paucity of information about the impact of upper extremity (UE) injuries on patient outcomes, particularly after major trauma.

METHODS

Data were obtained from a statewide trauma registry. Cases were defined as major trauma cases (Injury Severity Score > 15) with (UE group) and without (no-UE group) an associated upper extremity injury. Multivariate analysis was performed to identify independent predictors of outcome.

RESULTS

Major trauma patients with UE injury were 1.5 times (p = 0.011) more likely than the no-UE group to have a length of stay greater than 7 days. After adjusting for age, mechanism of injury, and Injury Severity Score, UE injury was not an independent predictor of discharge destination.

CONCLUSION

In major trauma patients, the presence of an upper extremity injury is a significant predictor of length of stay, indicating a greater complexity and cost of care associated with this group of major trauma patients.

Severe upper extremity injuries in frontal automobile crashes: the effects of depowered airbags

BACKGROUND

The purpose of this study was to determine the effects of depowered frontal airbags on the incidence of severe upper extremity injuries.

METHODS

The National Automotive Sampling System database files from 1993 to 2000 were examined in a study that included 2,413,347 occupants who were exposed to an airbag deployment in the United States.

RESULTS

Occupants exposed to a depowered airbag deployment were significantly more likely to sustain a severe upper extremity injury (3.9%) than those occupants exposed to a full-powered airbag deployment (2.5%) (P=.01). Full-powered systems resulted in an injury distribution of 89.2% fractures and 7.9% dislocations compared with depowered systems with 55.3% fractures and 44.3% dislocations.

CONCLUSIONS

Although depowered airbags were designed to reduce the risk of injuries, they appear to have increased the overall incidence of severe upper extremity injuries through a shift from long bone fractures to joint dislocations.

The Effects of Depowered Airbags on Skin Injuries in Frontal Automobile Crashes

The purpose of this study was to determine the effects of depowered frontal airbags on the incidence of skin injuries. The National Automotive Sampling System database files from 1993 to 2000 were examined in a study including 2,246,524 occupants exposed to airbag deployment in the United States. There was no significant difference between full-powered and depowered airbags, with 60.2 percent of those exposed to a full-powered deployment sustaining a skin injury versus 59.5 percent of occupants exposed to a depowered airbag (p = 0.19). Whether occupants were exposed to a full-powered airbag (1,936,485 occupants) or a depowered airbay (310,039 occupants), the majority of skin injuries were to the upper extremity and the face. Regardless of airbag power, the overwhelming majority of the skin injuries were minor (99.8 percent). There was not a significantly greater risk of injury from any source for occupants exposed to a depowered airbag or a full-powered airbag (p = 0.87). The data suggest that the implementation of depowered airbags did not affect the number, seriousness, location, or source of skin injuries.

Air bags and the skin

Air bags, fitted in the majority of new automobiles, are safety devices activated when a sudden deceleration causes the ignition of a propellant cartridge containing sodium azide. The bag is inflated by nitrogen liberated during the combustion. Deployment releases various high-temperature gases, including nitrogen and carbon dioxide, and produces sodium hydroxide, a highly irritant alkaline substance. In about 7%-8% of cases, air bags cause dermatologic injuries such as traumatic lesions, irritant dermatitis, and chemical and thermal burns. Nondermatologic lesions, such as ocular damage (alkali keratitis, corneal abrasions), ear lesions, bone fractures, and contusive damage can also be caused by air bag deployment.

Analysis of Burn Injuries in Frontal Automobile Crashes

The purpose of this study was to investigate burn injuries resulting from frontal automobile crashes and to determine the effects of frontal airbags on the incidence of burn injuries. The study included 25,464 individual cases from the National Automotive Sampling System database files for the years 1993 to 2000. Occupants were at a significantly higher risk to sustain a burn injury when exposed to an airbag deployment (1.54%) compared with those who received a burn injury when not exposed to an airbag deployment (0.02%; P = 0.02). In contrast to previous publications, this study found that 1.53% of front seat occupants exposed to an airbag deployment sustained an airbag-induced burn injury. The vast majority of airbag-induced burn injuries were minor (98.7%); however, in cases with no airbag deployment, the burns were often much more serious, including fatal burns (29.6%). Occupant weight, height, sex, seatbelt use, and seat position were all found not to be significant in predicting the risk of airbag induced burn injury, whereas age and crash velocity were found to be significant.

Effects of airbag deployment: lesions, epidemiology, and management

Airbags are restraining safety devices, but their activation may sometimes induce injuries during road accidents. Rapid deceleration due to an impact causes the ignition of a sodium azide cartridge, which releases nitrogen gas to inflate the nylon rubber bag. Numerous high-temperature gases, sodium hydroxide, carbon dioxide, and various other metallic oxides are also released producing a corrosive alkaline aerosol. Cutaneous and extracutaneous injuries due to airbag deployment may occur. Cutaneous injuries are frequent, and consist of irritant dermatitis, and chemical and thermal burns. Furthermore, numerous kinds of traumatic lesions (abrasions, friction burns, and lacerations) may be observed. Extracutaneous damage may involve the eyes, ears, cardiovascular system, nerves, joints, and bones. The nature of airbag lesions, their frequency, and management are reported. Even though the majority of airbag lesions are minor and do not require hospitalization, correct diagnosis and the choice of the most suitable treatment are necessary.

The development, validation and application of a finite element upper extremity model subjected to air bag loading

Both frontal and side air bags can inflict injuries to the upper extremities in cases where the limb is close to the air bag module at the time of impact. Current dummy limbs show qualitatively correct kinematics under air bag loading, but they lack biofidelity in long bone bending and fracture. Thus, an effective research tool is needed to investigate the injury mechanisms involved in air bag loading and to judge the improvements of new air bag designs. The objective of this study is to create an efficient numerical model that exhibits both correct global kinematics as well as localized tissue deformation and initiation of fracture under various impact conditions. The development of the model includes the creation of a sufficiently accurate finite element mesh, the adaptation of material properties from literature into constitutive models and the definition of kinematic constraints at articular joint locations. In order to make the model applicable for full-scale simulations, it was coupled with a computationally efficient human model. The model was validated against available cadaver experiments, including static and dynamic three-point-bending tests to the arm and forearm, as well as frontal air bag to forearm impact tests. The sensitivity of the model to changes in air bag properties and upper limb orientation are demonstrated by performing parametric studies. It is shown that the risk of forearm fracture increases substantially with proximity to the deploying frontal air bag and air bag aggressiveness, which corresponds to experimental findings. However, it is shown that increasing the forearm supination angle is protective for the occurrence of forearm fracture. In conclusion, the developed model proves to be a useful research tool to investigate trends in injury severity as a result of a changing frontal air bag to upper extremity loading environment.

The effects of airbag deployment on severe upper extremity injuries in frontal automobile crashes

The purpose of this study was to investigate severe upper extremity injuries resulting from frontal automobile crashes and to determine the effects of frontal airbags. The National Automotive Sampling System database files from 1993 to 2000 were examined in a study that included 25,464 individual cases that occurred in the United States. An analysis of the cases indicated that occupants exposed to an airbag deployment were statistically more likely to sustain a severe upper extremity injury (2.7%) than those occupants not exposed to an airbag deployment (1.6%) (P =.01). In particular, 0.7% of occupants exposed to an airbag deployment sustained a severe upper extremity injury specifically from the airbag. In addition, when in crashes with an airbag deployment, older occupants were at a higher risk for severe upper extremity injury, as well as occupants in crashes with higher changes in velocity.

Effect of airbag deployment on head injuries in severe passenger motor vehicle crashes in Ontario, Canada

BACKGROUND

The purpose of this study was to identify and analyze factors contributing to both airbag deployment and resulting head injuries (HIs) and to quantify the effect of airbag deployment on head injuries, in terms of odds of head injury and severity, in severe motor vehicle collisions (MVCs).

METHODS

Data were derived from severely injured (Injury Severity Score [ISS] > 12) drivers treated at Ontario's lead trauma hospitals (n = 1,272), and included all MVC driver deaths in the province (n = 665) from 1997-98. We conducted an epidemiologic description and a case-control study to compare drivers with and without HIs. Statistical analysis included Pearson's chi2, Wilcoxon rank-sum, and multiple logistic regression tests.

RESULTS

Seventy-one percent of drivers were men, peaking in the 25- to 34-year age group. The most common impact involved multiple vehicles (62%) approaching each other. Overall, 59% of crashes had a frontal location of impact. HIs were significantly associated with a lower age (median, 36 vs. 43 years), seat belt use (53% vs. 59%), and airbag deployment (7% vs. 10%), with higher ISS (median, 34 vs. 22), ejection (20% vs. 10%), and mortality rate (44% vs. 35%). Airbag deployment was associated with higher age and seat belt use, and lower ISS, ejection, and deaths. Importantly, there were fewer HIs with the deployment of an airbag (64% vs. 73%) and a lower severity of HI. When logistic regression was used to control for the effects of possible confounders, airbag deployment was not statistically associated with one's odds of HI (odds ratio, 0.827; 95% confidence interval, 0.560-1.220), but ISS, age, and ejection were.

CONCLUSION

Airbag deployment did not significantly lower a driver's odds of head injury in a severe MVC, but it did significantly lower the severity of head injury. This is a significant finding, given that 72% of our study population sustained a head injury and the importance of lowering the severity of these head injuries in terms of patients' ultimate outcome. The most important factor associated with head injuries was ejection, which nearly doubled a driver's odds of head injury (odds ratio, 1.759; 95% confidence interval, 1.201-2.577). This reinforces the supplementary protective effect of an airbag and that "buckling up" and keeping occupants in the vehicle is of primary importance in the prevention of head injuries.

Effect of air bags and restraining devices on the pattern of facial fractures in motor vehicle crashes

OBJECTIVE

To examine the relationship between the use of restraining devices and the incidence of specific facial fractures in motor vehicle crashes.

DESIGN

Retrospective analysis of patients with facial fractures following a motor vehicle crash.

SETTING

University of Alabama at Birmingham Hospital level I trauma center from 1996 to 2000.

PATIENTS

Of 3731 patients involved in motor vehicle crashes, a total of 497 patients were found to have facial fractures as determined by International Classification of Diseases, Ninth Revision (ICD-9) codes. Facial fractures were categorized as mandibular, orbital, zygomaticomaxillary complex (ZMC), and nasal.

RESULTS

Use of seat belts alone was more effective in decreasing the chance of facial fractures in this population (from 17% to 8%) compared with the use of air bags alone (17% to 11%). The use of seat belts and air bags together decreased the incidence of facial fractures from 17% to 5%.

CONCLUSIONS

Use of restraining devices in vehicles significantly reduces the chance of incurring facial fractures in a severe motor vehicle crash. However, use of air bags and seat belts does not change the pattern of facial fractures greatly except for ZMC fractures. Air bags are least effective in preventing ZMC fractures. Improving the mechanics of restraining devices might be needed to minimize facial fractures.

Air bag injuries--a literature review in consideration of demands in forensic autopsies

Air bags have been implicated in saving lives and reducing morbidity associated with motor vehicle crashes since their introduction in the mid-1970s. However, there is increasing evidence showing that air bags can be a source of injury and even death in certain circumstances. As the number of air bag-equipped vehicles increases, air bag-related injuries have occurred more frequently. Thus, a greater awareness of air bag-related injuries is required in forensic autopsies. Here, we review thoroughly the literature concerning air bag-related injuries with special regard to their nature and causative mechanisms, and summarize air bag-related injuries observed in adults, children and infants.

Burn injury secondary to air bag deployment

The efficacy of air bags has been proven in diminishing the rate of fatalities and severity of injury in motor vehicle crashes. Unfortunately, as with any developing technology, new problems have been encountered that are directly attributable to the deployment of the air bag itself. Most air bag-related injuries are minor and, surprisingly, more than 7% are burns typically involving the upper extremity or head or neck. Fortunately, these are superficial burns that usually require only expectant therapy, but a high degree of suspicion in these circumstances is needed to make the proper diagnosis.

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.

Mortality reduction with air bag and seat belt use in head-on passenger car collisions

To assess the efficacy of occupant protection systems, the authors measured the mortality reduction associated with air bag deployment and seat belt use for drivers involved in head-on passenger car collisions in the United States. They used a matched case-control design of all head-on collisions involving two passenger cars reported to the Fatality Analysis Reporting System in 1992-1997, and driver mortality differences between the paired crash vehicles for air bag deployment and seat belt use were measured with matched-pair odds ratios. Conditional logistic regression was used to adjust for multiple effects. There were 9,859 head-on collisions involving 19,718 passenger cars and drivers. Air bag deployment reduced mortality 63% (crude odds ratio (OR) = 0.37, 95% confidence interval (CI): 0.32, 0.42), while lap-shoulder belt use reduced mortality 72% (OR = 0.28, 95% CI: 0.25, 0.31). In a conditional logistic model that adjusted for vehicle (rollover, weight, age) and driver (age, sex) factors, air bags (OR = 0.71, 95% CI: 0.58, 0.87) and any combination of seat belts (OR = 0.25, 95% CI: 0.22, 0.29) were both associated with reduced mortality. Combined air bag and seat belt use reduced mortality by more than 80% (OR = 0.18, 95% CI: 0.13, 0.25). Thus, this study confirms the independent effect of air bags and seat belts in reducing mortality.

Acute cervical spinal cord injury secondary to air bag deployment without proper use of lap or shoulder harnesses

The authors present a case report of a patient with cervical central spinal cord syndrome caused by a hyperextension injury after a motor vehicle collision in which the air bag deployed in the absence of shoulder or lap belt harnesses. The potential for cervical spine and spinal cord hyperextension injuries in passengers positioned in front of air bags without proper use of shoulder or lap belt harnesses is discussed. Cervical central spinal cord quadriplegia occurred with cervical spondylosis and kyphosis that was managed by early three-level cervical corpectomy in a 58-year-old patient. Early improvement in the patient's neurological status occurred but was incomplete at the time of this report. Cervical hyperextension injuries are possible in passengers positioned in the front seat of cars with air bags when shoulder or lap belt harnesses are not used properly. Previous biomechanical studies have documented the potential for these types of injuries.

Atlanto-occipital dislocation: an unusual lethal airbag injury

Airbag-induced injury fatality is increasing in frequency. We present the case of a 6-year-old passenger who sustained a fatal atlanto-occipital dislocation associated with airbag deployment in a low-speed motor vehicle crash. The current literature regarding airbag fatalities and methods to ameliorate airbag-induced injury are reviewed.

A retrospective review of air bag deaths

OBJECTIVE

To describe occupant and crash characteristics in the first 27 publicly released investigations of air-bag-related fatalities.

METHODS

A retrospective review of the first 27 released crash investigations of air-bag-induced fatalities was conducted. Data were obtained by the National Highway Traffic Safety Administration.

RESULTS

Three separate groups of occupants are described: adult drivers, school-aged children riding in the right front passenger seat, and infants installed into rear-facing infant car seats placed into the right front passenger seat. Female drivers were significantly likely to be short-statured. Male drivers tended to be slumped over the wheel. Eleven children (100%) were improperly restrained and thrown forward by preimpact braking. Adults tended to have serious chest injuries, while children tended to have CNS or neck injuries. All three infants had fatal CNS injuries. The average deltaV (change in the vehicle's velocity at the moment of impact) was 12 mph and the average bumper crash was 8.8 inches.

CONCLUSIONS

Air bags can cause fatal injury to car occupants in low- or moderate-speed crashes. Data suggest that proximity to the air bag at the time of deployment is the critical risk factor for fatal injury.

Air bag-associated injury to a child in the front passenger seat

We report the case of a 3.5-year-old front seat passenger who suffered significant head and neck injuries as a result of air bag deployment in a collision of <30 mph. These lesions included multiple abrasions of the lower half of the face, nose, forehead, and right ear, torn frenula, conjunctival petechiae, comminuted fractures of the left and right lateral frontal regions and right parietal bone, diastatic fracture of the coronal suture, subgaleal and subarachnoid hemorrhages, cortical contusions, subluxation of the atlantooccipital joint, and fracture of the C4 vertebral body. These lesions are consistent with trauma secondary to the deploying air bag and the head striking the interior of the car. The findings in this case further support the Centers for Disease Control and Prevention (CDC) guidelines of keeping children properly restrained, preferably in the back seat, or as far as possible from air bags.