Research in biomechanics of occupant protection

Effectiveness of lumbar motion style acupuncture treatment on inpatients with acute low back pain: A pragmatic, randomized controlled trial

BACKGROUND AND PURPOSE

This parallel, single-center, pragmatic, randomized controlled study aimed to investigate the effectiveness and safety of motion style acupuncture treatment (MSAT; a combination of acupuncture and Doin therapy) to reduce pain and improve the functional disability of patients with acute low back pain (aLBP) due to road traffic accidents.

MATERIALS AND METHODS

Ninety-six patients with aLBP admitted to the Haeundae Jaseng Hospital of Korean Medicine in South Korea due to traffic accidents were treated with integrative Korean medicine (IKM) with additional 3-day MSAT sessions during hospitalization (MSAT group, 48 patients) or without (control group, 48 patients), and followed up for 90 days.

RESULTS

The mean numeric rating scale (NRS) scores of low back pain (LBP) of the MSAT and control groups were both 6.7 (95% confidence interval [CI]: 6.3, 7.1) at baseline. After completing the third round of all applicable treatment sessions (the primary endpoint in this study), the mean NRS scores of the MSAT and control groups were 3.76 (95% CI: 3.54, 3.99) and 5.32 (95% CI: 5.09, 5.55), respectively. The difference in the mean NRS score between the two groups was 1.56 (95% CI: 1.25, 1.87).

CONCLUSION

IKM treatment combined with MSAT can reduce pain and improve the range of motion of patients with aLBP.

TRIAL REGISTRATION

This trial is registered at ClinicalTrial.gov (NCT04956458).

Blunt injury of liver: mechanical response of porcine liver in experimental impact test

OBJECTIVE

The liver is frequently injured in blunt abdominal trauma caused by road traffic accidents. The testing of safety performance of vehicles, e.g. belt usage, head support, seat shape, or air bag shape, material, pressure and reaction, could lead to reduction of the injury seriousness. Current trends in safety testing include development of accurate computational human body models (HBMs) based on the anatomical, morphological, and mechanical behavior of tissues under high strain.

APPROACH

The aim of this study was to describe the internal pressure changes within porcine liver, the severity of liver injury and the relation between the porcine liver microstructure and rupture propagation in an experimental impact test. Porcine liver specimens (n = 24) were uniformly compressed using a drop tower technique and four impact heights (200, 300, 400 and 500 mm; corresponding velocities: 1.72, 2.17, 2.54 and 2.88 m s^-1). The changes in intravascular pressure were measured via catheters placed in portal vein and caudate vena cava. The induced injuries were analyzed on the macroscopic level according to AAST grade and AIS severity. Rupture propagation with respect to liver microstructure was analyzed using stereological methods.

MAIN RESULTS

Macroscopic ruptures affected mostly the interface between connective tissue surrounding big vessels and liver parenchyma. Histological analysis revealed that the ruptures avoided reticular fibers and interlobular septa made of connective tissue on the microscopic level.

SIGNIFICANCE

The present findings can be used for evaluation of HBMs of liver behavior in impact situations.

Development and Full Body Validation of a 5th Percentile Female Finite Element Model

To mitigate the societal impact of vehicle crash, researchers are using a variety of tools, including finite element models (FEMs). As part of the Global Human Body Models Consortium (GHBMC) project, comprehensive medical image and anthropometrical data of the 5th percentile female (F05) were acquired for the explicit purpose of FEM development. The F05-O (occupant) FEM model consists of 981 parts, 2.6 million elements, 1.4 million nodes, and has a mass of 51.1 kg. The model was compared to experimental data in 10 validation cases ranging from localized rigid hub impacts to full body sled cases. In order to make direct comparisons to experimental data, which represent the mass of an average male, the model was compared to experimental corridors using two methods: 1) post-hoc scaling the outputs from the baseline F05-O model and 2) geometrically morphing the model to the body habitus of the average male to allow direct comparisons. This second step required running the morphed full body model in all 10 simulations for a total of 20 full body simulations presented. Overall, geometrically morphing the model was found to more closely match the target data with an average ISO score for the rigid impacts of 0.76 compared to 0.67 for the scaled responses. Based on these data, the morphed model was then used for model validation in the vehicle sled cases. Overall, the morphed model attained an average weighted score of 0.69 for the two sled impacts. Hard tissue injuries were also assessed and the baseline F05-O model was found to predict a greater occurrence of pelvic fractures compared to the GHBMC average male model, but predicted fewer rib fractures.

Occupant and Crash Characteristics of Elderly Subjects With Thoracic and Lumbar Spine Injuries After Motor Vehicle Collisions

STUDY DESIGN

Retrospective study of a prospectively gathered database.

OBJECTIVE

To investigate the incidence and pattern of thoracic and lumbar (T and L) spine injuries among elderly subjects involved in motor vehicle collision (MVC).

SUMMARY OF BACKGROUND DATA

Adults age 65 and older currently constitute more than 16% of all licensed drivers. Despite driving less than the young, older drivers are involved in a higher proportion of crashes. Notwithstanding the safety features in modern vehicles, 15.8% to 51% of all T and L spine injuries result from MVCs.

METHODS

Crash Injury Research and Engineering Network database is a prospectively maintained, multicentered database that enrolls MVC occupants with moderate-to-severe injuries. It was queried for T and L spine injuries in subjects 65 and older. 142 Crash Injury Research and Engineering Network files for all elderly individuals were reviewed for demographic, injury, and crash data. Each occupant's T and L injury was categorized using a modified Denis classification.

RESULTS

Of 661 elderly subjects, 142 (21.48%) sustained T and L spine injuries. Of the 102 major injuries, there were 63 compression, 20 burst and 12 extension fractures. Seatbelt use predisposed elderly subjects to compression and burst fractures, whereas seatbelt and airbag use predisposed to burst fractures. Deployment of airbags without seatbelt use appeared to predispose elderly subjects to neurological injury, higher Injury Severity Score, and higher mortality. Occupants using 3-point belts who had airbags deployed during the collision had the lowest rates of fatality and neurological injury.

CONCLUSION

T and L spine injuries in the elderly are not uncommon despite restraint use. Whereas seatbelts used alone and in conjunction with airbag deployment reduced fatalities and neurological injuries in the elderly, deployment of airbags in occupants without seatbelts predisposed to more severe injury.

Hybrid cadaveric/surrogate model of thoracolumbar spine injury due to simulated fall from height

A fall from high height can cause thoracolumbar spine fracture with retropulsion of endplate fragments into the canal leading to neurological deficit. Our objectives were to develop a hybrid cadaveric/surrogate model for producing thoracolumbar spine injury during simulated fall from height, evaluate the feasibility and performance of the model, and compare injuries with those observed clinically. Our model consisted of a 3-vertebra human lumbar specimen (L3-L4-L5) stabilized with muscle force replication and mounted within an impact dummy. The model was subjected to a fall from height of 2.2 m with impact velocity of 6.6 m/s. Kinetic and kinematic time-history responses were determined using spinal and pelvis load cell data and analyses of high-speed video. Injuries to the L4 vertebra were evaluated by fluoroscopy, radiography, and detailed anatomical dissection. Peak compression forces during the fall from height occurred at 7 ms and reached 44.7 kN at the ground, 9.1 kN at the pelvis, and 4.5 kN at the spine. Pelvis acceleration peaks reached 209.9 g at 8 ms for vertical and 62.8 g at 12 ms for rearward. Tensile load peaks were then observed (spine: 657.0 N at 47 ms; pelvis: 569.4 N at 61 ms). T1/pelvis peak flexion of 68.3° occurred at 38 ms as the upper torso translated forward while the pelvis translated rearward. Complete axial burst fracture of the L4 vertebra was observed including endplate comminution, retropulsion of bony fragments into the canal, loss of vertebral body height, and increased interpedicular distance due to fractures anterior to the pedicles and a vertical split fracture of the left lamina. Our dynamic injury model closely replicated the biomechanics of real-life fall from height and produced realistic, clinically relevant burst fracture of the lumbar spine. Our model may be used for further study of thoracolumbar spine injury mechanisms and injury prevention strategies.

Factors related to seatbelt-wearing among rear-seat passengers in Malaysia

The benefit of wearing a rear seatbelt in reducing the risk of motor vehicle crash-related fatalities and injuries has been well documented in previous studies. Wearing a seatbelt not only reduces the risk of injury to rear-seat passengers, but also reduces the risk of injury to front-seat occupant who could be crushed by unbelted rear-seat passengers in a motor vehicle crash. Despite the benefits of wearing a rear seatbelt, its rate of use in Malaysia is generally low. The objective of this study was to identify factors that are associated with the wearing of a seatbelt among rear-seat passengers in Malaysia. Multinomial logistic regression analysis of the results of a questionnaire survey of 1651 rear-seat passengers revealed that rear-seat passengers who were younger, male, single and less educated and who had a perception of a low level of legislation enforcement, a lower risk-aversion and less driving experience (only for passengers who are also drivers) were less likely to wear a rear seatbelt. There was also a significant positive correlation between driver seatbelt and rear seatbelt-wearing behaviour. This implies that, in regards to seatbelt-wearing behaviour, drivers are more likely to adopt the same seatbelt-wearing behaviour when travelling as rear-seat passengers as they do when driving. These findings are crucial to the development of new interventions to increase the compliance rate of wearing a rear seatbelt.

Structural etiology of chronic low back pain due to motor vehicle collision

OBJECTIVE

To estimate prevalence rates of discogenic, facet, and sacroiliac joint pain, and describe clinical features of chronic low back pain patients whose symptoms were initiated by motor vehicle collisions.

DESIGN

Retrospective chart review.

SETTING

Academic spine center.

PATIENTS

Twenty-seven motor vehicle collision-induced chronic low back pain patients were included after undergoing diagnostic procedures.

INTERVENTIONS

Lumbar provocation discography, dual diagnostic facet joint blocks, and intra-articular sacroiliac joint injections.

METHODS

Enrolled patients underwent diagnostic procedures based on clinical presentation until the pain source was identified. The prevalence of each source of low back pain was estimated. Clinical, categorical, and continuous characteristics within the source groups were calculated with SAS v.9.2 (SAS Institute Inc., Cary, NC).

OUTCOME MEASURES

Etiology and prevalence were analyzed for each diagnosis group.

RESULTS

Of the 27 patients, 15/27 (56%) were diagnosed with discogenic pain, 7/27 (26%) with sacroiliac joint pain, and 5/27 (19%) with facet joint pain. Seventy-eight percent were female. Mean age was 42.5 years (standard deviation = 10.4) with median duration of symptoms of 24 months (interquartile range = 6-48).

CONCLUSIONS

Our study is the first to demonstrate that diagnostic spinal injections can identify particular spinal structures, namely the intervertebral disc, facet joint, and sacroiliac joint, as the specific source of chronic low back pain due to inciting motor vehicle collisions. The most common source of motor vehicle collision-induced chronic low back pain appears to be the disc followed by the sacroiliac and facet joints.

Spinal injuries in pedestrians struck by motor vehicles

STUDY DESIGN

Retrospective study of consecutive patients that were struck by motor vehicles and sustained spinal injuries over a 6-year period from 1997 to 2003.

OBJECTIVE

To determine spinal injury patterns and associated injuries in pedestrians struck by motor vehicles.

SUMMARY OF BACKGROUND DATA

Motor vehicle accidents involving pedestrians are associated with high morbidity and mortality rates.

METHODS

All injured patients admitted to Level I Trauma and Regional Spinal Cord Injury Center were reviewed retrospectively to identify those who were struck by motor vehicles and sustained injury to the spinal column. Before 2001, clearance of the thoracolumbar (TL) spine was performed by plain radiographs. Beginning in 2001, such clearance was performed by helical truncal computed tomography of the chest/abdomen/pelvis (CT/CAP) that was performed to evaluate potential visceral injuries.

RESULTS

Of the 1672 patients who were struck by motor vehicles, 135 patients (8%) were found to have spinal injuries. Cervical injuries were found in 35%, thoracic in 19%, lumbar in 37%, and sacral injuries in 27%. Associated injuries were present in 99% of the patients. By relative risk analyses, there were no regional associations between injuries of the TL spine and injuries to the chest and abdomen. Patients frequently had combinations of injuries in distant locations, presumably from a "double-impact" injury mechanism. Before initiation of the CT/CAP protocol to clear the TL spine, 7% of patients had injuries initially missed by TL radiographs.

CONCLUSIONS

Spinal injuries in pedestrians struck by motor vehicles are more evenly distributed throughout the spinal column and more often coexist with injuries to remote organs compared with car occupants and motorcyclists where regional tendencies and isolated spinal injuries are more frequent. A systematic approach to both diagnosis and treatment is, therefore, necessary. Helical truncal CT, performed to evaluate visceral injury, effectively screens for TL fractures.

Pediatric lumbar Chance fractures in British Columbia: chart review and analysis of the use of shoulder restraints in MVAs

Chance fractures of the skeletally immature spine classically occur in frontal motor vehicle accidents (MVAs) when the occupants are restrained by a lap belt only and undergo traumatic hyperflexion of the torso during the impact. We retrospectively examined all MVA-related Chance fractures at British Columbia's Children's Hospital since 1986, by collecting injury and seat-belt use information from chart data and imaging studies. Twenty-six patients were included in the study, 14 wore a lap belt only, seven wore a three-point restraint properly, and five were reportedly misusing the shoulder portion of a three-point restraint. The subjects ranged in age from 3 to 16 with a mean age of 10.6 years. Eleven of the 26 (42%) patients sustained abdominal viscera injuries, seven of the 26 patients suffered neurologic injury (spinal cord and/or spinal nerve injury) associated with their spinal fracture, with two cases of complete paralysis, and there was a 38% incidence of head injury. Concomitant injuries (i.e. to the head, abdomen and abdominal contents) tended to be mitigated by the presence of a properly worn shoulder restraint. This leads to the conclusion that Chance fractures can be sustained even when the occupant is using a shoulder belt to restrain their torso. The mechanism responsible for this is unknown. This may indicate that Chance fractures can be caused by a lesser degree of torso hyperflexion than previously thought. Alternatively, we also speculate that Chance fractures can occur while the torso is restrained by the shoulder belt if the hips submarine beneath the lap belt and the torso experiences hyperflexion secondary to forward excursion of the pelvis and legs during the collision. Future work is necessary to confirm these mechanisms and to find ways to prevent them. These studies will need to use computational or experimental child surrogates that can sit in a slouched posture and submarine during a collision.

Cervical spine injuries associated with the incorrect use of airbags in motor vehicle collisions

STUDY DESIGN

Retrospective database review and analysis.

OBJECTIVE

The purpose of this study is to determine the rate of cervical spine injuries with correct and incorrect use of front driver and passenger-side airbags. Summary of Background Data. Although there are abundant literature showing reduced injury severity and fatalities from seatbelts and airbags, no recent studies have delineated the affect of incorrect use of airbags in cervical spine injuries.

METHODS

The database from the Pennsylvania Trauma Systems Foundation was searched for drivers and front-seat passenger injuries from 1990 to 2002. The resulting records were then grouped into those using both seatbelt and the airbag, airbag-only, seatbelt-only, and no restraints. The data were then analyzed for frequency of cervical spine fractures with or without spinal cord injury and injury severity indexes.

RESULTS

The drivers using the airbag-only had significantly higher rate (54.1%) of cervical fractures than those using both airbag and a seatbelt (42.1%). Overall, drivers using the airbag-alone were 1.7 times more likely to suffer a cervical spine fracture than those using both protective devices. Likewise, passengers using the airbag-alone were 6.7 times more likely to suffer from a cervical spine fracture with spinal cord injury than those using both protective devices. In addition, the injury severity indexes (Glasgow coma scale, Injury Severity Score, Intensive Care Unit stays, and Total Hospital days) were significantly worse in patients who used an airbag-only.

CONCLUSION

Airbag use without the concomitant use of a seatbelt is associated with a higher incidence of cervical spine fractures with or without spinal cord injuries. Airbag misuse is also associated with higher Injury Severity Score, lower Glasgow coma scale, and longer intensive care unit and total hospital stays, indicating that these patients suffer worse injury than those who use the airbag properly.

Engineering better wheelchairs to enhance community participation

With about 2.2 million Americans currently using wheeled mobility devices, wheelchairs are frequently provided to people with impaired mobility to provide accessibility to the community. Individuals with spinal cord injuries, arthritis, balance disorders, and other conditions or diseases are typical users of wheelchairs. However, secondary injuries and wheelchair-related accidents are risks introduced by wheelchairs. Research is underway to advance wheelchair design to prevent or accommodate secondary injuries related to propulsion and transfer biomechanics, while improving safe, functional performance and accessibility to the community. This paper summarizes research and development underway aimed at enhancing safety and optimizing wheelchair design.

The effect of unrestrained rear-seat passengers on driver mortality

BACKGROUND

It is well documented that seat belt usage effectively reduces the severity of motor vehicle occupant injuries and fatalities in roadway crashes. This research examines how the presence of an unrestrained rear-seat passenger seated directly behind an airbag and/or belt-restrained driver affects the driver's risk of injury in two different idealized crash scenarios. Empirical data used in the study was obtained from four sled tests conducted with various size Hybrid III crash test dummies.

METHODS

Three tests simulated a frontal (head-on) impact between two vehicles. The first established the baseline condition: a driver dummy restrained by a belt and an airbag system, with an identical belt-restrained dummy seated directly behind. The other two frontal-mode tests involved different size driver dummies restrained in the same manner, with different size unrestrained dummies behind them. A fourth test featured an angled driver-side impact crash with a restrained driver and unrestrained rear seat passenger.

RESULTS

In both of the latter cases the driver incurred a high likelihood of severe head and chest injuries relative to that inferred in the baseline exposure. The last test featured two identical dummies in a simulated lateral (driver-side) inter-vehicular impact using a belt-restrained (only) driver and an unrestrained rear-seat passenger. Driver mortality was not significantly affected in this configuration.

CONCLUSION

Unrestrained rear-seat passengers place themselves as well as their driver at great risk of serious injury when involved in a head-on crash.

Prehospital triage of trauma patients: a trauma surgeon's perspective

A number of triage tools have been developed and used to make triage decisions. Studies have demonstrated better outcomes in patients who receive care in trauma centers. The field triage decision scheme from the American College of Surgeons Committee on Trauma involves patient triage based on the presence of physiologic derangement, specific anatomic injuries, mechanism of injury, and comorbid factors. Issues such as distance to a trauma center (rural areas) and methods of transport (e.g., air, ground) complicate the prehospital triage of trauma patients. The best system for a given community or region is one that begins with a triage scheme that is evidence based to the greatest extent possible but is then modified based on community or regional resources and geography. Delivering the severely injured trauma patient to a facility that can provide optimal care, in the shortest amount of the time, remains the overarching principle.

Motor vehicle restraint system use and risk of spine injury

OBJECTIVE

Motor vehicle collision (MVC)-related spinal injury is a severe and often permanently disabling injury. In addition, strain injuries have been reported as a common outcome of MVCs. Although advances in automobile crashworthiness have reduced both fatalities and severe injuries, the impact of varying occupant restraint systems (seatbelts and airbags) on thoracolumbar spine injuries is unknown. This study examined the relationship between the occurrence of mild to severe cervical and thoracolumbar spine injury and occupant restraint systems among front seat occupants involved in frontal MVCs.

METHODS

A retrospective cohort study was conducted among subjects obtained from the 1995-2004 National Automotive Sampling System. Cases were identified based on having sustained a spine injury of >/=1 on the Abbreviated Injury Scale (AIS), 1990 Revision. Risk risks (RRs) and 95% confidence intervals (CIs) were computed comparing occupant restraint systems with unrestrained occupants.

RESULTS

We found an overall incidence of AIS1 cervical (11.8%) and thoracolumbar (3.7%) spinal injury. Seatbelt only restraints were associated with increased cervical AIS1 injury (RR = 1.40, 95% CI 1.04-1.88). However, seatbelt only restraints showed the greatest risk reduction for AIS2 spinal injuries. Airbag only restraints reduced thoracolumbar AIS1 injuries (RR = 0.29, 95% CI 0.08-1.04). Seatbelt combined with airbag use was protective for cervical AIS3+ injury overall (RR = 0.29, 95% CI 0.14-0.58), cervical neurological injury (RR = 0.19, 95% CI 0.05-0.81), and thoracolumbar AIS3+ injury overall (RR = 0.20, 95% CI 0.05-0.70).

CONCLUSIONS

The results of this study suggest that seatbelts alone or in combination with an airbag increased the incidence of AIS1 spinal injuries, but provide protection against more severe injury to all regions of the spine. Airbag deployment without seatbelt use did not show increased protection relative to unrestrained occupants.

Head injuries in airbag-equipped motor vehicles with special emphasis on AIS 1 and 2 facial and loss of consciousness injuries

OBJECTIVES

Safety of the airbag supplemental restraint system (airbag) is a well-known concern. Although many lives are saved each year through airbag use, injuries continue to occur, especially to the head. Airbag safety research has focused primarily on severe injuries, while minor and moderate injuries have been largely ignored.

METHODS

In this study, 205,977 injury cases from the 1995 to 2001 National Automotive Sampling System (NASS)/ Crashworthiness Data System (CDS) were surveyed to determine the prevalence of AIS 1 and 2 facial and brain loss of consciousness (LOC) injuries and determine if these injuries are a concern. The query was focused on frontal impacts in vehicles equipped with airbags. Only occupants wearing appropriate seatbelts were included in this study so that the airbag would provide occupant protection under optimal conditions. Of the 205,977 injury cases studied, 2.4% met this criterion.

RESULTS

From the data gathered, the trends seem to indicate an increase in these specific injuries, both in terms of the total number and the proportion to all injury cases. In 1995, AIS 1 and 2 head injuries accounted for 96.5% of all head injuries caused by airbags. By 2001, the percentage had risen 3.0% to 99.5%. Injuries occurring in vehicles equipped with first-generation versus second generation airbags were compared, and data seem to suggest that there is a higher rate of minor and moderate head injuries when occupants are in second-generation airbag-equipped vehicles, even when appropriate lap and shoulder belts are used.

CONCLUSIONS

The short timeframe surveyed prevents drawing meaningful conclusions about statistical significance, but the graphical representations of the data in this study underscore an urgent need for further investigation based on current trends in order to understand the issue of minor and moderate head injury prevention in regard to airbags.

Risk of injury for occupants of motor vehicle collisions from unbelted occupants

OBJECTIVE

Unbelted occupants may increase the risk of injury for other occupants in a motor vehicle collision (MVC). This study evaluated the association between occupant restraint use and the risk of injury (including death) to other vehicle occupants.

DESIGN

A population based cohort study.

SETTING

United States.

SUBJECTS

MVC occupants (n = 152 191 unweighted, n = 18 426 684 weighted) seated between a belted or unbelted occupant and the line of the principal direction of force in frontal, lateral, and rear MVCs were sampled from the 1991-2002 National Automotive Sampling System General Estimates System. Offset MVCs were not included in the study.

MAIN OUTCOME MEASURE

Risk ratios and 95% confidence intervals for injury (including death) for occupants seated contiguous to unbelted occupants compared to occupants seated contiguous to belted occupants. Risk ratios were adjusted for at risk occupant's sex, age, seating position, vehicle type, collision type, travel speed, crash severity, and at risk occupants' own seat belt use.

RESULTS

Exposure to unbelted occupants was associated with a 40% increased risk of any injury. Belted at risk occupants were at a 90% increased risk of injury but unbelted occupants were not at increased risk. Risks were similar for non-incapacitating and capacitating injuries. There was a 4.8-fold increased risk of death for exposed belted occupants but no increased risk of death for unbelted occupants.

CONCLUSIONS

Belted occupants are at an increased risk of injury and death in the event of a MVC from unbelted occupants.

Tips and falls during electric-powered wheelchair driving: effects of seatbelt use, legrests, and driving speed

OBJECTIVE

To measure the response of a test dummy while traversing common obstacles encountered by users of electric-powered wheelchairs (EPWs) to determine whether optimal wheelchair fit, use of seatbelts, and driving speed affect the frequency and severity of EPW tips and falls.

DESIGN

Repeated-measures comparison study.

SETTING

Constructed environment both in and around a Veterans Affairs medical center.

PARTICIPANT

A 50th percentile Hybrid II anthropometric test dummy (ATD) was used to simulate a person driving an EPW.

INTERVENTIONS

The ATD was driven in 4 different EPWs over commonly encountered obstacles at speeds of 1 and 2m/s, with and without the use of a seatbelt, and at varying legrest heights.

MAIN OUTCOME MEASURES

The response and motion of the ATD were observed and recorded as no fall, loss of control (the ATD falls forward or sideways but remains in the EPW), the ATD falls out of the EPW, or the EPW tips completely.

RESULTS

A total of 97 adverse events out of 1700 trials were recorded: 88 were losses of control (instability) and 9 were ATD falls. No complete tips of any EPW occurred. Univariate statistical analysis indicated a significant relationship between the adverse events and the use of seatbelts, legrest condition, and test obstacles (P<.05). A mixed-model analysis confirmed the significant relationships between the adverse events and the use of seatbelts, legrest condition, and test obstacles (P<.05). However, the mixed model indicated that (1) there was no significant relationship between the adverse events and driving speed and (2) no one obstacle was designated to be the most problematic.

CONCLUSION

Persons who use EPWs should use seatbelts and legrests while driving their EPWs, and clinicians should include common driving tasks when assessing the proper set-up of EPWs.

Correlation of head injury to vehicle contact points using crash injury research and engineering network data

Head injury is the most common cause of morbidity and mortality in motor vehicle crashes. Efforts to improve vehicle design, which minimize forces exerted to the occupant's head, may lead to a reduction in the frequency and severity of head injury. We therefore set out to identify mechanisms producing severe head injury in motor vehicle crashes (MVC) derived from the crash injury research and engineering network (CIREN) database. CIREN combines crash site analysis, vehicle damage assessment, and occupant kinematics in relation to the occupant's injuries. From the Seattle CIREN database of 101 cases, compiled from 1997 to 1998, we selected those crashes in which the occupant sustained severe head injury (abbreviated injury score, AIS>or=4) for analysis. We examined crash mechanism, energy transfer, point of head contact, vehicle intrusion and resulting injuries. There were 15 cases with severe head injury. These were primarily due to side impacts (n=10) in comparison to front impacts (n=5). The average net change in velocity (delta velocity, DV) was 15 mile/h (range 4-29 mile/h). In cases where the primary point of head contact could be elucidated the B-pillar predominated (4 cases, 33.3%) followed by the striking external object (2 cases, 16.7%), A- (1 case, 8.3%) and C- (1 case, 8.3%) pillars, roof side rail (1 case, 8.3%), windshield header (1 case, 8.3%), windowsill (1 case, 8.3%) and airbag (1 case, 8.3%). In this series the predominant mechanism of head injury was lateral impacts, especially those in which the victims' heads struck the B-pillar. The need for improved head protection from lateral impacts is indicated.

Foot and ankle injuries in motor vehicle accidents

BACKGROUND

We studied foot and ankle (F/A) injuries that occurred in motor vehicle accidents treated in a Level 1 trauma center.

METHODS

The records of F/A injuries of 2248 consecutive orthopedic patients were reviewed to find foot and ankle injuries.

RESULTS

Pilon fractures were common. Motor Vehicle Accident (MVA) occupants with F/A injuries had a higher injury Severity Score than those without (17.9 vs. 11.6, p <. 001). MVA F/A injury risk was higher without restraint [relative risk ratio (rrr) 1.68, p <. 0032] than with restraint except for air bagged drivers who were similar to unrestrained drivers (rrr 1.18, p > .05, NS).

CONCLUSION

Patients with F/A injuries may have serious associated injuries. Air bags may not protect feet.

Fatal cardiovascular injuries to the unbelted occupant associated with airbag deployment: two case-reports

We present two forensic autopsy cases of unbelted occupants associated with the airbag deployment in motor vehicle collisions. Both victims suffered from cardiovascular injuries which were the cause of death. Case 1: A 50-year-old man sustained a contusion on the left anterior chest with rib fractures and laceration of the intrapericardial inferior vena cava, the right ventricle, and the right pleuropericardium. Case 2: A 40-year-old man sustained multiple rib fractures, sternal fracture, and the rupture of the right ventricle. Autopsies and vehicle examinations revealed that both victims' chest seemed to strike the steering wheel through the deployed airbag. Therefore, we determined that the source of blunt impact force is the steering wheel through the airbag rather than airbag deployment only. In light of these two cases, we learned that the steering wheel should be considered as the blunt impact force inducing cardiovascular injuries even in cases in which the airbag has been deployed.

Driver air bag effectiveness by severity of the crash

OBJECTIVES

This analysis provided effectiveness estimates of the driver-side air bag while controlling for severity of the crash and other potential confounders.

METHODS

Data were from the National Automotive Sampling System (1993-1996). Injury severity was described on the basis of the Abbreviated Injury Scale, Injury Severity Score, Functional Capacity Index, and survival. Ordinal, linear, and logistic multivariate regression methods were used.

RESULTS

Air bag deployment in frontal or near-frontal crashes decreases the probability of having severe and fatal injuries (e.g., Abbreviated Injury Scale score of 4-6), including those causing a long-lasting high degree of functional limitation. However, air bag deployment in low-severity crashes increases the probability that a driver (particularly a woman) will sustain injuries of Abbreviated Injury Scale level 1 to 3. Air bag deployment exerts a net injurious effect in low-severity crashes and a net protective effect in high-severity crashes. The level of crash severity at which air bags are protective is higher for female than for male drivers.

CONCLUSIONS

Air bag improvement should minimize the injuries induced by their deployment. One possibility is to raise their deployment level so that they deploy only in more severe crashes.

Injuries of the thoracolumbar spine associated with restraint use in head-on motor vehicle accidents

Many authors have described spinal and bodily injuries associated with seat belt use. However, most reports have focused primarily on lap seat belts and resultant flexion-distraction injuries. This retrospective chart review studies the relation between the specific type of restraint or air bag and the resultant thoracolumbar spinal injury subtype and associated bodily injuries. The charts of 221 patients who had sustained thoracolumbar fractures in motor vehicle accidents during a 10-year period were reviewed, and 37 patients were identified whose accidents were clearly described as a frontal collision and whose specific form of restraint was recorded. Among the 15 patients who used a shoulder strap and lap belt device (three-point restraint), 12 patients sustained burst fractures (80%) compared with 4 of the 14 patients (28.6%) restrained with lap seat belts alone. Life-threatening intraabdominal injuries occurred in 57.1% of lap-belted victims and in 26.7% of patients who used three-point restraints, and the character of these injuries also differed. No patients in an automobile in which an air bag deployed sustained major associated bodily injuries. Among restrained occupants of head-on motor vehicle accidents who have sustained a thoracolumbar fracture, patients using lap belts are more likely to sustain the classic flexion-distraction injury patterns, whereas patients using three-point restraints may sustain a higher incidence of burst fractures. In addition, three-point restraints are associated with a decreased risk of intraabdominal injury compared with lap seat belts.

A case of strangulation by a vehicle seat belt

A healthy 23-year-old man wearing a three-point seat belt suffered from a roll-over traffic accident. When the man was found, the fastened seat belt had loosened and the diagonal belt was tightened against the neck. Autopsy findings revealed ligature marks on the surface of the neck, hemorrhages in the muscles of the neck, petechial hemorrhages in palpebral conjunctivae and viscera, dark red liquid blood in the heart cavities and visceral congestion. We concluded that the man died of strangulation by the seat belt. In this case, the loose belt allowed the body to move and subsequently the diagonal belt applied external pressure to the neck while the car was rolling over. Although there have been several reports of neck injuries due to diagonal belts, this is the first report of strangulation by a properly used three-point belt in a roll-over vehicle accident.

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.

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.

Bilateral pneumothorax following air bag deployment

Air bags have been shown to decrease mortality from automobile accidents. Herein is a unique case of bilateral pneumothorax following deployment and rupture of an air bag with no other associated chest trauma. One may posit that rupture of the air bag allowed high-pressure gases to be expelled into the patient's lungs resulting in explosive barotrauma.

Patterns of injury associated with automobile airbag use

The wide use of automobile airbags has undoubtedly reduced the mortality and the incidence of serious injuries from motor vehicle accidents. However, automobile airbags appear to be associated with a variety of injuries including fatal injuries, ocular injuries, upper limb and chest injuries. Further improvements in airbag design together with education of the general public in their use should help reduce airbag-related injuries.

Airbag-induced lethal cervical trauma

In a frontal collision of a car (taxicab) perpendicular into a streetcar with an impact speed of approximately 30 kph (20 mph), the driver survived with minor injuries. The front-seat passenger was extremely "out-of-position," with her seat positioned nearly fully forward. This in combination with her short stature led to fatal injuries resulting from the inflating airbag (U.S.-type) striking against her face and chin. At the scene, she was found essentially clinically dead, but was resuscitated and died finally 13 days later. Postmortem examination showed a complete disruption of all ventral ligaments between the base of the skull and the first and second vertebrae, a nearly complete ventral rupture of the medulla, and diffuse axonal injury of the brain.

Air bag--mediated injury in the emergency department population

As the number of passenger vehicles equipped with air bags increases, the hazards associated with their use become more apparent. Certain occupants are at a greater risk of injury, depending on their size or their location in the vehicle. A predictable pattern of injury can be found; therefore a careful history and physical assessment are critical to avoid missing significant injuries.

Severe head injury caused by airbag deployment

Passenger-side airbags are present in over 21 million automobiles and will be required on all passenger vehicles by the model year 1999. Although airbags are effective supplemental restraint systems and have saved over 1,500 lives, airbag-related injuries have been reported. The National Highway Traffic Safety Administration recently reported 15 child deaths caused by airbag deployment. All of these children were believed to be improperly restrained in the front passenger position of a car equipped with a passenger-side airbag. This case represents the first serious injury caused by airbag deployment in a child that was properly positioned in an approved child restraint.