Injury trends of passenger car drivers in frontal crashes in the USA.

Injuries trends of passenger car drivers in head-on collisions are identified based on crash data extracted from the National Automotive Sampling System. Annual injury incidence levels are estimated for years 1990-2007. Over that period, the number of crashes is predicted to rise by 71%. However, the number of serious injuries to drivers is expected to rise by only 41% and driver fatalities are anticipated to decrease by 9%. Meantime, the types of injuries suffered by drivers are changing. Year-to-year shifts in injury patterns result from changes in vehicle size classes within the US vehicle fleet population and increases in seat belt use and air bag availability. The effectiveness of air bags in saving lives is estimated to be 30%, and with more air bag-equipped cars on the road, the probability of sustaining a life-threatening head or a torso injury is reduced. Air bags, however, are not as effective in preventing upper and lower extremity injuries, and thus arm and leg injuries will become more prevalent in years to come.

Linear and quasi-linear viscoelastic characterization of ankle ligaments.

The objective of this study was to produce linear and nonlinear viscoelastic models of eight major ligaments in the human ankle/foot complex for use in computer models of the lower extremity. The ligaments included in this study were the anterior talofibular (ATaF), anterior tibiofibular (ATiF), anterior tibiotalar (ATT), calcaneofibular (CF), posterior talofibular (PTaF), posterior tibiofibular (PTiF), posterior tibiotalar (PTT), and tibiocalcaneal (TiC) ligaments. Step relaxation and ramp tests were performed. Back-extrapolation was used to correct for vibration effects and the error introduced by the finite rise time in step relaxation tests. Ligament behavior was found to be nonlinear viscoelastic, but could be adequately modeled up to 15 percent strain using Fung's quasilinear viscoelastic (QLV) model. Failure properties and the effects of preconditioning were also examined.

Dynamic injury tolerances for long bones of the female upper extremity.

This paper presents the dynamic injury tolerances for the female humerus and forearm derived from dynamic 3-point bending tests using 22 female cadaver upper extremities. Twelve female humeri were tested at an average strain rate of 3.7+/-1.3%/s. The strain rates were chosen to be representative of those observed during upper extremity interaction with frontal and side airbags. The average moment to failure when mass scaled for the 5th centile female was 128+/-19 Nm. Using data from the in situ strain gauges during the drop tests and geometric properties obtained from pretest CT scans, an average dynamic elastic modulus for the female humerus was found to be 24.4+/-3.9 GPa. The injury tolerance for the forearm was determined from 10 female forearms tested at an average strain rate of 3.94+/-2.0%/s. Using 3 matched forearm pairs, it was determined that the forearm is 21% stronger in the supinated position (92+/-5 Nm) versus the pronated position (75+/-7 Nm). Two distinct fracture patterns were seen for the pronated and supinated groups. In the supinated position the average difference in fracture time between the radius and ulna was a negligible 0.4+/-0.3 ms. However, the pronated tests yielded an average difference in fracture time of 3.6+/-1.2 ms, with the ulna breaking before the radius in every test. This trend implies that in the pronated position, the ulna and radius are loaded independently, while in the supinated position the ulna and radius are loaded together as a combined structure. To produce a conservative injury criterion, a total of 7 female forearms were tested in the pronated position, which resulted in the forearm injury criterion of 58+/-12 Nm when scaled for the 5th centile female. It is anticipated that these data will provide injury reference values for the female forearm during driver air bag loading, and the female humerus during side air bag loading.

Lower limb response and injury in frontal crashes.

This article examines two observational and two experimental data sets that emphasize lower limb injuries in passenger car crashes. Statistics show that 60% of moderate-to-severe below-knee injuries sustained by front seat occupants in head-on crashes occur with > 3 cm of footwell intrusion. Moreover, crash tests and computer simulations of car-to-car frontal offset collisions show no causal relationship between the magnitude of footwell intrusion and the axial load measured in the dummy leg. This article correlates below-knee injuries with several factors that influence their frequency and severity, such as the vehicle change in velocity, the magnitude of footwell intrusion, the rate and timing of the intrusion and the size of the vehicle. The vehicle change in velocity and the intrusion rate and timing had the greatest influence on the risk of lower limb injury, while the other factors had much less of an effect.

Crash simulations of wheelchair-occupant systems in transport.

A nonlinear multirigid body dynamic computer model has been developed to simulate the dynamic responses of a wheelchair-occupant system in a vehicle during a crash. The occupant, restrained by safety belts, is seated in a wheelchair that is, in turn, tied down in a vehicle. Validated extensively by crash sled tests at three laboratories, this model has been used to predict the responses of wheelchair-occupant systems in various crash environments. To evaluate the crashworthiness of different wheelchair tie-downs, the sensitivity of several design parameters, such as tiedown stiffness, wheel stiffness, and tiedown positions, has been studied using this model, and optimal values of these parameters for the wheelchair-occupant system have been obtained. Moreover, the model has been used to study the sensitivity of crash sled test pulse corridors in an effort to develop a sled test standard. It has been found that an existing ISO corridor allows large variation and should be "tightened." The model was implemented using a version of the multibody dynamic simulator, the Articulated Total Body program.

A technique for using strain gauges to evaluate airbag interaction with cadaveric upper extremities.

Radius and ulna fractures from airbag deployment onto the forearm have been reported in the literature. Based on laboratory experiments with eight cadaveric upper extremities, this paper presents a method for using strain gages to evaluate upper extremity loading during airbag deployment. The technique provides strain rates, bending moments, and time of fracture for the radius and ulna. Planar rosettes (350 omega, 5% strain) were selected as the best choice given the application to bone with a rosette being placed mid-shaft on both the anterior and posterior surfaces of the radius and ulna. Forearm incisions were intended to be minimally invasive and to limit damage to the interosseous membrane. The bone surface was prepared with Ether, and the gauges were bonded to the surface with methyl-2-cyanoacrylate. A thin latex cover was installed over the surface of the rosettes to isolate the gauges from the surrounding tissue. Strain relief of the gauges was provided by securing the wire leads to the bone with tie-wraps, as well as suturing the wires to the skin. With this technique all gauges reported accurate data throughout the duration of the impact.

Air and knee bolster restraint system: laboratory sled tests with human cadavers and the Hybrid III dummy.

UNLABELLED: Growing evidence from data base and laboratory studies demonstrates effective occupant protection with the airbag supplemental restraint and seatbelt restraint system. Concern that drivers of vehicles equipped with airbags may assume adequate protection without concomitant seatbelt use prompted the study of unbelted occupant behavior in frontal crashes. OBJECTIVE: To evaluate the crash protection afforded unbelted drivers in airbag-equipped vehicles. DESIGN: Six laboratory sled tests were conducted with a production driver's side airbag and knee bolster restraint system but without a seatbelt restraint system. MATERIALS AND METHODS: Four human cadavers and the Hybrid III dummy were used as occupants in 32 km/h and 48 km/h tests with a simulated mid-size vehicle. MEASUREMENTS AND MAIN RESULTS: Head contact with the windshield/header region of the simulated vehicle and abdominal impingement on the lower rim of the steering wheel were noted in all tests. Autopsy examinations and radiographic images identified extensive spinal and thoracic trauma in addition to lower extremity and facial injuries. Injury Severity Scores were considered severe to critical for all occupants. CONCLUSIONS: The evidence suggests the need to emphasize the use of seatbelts in conjunction with airbags and to develop a redesigned airbag and knee bolster system to control occupant kinematics and loading more effectively.