ABDOMINAL INJURY IN MOTOR-VEHICLE CRASHES

A review of the biomechanical and epidemiological literature on abdomen injury in motor-vehicle crashes was performed. Results of this review demonstrate that (1) there are limited data on abdomen injuries in real-world crashes of newer model airbag-equipped vehicles, (2) there are insufficient useful data on the force-deflection characteristics of the abdomen under loading conditions that represent those that occur to near-side occupants in T-type side impacts, (3) data are needed on the response of the abdomen to lap-belt loading using realistic belt geometry and loading conditions, and (4) data are needed on the dynamic response of spleen tissue and on failure criteria for spleen and liver tissue. To address the first identified need, analyses of the NASS and CIREN datasets were performed to determine how abdomen injuries occur in frontal and side crashes of airbag-equipped vehicles when seatbelt use is high. Based on the NASS analysis, approximately 19,000 adult occupants sustain AIS 2+ abdomen injuries each year, with just over half of these injuries occurring in frontal collisions. The risk of abdomen injury is 3 to 8 times higher for unbelted occupants compared to belt-restrained occupants in frontal impacts, but airbag deployment does not substantially affect abdomen injury risk. Overall, seatbelt use reduces abdomen injury risk in side impacts for both near- and far-side occupants. Near-side right-front passengers have the highest risk of AIS 3+ abdomen injuries in side impacts, with a risk level that is 2.7 times higher than for drivers in left-side impacts. The risks of injury to the liver, spleen, kidney, and hollow organs do not vary with occupant age in frontal or near-side impacts. Analysis of the relationship between abdomen injury and rib fractures indicates that the odds of an abdominal injury are much higher if the occupant also sustains AIS 2+ rib fractures. These results indicate that loading conditions likely to cause abdomen injuries are also likely to cause rib fractures, suggesting that the abdomen is rarely loaded in isolation in vehicle crashes. The CIREN dataset was used to analyze occupant contacts with vehicle interior components that were attributed to abdomen injuries. For drivers in frontal impacts, the steering-wheel and lap/shoulder belt were most often coded as the sources of abdomen injury. For right-front passengers in frontal impacts, the airbag, lap/shoulder belt, and instrument panel are commonly coded sources for abdominal loading and injury. The mean deltaV for drivers with abdomen injuries attributed to steering-wheel contact is higher than for abdomen injuries to drivers without steering-wheel contact (57 vs. 47.5 kph, p=0.011). Unbelted drivers restrained by a frontal-impact airbag had greater proportion of steering-wheel contacts than expected, while drivers restrained by both lap/shoulder belts and frontal-impact airbags had fewer steering-wheel contacts than expected. For near-side occupants who sustained both liver and spleen injuries in side impacts, the mean residual lateral door intrusion was 35 cm, while for near-side occupants who sustained only a liver or a spleen injury in side impacts, the mean lateral door intrusions ranged from 22 to 27 cm. Because the risk of abdomen injury is highest for near-side occupants in side impacts, an analysis of FMVSS 214 and SNCAP data was performed to characterize near-side occupant loading by the intruding door in T-type side impacts. Results of this analysis indicate that door velocity at the time of initial contact with the abdomen is between 8 m/s and 12 m/s in these staged tests. Results of this study indicate that the highest priority for future research on abdomen injuries should be to define abdomen force-deflection characteristics for near-side occupants in T-type impacts using high-speed loading conditions that better represent those that occur in real-world crashes.