Chest and abdominal injuries caused by seat belt loading.

Injuries will inevitably occur when restraining loads are exerted on a car occupant by a seat belt during a crash. This study investigated the nature, frequency, and severity of such injuries to the chest and abdomen. Vehicle, occupant, and injury details were obtained from accidents occurring in the Midlands of England. The sample was chosen with emphasis on fatal and serious injuries while also representing slight injuries as rated by the British government scheme. All causes of injuries to 3,276 front-seat restrained occupants were considered. 29.6% had a minor (Abbreviated Injury Scale [AIS] 1) injury caused by seat belt loading, more than from any other cause. The study went on to focus on 1,025 occupants sustaining injuries caused solely by seat belt loading. Of those, 19.4% sustained chest/abdominal injuries rated at Maximum AIS > or = 2 with sternum fractures predominating, and 4.5% were rated at Maximum AIS > or = 3. Occupants were not excluded if they had injuries at other body regions enabling the frequency and severity of head injuries to be considered also. The role played by impact type, speed change at impact, seat belt usage problems, and some aspects of occupant characteristics were investigated. While females were at much greater risk of serious injury (AIS > or = 3) when aged > or = 70 years, the effects of aging were more obvious in the cases with chest injuries rated at AIS 2. Serious chest injuries were predominantly a function of higher speed changes at impact. Occupant height and weight were shown to influence injury outcome, and the study concluded that work is required to further define occupants most at risk. Comparisons were made with two studies into other types of injury at other body regions, and injuries rated AIS > or = 2 caused by seat belt loading were seen to be relatively unlikely. It must also be stressed that casualties sustained seat belt injuries would most likely have received more severe injuries had a seat belt not been worn.