The effects of occupant age on patterns of rib fractures to belt-restrained drivers and front passengers in frontal crashes in Japan.

The injuries sustained by elderly car occupants in traffic accidents are usually more severe than those of younger occupants. Accident statistics data show that injuries to elderly occupants frequently occur in the chest. Belted drivers and front seat passengers in cars involved in frontal collisions were investigated using detailed data on traffic accidents in Japan. From a total of 246 vehicle occupants, the total number of injuries among the 167 occupants listed as injured was 462. Most of the injuries to the chest were minor ones such as skin abrasions or contusions. However, 21 occupants sustained rib fractures and 7 persons even sustained internal organ injuries. Younger occupants appeared not to sustain rib fractures even in higher impact collisions. Conversely, elderly occupants frequently experienced rib fractures near the seat belt line even under lower impact severity. It was also typically observed that rib fractures in case of airbag deployment were more often found in the lower part of chest compared with those cases of seat belt restraint alone. Symptoms of these differences in injury are described in detail in consideration of the gender and age of occupants, airbag deployments, and accident severity. In addition, regression analysis was carried out to evaluate the influence of age on rib fractures. Results show that rib fractures in elderly occupants occur at a delta V 30 km/h lower than that of younger occupants.