The influence of age on injury severity of restrained front seat occupants in head-on collisions

This excerpt is part of a large-scale retrospective study on the interrelationship between accident severity and injury severity. A multivariate analysis of 319 cases of restrained front seat occupants involved in car-to-car head-on collisions showed the significant influence of the energy equivalent speed (EES) and age of the occupants on the number of rib fractures and sternum fractures. Three hundred occupants sustained no rib fractures, nine occupants one to 16 rib fractures, and ten occupants 17 to 32 rib fractures. In these three groups the EES increased from 35 km/h (no rib fractures) to 55 km/h (one to 16 rib fractures) and to then to 67 km/h (17 to 32 rib fractures). The average age in these groups was 34, 55 and 57 years respectively. Twenty-four occupants sustained sternum fractures. The average values of the EES and the average age were: in the group with sternum fractures: 56 km/h; 50 years old; in the group without sternum fractures: 35 km/h; 34 years old. The probability of sustaining fatal injuries in a head-on collision depended on the EES as well as the age of the occupant. At an EES of 60 km/h the probability of fatal injuries was 0.05% in the group < 30 years and 35% in the group > 59 years. Fifty-eight per cent of the occupants with sternal fractures had rib fractures as well; 46% of the occupants with rib fractures also had sternal fractures. The results were compared to the results of 185 post-mortem simulations of head-on collisions from the year 1973 to 1978. In post-mortem simulations the number of rib fractures and sternum fractures was influenced by vehicle decelerations and the age of the test subjects. The number of rib fractures increased at higher collision speeds, higher decelerations and increased age; the number of sternum fractures increased at higher deceleration and increased age of the test subjects. Seventy-two per cent of the test subjects with sternal fractures had rib fractures; 91% of the subjects with rib fractures had sternal fractures.