THE EFFECT OF DRIVER RESTRAINT ON THE LOCATION OF COMPRESSIVE INJURIES TO THE LOWER LIMB FOLLOWING MOTOR VEHICLE ACCIDENTS

Abstract

The aim of this study was to analyse compressive injuries to the lower limb with data obtained from crash reconstruction to examine injury mechanics (IM’s) and aid car safety.

Prospectively gathered injury and crash reconstruction data were examined from drivers sustaining femoral and/or acetabular fractures (including hip dislocations) following frontal collisions. There were 23 femoral fractures, 21 acetabular and 4 patients with combined femoral and acetabular fractures. It was hypothesised that different IM’s accounted for the relative exclusivity in injury distribution.

There were no statistically significant differences between the two groups with regards to age, weight, height, injury severity scores (ISS) and the relative velocity of impact (mean of 32 and 26mph for femoral and acetabular fractures respectively). Damage to the knee bolster on the side of injury was evident in 21 femoral fractures (1 car burnt out) and 18 acetabular (1 car burnt out). Females were more likely to sustain a femoral fracture than males (71% versus 45%).

Femoral and acetabular fractures do appear to be the result of compressive loadings to the femur as evident by damage to the knee bolsters. Both fracture types arise from low velocity impacts but the IM’s appear different. The driving position of females or their anthropomorphic differences may account for their higher propensity for femoral injury. The deployment of an airbag while not wearing a seatbelt may cause the occupant to ‘submarine’ beneath the airbag. Subsequent impact of the knee against the bolster may impart different energy loading characteristics to the femur to that of belted occupants. Knee bolster design may thus be of importance in injury modification. Assuming that acetabular fractures are associated with greater morbidity than femoral fractures, these data further support the advice that seatbelts be worn.