The incidence of pelvic and lower extremity fractures is examined by reference to data extracted from police and hospital records. It is shown that the incidence and number of fractures to the pelvis and the lower extremities is strongly dependent on the age of the struck pedestrian and the speed of the vehicle.
Pelvic injuries are shown to be more common in elderly females than in other age groups and it is suggested that this is due to elderly females being more likely, with current vehicle front end heights, to sustain a direct blow at the level of the pelvis.
Pubic rami fractures appear to result when there are distributed impact forces at the level of the pelvis and acetabular fractures occur when there are concentrated forces applied to the greater trochanter.
Injuries to the knee joint ligaments are shown to occur when there is an impact in the vicinity of the knee joint and can occur at speeds as low as 20 km/h although for complete rupture an impact speed of at least 35 km/h is required.
It is suggested that the use of a simple impactor to control front structure compliance may not be sufficient and that a test procedure which controls hip reaction forces and knee joint angulation may be necessary.