Pelvic injury in simulated automotive side impact: Effects of loading rate on fracture etiology

Side impact collisions in the automobile environment often result in fractures of the acetabulum and pelvis. The objective of this study was to determine if the fracture type in the pelvis is a function of impact loading rate. It was hypothesized that higher loading rates would cause acetabular fractures, and lower loading rates would result in pubic rami fractures. Simulated side-impact experiments using 15 whole fresh pelves were conducted. The pelves were laterally impacted with a drop tower and the loading rate was controlled by changing the constraints placed on the contralateral side of the pelvis. In the impacts where loading rate was high (8.16 kN/msec), either no fracture (n=5) or acetabular wall fractures (n=4) resulted. In the cases where loading rate was slower (1.59 kN/ms), almost all impacts (5 of 6)resulted in pubic rami fractures.