Effects of trochanteric soft tissues and bone density on fracture of the female pelvis in experimental side impacts.

Pelvic fractures continue to be a source of morbidity and mortality for occupants in motor vehicle side impacts, especially among women. Previous studies have produced fracture tolerances for the female pelvis, yet the roles of soft tissues and bone quality remain unclear. Presently, we studied the influence of trochanteric soft tissue thickness (T) and total hip bone mineral density (BMD) on pelvic fracture of 10 female human pelves subject to lateral impact centered over the greater trochanter. Multiple impacts of increasing severity were performed and impact force, energy, impulse, compression, and viscous criteria were quantified. BMD and T were found to be additive predictors of the fracture force. For a given BMD, the force to fracture was significantly higher than that found previously using isolated pelvic bones. Impulse was found to positively correlate with T; however, maximum compression, viscous criterion, and energy to fracture were independent of BMD and T. The force tolerance at 25% probability of fracture found presently (3.16 kN) is substantially below previously reported values. The results suggest that the trochanteric soft tissue thickness and total hip BMD have a significant bearing on fracture outcome for the female pelvis in automotive side impact.