Bone density and trochanteric tissue thickness affect fracture of the female pelvis in side impact experiments

Etheridge, B. S.; Beason, D. P.; Eberhardt, A. W.

In spite of advances in occupant protection, pelvic fractures remain a source of morbidity and mortality in motor vehicle side impacts. Women are more frequently injured than men, leading automotive researchers to incorporate the SID-IIs (small female crash dummy) into side impact testing of passenger vehicles. Currently accepted fracture tolerances for the female pelvis are based on extrapolations from experimental results containing both men and women, and there is no unified theory that predicts pelvic fracture for a woman of a given body habitus under side impact conditions. The present report describes a two phase experimental study aimed at improving our understanding of pelvic fractures, with an emphasis on the roles of bone quality and soft tissues. The first phase, which explored the role of bone mineral density (BMD) on impact responses, involved drop tower tests on isolated bone-ligament specimens, both male and female. The second phase employed a linear impactor and intact specimens (females only) positioned on a sliding, inertially compensated seat, where the influence of trochanteric soft tissue thickness (T) along with BMD was studied. Positive correlations between the force to fracture the pelvic ring and BMD were observed in both sets of experiments. For the intact female specimens of Phase 2, the force to fracture correlated positively with BMD and T; while impulse correlated with T only. Maximum compression, viscous criterion, and energy to fracture, however, were independent of both BMD and T. As anticipated, the force to fracture an intact pelvis was greater than that of an isolated bone-ligament specimen, for a given BMD. The force tolerance at 25% probability of fracture for the intact female specimens (average age = 76) was 3.16 kN, which is substantially below previously reported estimates for the 5th percentile female.

Year

Entry

1989

Viano DC. Biomechanical responses and injuries in blunt lateral impact. In: Proceedings of the 33rd Stapp Car Crash Conference. October 4-6, 1989; Washington, DC. Warrendale, PA: Society of Automotive Engineers:113-142. SAE 892432.

2003

Di Domenico L, Nusholtz G. Comparison of parametric and non-parametric methods for determining injury risk. In: Proceedings of the SAE World Congress & Exhibition. March 3-6, 2003; Detroit, MI. Warrendale, PA: Society of Automotive Engineers. SAE 2003-01-1362.

1982

Cesari D, Ramet M. Pelvic tolerance and protection criteria in side impact. In: Proceedings of the 26th Stapp Car Crash Conference. October 20-21, 1982; Ann Arbor, MI. Warrendale, PA: Society of Automotive Engineers:145-154. SAE 821159.

1999

Thomas P, Frampton R. Injury patterns in side collisions: a new look with reference to current test methods and injury criteria. In: Proceedings of the 43rd Stapp Car Crash Conference. October 25-27, 1999; San Diego, CA. Warrendale, PA: Society of Automotive Engineers:1-12. SAE 99SC01.

1980

Cesari D, Ramet M, Clair P-Y. Evaluation of pelvic fracture tolerance in side impact. In: Proceedings of the 24th Stapp Car Crash Conference. October 15-17, 1980; Troy, MI. Warrendale, PA: Society of Automotive Engineers:231-253. SAE 801306.