Effects of Loading Conditions on the Pelvic Fracture Biomechanism and Discrimination of Forensic Injury Manners of Impact and Run-Over Using the Finite Element Pelvic Model

Abstract

This study aimed to systematically simulate the responses of pelvic fracture under impact and run-over to clarify the effects of boundary and loading conditions on the pelvic fracture mechanism and provide complementary quantitative evidence for forensic practice. Based on the THUMS finite element model, we have validated the simulation performance of the model by a real postmortem human pelvis side impact experiment. A total of 54 simulations with two injury manners (impact and run-over), seven loading directions (0°, 30°, 60°, 90°, 270°, 300°, 330°), and six loading velocities (10, 20, 30, 40, 50, and 60 km/h) were conducted. Criteria of effective strain, Von-Mises stress, contact force, and self-designed normalized eccentricity were used to evaluate the biomechanism of pelvic fracture. Based on our simulation results, it’s challenging to distinguish impact from run-over only rely on certain characteristic fractures. Loads on the front and back were less likely to cause pelvic fractures. In the 30°, 60°, 300° load directions, the overall deformation caused a “diagonal” pelvic fracture. The higher is the velocity (kinetic energy), the more severe is the pelvic fracture. The contact force will predict the risk of fracture. In addition, our self-designed eccentricity will distinguish the injury manner of impact and run-over under the 90° loads. The “biomechanical fingerprints” based on logistic regression of all biomechanical variables have an AUC of 0.941 in discriminating the injury manners. Our study may provide simulation evidence and new methods for the forensic community to improve the forensic identification ability of injury manners.

Keywords

• pelvic fracture
• finite element
• impact
• run-over
• biomechanism
• forensic practice