Thresholds of Failure: Biomechanical Prediction of Hip and Acetabular Fractures in High-Velocity Dashboard Impacts

Lower extremity trauma, particularly femoral and acetabular fractures, remains a burden in frontal vehicle collisions. Despite advances in safety systems that have reduced head and torso injuries, lower extremity trauma persists. This study evaluated the biomechanical response and fracture initiation thresholds of the femur–pelvis system during dashboard impacts. A finite element (FE) model was developed in LS-DYNA, incorporating a femur and a hemipelvis with isotropic elastoplastic material properties. Impact scenarios were simulated against a vehicle dashboard at velocities ranging from 2 m/s to 13.4 m/s. Fracture initiation was evaluated using peak contact forces, von Mises stress, and effective plastic strain distributions. Joint lubrication was also assessed by varying the friction coefficients (0.01, 0.08 and 0.24). The validation results showed good agreement with the established literature and experimental ranges. Impact velocity was the primary determinant of injury severity, whereas friction coefficients had negligible influence on fracture onset. Under idealized boundary conditions, fracture initiation onset velocities were predicted as 5 m/s for the posterior acetabular wall, 5.5 m/s for the femoral head, and 10 m/s for the femoral neck. This FE framework effectively predicts injury mechanisms with reduced computational cost, providing quantitative metrics for dashboard crashworthiness and valuable insight into injury patterns.