Parametric Finite Element Studies of the Human Pelvis: The Influence of Load Magnitude and Duration on Pelvic Tolerance During Side Impact

The objective of this research was to further elucidate the biomechanical etiology of pelvis fracture under simulated automotive side impact conditions. The finite element (FE) method was used to evaluate pelvis fracture tolerance through a series of parametric tests to determine the effect of both force magnitude and duration of application. The results of FE analyses were compared to previous experimental cadaveric test data under the same load conditions to seek validation of the model. The hemi-pelvis FE model used in this study was a modified version of an earlier model, consisting of 2199 elements and 3161 nodes. Material behavior was defined per element using 524 Hookean-based material property values. Parametric dynamic analyses of the model were performed using the first 150 ms of the force-time history. Dynamic loading was applied as a linear ramp through the angle of the greater trochanter to the acetabulum, simulating a femur position in 90° flexion. Dynamic analysis of the model was performed in 2 phases. Phase I: Validation study: F = 6.25 kN with a rise time of Δt = 55.6 ms. Phase II: Parametric Studies: A) Three load cases with constant peak load F = 10 kN. Rise time varied: Δt = 20, 40, and 80 ms. B) Three load cases with constant rise time Δt = 25 ms. Load varied as follows: F = 5, 10, and 20 kN. These studies suggest that acetabular fracture of an isolated hemi-pelvis may be predicted using the finite element method. An increase in rise time for a constant peak load will increase the likelihood for isolated acetabular fracture. An increase in peak load for a constant rise time will increase the likelihood for pubic rami fracture.