A Finite Element Lower Extremity and Pelvis Model for Predicting Bone Injuries due to Knee Bolster Loading

Injuries to the knee-thigh-hip (KTH) complex in frontal motor vehicle crashes are of substantial concern because of their frequency and potential to result in long-term disability. Current frontal impact Anthropometric Test Dummies (ATDs) have been shown to respond differently than human cadavers under frontal knee impact loading and consequently current ATDs (and FE models thereof) may lack the biofidelity needed to predict the incidence of knee, thigh, and hip injuries in frontal crashes. These concerns demand an efficient and biofidelic tool to evaluate the occurrence of injuries as a result of KTH loading in frontal crashes. The MADYMO human finite element (FE) model was therefore adapted to simulate bone deformation, articulating joints and soft tissue behavior in the KTH complex. To validate this model, the knee-femur complex response was compared to results of post-mortem human subject (PMHS) experiments where a distributed load was applied to the knee while the femoral head rested on a fixed acetabular cup. The model was also validated against experimental whole KTH response data, in which the pelvis was fixed at the iliac wings and a distributed load was applied to the knee. These experiments showed that the acetabulum is the weakest structure in typical knee bolster loading, followed by femoral head and femoral shaft. The simulations replicated the experimentally observed force-deflection response and predicted the highest stress at the experimentally observed locations of bony fracture.