Biomechanical Evaluations of Hip Fracture Mechanism in Pedestrian Fall Accident

Abstract

Hip fracture is one of the most important topics in geriatric medicine because the number of this injury is increasing rapidly with the population of the elderly people. To clarify the mechanism of hip fracture and investigate the method of fracture prevention, we developed a fall simulation system which considers the boundary conditions at real fall accidents. Firstly, we constructed a pedestrian multibody model and compared the results of the fall simulations by the model with those of the volunteer fall experiment in a literature. The simulation results showed a distribution of fall direction similar to that of the experimental data. Next we developed a hybrid type simulation model which consists of a detailed finite element model of thigh and hip joint, and multibody model of the other parts of a whole human body. Using the hybrid model we conducted stress analyses of femur neck. The results showed that knee grounding fall caused hip fracture risk higher than the risk by a lateral impact on the greater trochanter. By comparing the regions of stress concentration, we estimated that a knee grounding causes a cervical fracture while a trochanter grounding may cause a trochanteric fracture.