Study On The Effect Of Age On Pedestrian Lower Extremity FE Modeling And Injury

Pedestrians are an exposed and vulnerable group without any protection in traffic collisions and thus have an extremely high risk of injuries in collisions,and the lower extremity injury comprise a large proportion of all injuries. With the problem of ageing society, more and more researchers pay attention to the elderly pedestrian safety, and some research indicate that the elderly pedestrians would suffer a higher risk of serious injury and death compared with the 50 th adult male. But the current pedestrian protection laws and human body finite element models have not considered the influence of pedestrian age. This paper focused on the modeling of human lower extremity finite element model with age characteristics, and study the injury mechanism of the elderly and the young.The effect of age on the mechanical properties of bone, ligaments and other biomaterials, as well as the influence of age on the geometry of lower extremity long bone were studied in this paper. And the GHBMC lower extremity FE model was improved based on the research results to develop a lower extremity FE model with age characteristics, including the material model renew and the femur and tibia geometry refine by using morphing techniques. Then the updated model was validated according to the biomechanical tests, including the long bone three point bending, knee joint four point bending, and lower extremity bending and shearing tests. Finally this model was used to reconstruct the lower extremity injuries in a real-word vehicle-pedestrian accident, and the lower extremity injury parameters of different ages are compared and discussed.The research results indicated that with aging the adult bone strength would gradually decreased, it meant the injury tolerance and injury mechanism would change with the aging, the fracture tolerance of femur and tibia all showed a decreasing trend, when people at his 80-year-old, his fracture tolerance of femur was only approximately 68%, tibia was 74% of the fracture tolerance at his 30-year-old. The updated lower extremity FE model had higher bio-fidelity with considering the changes of material properties and long bone geometry. The results of injury reconstruction further verified that the higher risk of lower extremity long bone fracture of the elderly in a traffic accident, the von Mises stress of the elderly was around100 MPa when femur fracture occurred, while it was about129 MPa for the young people. The von Mises stress of the elderly was around 114 MPa when tibia and fibula fracture occurred, while under this loading condition the young did not suffer any tibia or fibula fracture injury; the simulated injuries were coinciding with the hospital reports. The model showed a good capability to predict injury type and severity in vehicle-pedestrian impact.This study developed a pedestrian lower extremity FE model with detailed anatomical structure and age characteristics, and the model was used to study the injury mechanism of lower extremity in traffic accident, the work of this paper would be a theoretical reference for the study of lower extremity injury tolerance with considering the effect of age.