Development and validation of a pedestrian lower limb non-linear 3-d finite element model

Lower limb injury is becoming an increasingly important concern in vehicle safety for both occupants and pedestrians. To enable vehicle manufacturers to better understand the biomechanical effects of design changes, it is deemed beneficial to employ a biomechanically fidelic finite element model of the human lower limb. The model developed in this study includes long bones (tibia, fibula, femur) and flat bone (patella) as deformable bodies. The pelvis and foot bones are modeled as rigid bodies connected to the femur and tibia/fibula via rotational spring-dashpots. The knee is defined by scanned bone surface geometry and is surrounded by the menisci, major ligaments, and patellar tendon. Finite elements used to model include 6- and 8-node solids for cartilage, menisci, surrounding muscles, and cancellous bone; 3- and 4-node shells for skin and cortical bone; and nonlinear spring-dashpots for ligaments. Anatomical, physiological, and material properties data are from the literature while the bone surface geometry was scanned by a commercial source. Validation against published cadaver test results consisted of tibia and femur 3-point bending (lateralmedial and anterior-posterior) and whole limb lateral knee shear. Validation was performed under both static and dynamic loading conditions, until bone failure or ligament rupture. Additional dynamic validation with the lower limb in a seated orientation has not been completed, limiting current applications to the pedestrian impact condition. The validated models were employed to examine the effect of axial compressive force (the physiological condition) on tibia and femur lateral-medial and anterior-posterior bending under static conditions.