Biomechanical injury response of leg subjected to combined axial compressive and bending loading

Tibia fractures and dislocations among vehicle occupants injured in traffic collisions are costly and debilitating. The current criterion for predicting the occurrence of tibial shaft fracture in crash tests, the Tibia Index, relies on the combined bending and compressive strength at the mid-shaft location of the tibia. Recent studies have shown that tibial curvature and fibular load-sharing may influence the injury prediction of the leg and that the distal third section of the tibial shaft is the most commonly fractured shaft section in frontal crashes. In order to provide biomechanical injury data of the leg for a possible re-evaluation of the Tibia Index, the dynamic combined strength of twenty human legs at the distal third region was determined using varying axial compressive pre-load in the range of 2 to 8 kN followed by anterior-posterior impact loading close to the distal third region. The injury boundary of the leg in terms of the axial load and applied bending moment obtained from test data and from finite element simulations showed an opposed trend to that of the original Tibia Index. The data presented in the current study provides the necessary information about leg injury in combined loading to develop advanced human leg computational models.