Biomechanics of ankle and hindfoot injuries in dynamic axial loading.

Twenty-three Post Mortem Human Surrogate (PMHS) limbs were impacted using a test set up that was developed to simulate the loading conditions seen in a frontal collision. Articulation studies were performed on each limb prior to impact. Failure occurred at impact loads of 5.7+/-1.9 kN (resultant tibial failure load 6.4+/-1.9 kN) and the following injuries were generated: 9 intra-articular calcaneal fractures; 1 talar neck and 2 talar body fracture; 3 intra-articular distal tibial (pilon) fractures; 2 malleolar fractures; 3 soft tissue injuries and 3 had no detectable injury. The impact test conditions were replicated with a Hybrid III leg in a first attempt at developing injury risk functions for the dummy. This study has demonstrated the significance of preload through muscle tension and the intrinsic properties of PMHS specimens in the generation of severe ankle and hindfoot injury.