| Axial loading of the foot/ankle complex is an important injury mechanism in vehicular trauma responsible for severe injuries such as calcaneus, talus, and tibia pilon fractures. Axial loading may be applied to the leg externally in a car crash, by the toepan and/or pedals, as well as internally, by active muscle tension applied through the Achilles tendon during pre-impact bracing. In order to evaluate the effect of active muscle tension on the injury tolerance of the foot/ankle complex, axial impact tests were performed on isolated lower extremities with and without experimentally simulated muscle tension applied through the Achilles tendon. Acoustic emission was used to determine the exact time of fracture during the tests. The primary fracture mode was calcaneus fracture in both groups, but tibia pilon fractures occurred more frequently with the addition of Achilles tensioning. A survival analysis was performed on the combined injury data set using a Weibull regression model with specimen age, gender, mass, and level of Achilles tension as predictor variables. A closed-form solution was developed to calculate the risk of injury to the foot/ankle complex in terms of axial tibia force. Axial loading injury criteria that can be used predict injury to the foot/ankle complex in vehicle crash testing are presented for several types of dummy legs. |
