Loading rate and torsional moments predict pilon fractures for antipersonnel blast mine loading

Our objectives were to use force and strain data, radiographic and visual documentation, medical assessment to determine meaningful predictors of lower extremity morbidity, using a medically relevant antipersonnel landmine model. We wanted to determine if antimine protective footwear provide a measurable reduction in injury. Finally, we wanted to obtain empirical data for the development of injury threshold criteria, which can be used to enhance the predictive power of blast-rig data by establishing a correlation between human injury and force-based data. Twenty fresh frozen full human cadavers were used, and six groups of footwear representing a spectrum of protection were evaluated. Three mine threat levels were used. The cadaver lower extremities were instrumented with a uniaxial or multiaxial load cell placed in the proximal tibia. Strain gages applied to the distal tibia and calcaneus. The heel with protective measure was placed directly over the land mine. High-speed video (13,500 frames per second) and cineradiograpy was used to visually document the blast event. Load and strain data were sampled 100 kHz. Two orthopaedic traumatologists performed clinical dissection the lower extremity to determine the medical outcome which ranged from traumatic amputation to a closed, minimally displaced fracture of the talus and calcaneus. We found statistically significant predictors of pilon fractures were axial peak force, axial loading rate, anterior shearing force, and torsional peak moments. While some footwear offered modest protection against the smallest mines, no footwear we evaluated were able to reliably reduce injury to a level that would not require extensive hospitalization and rehabilitation. Keywords : bones, cadavers, injury probability, legs