Session VII - Foot & Ankle

Change in Lower Extremity Morbidity from Landmine Injury: An Analysis of New Protective Footwear

Robert M. Harris, MD, MAJ; Lanny Griffin, PhD; Roman Hayda, MD; Mark S. Rountree, SSG; Ricky Bryant; Nigel Rossitor, MD; Steve Mannion, MD, United States Army, Institute of Surgical Research, San Antonio, TX

Purpose: Landmine injuries have reached epidemic proportions in developing nations affecting combatants and civilians indiscriminately. Certain countries such as Cambodia have more than 10 million mines, placing US service members and humanitarian workers at risk in these areas. Antimine footwear has been developed, but never evaluated >from a medical outcome standpoint. The purposes of our study were 1. To evaluate the relative protection offered with various protective footwear, 2. Determine the in-situ forces experienced by the lower extremity under blast conditions, 3. Evaluate the medical outcomes of the lower extremity from activation of an antipersonnel mine.

Methods: Four fresh frozen full body human cadavers were used. They underwent evaluation with radiographs, CAT and MRI scans of both lower extremities from the pelvis to feet. Examination was performed before and after mine activation to determine the medical outcomes and to provide data for mathematical modeling. Four combinations of boots were evaluated: (group 1) the standard Army combat boot (CB), (group 2) the blast protective boot (BPB) alone; (group3) the standard combat boot with a blast protective overshoe (CB/OS), and (group 4) the blast protective boot with a protective overshoe (BPB/OS). The cadaver lower extremities were instrumented with a uniaxial load cell placed in the proximal tibia and strain gages applied to the distal femur. Each cadaver was suspended with the boot heel placed directly over the landmine. High-speed video (13,500 frames per second) was used to capture the blast event. Load and strain data were sampled at 7 kHz. Orthopaedic traumatologists examined the lower extremities to determine the medical outcomes.

Results: The peak loads recorded for all of the tests were on the order of 4000 N with a time to peak on the order of 200 microseconds. The strains in the femur were approximately 2000 UE with similar rise times. The medical outcomes were 1. CB (group 1) and BPB (group 2) had open mangled lower extremities with dirt and foreign bodies to mid-tibia. There was loss of most of the hindfoot and a fracture dislocation of the forefoot. The CB/OS (group 3) resulted in a closed injury with multifragmented fractures of the hindfoot and midfoot. The BPB/OS (group 4) resulted in a closed joint depression fracture of the calcaneous and a nondisplaced fracture of the talus and medial distal tibia.

Discussion: The results of this study suggest that morbidity from landmine injuries may be reduced with the wear of certain protective footwear. The injury patterns seen with CB (group 1) and BPB (group 2) would result in an open BKA with an increased risk for infection and requiring multiple surgeries to obtain soft tissue closure. CB/OS (group 3) resulted in a closed injury that is not salvageable from a reconstructive point, however would be able to undergo a BKA with primary closure and less risk of infection. BPB/OS (group 4) produced a closed injury that is amenable to operative fixation of the fractures. The results of this study suggest that practical mine protective measures are feasible. The best results appear when utilizing a blast protective boot/overshoe combination. The mechanism appears to result from dissipation of the blast energy during destruction of the overshoe. This allows the inner boot to dissipate the remainder of the blast energy in a manner that is not catastrophic to the lower extremity.