Lower Limb Posture Affects the Mechanism of Injury in Under-Body Blast

Abstract

Over 80% of wounded Service Members sustain at least one extremity injury. The ‘deck-slap’ foot, a product of the vehicle’s floor rising rapidly when attacked by a mine to injure the limb, has been a signature injury in recent conflicts. Given the frequency and severity of these combat-related extremity injuries, they require the greatest utilisation of resources for treatment, and have caused the greatest number of disabled soldiers during recent conflicts. Most research efforts focus on occupants seated with both tibia-to-femur and tibia-to-foot angles set at 90°; it is unknown whether results obtained from these tests are applicable when alternative seated postures are adopted. To investigate this, lower limbs from anthropometric testing devices (ATDs) and post mortem human subjects (PMHSs) were loaded in three different seated postures using an under-body blast injury simulator. Using metrics that are commonly used for assessing injury, such as the axial force and the revised tibia index, the lower limb of ATDs were found to be insensitive to posture variations while the injuries sustained by the PMHS lower limbs differed in type and severity between postures. This suggests that the mechanism of injury depends on the posture and that this cannot be captured by the current injury criteria. Therefore, great care should be taken when interpreting and extrapolating results, especially in vehicle qualification tests, when postures other than the 90°–90° are of interest.

An Experimentally Validated Finite Element Model of the Lower Limb to Investigate the Efficacy of Blast Mitigation Systems

“…No fractures were seen. The (Sommer and Olaf, 1994;McElhaney, 1966;Hansen et al, 2008) Cartilage Linearly elastic ρ = 1, E = 0.3, v = 0.3 (Kitaoka et al, 1994;Iwamoto et al, 2005;Shin et al, 2012) Ligaments Tensile-only non-linear spring Heel Fat Pad Quasi-linear viscoelastic ρ = 0.97, A = 0.1, B = 1.258, v = 0.495 (Grigoriadis et al, 2019 lower limb was also scanned after the second and final impact test and no fractures were seen. The target peak velocity of the loading plate was 5.2 m/s.…”

Experimental platforms to study blast injury

“…AnUBIS has been used in conjunction with postmortem human specimens (PMHSs) and instrumented anthropometric test devices (ATDs) to estimate the probability of injury as well as to assess the performance of protective equipment. Using both PHMSs and the Hybrid-III ATD, Grigoriadis et al 23 investigated whether changing the seated posture from 90°−90° alters the injurious outcome (Figure 5B). The study suggests that the force values obtained from the Hybrid-III when its placement deviates from the typical 90°−90° might be misleading if used to assess injury risk in the human lower extremity.…”