Injury Risk of the Human Leg Under High Rate Axial Loading

This paper proposes a new risk function for lower limb fractures from high rate axial loading, such as that expected in under vehicle explosions. The aim is to improve the prediction of such fractures based on the loads measured by an Anthropomorphic Test Device (ATD) during blast testing. This function has been created by combining data from six different peer-reviewed post mortem human subjects (PMHS) studies. The work, which led to the risk function, considered proximal tibia force as the primary indicator of fracture, with age, sex and body mass considered as covariates. Previous studies considered age as a linear covariate to allow the elderly PMHS population results to be mapped onto a younger population. The literature review as part of this study found, however, that bone strength varies non-linearly with age. Extrapolating bone strength linearly may therefore overestimate the strength of younger populations’ lower limbs. This study uses a non-linear variation of bone strength with age and optimised parameters within this function to produce a Weibull risk curve with a minimum spread. The function described is for loads on the human; for it to be applicable in vehicle testing, there is a need to account for the response of the ATD.