Abstract
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.
Highlights
The aim of this study is to generate a fracture injury risk function for the human leg applicable to high rate axial loads
A new fracture risk function applicable to high rate axial loads has been derived for the human leg by conducting a metaanalysis of available post mortem human subjects (PMHS) data
A key aspect of this function is that it is designed to provide a better prediction of the risk of lower limb injuries for a younger population, one that is more representative of military personnel that may be within military vehicles exposed to explosion threats, than the more elderly PMHS population for which the raw data is available
Summary
The aim of this study is to generate a fracture injury risk function for the human leg applicable to high rate axial loads. While the risk function is applicable to high rate loads produced by other means, this work was conducted to inform the development of criteria for assessing the likelihood of injury to personnel in military vehicles exposed to underbelly explosion threats. These assessments are based on the loads measured by an Anthropomorphic Test Device (ATD) during blast testing; criteria development is necessary to produce more appropriate risk functions for loads in the human leg and to account for the differences in the response of the human and ATD legs. This paper removes some of the variation within lower limb injury data, caused by factors such as age, sex and body mass
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