Computational modeling and muscular equivalence analysis of surrogate neck device multi-plane static stiffness

Abstract

Anthropometric test devices (ATDs) are human surrogate devices that are used in impact testing for the simulation and evaluation of helmet impact performance in American football. However, these ATD’s are often used outside of the scope of their original testing purposes, leading to an increased potential for misinterpretation of laboratory testing data. In this study a computational analysis was conducted of human neck muscular equivalence to that of the Hybrid III neckform using the HYOID OpenSim model scaled to 50th and 95th percentiles of human muscle mechanical properties. Neck bending was simulated in four directions (sagittal, coronal, 45° off-center, and transverse planes) and compared to experimental data on the Hybrid III neckform. In a muscle parameter optimization, maximum isometric force ( $F_o^M$ ) and passive fiber strain at $F_o^M$ ( ${\epsilon }_o^M$ ) were altered to match the stiffness responses of the HYOID model to the Hybrid III neckform. The Hybrid III sagittal plane flexion response was found to be non-physiologic, requiring a 275% increase in $F_o^M$ from the HYOID 50th percentile model. The extension response was moderately more physiologic, requiring only a 66% increase in $F_o^M$ . The Hybrid III neckform was consistently closer to the HYOID 95th percentile model in all planes of motion, suggesting a better match with collegiate/professional populations than the average male. Results from this work can be used as a baseline for future dynamic comparisons to improve the biofidelity of surrogate devices used in the laboratory testing of head protective equipment for American football.