Effect of posture on forces and moments measured in a Hybrid III ATD lower leg

Van Tuyl, John; Burkhart, Timothy A.; Quenneville, Cheryl E.

Affiliations

¹Department of Mechanical Engineering, McMaster University, Hamilton, Ontario, Canada

²Department of Mechanical and Materials Engineering, Western University, London, Ontario, Canada

³School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada

Abstract and keywords

Objective: Anthropomorphic test devices (ATDs) are used to assess real injury risk to occupants of vehicles during injurious events. In the lower leg, values from load cells are compared to injury criteria developed in cadaveric studies. These criteria are typically developed with the leg in a neutral posture, whereas the ATD may assume a wide range of postures during safety evaluation tests. The degree to which the initial posture of an ATD has an effect on the measured forces and moments in the lower leg is unknown.

Methods: A Hybrid III ATD lower leg was impacted in a range of postures under conditions representing a crash test, and peak axial force and adjusted tibia index injury measures were evaluated. Ankle posture was varied in 5° increments using a custom-made footplate, and dorsi/plantarflexion (20° DF to 20° PF) and in/eversion (20° IV to 5° EV) were evaluated. Tibia angle was also varied (representing knee flexion/extension) by ±10° from neutral.

Results: Peak axial force was not affected by ankle flexion or tibia angulation. Adjusted tibia index was lowest for plantarflexion, as well as for tibia angles representative of knee extension. Both peak axial force and adjusted tibia index were lowest for postures of great inversion and were highest in neutral or near-neutral postures.

Conclusions: The range of postures tested herein spanned published injury criteria and thus would have made the difference between pass and fail in a safety evaluation. In/eversion had the largest influence on injury metrics, likely due to the change in axial stiffness and altered impact durations in these postures. Results suggest increased injury risk at neutral or near-neutral postures, whereas previous cadaveric studies have suggested that in/eversion does not influence injury risk. It is unclear whether the ATD appropriately represents the natural lower leg for impacts in out-of-position testing. Great care must be taken when initially positioning ATDs for safety evaluations, because small perturbations in posture were shown herein to have large effects on the measured injury risk using this tool.

Keywords: anthropomorphic test device; impact; surrogate; tibia index; lower leg; posture

Links

DOI: 10.1080/15389588.2015.1089356

PubMed: 26376156

WoS: 000375036600009

History

Received: 2015-05-25

Accepted: 2015-08-27

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Cited By (2)

Year	Entry
2019	de Lange J, Quenneville CE. Evaluation of the distribution of forces on the foot under axial impact loading to assess variations among altered ankle postures between two ATD models. In: Proceedings of the 2019 International IRCOBI Conference on the Biomechanics of Injury. September 11-13, 2019; Florence, Italy.673-683.
2019	de Lange J. Biomechanical Tools for Assessing Foot and Ankle Injury Risk in Frontal Automotive Collisions [Master's thesis]. Hamilton, ON: McMaster University; 2019.