Assessment of Mechanical Characteristics of Ankle-Foot Orthoses

[+] Author and Article Information
Amanda Wach

Amanda Wach, MS, Department of Biomedical Engineering, Marquette University, Olin Engineering Center, Room 206, 1515 W. Wisconsin Avenue, Milwaukee, WI 53233

Linda McGrady

Medical College of Wisconsin, Milwaukee, WI

Mei Wang

Medical College of Wisconsin, Milwaukee, WI

M. Barbara Silver-Thorn

Marquette University, Milwaukee, WI

1Corresponding author.

ASME doi:10.1115/1.4039816 History: Received July 07, 2017; Revised March 05, 2018


Recent designs of ankle-foot orthoses (AFOs) have been influenced by the increasing demand for higher function from active individuals. The biomechanical function of the individual and device is dependent upon the underlying, and as yet unevaluated, mechanical characteristics of the AFO. Prior mechanical testing of AFOs has primarily focused on rotational stiffness to provide insight into expected functional outcomes; mechanical characteristics pertaining to energy storage and release have not yet been investigated. A pseudo-static bench testing method is introduced to characterize compressive stiffness, device deflection, and motion of AFOs of various designs. AFOs, donned over a surrogate limb, were compressively loaded at different joint angles to simulate the foot-shank orientation during various sub-phases of stance. In addition to force-displacement measurements, motion analysis of each AFO strut, proximal, and supramalleolar segments were analyzed. Although similar compressive stiffness values were observed for AFOs designed to reduce ankle motion, the corresponding strut deflection mechanisms differed based on the respective fabrication material. For example, strut deflection of carbon-fiber AFOs resemble column buckling deflection. Expanded clinical test protocols to include quantification of AFO deflection and rotation during subject use may provide additional insight into design and material effects on performance and functional outcomes, such as energy storage and release and protection of painful or sensitive limb structures. Understanding the behavior of these devices will improve orthotic prescription and future design development.

Copyright (c) 2018 by ASME
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