Characterizing the Mechanical Stiffness of Passive-Dynamic Ankle-Foot Orthosis Struts.

This was a bench test of struts only, not a whole orthosis on a person, so it does not show how the footplate, tibial cuff, or user biomechanics would change stiffness during running. Only two struts from each stiffness category were tested, so the values may not represent every strut made. The backward bending test reached only 0.09 rad (5°), which may not cover the full range of motion available during running. The struts came from one manufacturer, so the values may not apply to other passive-dynamic ankle-foot orthosis struts. No people with lower limb impairment were tested, so the study does not show pain, comfort, injury risk, or running performance.

The work was supported by a grant from the Defense for Health Affairs, Clinical Research Intramural Initiative, CDMRPL-17-0-DMI170709, and the funder is named as the U.S. Department of Defense. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Do not read the stiffness categories as a simple ladder that predicts ankle control during running. The measured increments between categories were uneven, categories 2 and 3 did not differ when pushed backward, and no people were tested.