Effect of quantitatively matched passive-dynamic ankle-foot orthoses on post-stroke gait

Arch, Elisa S.The plantar flexors play a critical role in moving the body forward during gait by eccentrically contracting to control shank rotation. Insufficient control of shank rotation due to plantar flexor weakness, a common post-stroke impairment, may result in gait dysfunctions. Plantar flexor function during gait, or lack thereof, can be quantified by the peak plantar flexor moment. Passive-dynamic ankle-foot orthoses (PD-AFOs) can be prescribed to improve post-stroke gait. PD-AFO bending stiffness is a key orthosis characteristic that can replicate many functions of the plantar flexors. However, outcomes with ankle-foot orthoses (AFOs) are variable, likely because of the orthosis characteristics not being properly matched to each individual’s needs. We have developed a novel design and prescription process that quantitatively matches PD-AFOs based on each individual’s level of plantar flexor weakness. However, preliminary data collected by our lab showed that individuals post-stroke were unable to fully use the quantitatively matched PD-AFOs. We hypothesized that providing the individuals with real-time biofeedback on how to properly use the PD-AFO would help acclimate them to PD-AFO use and help them reap full benefits from the orthosis. Thus, the purpose of this study was to first evaluate if the quantitatively matched PD-AFOs improved gait biomechanics (peak plantar flexion moment) better than the originally prescribed AFO. Then, we developed and evaluated if a real-time biofeedback tool helped individuals post-stroke more effectively use the PD-AFO while walking. Eleven individuals with chronic stroke (> six months post-stroke) underwent an instrumented gait analysis to gather baseline data. Using our design and prescription process, a carbon fiber PD-AFO was then quantitatively matched for each subject. Once the PD-AFOs were manufactured, seven of the subjects visited the lab for one evaluation visit and underwent an instrumented gait analysis using his/her Original AFO and the quantitatively matched PD-AFO. The other four subjects visited the lab for two evaluation visits and underwent an instrumented gait analysis with his/her Original AFO and the quantitatively matched PD-AFO and used the biofeedback tool. A one-way repeated measures ANOVA was performed on the subject’s mean peak plantar flexion moment between his/her Original AFO and the quantitatively matched PD-AFO. If a significant difference was observed, simulation modeling analysis (SMA) was then performed to determine which subjects achieved a significant difference between the two conditions. The subject’s mean peak dorsiflexion angle was compared to the range assigned to each individual post-stroke to determine if the subject was able to reach that targeted dorsiflexion range. A one-way repeated measure ANOVA was performed on the subject’s mean peak plantar flexion moment between pre-biofeedback and post-biofeedback for both evaluation visits. SMA was also performed to determine if a significant increase in mean peak plantar flexion moment was achieved pre- and post-biofeedback for each subject individually for both evaluation visits. The subject’s change in mean step length (pre- vs. post-biofeedback) while walking with the quantitatively matched bending stiffness PD-AFO was compared to the pre-feedback step length variability for both visits. Results showed that 9 out of the 11 subjects had a significant increase in mean peak plantar flexion moment from the Original AFO to the quantitatively matched PD-AFO. Furthermore, two of the four subjects, on the second evaluation visit, were able to reach their targeted dorsiflexion range post-biofeedback. However, the individual post-stroke’s mean peak plantar flexion moment and mean step length did not improve from pre- to post-biofeedback for either evaluation visit. This study’s findings begin to lay the foundation of a novel quantitative prescription process to improve the gait of individuals post-stroke.M.S.University of Delaware, Biomechanics and Movement Science Progra