Collaborative Research: Investigating the importance of biomimicry and customization in ankle-foot orthosis stiffness for restoring gait mechanics

Ankle braces are prescribed to make walking easier for people with disrupted ankle function. These braces can help some people, but many brace users still have difficulty walking. One reason braces may not provide benefit is that the ankle is complex, but most braces act like a simple spring. Another reason is that current methods for brace customization are based on trial and error as there is not a good model for how to change the brace’s properties to best meet each person’s needs. Ankle braces with tailored properties that better mimic normal ankle function may make it easier to walk for people with ankle injuries. The purpose of this study is to develop an ankle brace model with more complex properties based on typical ankle function. The project will evaluate how changing different model properties in the brace impacts how healthy and post-stroke people walk. Results from this study are expected to advance our understanding of how to design and prescribe personalized ankle braces and other assistive devices. This collaborative project between the University of Colorado at Boulder and the University of Delaware will investigate the potential benefits of passive ankle-foot orthoses (AFOs) with customized and biomimetic stiffness profiles. The project's goals will be achieved by first using AFO benchtop testing data to develop a control scheme for an AFO emulator that can effectively mimic both dual-stiffness and single-stiffness passive AFOs in both plantarflexion and dorsiflexion. Then, human-in-the-loop optimization (HILO) will be performed over a range of input control parameters for both dual-stiffness and single-stiffness profiles to determine how these optimized profiles affect walking function in (a) healthy individuals as a proof of concept and (b) individuals post-stroke. Walking speed will be used as the primary optimized outcome metric, with metabolic cost as a secondary metric. User-preferred parameters will also be determined and compared with the optimal parameters determined from HILO for each population. The fundamental knowledge gained from this study will provide critical understanding necessary to positively transform the way passive AFOs and other novel assistive devices are designed and customized. Such advancements will improve the quality of life of persons with disabilities by enhancing mobility. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.