Characterization and clinical trial of a Variable Friction Shoe, a new paradigm of reduced-constraint locomotor therapy for people exhibiting foot drop due to stroke

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Project Summary More than one million Americans present with foot drop after stroke and often develop compensatory strategies to avoid scuffing the foot. Current treatment for foot drop addresses the hazard of tripping by applying non- volitional torques to the ankle to prevent the foot from plantarflexing. The two most common such devices are the Ankle Foot Orthosis (AFO) and Functional Electrical Stimulation (FES), which both provide well-documented orthotic effects to help users walk while the device is worn. However, therapeutic effects are limited, and users rarely improve enough to cease needing their device. Accordingly, here we propose an alternative strategy that addresses the hazard of tripping even while allowing full volitional control of the ankle: an inexpensive Variable Friction (VF) shoe. Its outsole is high-friction during the stance phase of gait and low friction during swing; further, it produces a “click” when a scuff occurs. Evidence suggests that such feedback can enhance therapeutic outcomes. Our preliminary data suggests that the VF shoe is effective at increasing gait speed immediately (orthotic effect) and after long term use, even when the shoe is removed (therapeutic effect). Our central hypothesis is that allowing volitional motion of the ankle while mitigating the hazard of tripping coupled with gait-phased auditory biofeedback will result in improved gait for subjects with drop foot. Specifically, we hypothesize that the VF shoe will show significantly greater therapeutic effects than an AFO, yet maintain the desirable orthotic effect of the AFO. We arrange our work in two Aims. Specific Aim 1: Characterize the scuff-force reduction of the VF shoe over the lifetime of use. Critical to understanding the effects of the VF shoe is a characterization of the level of scuff-force reduction. Specific Aim 2: Evaluate the effects of the VF shoe on gait in individuals with chronic stroke and drop foot. During each 12-week phase of an AB-BA clinical trial, participants will walk for at least 30-45 minutes per day for at least 5 days per week at home. We expect that this work will validate our VF shoe as a tool for improving gait after stroke and will introduce a new paradigm for drop foot therapy: fully volitional ankle control while mitigating tripping. The results will lay the foundation for a future pivotal device trial on the VF shoe to assess clinical efficacy. Importantly, the VF shoe is simple, low-cost and easy-to-use, making wide-ranging home-based adoption feasible.