A decision support system for electrode shaping in multi-pad FES foot drop correction

Suzana Dedijer Dujović,Goran Bijelić,Nebojša Malešević,Jovana Malešević,Aleksandra Vidaković,Thierry Keller,Andrej M Savić,Ljubica Konstantinović

doi:10.1186/s12984-017-0275-5

Abstract

BackgroundFunctional electrical stimulation (FES) can be applied as an assistive and therapeutic aid in the rehabilitation of foot drop. Transcutaneous multi-pad electrodes can increase the selectivity of stimulation; however, shaping the stimulation electrode becomes increasingly complex with an increasing number of possible stimulation sites. We described and tested a novel decision support system (DSS) to facilitate the process of multi-pad stimulation electrode shaping. The DSS is part of a system for drop foot treatment that comprises a custom-designed multi-pad electrode, an electrical stimulator, and an inertial measurement unit.MethodsThe system was tested in ten stroke survivors (3–96 months post stroke) with foot drop over 20 daily sessions. The DSS output suggested stimulation pads and parameters based on muscle twitch responses to short stimulus trains. The DSS ranked combinations of pads and current amplitudes based on a novel measurement of the quality of the induced movement and classified them based on the movement direction (dorsiflexion, plantar flexion, eversion and inversion) of the paretic foot. The efficacy of the DSS in providing satisfactory pad-current amplitude choices for shaping the stimulation electrode was evaluated by trained clinicians. The range of paretic foot motion was used as a quality indicator for the chosen patterns.ResultsThe results suggest that the DSS output was highly effective in creating optimized FES patterns. The position and number of pads included showed pronounced inter-patient and inter-session variability; however, zones for inducing dorsiflexion and plantar flexion within the multi-pad electrode were clearly separated. The range of motion achieved with FES was significantly greater than the corresponding active range of motion (p < 0.05) during the first three weeks of therapy.ConclusionsThe proposed DSS in combination with a custom multi-pad electrode design covering the branches of peroneal and tibial nerves proved to be an effective tool for producing both the dorsiflexion and plantar flexion of a paretic foot. The results support the use of multi-pad electrode technology in combination with automatic electrode shaping algorithms for the rehabilitation of foot drop.Trial registrationThis study was registered at the Current Controlled Trials website with ClinicalTrials.gov ID NCT02729636 on March 29, 2016.

Highlights

Functional electrical stimulation (FES) can be applied as an assistive and therapeutic aid in the rehabilitation of foot drop
The efficacy of the decision support system (DSS) for finding the best subset of pads for inducing DF and plantar flexion (PF) was evaluated by comparing the set of pads suggested by the DSS (SetDSS) and the final set of pads that constituted the stimulation pattern selected by the clinicians (SetFIN)
Because the clinicians had the freedom to choose any combination of the Q-rated as well as non-suggested pads when they made their final decision, we reviewed the Q-values of the pads included in every SetFIN for inducing the two movements over all the therapy sessions

Summary

Introduction

Functional electrical stimulation (FES) can be applied as an assistive and therapeutic aid in the rehabilitation of foot drop. To avoid foot dragging during the swing phase of the gait, patients with foot drop adopt abnormal gait patterns characterized by hip hitching, circumduction and toe catch. These distortions of the gait pattern lead to a decrease in the gait velocity and walking endurance, longer stance and double support gait phases, an increased energy cost, instability and a tendency to trip and fall [2]. FES-based therapeutic and assistive devices for foot drop correction typically stimulate the common peroneal nerve in the swing phase of the gait to ensure foot lifting, i.e., the dorsiflexion (DF) of the ankle (for a review, see references [8, 9]). Producing plantar flexion (PF) with FES during the pre-swing phase of the gait results in better knee flexion, which facilitates the swing phase [10]

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