Response and Prediction of Improvement in Gait Speed From Functional Electrical Stimulation in Persons With Poststroke Drop Foot

Abstract

To describe changes in and predictors of comfortable gait speed (GS-C) after using a foot-drop stimulator (FDS; Bioness L300; Bioness Inc, Valencia, CA) for 42 weeks in persons who had sustained a stroke. Secondary analysis of prospective assessments. Multicenter clinical trial. A total of 99 subjects who had sustained a stroke ≥ 3 months earlier and who had GS-C ≤ 0.8 m/s and drop foot with a mean age of 60.7 years and a poststroke time of 4.8 years. GS-C was assessed at baseline and at 30 weeks with and without use of an FDS (therapeutic effect) and at 6, 12, 30, 36, and 42 weeks with use of an FDS (total effect). After subjects participated in 8 physical therapy sessions, an FDS was used for ambulation over the course of 42 weeks. Changes in mean GS-C over time, FDS "responder" status defined as either ≥ 0.1 m/s gain in GS-C (the minimal clinically important difference [MCID]) or advancing by one Perry Ambulation Category (PAC), and the incidence and nature of adverse events (AEs). A total of 74 (75%) and 69 (70%) of 99 subjects completed assessments at 30 weeks and 42 weeks, respectively. Baseline GS-C was 0.42 m/s without use of an FDS and 0.49 m/s with use of an FDS. GS-C improved to 0.54 m/s at 30 weeks without use of an FDS (effect size = 0.75) and 0.54, 0.55, 0.58, 0.60, and 0.61 m/s at 6, 12, 30, 36, and 42 weeks with use of an FDS, respectively (effect size 0.84 at 42 weeks). Half of the subjects achieved a maximum GS-C by 12 weeks. Approximately 18% were PAC responders and 29% were MCID responders for 30-week therapeutic effect, and 55% were PAC responders and 67% were MCID responders for 42-week total effect. After logistic regression, the following factors emerged as the strongest predictors of FDS responders: younger age, faster baseline GS-C and Timed Up and Go, and balance. At 42 weeks, 60% reported a device-related AE; 92% were mild and 96% were anticipated. When an FDS was used, GS-C improved progressively over 42 weeks, with ≥ 50% of patients achieving a clinically meaningful 42-week total effect and 50% achieving a maximum GS-C by 12 weeks. Younger patients with greater mobility levels may benefit most from use of an FDS. AEs were frequent, mild, and reversible.