Effectiveness of functional electrical stimulation of gait. Evaluating of modifications to the center of pressure for a hemiparetic patient

Abstract

Drop foot is the principal ambulatory anomaly impacting hemiplegic patients. The effectiveness of Functional Electric Stimulation (FES) on gait parameters in hemiplegics has been demonstrated over the medium and long term. Clinical evaluation of this setup and its’ effectiveness is not always easy; changes in gait parameters being difficult to measure solely by observation. Ideally, the application of FES should be done along with a 3-D analysis of the patient's gait, which can be a time-consuming procedure. The goal of this study is to evaluate dynamic changes in the center of pressure (COP), measured using an instrumented walkway, when applying FES. A mono-paretic patient, stable after frontal tumor surgery, was treated with FES of the fibularis communis nerve. The evaluation of gait, at a comfortable walking pace, was realized using an analysis of both spatio-temporal parameters and COP, obtained using the GAITRite walkway. The evaluation was conducted, immediately before and after application of FES. Spatio-temporal gait parameters (walking speed, stride length, cadence) were not modified by FES. Our analysis confirms an immediate ‘posteriorization’ of the COP upon initial application of FES. Net postero-anterior displacement of the COP was increased by FES. This study confirms the findings in the referenced literature, where during same-day evaluation, FES is shown to not modify spatio-temporal parameters. These modifications only being manifest during prolonged use. We observed changes in the net displacement of the COP on initial application of FES. This corroborates a recent study, which suggests that FES could have an immediate effect on weight transfer and thus increase gait stability. The evaluation of the displacement in the COP could represent a readily observable parameter in gauging the effectiveness of FES when applied to patients with drop-foot. This parameter could be easily and objectively measured with available tools such as an instrumented walkway.