Assessment of the metrological qualities of the inertial FOX Hikob compared to the reference system for adaptive trigger functional electrical stimulation to correct dropfoot in poststroke hemiplegic patients

Abstract

Eighty percent of poststroke patients are temporarily unable to walk without help, often with a dropfoot during the midswing phase. Functional electrical stimulation (FES) induces compensation of dropfoot by preprogrammed fixed stimulation, however they are not more effective than mechanical ankle foot orthesis. FES has the advantage of being able to provoke a physiological muscular contraction and respect the articular amplitude. Our objective is to evaluate the metrological quality of the inertial sensors for movement reconstruction in comparison to the gold standard motion analysis. The aim is to improve the SEF using adaptive triggers for dorsiflexion, in hemiplegic poststroke patients. Adults with supratentorial ischaemic or hemorrhagic stroke, presenting a foot-drop, able to walk 10 metres without human help, with or without a walking stick were included from May 2016 to June 2017. Patients with ankle dorsiflexion < 0° in knee extension were excluded. Synchronous gait analysis was performed using the VICON © system, the GAITRITE © walkway system and Fox Hikob inertial measurement unit (IMU). The main outcome is the measurement error for the dorsiflexion angle at the heel strike and midswing phase. Eleven patients included so far, 7 right sided hemiplegia, 8 male, mean age 56 years. To compare the IMU with the gold standard VICON, the measurement errors were estimated by Blant Altman analysis. Dorsiflexion angle measurements demonstrated a bias of 0.43° between the two techniques, with the limits of agreement [−13.46°; + 14.32°] during stance phases and a bias of 0.72° with agreement values [−16.19°; + 17.64°] during swing phases. The data treatment algorithms from IMU seem to be effective in measuring ankle dorsiflexion with small biases between techniques. The limits of agreement are too wide from a clinical perspective, probably due to a small sample size, but are narrow enough to warrant further technological research. Analysis of the full sample size will provide further information on the limits of agreement.