Jovana Jovic

Continuous gait cycle index estimation for electrical stimulation assisted foot drop correction

BackgroundWalking impairment after stroke can be addressed with the use of drop foot stimulators (DFS). Many studies have demonstrated that DFS improves walking speed, reduces spasticity and reduces the physiologic effort of walking. Current DFS, through activation of the common peroneal nerve, elicit ankle dorsiflexion during swing phase of gait. DFS are generally piloted by force sensing resistor placed in the shoe of the affected side with stimulation triggered ON by heel rise and triggered OFF by heel strike. A tilt sensor can also be used with stimulation triggered by the tilt of the shank of the affected leg. These triggering approaches are the standard for initiating stimulation. However, the real-time modulation of FES intensity to provide more optimized delivery of stimulation and also to regulate dorsiflexion in the presence of disturbances, such as fatigue and spasticity may increase the number of potential users of DFS. Concerning research domain, stimulators that would allow modulating the stimulation pattern in between heel rise and strike events would allow exploring new stimulation strategies. We propose to extract continuous information: the gait cycle index (GCI), from one inertial measurement unit (IMU) measuring shank tilt angle. In order to illustrate the use of this real-time information, we show the feasibility of piloting an electrical stimulator.Methods12 subjects with post-stroke hemiplegia participated. A wireless IMU was placed on the unaffected shank and was used to estimate GCI. Subjects performed 3 trials in each of the 3 conditions: C1 no stimulation aid, C2 electrical stimulation assistance triggered by heel switch, C3 electrical stimulation assistance triggered from GCI.Results1) the proposed algorithm was able to real-time estimate GCI, 2) events could be extracted from GCI information in order to trig a DFS.ConclusionThe estimation of the continuous GCI in individuals with stroke is possible. Events can be extracted from this information in order to trig a stimulator. These results are a first step towards the possibility to investigate new DFS paradigms based on real-time modulation of stimulation parameters.

Upper and lower body coordination in FES-assisted sit-to-stand transfers in paraplegic subjects — A case study

The objective of the work presented is to improve functional electrical stimulation (FES) assisted sit-to-stand motion in complete paraplegic individuals by restoring coordination between the upper part of the subject’s body, under voluntary control, and the lower part of the body, under FES control. The proposed approach is based on the observation of trunk movement during rising motion and a detection algorithm, which triggers a pre-programmed stimulation pattern. We present a pilot study carried out on one T6 paraplegic subject. We validated the ability of the subject to produce repeatable trunk acceleration during sit-to-stand transfers under FES and, the ability of the system to trigger the stimulator at the desired instant in time. We also analyzed the influence of the timing of leg stimulation, relative to the trunk acceleration profile, on upper limb efforts applied during sit-to-stand motion.

Coordinating Upper and Lower Body During FES‐Assisted Transfers in Persons With Spinal Cord Injury in Order to Reduce Arm Support

The goal of this study is to minimize arm forces applied during sit‐to‐stand (STS) transfers in persons with spinal cord injury (SCI) by using functional electrical stimulation (FES) applied to lower limbs muscles.