Neural Prostheses and Gait Performance: Model-Based Strategies

Study Overview
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Brief Summary
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The purpose of this research is to find the optimal patterns of functional electrical stimulation (FES) of muscles in the lower legs that will improve walking ability in those who have had a stroke and at the same time ensure walking stability. FES involves applying small electric currents to the nerves, which cause the muscles to contract. FES research projects vary from simple investigations of the therapeutic effects of exercise on muscle function and skin health, to more complex studies of functional movements such as standing or walking.

Detailed Description
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The study aims to find the optimal patterns of functional electrical stimulation (FES) of muscles in the lower legs that will improve walking ability in those who have had a stroke and at the same time ensure walking stability will be achieved through an analytical approach comprised of computational models and gait simulations to objectively determine patient-specific patterns of muscle activation. The investigators will develop a computer simulation of the dynamics of hemiplegic gait characterized by unilateral plantarflexor weakness. Then, the investigators will relate the results of the computer model results to real data collected from subjects with known plantarflexor weakness to provide a theoretical basis for improving gait efficiency and stability with FES.

Official Title
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Neural Prostheses and Gait Performance: Model-Based Strategies

Conditions
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Hemiplegia

Intervention / Treatment
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* Device: FES


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: This study includes stroke survivors greater than 18 years of age, >180 days from first clinical hemorrhagic or nonhemorrhagic stroke with: Unilateral hemiparesis with sufficient endurance and motor ability to ambulate >30 feet continuously without an AFO requiring no more than 25% physical help Berg Balance Scale score >23 without assistive devices Standing ankle dorsiflexion strength of <4/5 Foot-drop during ambulation with gait instability or inefficient gait defined as supervision need Possible use of physical assistance or assistive device (cane, walker) Evidence of foot-drop as seen by dragging or catching of affected toes during limb swing or circumducting affected limb Vaulting of the unaffected limb or hiking the affected hip to clear toes. Intact and electrically ex-citable lower motor neurons Ankle dorsiflexion to at least neutral while standing with electrical stimulation of common peroneal and tibial nerves without painful hypersensitivity to stimulation Adequate social support and stability Medically stable with intact skin in affected lower limb Willingness to comply during research procedures No systemic co-morbidities No history of potentially fatal cardiac arrhythmias i.e. ventricular tachycardia, supraventricular tachycardia and rapid ventricular response atrial fibrillation with hemodynamic instability No psychological problems or chemical dependency No acute medical complications such as depression or chronic anxiety requiring long term pharmacological therapy. Able-bodied controls must be of similar age, body mass and stature as those with hemiparesis and must be free of any medical and disabling orthopedic problems. Exclusion Criteria: In addition to failure to meet the inclusion criteria, participants will be excluded from the study for the following: Requires an ankle foot orthosis (AFO) to prevent knee flexion collapse in stance Excessive edema of affected extremity Absent sensation in affected limb History of potentially fatal cardiac arrhythmias such as ventricular tachycardia, supraventricular tachycardia, and rapid ventricular response, atrial fibrillation with hemodynamic instability Demand pacemakers or any implanted electronic systems Pregnancy Uncontrolled seizure disorder Ipsilateral lower limb lower motor neuron lesion Parkinson's disease Spinal cord injury Traumatic brain injury Multiple sclerosis Ankle plantar flexor contraction Severely impaired cognition and communication Painful hypersensitivity to neuromuscular stimulation of common peroneal nerve Knee hyperextension (genu recurvatum) that cannot be adequately corrected with peroneal nerve stimulation History of botulinum toxin to the lower extremity within the prior three months.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Arm 1: FES<br>Case-control study: pre- and post-stimulation (FES). | Device: FES<br>* Surface stimulation to contract the muscles in the lower extremity<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Walking Stability and Speed | This was a feasibility study of computational models and gait simulations to objectively determine patient-specific patterns of muscle activation. We developed computer models and walking simulations of hemiplegic gait from 8 subjects. We related the model results (muscle activations) to the optimized data collected from hemiplegic subjects & calculated the FES pattern to be delivered in 2 forms (open loop & foot switch triggered). The primary outcome measure turned out to be the feasibility of the methods because after developing our computer modeling and computational optimization framework we could only test walking with the 2 forms of FES at the same preferred walking speed on a treadmill. Thus, the simulated walking speed and the real walking speed pre and post FES turned out to be the same. Walking stability was measured with variability in work performed at the ankle. The additional volitional and FES biomechanical data that were measured are listed in the secondary measures. | pre-stimulation (volitional) and post-stimulation (FES), day of the study | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Peak Ankle Power | This is the peak ankle power during walking normalized by body weight. | Same day: pre-stimulation (volitional) and post-stimulation (FES), day of the study | 
| Positive Ankle Work | This is the amount of positive work performed by the ankle during walking normalized by body mass. | Same day; pre-stimulation (volitional) and post-stimulation (FES), day of the study | 
| The Impulse of the Anterior Ground Reaction Force Normalized by Body Mass. | The is the magnitude of ground reaction force over time per step in the anterior direction during walking. | Same day: pre-stimulation (volitional) and post-stimulation (FES), day of the study | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Electric Stimulation, Hemiplegia, walking