Clinical Study to Evaluate the Implantation of the ActiGait Drop Foot Stimulator System

The objective of this study is to evaluate the efficacy and safety of surgical procedure involving ActiGait - implantable drop foot stimulator.

Stroke is the third leading cause of death in the United States and other developed countries and a major source of disability. Prognosis for regaining the ability to walk is good, with 64% of those initially dependent in walking regaining independence by 3 months. However, many gait abnormalities persist. A conservative estimate suggests that 20% of stroke survivors have a drop foot. Drop foot following stroke is caused by paresis of the ankle dorsiflexor muscles. It prevents the patient from effectively swinging the leg during walking, causing an abnormal gait characterized by hip hitching and circumduction and toe catch. Walking speed in people with drop foot is often significantly reduced and the risk of stumbling or falling is high. The conventional treatment for drop foot is an ankle-foot orthosis (AFO). While AFOs are appropriate for many patients, in certain patient groups AFOs have significant limitations (e.g. in patients with strong spasticity, suffering from pronounced inversion, suffering from volume changes in the lower extremity, etc). An alternative way of treating drop foot is by means of functional electrical stimulation. Clinical studies evaluating the effectiveness of drop foot stimulation suggest that it provides many benefits to patients, such as an improved confidence in walking, increased walking speed and endurance, less effort during walking and reduced spasticity. Implantable systems such as ActiGait are considered therapeutic alternatives specifically for those patients for whom conventional treatments have failed. ActiGait system consists of an external module (antenna and control module), a foot switch transmitting to the external module and an implanted assembly (receiver, pulse train generator, electrodes). The objective of this study is to obtain additional evidence on safety of ActiGait implantation procedure and on its efficacy. The study will enrol 5 subjects that will be implanted and followed for 12 weeks. Efficacy outcomes will be assessed at the baseline and during two follow-up visits (week 6 and 12). Subjects will be asked to walk with and without their preferred walking at the baseline and with and without stimulation at follow-up visits.

Eligibility Criteria:
Inclusion Criteria:

* have a single sided hemiparesis persisting for more than 6 months due to a cerebro-vascular accident (CVA).
* be fully grown-up.
* have the ability to walk 20 meters in less than 2 minutes with or without walking aid but without the help of another person.
* have a reduced speed of walking.
* have the ability to stand upright with both heels touching the floor while hip and knee are in neutral position.
* have a passive range of movement of the affected ankle joint of at least 30 degrees.
* have a positive response to surface electrical stimulation of the peroneal nerve - i.e. muscle contraction which results in dorsiflexion of the ankle and improved gait.
* male or female older than 18 years of age.
* have signed written Informed consent to participate in the study.
* is willing and able to follow all study procedures including attendance at clinics for scheduled study visits.

Exclusion Criteria:

* peripheral nerve damage of the affected leg.
* severe or uncontrolled diabetes with peripheral nerve involvement.
* poor skin condition on the affected leg.
* a thickness of subcutaneous fat exceeding 3.5 cm in the region of the implant.
* inability to walk 100 meters without stopping prior to CVA (with or without a walking aid, but without the help of another person).
* poorly controlled epilepsy.
* need of Ankle Foot Orthosis (AOF) to maintain ankle stability.
* concomitant medical and psychological conditions which would limit the success of the ActiGait® system such as: active degenerative diseases of the back and lower limbs, visuo-spatial neglect, or drug abuse, personality disorders or poor cognitive function.
* concomitant medical and psychological conditions which would compromise the safety of the patient in connection with the implantation and use of the ActiGait system, such as: severe cardiac disease, uncontrolled hypertension or history of malignancy within the preceding five years.
* other active implanted devices such as demand pacemakers or implanted defibrillators, as mutual electromagnetic interference may distort the efficacy of both systems and expose the patient to dangerous situations.
* history of falls greater than once a week.
* pregnancy and lactation. Women of childbearing potential must maintain effective contraception during the study period, as judged by the investigator.
* previous participation in this study
* participation in an investigational drug trial within 4 weeks prior to enrolment.
* requirement of an interpreter
* use of external FES system to assist walking four weeks prior to enrolment
* MRI of the affected thigh that is inconsistent with safe implantation of the ActiGait
* history of falls greater than once a week.
* pregnancy and lactation. Women of childbearing potential must maintain effective contraception during the study period, as judged by the investigator.
* previous participation in this study.
* participation in an investigational drug trial within 4 weeks prior to enrolment.
* requirement of an interpreter.
* anatomic situation of the common peroneal nerve identified by pre-surgical MRI that could compromise the success of ActiGait).