Medical Device Daily

Today marks the start of National Stroke Awareness Month, and May marks the commercial release of the WalkAide System from Innovative Neurotronics (IN; Bethesda, Maryland), an electrical stimulation-based device for helping stroke survivors walk.

The WalkAide is the first in IN's line of functional stimulation products, designed to counter a form of paralysis or weakness in the leg known as “foot drop” in patients who have sustained damage to upper motor neurons or pathways to the spinal cord, as the result of a stroke, spinal cord injury, traumatic brain injury, multiple sclerosis or cerebral palsy.

Foot drop interferes with an individual's ability to flex the ankle and walk with a normal heel-to-toe pattern, causing them to drag or swing their leg around to the side. “That takes a lot of energy, puts a lot of stress on other muscle, joint [and] tendon ligament groups, and lot of these patients just won't walk,” Conrad Kufta, MD, IN's director of clinical development, told Medical Device Daily.

The WalkAide uses functional electrical stimulation that recreates a natural nerve-to-muscle response. This helps patients to walk normally “by reproducing the normal function that's been lost,” Kufta explained.

The device uses advanced sensor technology to analyze the movement of the patient's leg and foot, then sends electrical signals to the peroneal nerve, prompting the muscles to raise the foot at the appropriate time.

Jeff Martin, president of IN, told MDD that the best way to view the WalkAide is as “a brain in the box, because what we are doing is telling the nerve to contract the muscles so we can lift the foot.”

The WalkAide – “about the size of a pack of cigarettes,” Martin said – is a self-contained unit that consists of a battery-operated, single-channel electrical stimulator, attachment cuff, two electrodes and electrode leads. The device is applied directly to the leg below the knee and secured by a cuff. The WalkAide is designed for single-handed application and removal, especially helpful for individuals with weakness on one side of the body.

Since its FDA clearance in September 2005, the company has been busy training clinicians on the WalkAide, with 300 trained as of last month. Martin said the company expects to increase this number to 700 by July “so we will have literally coast-to-coast trained clinicians accessible to patients.”

The device is customized for each patient. During an initial visit with one of the company's clinicians, “the clinician will program the device so that it is in line with the patient's gait. Each device is made intelligent based on the patient through sophisticated software we've developed, called WalkAnalyst,” Martin explained. “Once it gets to the patient, it is extremely easy to use, it is just on/off, literally.”

Martin described the device as “very unobtrusive and easy to wear.” Based on clinical studies, he said, “we've found on average patients are using this 10 hours a day” and typically walk more than 1,000 steps per day with the help of the device.

In contrast to “not using any device or using just a brace in which the foot is very passive,” Kufta cited the WalkAide's advantages. “No. 1, you're going to walk better. No. 2, the general benefit that comes from being able to exercise is a bedrock principle of medicine. If you get people up and moving, you decrease atrophy, increase muscle strength…[increase] bone density, improve circulation and prevent deep vein thrombosis.” In addition, he said the device is much less bulky than a brace and does not require special footwear.

Kufta, a board-certified neurosurgeon, also highlighted the WalkAide's potential role in neuroplasticity, calling this “a very exciting area in neuroscience right now, which basically says that the central nervous system, with the proper sensory input, can reprogram itself in such a way as to restore some function that has previously been lost.”

“The implication of this is that down the road you will actually improve the basic underlying circuitry in the brain, [meaning] that patients may actually need less of a device in the future,” The WalkAide thus is a “logical device” in this process, he said.

“For a while this was wild speculation, almost science fiction, but now there are many, many avenues of evidence that are all converging on this.”

He said that IN has full-scale, statistically significant studies under way in the U.S. to further examine the WalkAide's ability to strengthen cortico-spinal pathways and retrain damaged communication channels between the brain and the leg.

Another study by the company, accepted for publication in Neurorehabilitation and Neural Repair, reports that the walking speed of patients wearing the WalkAide increased by nearly 50% after 12 months of use. The clinical trial also showed the number of steps taken per day by WalkAide users increased significantly over time.

“Patients were able to walk more swiftly and more efficiently,” Kufta said in a summary of the findings. “From the patient's point of view, if they can get wherever they want to go more efficiently, with less discomfort and they're more stable, they tend to be much more active in general.”

Other U.S. studies under way are focusing on health economic and technology assessments, which will help to establish the value of the product and reimbursement levels, Martin said. He said the company will apply for coverage by third-party payers. The device will be priced at $4,495.

The WalkAide, according to Martin, represents “the first nationwide introduction of a device based on Myo-Orthotics technology” – a term coined by the company to describe the merging of orthotic technology with electrical stimulation.

IN, a wholly owned subsidiary of Hanger Orthopedic Group (also Bethesda), was formed in 2004 to commercialize emerging Myo-Orthotics technologies developed at research centers and universities that use neuromuscular stimulation to improve the functionality of an impaired limb.

Martin explained that IN “acts as a portal” to bring technology – such as the WalkAide, which originated at the University of Alberta (Edmonton) – to final development and commercialization. And IN's relationship with both the clinical care arm and the product distribution arm of Hanger Orthopedic “means,” he said, that “IN can get a product to market much more quickly than other manufacturers.”