Biomedical Engineers Use Electrical Stimulus to Help Patients Lift Their Feet
October 1, 2007
Physical Therapists are helping people with central nervous system disorders learn to walk again. A wireless computer-enabled device aids those suffering from a condition called foot drop, which happens when someone cannot raise the front part of the foot to accommodate a smooth gate. When an individual swings his or her legs forward, a sensor in the shoe signals a microprocessor, which sends an electrical pulse to the nerve that controls the foot, lifting it, and allowing the patient to walk smoothly.
Hamburg, Penn. -- For stroke patients or people living with multiple sclerosis or cerebral palsy, one of the most difficult, but very common, side effects of their condition is paralysis of part of the body. But now, a new device is giving some patients their life back.
For Lorrie Hemerly, a short walk with her husband, Jeff, is reason to celebrate. Just a few months ago, it was impossible to keep up. Multiple sclerosis had rendered her right leg nearly useless.
"It was one of my first questions when they told me I had MS. Was I going to wind up in a wheelchair?" Hemerly says. But now, physical therapists are using a new wireless, computer-controlled device to help people with central nervous system disorders. Hemerly suffers from what is known as "Foot Drop." She's not able to raise her toes while she's walking.
That's where the "NESS" L-300 comes in. "NESS" stands for neuromuscular-electrical-stimulation-system. The NESS has three parts -- a sensor inside the user's shoe with a transmitter that is clipped onto the heel, the brace at the knee, and a small, hand-held control unit.
When Hemerly steps down on her heel, the transmitter sends a wireless signal to her brace. Then, two electrodes send a timed, electrical pulse to the nerves that control the paralyzed foot.
"That is the one that you're stimulating during what's called the 'swing phase,' when you want the leg to be able to go up and through without issue," says Kathy Slezak, physical therapist at Good Shepherd Rehabilitation Network in Allentown, Penn.
Hemerly can control the "NESS." When she's tired, her foot starts to drag, so she can increase the electrical stimulation.
But the biggest benefit? Hemerly says the device has greatly increased her stability. This first-time grandma said she couldn't hold little McKenzie and walk at the same time. Now, that's changed.
"It gives you a little bit more confidence now. You can do a bit more," Hemerly says.
Patients say they can feel the electrical charge going into their leg, but it's not painful, and they get used to it quickly. Physical therapists say they've had the most success with patients who have paralysis on only one side of the body. Good Shepherd Rehabilitation Network is the only in-patient beta-testing site for the technology in the United States.
Earlier this year, the FDA approved the NESS L300 to help provide a more natural gait and improved mobility for people with neurological disorders, such as stroke patients, those with traumatic brain injury, multiple sclerosis, or incomplete spinal cord injury. When an individual walks, he or she alternately swings his or her legs forward. During this phase of gait, the L300 electrically stimulates the muscles in a paralyzed leg to lift the foot. It is a form of functional electrical stimulation (FES). The manufacturer, Bioness, is testing its latest product at two sites in the US.
HOW WE WALK:
Walking is different from a running gait because only one foot at a time lifts off the ground. During forward motion, the leg that leaves the ground swings forward from the hip, like a pendulum. Then the leg strikes the ground with the heel and rolls through the toe in a motion similar to an inverted pendulum. The motion of the two legs is coordinated so that one foot or the other is always in contact with the ground -- a so-called 'double pendulum' strategy.
The process of walking recovers about 60% of the energy expended thanks to the pendulum dynamics and the ground reaction force. (The legs act as long levers that transfer ground reaction force to the spine.)