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Mind-controlled bionic leg heralded as breakthrough

By Catholic Online (NEWS CONSORTIUM)
September 27th, 2013
Catholic Online (www.catholic.org)

In what is being heralded as "a groundbreaking development," by lead author Levi Hargrove, a biomedical engineer and research scientist at RIC, the first successful trials of a bionic leg have proved successful. Test subject 32-year-old Zac Vawter, having lost his lower right leg in a motorcycle accident years ago, has been fitted with an artificial limb that uses neur-osignals from his upper leg muscles to control the prosthetic knee and ankle.

LOS ANGELES, CA (Catholic Online) - The limb is the first thought-controlled bionic leg. "It allows people to seamlessly transition between walking along level ground and going up and down stairs and slopes," Hargrove says.

According to scientists at the Rehabilitation Institute of Chicago, only thought-controlled bionic arms have been available to amputees.

Vawter, fitted with an experimental "bionic" leg, climbed the 103 flights to the top of Willis Tower in Chicago in October of last year.

When Vawter thinks he wants to move his leg, the brain signal travels down his spinal cord and through peripheral nerves. This is then picked up by electrodes in the bionic leg.

The prosthesis allows a normal, smooth gait no matter the incline, quite unlike the previous robotic models currently on the market. The cost of the limb has not yet been determined - but a version could be available to the more than one million Americans with leg amputations within three to five years. 

"It makes a phenomenal difference," Vawter says, a software engineer from Yelm, Washington. Becoming aware of the institute's work on bionic arms, Vawter and his surgeon contacted Hargrove and the team developing the prosthesis. Vawter would travel to the institute periodically over the next few years.

Vawter would remove his mechanical leg, slip into the bionic one, and run through a set of experiments the scientists devised. After multiple revisions to the leg's software and two major revisions to the leg's mechanics, Vawter says he can walk up and down stairs the way prior to the amputation.

"My sound leg goes up every step first, and I'm just dragging the prosthetic leg along behind me." But with the bionic leg, "I go leg over leg," he says. "The bionic leg listens to the various signals from my nerves and responds in a much more natural way."

The thought-controlled bionic leg is highly sophisticated. In additional to mechanical sensors, it has two motors, complex software, and a set of electrodes - essentially antennae - in its socket that pick up the tiny electrical signals that muscles in the upper leg generate when they contract.

In the process, two electrodes pick up signals from the hamstring muscle, where the nerves that had run through Vawter's lower leg were redirected during the amputation. "So when Zac is thinking about moving his ankle, his hamstring contracts," Hargrove says.

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