Man Controls Bionic Leg with Thoughts

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A 32-year-old man who lost his leg below the knee after a motorcycle accident four years ago now has a robotic prosthesis he can control with his mind, according to a new report of his case.

While similar technology has allowed amputees to control bionic arms with their thoughts, Zac Vawter is the first amputee with a thought-controlled bionic leg, the researchers say.

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The robotic leg -- which decodes the electrical signals traveling through Vawter's remaining leg muscle -- not only interprets the patient's intended movements, but also has a motor in the knee and ankle, which helps him push himself up stairs and perform other activities. [5 Crazy Technologies That Are Revolutionizing Biotech]

Using his robotic leg, Vawter can seamlessly transition between sitting, walking and ascending and descending stairs and ramps, according to the report.

In contrast, most lower-leg prosthetics available today are passive, like a spring, which means people with those devices have to use their intact limb to pull the prosthetics behind them, said study researcher Levi Hargrove, of the Rehabilitation Institute of Chicago (RIC) Center for Bionic Medicine. And the lower leg prosthetics that do have motors are either controlled by a remote, or require the patient to perform exaggerated movements (like kicking their leg very far back) before changing activities, Hargrove said. [Video: Robotic Leg Prosthesis Controlled with Thoughts]

Vawter said his thought-controlled robotic leg "responds much more appropriately to the environment, and where I want to go, and how I want to walk."

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For example, when wearing a conventional prosthetic and walking up stairs, he has to put the same foot first on each step he climbs. "Whereas with this leg, it's more so that I just interact with my environment how a normal person would," and can walk up stairs foot over foot, he said.

While more needs to be done to improve the technology, the researchers hope to have it available in clinics within five years.

How It Works

When a person thinks about moving their lower limb, a signal from the brain is sent down the spinal cord and through nerves to muscles in the leg, Hargrove said.

But when an amputation occurs, nerve signals that would have gone to the knee or ankle, for instance, aren't able to deliver their message to muscle. To overcome this problem, the researchers first performed a surgery on Vawter to redirect his nerve signals, so that signals that would have gone to the lower leg instead go to the healthy hamstring muscle, in the top part of his leg.