The First Mind-Controlled Bionic Leg Steps Into Reality

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Brian Kersey / AP

A team of scientists are getting closer to the holy grail of brain-powered prosthetics by developing the first advanced-movement prosthetic leg that communicates with the wearer’s mind.

Zac Vawter, 31, lost his leg just above the knee in a 2009 motorcycle accident. But today he’s the “test pilot” for the first bionic leg that can complete tasks like going up stairs or down slopes, all controlled by Vawter’s mind. A study announcing the progress of the limb is published today in The New England Journal of Medicine.

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The leg is the brainchild of a collaborative group of engineers, neuroscientists, surgeons, and prosthetists at the Rehabilitation Institute of Chicago, funded with a $8-million grant from the Army. Similar technology has been used in the past for arm prosthetics, but this is the first prosthetic leg to communicate with the wearer’s mind. All Vawter has to do is imagine his toes curling or the gait of walking down the stairs, and the leg puts his thoughts into motion.

The prosthetic limb uses sensors that rely on what are called reinnervated nerves, which are nerves that were formerly used to control Vawter’s leg muscles, but are surgically rewired to control his limb. The prosthetic reads the contractions from the muscles and nerves and makes the necessary movements in the knee and ankle joints that are part of the leg.

Vawter told Bloomberg in an interview, “In my mind, it’s still the same thing in terms of moving my ankle down or up, or extending my leg forward or back. It’s just walk like I would normally walk. It’s not special training or buttons or tricks. That’s a big piece of what I think is groundbreaking and phenomenal about this work.”

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Innovation in prosthetics is growing. Prosthetic limbs are no longer simply walking sticks that provide balance. There are more and more robotic limbs that move in ways that feel and look natural to wearers. For instance, Dr. Hugh Herr, Director of Biomechatronics at MIT and Founder and Chief Technology Officer of the prosthetic brand iWalk, has perfected the robotics in his company’s prosthetic limbs to replicate the calf muscles and Achilles tendon, which provide a push-off that helps propel the user and normalize their gait.

But don’t expect this new leg to be efore the new limb can be made available for people who need it, researchers say it still needs to be refined. Currently, Vawter only wears the leg for one week every couple of months when he visits the researchers in Chicago. California company Freedom Innovations LLC is also working to make the machine quieter and smaller.