First Bionic Leg Allows Mind to Control Movement in Study

Zac Vawter, a software engineer who lives in the Seattle area, already knew about advances in bionic technology when a motorcycle wreck led to the amputation of his right leg just above the knee in 2009.

As doctors at Harbor View Medical Center in Seattle battled for three days to try to save his leg, Vawter asked about the method that uses the mind to move a prosthetic limb. The technology had previously been used only in arms.

Software Engineer Zac Vawter is considered the “test pilot” of a bionic leg that can tackle slopes, stairs and in-chair movement markedly better than existing devices. Source: Rehabilitation Institute of Chicago via Bloomberg

Four years and an $8 million grant from the U.S. Army’s Telemedicine and Advanced Technology Research Center later, Vawter is considered the “test pilot” of the bionic leg that can tackle slopes, stairs and in-chair movement markedly better than existing devices. A team of researchers led by Levi Hargrove from the Rehabilitation Institute of Chicago’s Center for Bionic Medicine reported their results with the novel prosthetic in the New England Journal of Medicine.

“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,” Vawter said in a telephone interview. “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.”

Additional refinements are needed to make the thought-controlled bionic leg commercially viable, Hargrove said in a telephone interview. Vawter is allowed to use the machine only a week at a time during visits every few months to the clinic in Chicago. Freedom Innovations LLC, a closely held company based in Irvine, California, is working on making the motorized machine smaller, quieter and more robust.

Prosthetic Evolution

It’s been an evolutionary process. Most prosthetic legs work like a walking stick with springs, giving the patient something on which to balance. The next step up, robotic prosthetics, are further advanced with remote controls and embedded sensors that measure how much weight they must bear, the knee position and the way a person is turning, like mobile phones determine orientation. The thought-controlled device goes further, harnessing nerves that formerly regulated the leg’s movement to maneuver the prosthetic leg.

The new leg allows Vawter to seamlessly transition between walking and standing, with the biggest difference showing up when he is climbing stairs. With a standard prosthetic leg, Vawter always steps up first with his healthy left leg, then pulls the right leg along. With the thought-controlled leg, he is able to walk foot-over-foot, he said. Someone watching him climb wouldn’t know he had a prosthesis based on his gait, Hargrove said, though they may hear the motor whirring.

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