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When sculptor Terry Karpowicz was 27 years old, he lost his right leg to a motorcycle accident. Since then, he has navigated life with a series of prosthetic legs that require him to adjust to their unnatural movements.

Thanks to a breakthrough in bionics, Karpowicz, now age 67, can experience the future of prosthetic limbs at the Rehabilitation Institute of Chicago (RIC) with a thought-controlled bionic leg that learns his movements and adjusts with each step. It does the work for him.

Today¡¯s issue of the Journal of the American Medical Association features RIC¡¯s clinical trial, which presents applications for the world¡¯s first thought-controlled bionic leg prosthesis that does not require nerve redirection surgery or implanted sensors.

Levi Hargrove, PhD, led this research at RIC¡¯s Center for Bionic Medicine. His team developed a system to use neural signals to safely improve limb control of a bionic leg ¨C a significant milestone in the rapidly-growing field of bionics.

¡°The bionic leg¡¯s intelligent engineering allows amputees to transition seamlessly between sitting, standing and walking, as well as ascending and descending stairs and ramps,¡± said Hargrove. ¡°This leg¡¯s intuitive thought control appears to work as well without nerve redirection surgery and does not require implants to be placed into the body. By not limiting our potential users to those with surgery or implants, we have the ability to help many more of the 1 million people in the U.S. with leg amputations.¹¡±

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Seven lower-limb amputees participated in RIC¡¯s randomized, clinical trial, which was the first of its kind.

When nerves instruct muscles to contract, these contractions generate tiny electric signals, called electromyographic (EMG) signals. An advanced computer program at RIC analyzes these EMG signals from sensors on the robotic leg. The program instantaneously decodes the type of movement the user is trying to perform, then sends those commands simultaneously to the robotic leg¡¯s motorized knee and ankle to produce coordinated movements.

Combining muscle signals with robotic sensors not only maximizes the system¡¯s ¡°intuition,¡± it does so without invasive surgery or implants. As a result, more amputees than ever before could have access to a bionic leg.

With support from both the US Army¡¯s Congressionally Directed Medical Research Program and the National Institutes of Health, RIC is working to provide at-home bionic leg testing for members of the military and the general public in the next three to four years. 

Karpowicz, who creates large-scale sculptures of granite and steel in his Chicago studio, appreciates how the leg could change his life ¨C and how it already has.

¡°Participating in this RIC study allows me to help advance scientific knowledge and preview the way of the future,¡± said Karpowicz. ¡°This bionic leg lets me move naturally, like I did before my amputation. For the first time in more than 30 years, I can experience my environment without thinking about which movement I want to make, because this leg does the thinking for me.¡±

¹K. Ziegler-Graham, ¡°Estimating the Prevalence of Limb Loss in the United States: 2005 to 2050,¡± Arch Phys Med Reabil, vol. 89, pp. 422-429, 2008.