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A team of researchers at the Rehabilitation Institute of Chicago (RIC) has revealed clinical applications for the world’s first thought-controlled bionic leg—a significant milestone for lower limb amputees in the rapidly growing field of bionics. RIC's Center for Bionic Medicine developed a system to use neural signals to safely improve limb control of a bionic leg. The leg features intelligent engineering, meaning that it can learn and perform activities including seamless transitions between sitting, walking, ascending, and descending stairs and ramps and repositioning the leg while seated. This vastly improves upon prosthetic legs that only use robotic sensors and remote controls and do not allow for intuitive thought control of the prosthetic, the researchers say.

The case study, detailed in the New England Journal of Medicine, focuses on RIC research subject Zac Vawter, a lower-limb amputee who underwent targeted muscle reinnervation surgery, a procedure developed at RIC and Northwestern University in 2009, to redirect nerves from damaged muscle in his amputated limb to healthy hamstring muscle above his knee. When the redirected nerves instruct the muscles to contract, sensors on the patient’s leg detect tiny electrical signals from the muscles. A specially-designed computer program analyzes the signals and data from sensors in the leg, instantly decodes the type of movement being attempted, and sends commands to the robotic leg. Using muscle signals, instead of robotic sensors, makes the system safer and more intuitive.

The US Army's Telemedicine and Advanced Technology Research Center (TATRC) funded the RIC study with an $8 million grant to improve the control of advanced robotic leg prostheses by adding neural information to the control system. Due to the size of the grant, RIC was able to accomplish these breakthrough innovations in just four years. The partnership aims to make bionic legs available for in-home testing for both the military and civilian populations within the next five years.

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