29th September 2013

World's first mind-controlled bionic leg

This week, the science of bionics helped over 1 million Americans with leg amputations take a giant step forward.

The Rehabilitation Institute of Chicago (RIC) has revealed clinical applications for the first thought-controlled bionic leg in New England Journal of Medicine. This innovative technology represents a significant milestone in the rapidly growing field of bionics. Until now, only thought-controlled bionic arms were available to amputees.

Levi Hargrove, PhD, the lead scientist of this research at RIC's Center for Bionic Medicine, developed a system to use neural signals to safely improve limb control of a bionic leg.

"This new bionic leg features incredibly intelligent engineering," said Hargrove. "It learns and performs activities unprecedented for any leg amputee – including seamless transitions between sitting, walking, ascending and descending stairs and ramps and repositioning the leg while seated."

This method improves upon prosthetic legs that only use robotic sensors and remote controls and do not allow for intuitive thought control of the prosthetic.

The case study focuses on Zac Vawter, an amputee who had targeted muscle reinnervation surgery 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. Specially-designed computer software analyses these signals and data from sensors in the robotic leg. It instantaneously decodes the type of movement the patient is trying to perform and then sends those commands down to the robotic leg. Using muscle signals, instead of robotic sensors, makes the system safer and more intuitive.

"The bionic leg is a big improvement compared to my regular prosthetic leg,” said Vawter. “It responds quickly and more appropriately, allowing me to interact with my environment in a way that is similar to how I moved before my amputation. For the first time since my injury, the bionic leg allows me to seamlessly walk up and down stairs and even reposition the prosthetic by thinking about the movement I want to perform. This is a huge milestone for me and for all leg amputees."

The US Army’s Telemedicine and Advanced Technology Research Center (TATRC) funded the study with an $8 million grant to improve the control of robotic leg prostheses by adding neural information to the control system. Due to this unusually large grant, RIC was able to accomplish these breakthrough innovations in only four years. It is unknown what the eventual cost of supplying these bionic legs to patients will be. However, TATRC and RIC intend to make them available for in-home testing for both military and civilian populations within the next three to five years.

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