A press release from Rehabilitation Institute of Chicago (RIC) highlights how bionics for leg amputations has helped one million Americans walk again. The release also revealed clinical applications for the world’s first thought-controlled bionic leg. This technological innovation represents a significant milestone in the field of bionics. Until now, only thought-controlled arms were available to amputees.

Levi Hargrove, PhD, the lead scientist of this research, developed a system to use neural signals to improve limb control of bionic legs.

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

The case study focused on RIC research subject Zac Vawter, a lower limb amputee who underwent targeted muscle reintervention surgery in 2009. This procedure was developed by RIC and Northwestern University. Nerves were redirected from damaged muscle in his amputated lib to a healthy hamstring muscle above his knee. Once the redirected nerves instruct the muscle to contract, sensors on the leg detect the tiny electrical signals from the muscle. A computer program analyzes those signals and data from the sensors in the robotic leg. At the same time, it decodes the type of movement the person is trying to perform and then sends a command to the robotic leg. The use of muscle signal instead of robotic sensors makes the system safer and much more intuitive.

“The bionic leg is a big improvement compared to my regular prosthetic leg,” stated Vawter. “The bionic leg 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 this study with an $8 million grant to improve the control of advanced robotic leg prosthetics by adding neural information to their control system.

The world’s first thought-controlled bionic leg is described in greater detail in the current issue of the New England Journal of Medicine.