Late last year we told you about Zac Vawter, recipient of the first mind-controlled prosthetic leg. Now, after extensive testing and a series of important tweaks, the device is ready for actual clinical applications. Your cyborg future awaits.

Until now, the only thought-controlled prosthetics available to amputees were bionic arms. But the new leg will soon be available to the more than one million Americans with leg amputations. It was developed by lead scientist Levi Hargrove at the Rehabilitation Institute of Chicago.

The leg’s movements are controlled by a person’s original nerves, which are redirected to a small area of the thigh muscle. When these redirected nerves instruct the muscles to contract, sensors on the amputee’s leg detect tiny electrical signals from the muscles. These signals are then analyzed by a specially-designed computer program which instantaneously decodes the type of movement the patient is trying to perform (like moving the knee or ankle). It then sends these commands to the robotic leg.


So, by using muscle signals (rather than robotic sensors), the system is more intuitive, robust, and safer.

“This new bionic leg features incredibly intelligent engineering,” said Hargrove in a RIC release. “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.” The entire thing weighs about 10 pounds (4.5 kg).


The leg is a vast improvement over legs that use only robotic sensors and remote controls — devices that don’t allow for intuitive thought control of the prosthetic.

“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.”


Of course, the next step (aside from making the leg more responsive and capable of fine motor movements), will be to endow it with the sense of touch.

Read the entire study at the New England Journal of Medicine: “Robotic Leg Control with EMG Decoding in an Amputee with Nerve Transfers.”


Images: RIC.