After losing his lower leg in a motorcycle accident four years ago, 32-year-old Zac Vawter has undergone experimental surgery to become the recipient of the world’s first thought-controlled bionic leg. Developed at the Rehabilitation Institute of Chicago (RIC), the groundbreaking bionic limb decodes neural signals from redirected nerves in Vawter’s upper leg to enable him to have improved, intuitive control over his movement.
Seattle-based software engineer Vawter explained in a statement that the bionic leg “is a big improvement compared to my regular prosthetic leg,” adding that “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.” He continued to Bloomberg “[I] just walk like I would normally walk. It’s not special training or buttons or tricks.”
It’s a sequence that much of us take for granted—we wish to interact with our environment in a given way, we think about an action, and our limbs perform that action. The procedure developed by RIC and Northwestern University to simulate those behaviors with a prosthetic is really quite remarkable. Shortly after his accident in 2009, Vawter underwent targeted muscle reinnervation surgery to redirect nerves from damaged muscle in his amputated lower leg to healthy hamstring muscle above his knee.
From there, RIC explains:
“…the redirected nerves instruct the muscles to contract [and] sensors on the patient’s leg detect tiny electrical signals from the muscles. A specially-designed computer program analyzes 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 to the robotic leg. Using muscle signals, instead of robotic sensors, makes the system safer and more intuitive.”
While it’s certainly a complex process, the end result reportedly allows for smooth and seamless movement and a prosthetic leg that “learns and performs activities unprecedented for any leg amputee,” according to Dr. Levi Hargrove, lead researcher on the project.
The bionic leg is not the world’s first bionic limb—bionic arms have been developed by Johns Hopkins University, RIC and others—but it is the first bionic leg to be controlled by thought alone, with no buttons or additional triggers involved. Moreover, the bionic leg is safer than other robotic legs—according to Bloomberg “The rate of errors, including the risk of falls, was shaved to just 1.8 percent with the new device, down from 12.9 percent with the standard robotic leg prosthesis.”
An $8 million grant from the US Army’s Telemedicine and Advanced Technology Research Center (TATRC) funded the development of the bionic leg, with the aim that prosthesis might be available for in-home testing by some of the 1,200 lower leg amputees who have served in the military, and some of the one million US civilians who might benefit within the next three to five years.