After a motorcycle accident in 2009 that resulted in the amputation of his knee and lower leg, it seemed unlikely that Zac Vawter would ever be walking up stairs and down a ramp again, not to mention being able to kick a football. However, at age 32, Vawter has become the first person to control a robotic leg with his mind.
The science of bionics has already helped more than one million Americans with amputations take a giant step forward, but innovative new technology is now making a major leap.
Previously only thought-controlled bionic arms were available to amputees, but the Rehabilitation Institute of Chicago has developed a system that utilizes neural signals to improve limb control of a bionic leg, improving on prosthetic legs that typically relied on robotic sensors and remote controls and that have not allowed for intuitive thought control of the prosthesis.
“This new bionic leg features incredibly intelligent engineering,” said Levi Hargrove, PhD, the lead research of the project at RIC’s Center for Bionic Medicine in a statement. “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 builds on past research which showed that paralyzed people could move robotic arms using their thoughts, while other studies showed that able-bodied people could walk utilizing robotic legs controlled by their brains. This research takes things a step further as it uses muscle signals to amplify messages sent by the brain when the person intends to move.
In this case study, Vawter underwent targeted muscle reinnervation surgery – a procedure developed at RIC and Northwestern University – in 2009 that redirected nerves from his damaged muscles in the amputated limb to healthy hamstring muscle above his knee.
These redirected nerves instruct the muscles to contract, while sensors on Vawter’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 is then able to instantaneously decode the types of movement a patient is trying to make and relays those commands to the robotic leg.
By using muscles signals instead of robotic sensors the system is reportedly safer and, more importantly, more intuitive.
“The bionic leg is a big improvement compared to my regular prosthetic leg,” said 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.”
This study was funded by the US Army’s Telemedicine and Advanced Technology Research Center (TATRC), which included an $8 million grant to improve the control of advanced robotic leg prostheses by adding neural information to the control system. It was this grant which was able to help create this breakthrough.
The research findings could help the more than 1,200 leg amputees in the United States, who are recently injured servicemen and women.
“We are pleased to partner with the RIC Center for Bionic Medicine in the development of user intent controlled bionic limbs,” said Col. John Scherer, director of the Clinical and Rehabilitative Medicine Program at the US Army Medical Research and Materiel Command. “We appreciate the opportunity to sponsor this life-changing effort to provide military amputees with as much physical functionality as possible, as soon as possible.”
The researchers hope that other people with missing limbs will be able to utilize this technology within the next three to five years. A report of the findings of this research were published in The New England Journal of Medicine.
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