Researchers have recently developed a type of prosthetic leg that can connect to the human nervous system, allowing it to function just like a natural limb.
Since birth, Amy Pietrafitta has learned to walk seven times. She was once a regular child like her peers, but in 2018, an industrial fire severely burned her left leg, resulting in its amputation.
Prosthetic leg tested with brain signal control interface at MIT. (Source: CNN)
Since then, her daily activities, such as running, rowing, and walking, have been reliant on various prosthetic legs. She has also attempted to take her first steps with many different types of prosthetics.
However, when she tried on a newly released bionic prosthetic leg, she immediately felt as if she had never lost her left leg. The 47-year-old woman from Massachusetts told CNN, “I feel like I have never had my leg amputated. This is the happiest moment of my life.”
Amy is part of a research project exploring a new neuroprosthetic technique at the Massachusetts Institute of Technology (MIT). Her left leg was amputated using a method known as AMI, which preserves the neural signals exchanged between the muscles of the amputated leg and the brain.
This neuroprosthetic technique uses highly connected neural points between the amputated leg and the prosthetic to link the prosthetic to the brain. This connection enables the sensors in the prosthetic to sense position and movement, relaying information back to the user, and allowing them to regain a natural sensation: the brain perceives their self-movement and spatial orientation.
A study on the neuroprosthetic technique, published in the medical journal Nature Medicine in early July this year, indicates that volunteers who underwent leg amputation using the AMI technique were able to walk 41% faster while using the new technology-equipped prosthetic. This speed is comparable to that of a normal person in daily activities. Moreover, the study found that users could operate the bionic leg even with just 18% of their natural sensory capacity.
Dr. Hugh Herr, the lead researcher and author of the study, who also lost both legs in a snowstorm accident, shared his insights about the new device: “It feels very natural. It’s as if these legs are made of bone and flesh. This is likely because the brain does not recognize that the natural leg has been amputated, as the signals are still transmitted to the target normally.”
Hugh added that this is the first bionic leg that can be entirely controlled by the human nervous system, enabling amputees to walk normally. He initiated the project after noticing a trend in creating prosthetics controlled by robotic algorithms rather than the human nervous system.
Dr. Hugh Herr, a researcher in the project, is also an amputee. (Source: CNN).
“We want to recreate the amputated parts of the human body. We want to create something that provides those out there with what they have always sought, rather than just beautiful devices controlled by robots,” he stated.
To test the functionality of the new prosthetic, 14 volunteers were divided into two groups using this device. Among them, half underwent AMI surgery, while the other half did not.
According to Amy and Dr. Matthew J. Carty, the lead surgeon and co-author of this study, the results show that users who had the AMI technique for their leg amputation had better spatial awareness, including navigating slopes, stairs, pathways with obstacles, and even uneven terrains, created in the style of the television show “American Ninja Warrior” — where participants must overcome various obstacles on their way to victory.
Amy also noted that the new technology allows users to adjust their speed, something not possible with traditional prosthetics. It helps users avoid the hassle of changing prosthetics, providing a more natural feeling. “The prosthetic feels very natural… At that moment, I felt ready to run. I just wanted to let go of the assistive device and run immediately,” Amy shared.
Typically, prosthetic users struggle to achieve a gait similar to that of non-amputees. According to Amy, the bionic prosthetic would help address this issue. Thus, the new prosthetic not only solves mobility challenges but also aids amputees in reintegrating into society. She said: “This means I can restart my life… I will be able to go out and live the way I want.”
According to a report by the U.S. Agency for Healthcare Quality Research published in 2018, approximately 1.9 million Americans are living with limb loss, a figure expected to double by 2050.
Hugh stated that his team aims to bring the neuro-signal-controlled prosthetic to market within the next five years. This would be great news for those unfortunate enough to lose their legs.
