Bionic leg makes walking faster and easier for amputees, trial shows
A brain-controlled bionic leg ensures that people with an amputation can walk faster and take stairs and obstacles more easily, according to a groundbreaking study.
The device allows the wearer to bend, point and rotate the prosthetic foot using only their thoughts. This resulted in a more natural gait, improved stability on stairs and uneven terrain, and a 41% increase in speed compared to a traditional prosthesis. The bionic leg works by measuring activity in the patient’s remaining leg muscles and uses those signals to control an electrically powered ankle.
“No one has been able to demonstrate this level of brain control that produces a natural gait, where the human nervous system controls the movement, rather than a robot control algorithm,” said Prof. Hugh Herr, co-director of the K Lisa Yang. Center for Bionics at the Massachusetts Institute of Technology (MIT) and the senior author of the study.
“Not only can they walk on a flat surface, but they can also walk or dance with it as they have complete control over their movements,” he added.
Herr himself has undergone two leg amputations. He lost both legs to severe frostbite when he was caught in a snowstorm while rock climbing in 1982. Although his first amputations were decades ago, he hopes to undergo revision surgery in order to benefit from a similar pair of bionic legs in the future.
“I’m thinking about doing that for both of my legs in the next few years,” he said.
In the process, published in Naturopathyseven patients received the bionic leg and compared to seven patients with traditional amputations. Patients reported less pain and less muscle atrophy after the groundbreaking surgery required to control the bionic leg, which preserves the natural connections between leg muscles. The patients were also more likely to feel that their prosthetic limb was part of their body.
“(With) a prosthesis that is not controlled by the brain, patients view it as a tool, like a carpenter would view his hammer,” Mr. said. “When the person can directly control and feel the movement of the prosthesis, it really becomes part of the person’s anatomy. That can be quite emotional for the subjects undergoing this procedure.”
The device requires patients to undergo a new form of amputation called below-the-knee amputation agonist-antagonist myoneural interface (AMI)The surgery aims to preserve two pairs of muscle connections, which in a healthy leg are used to flex and point the foot and tilt the foot from side to side.
During a conventional amputation these connections are severed, but during an AMI surgery the remaining muscles are reconnected. This means that even though the patient’s own leg is gone, their muscle contractions can be monitored and translated using an algorithm into movements of the electrically powered ankle.
The surgery can be performed during a primary amputation, or the muscles can be reconnected after the initial amputation as part of a revision procedure.
Dr. Sigrid Dupan, a prosthetics expert at University College Dublin, who was not involved in the research, said it was exciting to see progress being made in the field of prosthetics, taking advantage of the inherent capabilities of the body and brain instead of increasingly complex technology.
“The research shows impressive results for walking speed, but I think the results regarding how people can cope with different terrain will have a greater impact on people’s lives,” she said. “I look forward to seeing how this research develops and would like to see wider implementation of this surgical approach.”
The MIT team hopes to have a commercial version of the leg available within five years, so that more patients can benefit. “It will be a game changer in clinical care for so many patients around the world,” Mr. said. “We’re very passionate about making this technology available to the patients who need it.”