A groundbreaking clinical trial has demonstrated that a brain-controlled bionic leg significantly improves mobility for individuals with amputations, allowing for more natural and efficient movement. The device enables users to control the prosthetic limb with their thoughts, leading to enhanced gait, improved stability, and a substantial increase in walking speed.
The bionic leg, developed by researchers at the Massachusetts Institute of Technology (MIT), works by interpreting signals from the patient’s residual leg muscles to control an electrically powered ankle. This allows the wearer to flex, point, and rotate the foot of the prosthetic using their thoughts alone, mimicking natural leg movements.
Enhanced Mobility and Control
The trial, published in Nature Medicine, involved seven patients who received the bionic leg and were compared to a control group of seven patients with traditional amputations. The results showed a 41% increase in walking speed among those using the bionic leg. Participants also reported improved stability when navigating stairs and uneven terrain.
"No one has been able to show this level of brain control that produces a natural gait, where the human’s nervous system is controlling the movement, not a robotic control algorithm," said Prof Hugh Herr, co-director of the K Lisa Yang Center for Bionics at MIT and the senior author of the study.
Agonist-Antagonist Myoneural Interface (AMI) Surgery
The bionic leg requires a novel below-the-knee amputation surgery called agonist-antagonist myoneural interface (AMI). Unlike conventional amputations where muscle connections are severed, AMI surgery preserves two pairs of muscle connections used to flex and point the foot and tilt the foot side to side. These reconnected muscles allow for monitoring of muscle contractions, which are then translated into movements of the prosthetic ankle via a sophisticated algorithm.
Patients who underwent the AMI surgery reported less pain and muscle atrophy, and were more likely to feel that the prosthetic limb was integrated as part of their body. "When the person can directly control and feel the movement of the prosthesis it becomes truly part of the person’s anatomy. That can be quite emotional for the subjects that undergo this procedure," Herr noted.
Expert Commentary and Future Directions
Dr. Sigrid Dupan, a prosthetics expert at University College Dublin, who was not involved in the study, praised the advance. "The study shows impressive results for the walking speed, but I think the results related to how people are able to cope with differences in terrain will have a more profound impact on people’s lives," she said.
The MIT team is optimistic about the future, aiming to make a commercial version of the bionic leg available within five years. "It’s going to lead to a step-change in clinical care for so many patients around the world," Herr stated. "We’re very passionate about getting this technology out to the patients who need it."
