While similar technology has allowed amputees to control bionic arms with their thoughts, 32-year-old Zac Vawter is the first amputee with a thought-controlled bionic leg, the researchers said.
The robotic leg-which decodes the electrical signals traveling through Vawter's remaining leg muscle-not only interprets the patient's intended movements, but also has a motor in the knee and ankle, which helps him push himself up stairs and perform other activities, Discovery News reported.
Using his robotic leg, Vawter can seamlessly transition between sitting, walking and ascending and descending stairs and ramps.
When a person thinks about moving their lower limb, a signal from the brain is sent down the spinal cord and through nerves to muscles in the leg.
But when an amputation occurs, nerve signals that would have gone to the knee or ankle, for instance, aren't able to deliver their message to muscle.
To overcome this problem, the researchers first performed a surgery on Vawter to redirect his nerve signals, so that signals that would have gone to the lower leg instead go to the healthy hamstring muscle, in the top part of his leg.
Then, electrodes were placed on his leg to detect electrical signals from the muscle contractions.
A computer program decodes the signals to interpret the patient's movement. Mechanical sensors on the robotic leg (including an accelerometer and a gyroscope) also collect data to help with control.
While more needs to be done to improve the technology, the researchers hope to have it available in clinics within five years.
The study is published in the New England Journal of Medicine.