New bionic leg moves with thoughts and reflexes

Lee Majors in the Six Million Dollar Man - Newsreel
The concept of bionic limbs entered popular culture in the 1970s series 'The Six Million Dollar Man' starring Lee Majors. | Photo: Scene from The Six Million Dollar Man.

A new type of bionic limb controlled by the brain and spinal cord is giving speed and balance back to amputees.

A study report published in Nature Medicine said some participants in clinical trials were able to walk roughly as fast as people without amputations using the robotic leg.

“The bionic limb uses a computer interface that amplifies nerve signals from muscles in the remaining part of the leg and allows the wearer to move the prosthesis with their own thoughts and natural reflexes,” the report said.

“In a clinical trial involving 14 people, participants with this interface were able to walk 41 percent faster than were those with standard robotic legs.

“They also had better balance and ability to change their speed, climb stairs and step over obstacles.”

Study co-author Hugh Herr from Massachusetts Institute of Technology in Cambridge said the limb was made of titanium, silicone and electromechanical components but felt natural and moved naturally “without even conscious thought”.

Most existing bionic artificial limbs rely on “preset algorithms” to drive movement and can automatically switch between predefined modes for various walking conditions, the Nature report says.

Professor Herr and his colleagues developed an interface that controls the robotic limb with signals from the nerves and muscles that remain after amputation.

“It gives the user such a high flexibility that is much closer to how the biological leg works,” Tommaso Lenzi, a biomedical engineer at the University of Utah in Salt Lake City, told Nature.

“People who have an amputation want to feel in control of their limbs. They want to feel the limb to be part of their body.”

The full report is on the Nature website.