Bionic leg could become a reality

Daniswicz, a sophomore at Northwestern University who lost her lower leg to bone cancer, is training the computer to recognize slight movements in her thigh so she can eventually be fitted with a “bionic” leg — a robotic prosthesis she would control with her own nerves and muscles. We’re really integrating the machine with the person,” said Levi Hargrove, a research scientist at the Rehabilitation Institute of Chicago’s Center for Bionic Medicine who is leading the project.

Daniswicz is part of a clinical trial sponsored by the United States Army that is using electromyography — electrical signals produced by muscles — and pattern recognition computer software to control a new generation of robotic limbs.

Electrodes attached to nine different muscles in the thigh act as antennas, picking up electrical signals sent from the nerves to the muscles. These signals are fired in a specific pattern depending on how a person intends to move.

With a bit of training, the computer can learn a person’s signal pattern for when they want to bend a knee or flex an ankle and it makes the virtual reality avatar move.

“The way most prosthetics work now is you have mechanical sensors. You have to push and interact with them,” Hargrove said. “With this, you measure the actual neural intent and have that tell the motor what to do.” Researchers at the institute have already developed prosthetic arms directed by nerve impulses. But a robotic leg would give lower limb amputees a new kind of freedom, allowing them to climb stairs more safely and with more natural motion.

Daniswicz has been training her computer avatar since January and she can now instruct it to bend and straighten its knee, and flex and straighten its ankle, just by making slight movements in her thigh muscles.

“Hailey has taught the computer what to do, and now, whenever she does it, it listens, interprets and makes the leg on the virtual reality avatar move,” Hargrove said.

The team had expected patients to be able to operate the knee joint, but were surprised they could control the ankle without needing surgery, Hargrove and colleagues reported this week in the Journal of the American Medical Association.