Researchers have shown a combination of special surgery and a bionic limb can enhance walking speed in some amputees by 40 percent, within the range of able-bodied individuals.

MIT professor Hugh Herr - himself an amputee - worked with colleagues to develop a technique to build a neuroprosthetic interface during or after amputation to control prosthetic limbs and provide feedback from the bionic prosthesis to the brain.

"We're at a point in history where the convergence of surgical and regenerative technologies with novel electromechanical interfaces is going to lead to a step function in clinical care for so many patients around the world," Herr told reporters before his team's paper was published in the journal Nature Medicine today.

The technique relies on a surgical neuroprosthetic interface combined with a biomechanical prosthetic limb.

The former is created surgically by connecting agonist-antagonist muscle pairs - which together move a joint one way or another - with sensing electrodes. Surgically built within the muscle and tissue left after amputation - technically known as the residuum - the muscle pairs control the prosthetic limb, but also convey feedback about the position and movement of the artificial appendage. The researchers said the surgery could be performed during or sometime after an amputation procedure.

"When the participants think, those actions are recorded from the dynamics of the muscles and that's reflected in the movements - or the forces or torques - in the prosthesis. And then when the prosthesis actually moves, the persons feel that movement as a natural proprioceptive sensation," Herr said.

Only around 18 percent of the muscle tissue is needed to provide natural proprioceptive sensations, the study found.

The research involved a clinical trial of 14 participants with below-the-knee amputation of one leg. All used a bionic prosthetic leg, but only seven also had the neuroprosthetic interface procedure.

The study found that the walking speed of participants with the neuroprosthetic interface was on average 41 percent greater than those without. Walking performance also improved in real-world environments including slopes, stairs, and obstructed pathways, the research found.

Known as the agonist-antagonist myoneural interface (AMI), the procedure has been performed on about 60 patients, Herr said, and is "well framed." He said he expected it would be five years before a commercial product is available for interfaces to the bionic prosthesis. "So it won't be very long until this is available for clinical care." ®

https://www.theregister.com//2024/07/02/bionic_leg_interface_mit/