The Robotics, Optimization and Assistive Mobility (ROAM) lab in Notre Dame’s College of Engineering tested control mechanisms for powered lower-limb prostheses that would allow users to control ankle movement, giving them a sense of volition while improving comfort and safety.
The research team, led by ROAM’s director, Patrick Wensing, PhD, included Adam Waugh, CPO, with Transcend Orthotics and Prosthetics’ South Bend, Indiana, facility.
The team tested three control mechanisms with Laura Light, who was born with fibular hemimelia and has used a prosthesis since she was 18 months old.
Tests included volitional control, based on myoelectric sensors that allowed Light to control the rollover movement of the ankle, and autonomous control that automatically boosts ankle roll based on preprogrammed angles similar to available motorized prostheses. The third controller combined the advantages of the other two.
Light walked on the treadmill for two minutes with each system while her gait was recorded to evaluate how natural it appeared. Data was also collected to determine how well the myoelectric sensors picked up and responded to her muscle signals.
“This has gone better than we imagined,” Wensing said after the experiment. “There are lots of myoelectric solutions out there for prosthetic hands. But there are less for legs because you have to avoid falls to ensure safety.”
Light heard about Wensing’s research from a news story and reached out by email. She said she was glad to volunteer for testing even though it could be years before the now-bulky technology shrinks and reaches the commercial market.
“The foot I’m currently wearing is a good foot, but it does have some limitations as far as the natural rollover, because the ankle’s pretty much fixed,” Light said. “This foot, I think, will be huge because it’ll adjust to the terrain that I’m on. I can do things like hiking and do it more naturally and be a little bit less nervous about doing it.”
Other advantages Light discovered during the tests included standing on tiptoes, walking backward, and being able to rotate the foot all the way down to the floor while sitting.
“To me, that’s huge, because I’ve never been able to sit with my foot sitting down,” she said. “It’s always taking up so much room, which is frustrating when you’re in a tight space. Also, just having a natural gait would save my hip and ultimately my lower back.”
“We want these devices that people are going to wear to get better over time, and people to get better at using them, and we’re trying to tease out how we can accelerate that process,” said Wensing.
Besides the lower-limb prosthetic device, Wensing’s ROAM lab also works on four-legged robots and lower-body exoskeleton systems. His exoskeleton work aims to use more conventional sensors that would allow people with spinal cord or stroke injuries to improve control of their gait.
“I am very excited about the potential,” said Chandan Sen, PhD, a specialist in wound healing at the Indiana University School of Medicine. “It could be transformative in ensuring the long-term health of the residual limb of amputees. This is critical for the overall well-being of such patients.”
“We were excited for the opportunity to offer our support and assist with this research,” Waugh said. “Every patient who has benefited from any number of complex devices [researchers] to thank for their dedication to the advancement of the technology used within the prosthetic industry.
Waugh said allowing patients to move their own foot more actively would open the door to new activities and help with fatigue. Light agreed, noting that she had torn up the knee of her other leg by overcompensating through the years.
“This will likely increase blood flow to the leg, decrease volume fluctuations with use, and improve sound-side limb health overall,” Waugh said. “While the research is still in its early stages, I believe it will improve the lives of many people in the future.”
Editor’s note: This story was adapted from materials provided by Notre Dame.
