By Chris Casey | University Communications
AURORA, Colo. - When people lose an arm or a leg, the nerves that control the limbs continue sending signals to the muscles left behind. Decoding those signals to articulate natural movement in a sophisticated prosthetic is the goal of research being conducted by Richard Weir, PhD, associate research professor.
Weir's work in the College of Engineering and Applied Science, Department of Bioengineering, is focused on developing a prosthetic hand and fingers that provide a full range of movement as well as a sense of touch for persons with arm amputations.
The key is the development of Implantable MyoElectric Sensors (IMES), rice-sized capsules that will be implanted into muscles in the forearm. The sensors wirelessly transform muscle signals into signals that can be used to control hand and finger movement. The goal is to give the prosthesis the full 22 degrees of movement articulated in a human hand and wrist.
Current technology provides a control interface that only allows two commands to be delivered to the prosthetic hand -- to open and close, Weir said.
After a decade of research on this formidable challenge, Weir and his collaborators -- the Alfred Mann Foundation, Illinois Institute of Technology and Sigenics, Inc. -- are on the cusp of seeing IMES technology reinnervate muscle in amputees, and potentially transform their long-term lives. "It's pretty exciting," Weir said. "If we can go into each of the 18 muscles in the forearm with sensors that give 18 control signals rather than the two we have at the moment, that would advance the science."
The first version of the IMES, in a trial led by the Alfred Mann Foundation, will be tested this spring at Walter Reed Army Medical Center in Bethesda, Md.
"If they work well, this will completely change the way the devices are controlled," Weir said. "We'll be able to do much more than just the open-close type of approach."
The goal is to create a prosthesis that an amputee can control for the remainder of his or her life. So far in lab settings, Weir said, neurally controlled prosthetics are functional for two to three years. He pointed out that operating such a prosthesis in day-to-day life for an extended period of time "is a much different kettle of fish."
Weir previously worked with a team at the Rehabilitation Institute of Chicago on a neurally controlled hand, which was part of a project to develop a physiological replacement for the human arm. The Defense Advanced Research Projects Agency (DARPA) initiative assigned different teams to various parts of the arm, such as the elbow, shoulder and hand. Weir was the architect of the hand, and the team's prototype was featured in a 2010 National Geographic cover story on advances in prosthetics.
Ultimately, DARPA re-oriented the project to focus on developing a brain-machine interface to help patients with high-level spinal cord injuries.
Weir opted to continue with the neural and muscle interfaces in the arm because a brain-machine interface has a risk-benefit ratio that's not necessarily justified for people with amputations. Also, he said, amputees already have been through trauma and are resistant to more invasive surgery that is required for brain machine interfaces.
The IMES research is being supported by a grant from the National Institutes of Health from the National Institute on Bioimaging and Bioengineering.
Assisting in Weir's research are students from CU Denver | Anschutz Medical Campus's newly formed Bioengineering Department and the Mechanical Engineering department as well as students from CU-Boulder and the Colorado School of Mines.
"Hopefully, we'll get to the point where we're doing an implantation here in Denver," he said.
Weir comes from a family of medical and engineering professionals. His father was the professor of medicine at Trinity College Dublin and an uncle ran an engineering company in London. Weir's twin sister lost a hand in a lawn-mower accident when she was 5.
"It's probably all of that" that contributed to his interest in arm prosthetics, he said.
(Photo: From left, Jacob Segil, a third-year doctoral student in Mechanical Engineering at CU-Boulder, and Richard Weir, Phd, associate research professor in the Department of Bioengineering at the University of Colorado Denver | Anschutz Medical Campus, work on advanced hand and finger prosthetics in a lab at the Anschutz Medical Campus.)