A team of researchers led by a Worcester Polytechnic Institute (WPI) professor have teamed up to develop wireless sensors to improve the performance of prosthetics for individuals with upper limb amputations.
According to the Amputee Coalition, there are nearly two million people living with limb loss in the United States, and approximately 185,000 amputations occur in the United States annually.
Existing wired sensors detect the electrical activity of remnant muscle tissue in the arm—in a manner similar to how a cardiologist detects the electrocardiogram activity of a patient’s heart—and use this signal to control the movement of a hand-wrist prosthesis. Since most of the muscles that control the hand actually reside within the forearm, this technique is successful for many people with limb-absence.
“This wireless sensor technology will have a major impact for individuals with limb absence and allow them to control their hand and wrist prostheses,” said Ted Clancy, professor of electrical and computer engineering at WPI, in a statement.
Clancy has been collaborating with consultant Debra Latour on prosthetics projects for five years. Latour, an assistant professor of occupational therapy in the Division of Occupational Therapy program at Western New England University, was born without a right hand. The other key member of the research team is Todd Farrell, director of research at Liberating Technologies, Inc. (LTI), Holliston, Mass.
In making the transition from wired to wireless sensors, researchers had to consider the structure of the overall prosthetic device. Historically, Clancy said, artificial limbs are attached to the body with a molded plastic socket that is form-fit onto the natural tissue. However, he noted, there is “recent movement in the field to move away from (a socket) and instead use what’s called osseointegration.”
Under osseointegration, a prosthesis would be attached to a metal rod that has been surgically implanted into the bone. “So you no longer need a socket and have a much more rigid attachment, which is tremendously important,” said Clancy. “But now all of these wired sensors you would use to control the device have nowhere to go.”
In effect, Clancy said, wires would be hanging loose and could potentially become caught on objects and pose other problems.
To address the challenge, Clancy and his colleagues plan to place silver dollar-sized wireless sensors on remnant arm muscle locations. Clancy said they plan to start with two sensors, which could expand to up to eight or more sensors primarily for better control.
“The idea is to create a standardized system that is more space-efficient that could be readily adapted onto various products,” said Clancy.
Xinming Huang, professor of electrical and computer engineering at WPI, is focused on programming the sensors in order to optimize battery power. “We are looking for devices that are stingy in battery power so that (sensors) can be worn throughout the day,” said Huang.
Once the technology has been tested on amputees, Clancy and the team at LTI plan to have the technology evaluated commercially.
This research builds on previous studies conducted by Clancy and colleagues. Two years ago, the WPI research team collaborated with LTI to develop a more versatile hand-wrist prosthesis that would give users the ability to move more naturally by enabling a hand and wrist to work simultaneously.