A Worcester Polytechnic Institute (WPI) professor, a local prosthetics company, and an occupational therapist with limb absence have teamed up to develop wireless sensors to improve the performance of prosthetics for individuals with upper limb amputations.
“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.
Clancy is working with Todd Farrell, director of research at Liberating Technologies, Inc. (LTI) of Holliston, Mass., principal investigator on the grant, and Debra Latour, an assistant professor of occupational therapy in the Division of Occupational Therapy program at Western New England University. Latour, a consultant on the project, was born without a right hand. For this research, Clancy received a two-year, $400,000 subaward from LTI, which received funding from the Department of Defense.
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.
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 the osseointegration technique, 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.”