Navy developing ‘smart’ prosthesis to relieve pain, infection

The U.S. Office of Naval Research has partnered with Walter Reed National Military Medical Center, the Naval Research Laboratory and multiple universities to develop a “smart leg,” which will be equipped with sensors to monitor walking gait, as well as alert users of wear, tear and infection risk.

According to a press release, the goal of the partnership is to provide better options for veterans who use prosthetics, but often experience pain and infection in their residual limb. The researchers call their smart leg the monitoring osseointegrated prostheses (MOIP).

“This new class of intelligent prostheses could potentially have a profound impact on warfighters with limb loss,” Liming Salvino, PhD, MS, a program officer in the Office of Naval Research warfighter performance department, said in the release. “MOIP not only can improve quality of life, but also usher in the next generation of prosthetic limbs.”

As an osseointegrated prosthesis, MOIP uses a titanium fixture implanted into the femur. According to the researchers, the bone grows at the connection point with the implant, and leaves a small metallic connector that protrudes from the residual limb. The prosthesis can be attached or detached at will. As a result, patients with MOIP could experience less pain, a more fluid gait and a more stable, better-fitting limb, according to the release.

However, because of the metal protrusion, there is a greater risk for infection. To address this, researchers are developing electrochemical “sense-and-respond” and “smart skin” technologies. This includes a bio-compatible sensor array implanted within an amputee’s residual limb, combined with additional sensors on the osseointegrated prostheses. According to the researchers, the array tracks changes in body temperature and pH balance —symptoms of possible infection. It also monitors how well the bone and prosthetic limb fuse together and heal, allowing practitioners to significantly decrease recuperation time for patients.

According to the release, researchers have created a MOIP sensor array prototype, using osseointegrated prosthetics and synthetic bone models at the University of Michigan. They hope to have a new, improved model ready for clinical trials early next year.

“One game-changing application of this technology would be as a tool to inform doctors when prosthetics can be safely loaded after surgery, leading to more accurate determination of when patients are ready for physical therapy after receiving a new prosthetic,” Jerome Lynch, PhD, MS, a University of Michigan engineering professor who is overseeing the sensor array’s development, said in the release. “Right now, doctors study X-ray images of a limb when making that determination.”


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