'Smart' prosthetics monitor for infection, stress

October 06, 2017 // By Rich Pell
Scientists at the Office of Naval Research (Arlington, VA) have developed a new "smart" prosthetic leg that is fitted with sensors to monitor for infection and stress.

Called the Monitoring OsseoIntegrated Prostheses (MOIP), the artificial limb is equipped with specially designed sensors to monitor walking gait, alert wearers of prosthetic wear, and warn of potential infection risk. The prosthesis was specifically designed to address issues frequently encountered with traditional leg prosthetics, which can be painful to wear and prone to causing infection.

"This new class of intelligent prostheses could potentially have a profound impact on warfighters with limb loss," says Dr. Liming Salvino, a program officer in ONR's Warfighter Performance Department. "MOIP not only can improve quality of life, but also usher in the next generation of prosthetic limbs."

Traditional leg prosthetics typically fit amputees via a socket that encloses the residual limb, exerting pressure on the limb's soft tissue and causing pain and chafing, sores and blisters, and possible infection. Such prosthetics often require frequent adjustment - which is both time consuming and costly - and amputees often choose a wheelchair as a preferable alternative.

The MOIP limb alternative instead features a titanium fixture that is surgically implanted into the thigh bone (or femur) of the amputee. The bone grows - or "osseointegrates" - at the connection point, leaving only a small metallic connector protruding from the remaining leg, from which an artificial limb can be attached or detached at will.

While this approach addresses many of the pain and motion issues associated with traditional artificial limbs, infection risk remains from the metal connector that protrudes from the residual limb. To address the issue, say the researchers, they are developing both electrochemical sense-and-respond approaches and "smart" skin technologies.

These include a bio-compatible sensor array embedded within an amputee's residual limb, as well as additional sensors on the MOIP prosthetic itself. According to the ONR scientists, the biocompatible sensor array is the first technology of its kind, and tracks changes in body temperature and pH balance - both indicators of possible infection.

The array also monitors how