ARLINGTON, Va. — Traditional leg prosthetics enable amputees to maintain mobility and lead more active lives. But these prosthetics depend on soft limb tissue to function and can be painful to wear, resulting in awkward walking motion and possible skin infection.
To improve the options available to warfighters, the Office of Naval Research (ONR) is partnering with Walter Reed National Military Medical Center, the Naval Research Laboratory and several universities to develop a “smart” artificial leg — equipped with specially designed sensors to monitor walking gait, alert users to prosthetic wear and tear, and warn of potential infection risk.
It’s called the Monitoring OsseoIntegrated Prostheses, or MOIP.
“This new class of intelligent prostheses could potentially have a profound impact on warfighters with limb loss,” said 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.”
Leg prosthetics most commonly fit amputees’ residual limbs via a socket that encloses the limb like a wooden clog. Because the socket exerts pressure on the limb’s soft tissue, pain and chafing, sores and blisters, and infection can occur. Amputees often must have their socket prosthetics adjusted regularly, which is inconvenient and costly. Consequently, many amputees give up prosthetics for wheelchairs.
MOIP uses an alternative limb type called an osseointegrated prosthetic — which includes a titanium fixture surgically implanted into the thigh bone, or femur. Bone grows, or “osseointegrates,” at the connection point with the implant, leaving only a small metallic connector protruding from the remaining leg. An accompanying artificial limb then can be
attached or detached at will. The same procedure can be performed for upper limbs.
The advantages of osseointegrated prosthetics include less pain, a fluid walking motion and a
more stable, better-fitting limb. But because metal sticks out of the residual limb, infection is a
constant risk. To address this issue, MOIP will focus on infection detection, eradication and
prevention—by developing both electrochemical sense-and-respond approaches and “smart” skin
This includes a critical bio-compatible sensor array embedded within an amputee’s residual
limb — coupled with additional sensors on the osseointegrated prosthetic itself. The first
technology of its kind, the array tracks changes in body temperature and pH balance, indicators
of possible infection. It also monitors how well the bone and prosthetic limb fuse together and
heal, allowing doctors to dramatically speed the recuperation process of warfighters.
Over time, the sensors evaluate the prosthetic’s strength, how much stress a user’s body places
on it, and any changes to movement and walking gait.
“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,” said Dr. Jerome Lynch,
a University of Michigan engineering professor who is overseeing the sensor array’s
development. “Right now, doctors study X-ray images of a limb when making that
“Because the sensors transmit information wirelessly, doctors also could potentially study patient
data via a handheld reader,” said Lynch. “Think of it as an extremely specialized Fitbit. This
could dramatically improve the recovery and long-term quality of life for patients.”
Lynch and his team successfully created a MOIP sensor array prototype using osseointegrated
prosthetics and synthetic bone models manufactured onsite at the University of Michigan. While
this prototype was successful in laboratory tests, they hope to have a new, improved model ready
for clinical trials early next year.
Warren Duffie Jr. is a contractor for ONR Corporate Strategic Communications.
About the Office of Naval Research
The Department of the Navy’s Office of Naval Research provides the science and technology
necessary to maintain the Navy and Marine Corps’ technological advantage. Through its
affiliates, ONR is a leader in science and technology with engagement in 50 states, 55 countries,
634 institutions of higher learning and nonprofit institutions, and more than 960 industry
partners. ONR, through its commands, including headquarters, ONR Global and the Naval
Research Laboratory in Washington, D.C., employs more than 3,800 people, comprising
uniformed, civilian and contract personnel.