A smart prosthetic knee with in-vivo diagnoses

Apr 22, 2014 by Sandy Evangelista
Credit: Alain Herzog

The task was to develop intelligent prosthetic joints that, via sensors, are capable of detecting early failure long before a patient suffers. EPFL researchers have taken up the challenge.

Today, nearly 4 million people worldwide must suffer through operations to replace defective joints. In the coming years, the number of procedures on will multiply by 7. EPFL researchers have developed sensors, integrated into the polyethylene part of the , that can perform a diagnosis of the interior, improving and thereby helping patients, in some cases, avoid a new operation.

There are three leading causes of this surgical boom: the development of recreational sports that particularly affect the knee and eventually cause osteoarthritis, obesity – a sport in itself for the joint that must bear the , and lesions that are present in cartilage. Once the arthroplasty has been performed, the prosthesis set, and the operating field closed, the biggest problem for the doctor is that the only feedback is the patient's qualitative and subjective assessment. If the prosthesis is misaligned or if it unseals, which occurs in about 20% of cases, this causes significant pain, and it is very difficult to quantify.

Arash Arami of the Laboratory of Movement Analysis and Measurement (LMAM) devoted part of his thesis to the question of unsealing in the prosthesis. He chose the knee because it is a complex joint that is often injured. With an algorithm he developed, he could precisely calculate the micromovements of the prosthesis and detect, via vibration, any loosening. Then, using sensors implanted in a prosthesis mounted on a mechanical knee simulator, he could demonstrate how it reacts to applied forces.

Credit: Alain Herzog

Brigitte Jolles-Haeberli, head of prosthetic knee surgery at the University Hospital of Lausanne and EPFL's Interinstitutional Center of Translational Biomechanics, collaborated closely on this project. "Even when a prosthesis has been properly installed, some people experience persistent pain. One is at a loss for how to concretely help without resorting to painkillers or physiotherapy." Even if it is possible to see the problems of sealing or alignment – through an x-ray coupled with a bone scan – doctors still have no way to detect the cause. "With this new information about the prosthesis, we could take preventative measures and explore other avenues of gait rehabilitation without necessarily having to resort to a new surgery."

Five EPFL laboratories have joined in a project funded by the National Science Foundation. To help the industry integrate new tools into smart prostheses, the scientists decided to put these sensors in the middle part, which is the polyethylene insert. This material is common to all knee prostheses, regardless of manufacturer.

"It makes sense that all these inserts have more or less the same shape and therefore the same volume, and if we can instrumentalize it without touching the femoral or tibial part, it will be easier for the industry to implement. But this will not happen immediately, because we must first show how these represent a real benefit for both patients as well as doctors and the industry," concluded Kamiar Aminian who directs the LMAM.

Explore further: Researchers develop ultramodern forearm prosthesis

add to favorites email to friend print save as pdf

Related Stories

Infected prosthetic knees cause problems

Dec 06, 2010

The number of people that undergo an operation to have a prosthetic knee joint is increasing. One reason is that the population is getting older, another is that people are also getting heavier, which is a factor in the development ...

Researchers develop ultramodern forearm prosthesis

Feb 12, 2014

Researchers of the University of Twente (UT) and Roessingh Research and Development (RRD) have developed a system which can significantly improve the functionality of forearm prostheses. Using the activity ...

Recommended for you

Off-world manufacturing is a go with space printer

Dec 20, 2014

On Friday, the BBC reported on a NASA email exchange with a space station which involved astronauts on the International Space Station using their 3-D printer to make a wrench from instructions sent up in ...

First drone in Nevada test program crashes in demo

Dec 19, 2014

A drone testing program in Nevada is off to a bumpy start after the first unmanned aircraft authorized to fly without Federal Aviation Administration supervision crashed during a ceremony in Boulder City.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.