Sensor under development will help accommodate prosthesis fit changes

Researchers at Sandia National Laboratories are working to develop a sensor that will show how a prosthetic limb changes throughout the day, along with a system that automatically accommodates those changes.

Led by researcher Jason Wheeler, PhD, the Intelligent Systems, Robotics and Cybernetics group hopes to find a company that wants to market the sensor system once additional testing and refinement is complete.

“The thing that prevents people from wearing a prosthesis or being satisfied with their prosthesis is comfort,” Wheeler stated in a press release. “Even if you have a high-technology limb, if it is not comfortable, people won’t wear it.”

Wheeler and colleagues developed a small sensor, about the size of a quarter, to be placed inside the socket where it will monitor fit and detect changes.

Wheeler said Sandia’s sensor is unique because it detects differences in normal pressure and shear forces. Shear forces cause such problems as rubbing, blisters and abrasions, but no appropriately sized commercial sensing system can monitor them, according to Wheeler.

“This extra information gives you better ability to know when you need to make modifications because the shear pressures tend to be a little more sensitive to changes in socket shape than normal pressures,” he stated.

Sandia’s system automatically adjusts socket shape by moving fluid into bladders inside a liner made of elastomeric material similar in thickness to a gel liner. The system adjusts to limb changes by placing bladders inside the liners, and filling the bladders using valves and pressurized liquid on the outside of the liner. Prototypes have been developed to fill and empty the bladders automatically, but Wheeler said more research is needed to determine when it is best to add and remove fluid.

“Being able to put additional fluid volume locally, where you lost it, is an important component,” Wheeler said.

Sandia, through a partnership with the University of Washington, has performed limited testing with a prototype sensor liner. The sensor and bladder systems have not yet been tested together as a closed loop system.

“Right now, we don’t really understand the right method to control the fluid movement,” Wheeler said. “When you walk you have all these different signals and they are telling you something, but due to limited research in this area it is not entirely obvious what the signals mean. We need to do more studies to learn what those signal changes mean about how to adjust socket shape.”

Development is continuing and more amputee testing is needed, but the technology “is getting mature enough where before too long, if we want it to be successful, we are going to have to hand it off to a commercial entity to market it,” Wheeler said.

Disclosure: Wheeler has no relevant financial disclosures.

Leave a Reply

Your email address will not be published.