Self-Powered Prosthetic Leg Developed, Patented, Licensed

Craig Hutto, left, and Michael Goldfarb. (John Russell, Vanderbilt University)

Vanderbilt University engineers in Nashville have developed a prosthetic lower leg, which allows amputees to walk without the leg-dragging that characterizes conventional artificial legs. The university has patented basic elements of the device’s design, and licensed the technology to a California company for commercial development.

The prosthesis is as much an electronic as an assistive device, and includes battery-powered sensors, microprocessors, and motors. Its developers say the device is the first prosthetic with powered knee and ankle joints that operate in unison, as well as sensors that monitor the user’s motion. Those sensors feed data to microprocessors to predict the person’s attempted movements, and operate the device to help the wearer make those movements.

The prosthetic leg is the result of seven years of research by Vanderbilt’s Center for Intelligent Mechatronics, directed by engineering professor Michael Goldfarb. The project was initially funded by National Science Foundation and later by National Institutes of Health.

Goldfarb and his colleagues designed the prosthesis for day-to-day use. The device makes it easier for the wearer to walk, sit, stand, and go up and down stairs and ramps. Tests have shown that users equipped with the device naturally walk 25 percent faster on level surfaces than when they use passive lower-limb prosthetics, since it requires 30 to 40 percent less of the user’s own energy to operate.

Craig Hutto, a 23-year-old amputee who has been testing the leg for several years, says “it’s totally different from my current prosthetic.” Hutto adds that “A passive leg is always a step behind me. The Vanderbilt leg is only a split-second behind.”

The device has gone through seven versions, including 15 upgrades of its electronics circuitry. Recent advances in the prosthesis have lowered the noise level of the device, and reduced its weight to about nine pounds — less than most adult lower legs. The battery can power the device for three days of normal activity, the equivalent of walking 13-14 kilometers.

The university has patented key elements of the prosthetic leg’s design and licensed the technology to Freedom Innovations of Irvine, California. The company develops prosthetic devices, including microprocessor-controlled products.

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