While most artificial feet and limbs do a pretty good job restoring mobility to people who have lost a leg, they said, there is still work to be done, witnessed by the fact that over half of amputees take a fall every year.
The secret to a natural walking gate lies in the ankle, the researchers at Michigan Technological University said, and they're working on an ankle-foot prosthesis that comes close to achieving the innate range of motion of this highly complex joint.
Their prototype computerized artificial legs have pressure-sensitive sensors on the bottom of the foot that detect how the amputee is walking and then send signals to a microprocessor that adjusts the prosthesis to make walking more natural.
Mechanical engineering Professor Mo Rastgaar and doctoral student Evandro Ficanha designed an ankle-foot that can move on two axes, incorporating a side-to-side roll as well as raising the toe up and down, mimicking the action of the human ankle.
Microprocessor-controlled prostheses currently on the market can move an artificial foot in only one direction, toe up and toe down, which is fine if you are marking time on a treadmill, Rastgaar said.
"But in reality, we never walk in a straight line for any length of time," he said. "When you walk and reach an obstacle, you have to turn, and there's always something in our way."
The Michigan researchers' prosthetic uses a thin, strong cable running from a control box to the ankle mechanism to turn the foot in almost any direction.