Bionic Leg Provides Amputees with a Natural Walk

An innovative lower-limb prosthetic allows amputees to walk without the leg-dragging gait characteristic of conventional artificial legs.

Developed by researchers at Vanderbilt University (Nashville, TN, USA), the prosthesis is designed for daily life ,making walking substantially easier for an amputee, as well as going up and down stairs and ramps, standing, or just sitting and rising from a chair. The latest advances in computer, sensor, electric motor, and battery technology have been integrated to provide powered knee and ankle joints that operate in unison, and sensors that monitor its user’s motion; microprocessors use this data to predict what the person is trying to accomplish, and operate the device in ways that facilitate these movements.

The device weighs about four kilograms--less than most organic human lower legs--and can operate for three days of normal activity (around 13 km to 14 km of continuous walking) on a single charge. The prosthetic’s hardware design has gone through seven revisions, and its electronics board has been redone 15 times, accommodating a range of improvements. One of the latest capabilities added is an antistumble routine that senses if the leg used is starting to falter, immediately lifting up the leg to clear any obstruction and replant the foot on the floor. Studies have shown that users equipped with the device naturally walk 25% faster on level surfaces than when they use passive lower-limb prosthetics.

“With our latest model, we have validated our hypothesis that the right technology was available to make a lower-limb prosthetic with powered knee and ankle joints,” said professor of mechanical engineering Michael Goldfarb, PhD, director of the Vanderbilt Center for Intelligent Mechatronics. “Our device illustrates the progress we are making at integrating man and machine.”

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