August 18, 2011

New Prosthetic Leg Allows For Fluid Movements

Researchers at Vanderbilt University have developed a new lower-limb prosthetic that allows amputees to walk with a natural gait.

The device uses new technology to give it bionic capabilities and is the first prosthetic with a powered knee and ankle joints that operate in unison. 

The prosthetic comes equipped with sensors that monitor its user's motion and has microprocessors to use this data to predict what the person is trying to do and operate the device in ways that facilitate these movements.

"When it's working, it's totally different from my current prosthetic," Craig Hutto, the 23-year-old amputee who has been testing the leg for several years, said in a University press release. "A passive leg is always a step behind me. The Vanderbilt leg is only a split-second behind."

Michael Goldfarb, the H. Fort Flowers Professor of Mechanical Engineering, said the bionic leg is the result of seven-year research effort at the Vanderbilt Center for Intelligent Mechatronics.

"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," Goldfarb said in the press release. "Our device illustrates the progress we are making at integrating man and machine."

Studies have found that users equipped with the device walk 25 percent faster on level surfaces than when they use passive lower-limb prosthetics. 

"Going up and down slopes is one of the hardest things to do with a conventional leg," Hutto said in a press release. "So I have to be conscious of where I go because I can get very tired walking up and down slopes. But that won't be a problem with the powered leg because it goes up and down slopes almost like a natural leg."

The prosthetic leg weighs about nine pounds and can operate for three days of normal activity on a single charge.

The engineers have also created an "anti-stumble routine" with the prosthetic. If the leg senses the user is going to stumble, it will lift up the leg to clear any obstruction and plant the foot on the floor.

There have been seven different versions of the prosthetic designed, and the researchers have redone its electronics 15 times.

Goldfarb said it was tough to make the prosthetic light and quiet enough, but the biggest challenge was developing the control system.

"As you add greater capability, you are also adding greater liability," he said in a press release. "Not only does the controller have to perform individual operations reliability, but it has to perform several operations at the same time and not get confused."

The project was funded by grants from the National Science Foundation and the National Institutes of Health.


Image Caption: Professor Michael Goldfarb, right, with amputee Craig Hutto who is wearing the new bionic leg developed at Vanderbilt. (John Russell, Vanderbilt University)


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