Then, electrodes were placed on his leg to detect electrical signals from the muscle contractions. A computer program decodes the signals to interpret the patient's movement. Mechanical sensors on the robotic leg (including an accelerometer and a gyroscope) also collect data to help with control.
Using the robotic leg, Vawter was able to walk on level ground, go up ramps and stairs, and transition between these activities without stopping. He was also able to use his thoughts to change the position of his lower leg while sitting down, something that cannot be done with current motorized leg prosthetics (which must be moved manually when sitting down).
Using only the mechanical sensors, Vawter's robotic leg incorrectly interpreted his activity about 12.9 percent of the time. But by using information from the electrodes, this error rate dropped to 1.8 percent. Reducing this error rate is important, because it can help prevent falls, Hargrove said.
The researchers said they want to make the robotic leg smaller, quieter and stronger, and reduce the error rate further.
The study was funded by an $8 million grant from the U.S. Army, and the goal is to make this technology available to servicemen and women, as well as civilians.
"We appreciate the opportunity to sponsor this life-changing effort to provide military amputees with as much physical functionality as possible, as soon as possible," Col. John Scherer, director of the Clinical and Rehabilitative Medicine Program at the U.S. Army Medical Research and Materiel Command, said in a statement.
The study is published in the September issue of the New England Journal of Medicine.
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