Sensors Help Amputees Restore Lost Muscle Function

Using advanced torque and accelerometer sensors, artificial intelligence and actuator technology, the second generation of Ossur Americas' motor-powered POWER KNEE^TM prosthesis is helping above-knee amputees restore lost muscle function and enables them to walk naturally without even thinking about their next move.

Ian Fothergill, Ossur's academy manager, says ground contact sensors and software algorithms control the knee, making it more natural and intuitive than any prosthesis before it. "The knee takes over the control of the user's balance when they are on it," he says. "That, of course, requires a different approach in terms of control."

Fothergill likens the POWER KNEE^TM to the Segway.

"If you lean forward (on a Segway), it accelerates to speed up, but it doesn't allow you to fall forward," he says. "(POWER KNEE^TM) is very intuitive. It uses the natural system of moving your body first and then your legs catching up with you."

Fothergill says amputees are constantly on guard, making sure their prosthetic is positioned correctly and wondering if the knee will buckle under their weight. With POWER KNEE^TM the user simply walks and the prosthesis does the rest. "(Amputees) are always guarding themselves," Fothergill says. "The POWER KNEE^TM now takes that thought process completely away from them."

According to Ossur, powered knee motion through actuator technology is possible simply by lifting the thigh muscle, which generates power according to the patient's needs. Specific levels of power management are needed depending on level ground walking, walking up or down stairs, sitting or standing.

Ossur, in partnership with Victhom Human Bionics, developed the first POWER KNEE^TM in 2006 for use mainly with the Dept. of Defense and the Veterans Healthcare Administration.

"The second generation is smaller, sleeker, quieter, lighter and is expected to become widely used in both unilateral and dual amputees," says Lt. Col. Dr. Paul F. Pasquina, chief, Integrated Dept. of Orthopedics and Rehabilitation at Walter Reed Army Medical Center and the National Naval Medical Center.

Army Lt. Col. Greg Gadson is the first in the world to receive the prosthetic knee, which is expected to be commercially available by 2010, according to Fothergill. Gadson, who lost both his legs after his truck was hit by a roadside bomb in Baghdad in 2007, was fit for the prosthesis at Walter Reed in April.

"Ossur is committed to providing these men and women with the most advanced technology available. Their sacrifice and dedication to their country has inspired us to work even harder to optimize their mobility," says Jon Sigurdsson, Ossur's president and CEO. "The result will be that the entire amputee population will eventually realize a more natural and safe form of walking."