C-Leg offers hope for those missing knee

Monday, Feb. 14, 2005 | 8:48 a.m.

Alicia Karau is one of 3,500 U.S. residents and 5,000 above-the-knee amputees worldwide who are benefitting from C-Leg technology.

C-Leg, a computer-controlled prostheses made of titanium and carbon, is a product of the Minneapolis-based Otto Bock HealthCare company that has been manufacturing prosthetic devices since it was founded in Germany in 1919.

The C-Leg, introduced in 1999, is described by the company as "a quantum leap" in the improvement of lower limb prosthetics. The "C" stands for computer.

"Our goal is to mimic the real limb, though it is difficult to recreate the group muscle movement in the knee," said Todd Anderson, a certified prosthetist, who has worked for the Otto Bock company for five years. "Still, we strive to restore human independence."

Otto Bock has been called the Henry Ford of prosthetics. He revolutionized the industry with the creation of life-like feet, ankles, knees and shins. His health care company came to the United States in 1958.

Over the years, Bock's scientists have found it difficult to recreate the simple act of walking for those who are missing a knee joint, Anderson said.

"While the knee is just a simple hinge, there are no artificial muscles so we have to use gravity and inertia to propel the patient," he said.

Through customized settings created via the use of a laptop computer, the C-Leg's microprocessor enables the wearer to walk in a natural manner by simulating the individual's normal gait.

The sensors monitor 50 times per second a person's movement and automatically adjust to compensate for changes in terrain to allow a wearer to walk over rough ground as well as smooth surfaces, the company says.

And unlike older style prosthetics where the wearer has to walk up and down stairs step-by-step, the C-Leg allows for step-over-step movement up and down stairs, similar to how a human leg performs.

The device also provides not only knee stability but also adapts to various walking speeds.

Also, the C-Leg is programed with a second mode of operation, allowing the wearer to, with the tap of a foot, switch to an activity that requires different movement, such as golfing, skiing or rollerblading, the company says.

The C-leg was developed between 1986 to 1992 by University of Alberta engineer Kelly James, who in 1992 sold it to Otto Bock HealthCare. The company worked on it for seven more years to create a smoother and stronger movement before marketing it to the public.

Anderson said that while a number of health insurance companies and Medicare reimburse the $45,000 cost of the C-Leg, others, including Karau's health maintenance organization, have not.

"There are so few above-the-knee amputees and the decision whether to reimburse the cost for them hinges on what insurance companies call 'medical necessity,' " Anderson said.

"They consider whether something is medically necessary for you to live. One answer to that is a pegleg or a wheelchair would suffice. Sometimes the system fails to define quality of life as an issue for medical necessity."

C-Leg success stories include a wearer who had to quickly walk down 70 flights of stairs to escape from the collapsing World Trade Center tower following the terrorist attacks of Sept. 11, 2001, and a wearer who made Department of Defense history as the first above-the-knee amputee to fly for the military.

The company says, to date, 68 soldiers wounded in the wars in Afghanistan and Iraq have been fitted for C-Legs.

Additional accessories to the C-Leg also are available, including a series of prosthetic feet that are manufactured in different flexed positions for different uses, including some that permit women amputees to wear high heels.

Still, Anderson cautions, the technology is nowhere close to creating $6 million men and bionic women.

"We are quite a ways away from creating a leg that functions as well as the human leg," he said. "But a person walking around in a well-fitted C-leg can appear as though he is not an amputee."