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Posted: 10:36 AM Nov 4, 2006
New Knees
Designed for women Hundreds of thousands of knee replacement surgeries are done every year. About two-thirds of the patients are women and, until now, there was a gender gap in the OR.
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Hundreds of thousands of knee replacement surgeries are done every year. About two-thirds of the patients are women and, until now, there was a gender gap in the OR.
Annie Beylerian is making medical history. She’s one of the first to receive a revolutionary new knee implant specifically designed for women.
“I couldn't walk," she says.
Dr. Michael Kelly, who helped design the new “gender solutions” knee, says it's shaped more like a woman's natural knee.
He says, "Women have a little different makeup in their knee’s anatomy than men do. If we were to look at that, they’re a little bit taller and they are a little bit narrower.”
A traditional implant is often too wide for a woman. The result can be pain and decreased function. The new gender-specific implant is designed for a better fit.
Dr. Kelly says, "You can see a very nice contour here. There’s a little bit different angle in the way the kneecap slides in and a little bit smaller amount of metal here, all to keep the patella-femoral mechanics. Or in plain terms, how your kneecap functions when you go up and down the stairs, or arise from a seat or drive a car.”
Replacement knees have been available in different sizes for years. This time it's the shape that counts.
Dr. Kelly says, "We went to right and lefts, which became even better than the symmetric knees which was one size kind of fit all and you figure out surgically how to correct it. But now this is just one step further.”
Dr. Kelly says that, for the moment, the gender solutions knee comes in one size. By the end of summer, it should be available in several sizes.
Fast Facts:
Knee Arthritis
The knee is a hinged joint that connects the lower thigh bone (femur) with the upper shin bone (tibia). When the knee moves, the knee cap (patella) slides in a groove on the end of the thigh bone. The bones are held in place with strong bands of tissue called ligaments and tendons.
The surfaces of the bones in the knee joint are covered with a strong, elastic cushion, called cartilage. In between the bones are pads of tissue, called menisci. There are two menisci in each knee to act as shock absorbers.
Chronic knee pain is usually caused by arthritis. The most common forms of knee arthritis are osteoarthritis, rheumatoid arthritis and traumatic arthritis. Osteoarthritis is a degenerative condition characterized by a gradual break down of cartilage. As the cartilage wears away, the bones in the joint can touch and rub against each other. Patients may experience stiffness, pain and decreased motion in the knee joint. The Arthritis Foundation estimates 21 million Americans have osteoarthritis (it also commonly affects the hips and lower back).
In rheumatoid arthritis, the lining of the joint (called the synovial membrane) becomes inflamed and swollen. Patients may experience joint pain, swelling, stiffness and redness in the affected knee. The lining starts to thicken. Eventually, the inflammation damages the bones and cartilage in the joint. About 2.1 million Americans have rheumatoid arthritis. It is two to three times more common in women than in men.
Traumatic arthritis is a condition that occurs after trauma to a joint. Over time, the cartilage is damaged. Symptoms may include knee pain and loss of motion in the joint.
Knee Replacement
Patients with knee arthritis may initially be treated with medications (over-the-counter and prescription), physical therapy, lifestyle modifications and supportive devices (like a cane or walker). When pain becomes severe, symptoms are disabling or the joint becomes deformed, doctors may recommend a knee replacement.
According to the American Academy of Orthopedic Surgeons, about 300,000 knee replacements are performed each year. There are several different designs and materials for prosthetic (man-made) knees. Most devices are made with a combination of metal and plastic components. Generally, knee prostheses contain three main parts: a strong metal femur component, a durable plastic tibia, and a plastic patella. During surgery, doctors remove the damaged portions of the patient’s knee and replace them with the prosthetic components.
A Better Option for Women
Current knee prostheses come in different sizes so they can be fitted to match a patient’s size. The designs were originally developed by taking average sizes of men’s and women’s knees and then developing a range of implants. However, research has shown that women have a slightly different anatomy from men. Females have a wider pelvis, which changes the angle of the knee joint. A woman’s kneecap is also a little thinner than that of a man. Although knee replacements have been very successful, some women have been disappointed in their functional outcome (often women still have some difficulty getting out of a chair or climbing stairs).
In May, the FDA approved a new replacement knee that was specifically designed for the female anatomy. It’s called the Gender Solutions™ High-Flex Knee. The design of the new knee was established by using CT imaging to create detailed images and “maps” of female knees. Compared to traditional prosthetic knees, the Gender Solutions Knee is more proportioned to the female anatomy. It has a narrower and thinner shape and more natural tracking ability (i.e., improved ability of the knee cap to glide over the femoral portion of the prosthesis).
Doctors have only recently begun implanting the new Gender Solutions knee. Several more sizes are expected to be available by the end of the summer. Zimmer, Inc. (the manufacturer) hopes the knee will be widely available by fall. For information, log onto the company’s website at http://www.pacewithlife.com, or call (877) GEN-KNEE.
Note: The doctor in this story, Michael Kelly, M.D., is one of the developers of the Gender Solutions™ High-Flex Knee. He is also a paid consultant for the manufacturer, Zimmer, Inc.
Web Resources
For information about the gender solutions™ high-flex knee, click here.
For general information about knee replacement:
For information on arthritis:
