By Tom Keppeler, Knee1 Staff
A prosthetic implant that may save the knees of many young, active arthritis victims will make its debut this week after 11 years of research and development.
Total knee replacement, a procedure in which the kneecap and the ends of both the shinbone and thighbone are replaced, is often prescribed to patients with severe bone-degenating conditions. However, existing implants only last between 10 and 15 years, and doctors are often reluctant to place them inside the legs of young patients, since they may outlive their implants.
However, Smith and Nephew Orthopedics has designed an implant that lasts 85 percent longer in tests that simulate the stresses inside the knee. The prosthetic components are made of zirconium that are heated and infused with oxygen to create a ceramic surface that is more durable than the conventional cobalt chrome alloy prosthetics. The material, which was approved by the Food and Drug Administration in 1996, has gone through two years of testing at New York's Hospital for Special Surgery (HSS) and recently received the hospital's approval for use in knees. The oxidized zirconium implant will make its debut to 11,000 surgeons this week at the annual meeting of the American Academy of Orthopedic Surgeons.
According to the HSS, roughly 209,000 people undergo knee replacement surgery every year. Knee replacement can often reduce or eliminate the pain caused by degenerative joint conditions such as rheumatoid or osteoarthritis. Most recipients are over 65, and, since most are not exceedingly active and may not outlive their implants, the need for revision surgery is low in this age group. However, 27 percent of TKR (total knee replacement) recipients are between 18 and 64, according to the HSS. Doctors are often reluctant to implant artificial knees in younger patients, as the need for a second or third replacement is high when implanting a prosthetic with a 10-year lifespan.
"Unfortunately, we are seeing more and more patients with severe arthritis earlier in life," Dr. Richard Laskin, chief of the Arthroplasty Council at HSS, said in a statement. "Until now, these patients were advised to postpone the replacement surgery and deal with the pain." Now, however, surgeons can implant ceramic knees in 40- or 50-year-old patients, drastically reducing their pain earlier in life.
In addition, the implants offer added benefits. The metal alloy used in current implants can scratch or pit, causing it to break down faster. According to the HSS, the ceramic implant is scratch-resistant. When it is wet, ceramic can glide smoothly along plastic, making for smoother motion than with metal-on-plastic, the statement said. Lastly, patients who are allergic to nickel, the metal most often used in the current implants, cannot currently receive total knee replacements. The ceramic implant, however, can be implanted safely in patients with nickel allergies, since it uses a zirconium alloy with no nickel. "We think it will last significantly longer than cobalt chrome implants," said Angie Craig, spokeswoman for Smith and Nephew. "In addition, doctors who see younger patients with a need for a total knee replacement will be able to
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