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Ceramic Hip Evaluation
"New Durable Total Ceramic Hip Replacement Being Evaluated at MCG"
The MCGHealth Joint Replacement Center is evaluating a new durable total ceramic hip, which may offer even the youngest patients a lasting solution to related pain and disability.
MCGHealth is one of 11 sites in the country evaluating the latest of these devices that replaces a diseased or damaged hip joint with a ceramic-covered ball and ceramic-lined cup device that has been used successfully in other countries but has yet to be approved for general use in the United States.
"We are hoping to make this a one-time operation," Dr. R. Scott Corpe, orthopedic surgeon, said of the ceramic-on-ceramic hip replacement. Over the next two years, he and Dr. Timothy R. Young, co-directors of the MCGHealth Center for Joint Replacement, will enroll about 100 active people age 21 and older in the study in which half will get the total ceramic hip and the remainder will get the current standard: a ceramic-covered head against a polyethylene (hard plastic) cup liner.
The life expectancy for the ceramic head in a polyethylene-lined cup is 10 to 15 years, so particularly younger patients end up with multiple, increasingly difficult and more costly surgeries over their lifetime. Difficulties arise because of bone loss at the surgery site, scarring of surrounding soft tissue, and accumulating debris as the plastic cup liner wears. "With each step you take, the hip joint supports six times your body weight," Dr. Corpe said. Problems begin when debris from the body or implant gets in between the ceramic head and plastic liner. The plastic begins to break down, triggering an immune response from the body that results in bone getting absorbed, and the implant getting loose and causing pain.
Still the ceramic-polyethylene combination is about 50 percent more durable than previous combinations, notably a metal ball and cup or metal ball and plastic-lined cup combination which can fleck off shards of metal that end up as trash in surrounding tissue. "The real problem with total hips over the last two decades, particularly with extending them to younger, more active people, has been the joint wearing and creating tiny little particles you can't even see. These in turn create a bad biologic reaction," Dr. Corpe said. Also, high blood levels of the metallic element chromium, which is foreign in the body, have been documented in some patients with metal balls and cups. Although much of the material is believed to be excreted by the kidneys, high levels may be associated with a possible risk of a tumor called sarcoma.
"Today we are looking for a solution to the problem of wear," Dr. Corpe said, and experience with the ceramic on ceramic coupling shows nearly a 1,000 percent decrease in wear over today's standard hip replacement
With refined engineering techniques, the ceramic in these artificial hips is nearly as hard as metal, a major improvement from previous ceramic-on-ceramic hips used in other countries that contained a larger-grained and more brittle version of the material. Even then the problem wasn't breakage or wear. Rather the major complaint was with fixation, and subsequent engineering improvements have resolved that problem. "Now we know how to very reliably and predictably fix the cup and stem pieces in," Dr. Corpe said.
Another plus of ceramic is that it attracts natural joint fluid which forms a protective, lubricating shield around itself. The only documented wear product is alumina, a metal derivative naturally found in the body. Dr. Corpe noted that some patients cite a greater awareness of the total ceramic hip than the ceramic on plastic, possibly because of the material's hardness.
He and Dr. Young are excited about the opportunity to offer the total ceramic hips as a potential permanent solution for patients who need hip replacements because of osteoarthritis, trauma or other problems. "I think this is possibly the second biggest advancement I've seen in 15 years of doing hip replacements," Dr. Corpe said. "The biggest was our ability to understand why implants fail in fixation to human bone. We have been pretty much able to defeat that problem over the past decade. Now that we know how to reliably fix these implants to bone, we want to eliminate the wear products. We think we can do that by going to an interface of ceramic on ceramic that is so inert that even the wear that does get produced is relatively harmless. This portends possibly a really permanent total hip."
Two previous studies of ceramic-on-ceramic hips have been completed at other medical centers, but the Food and Drug Administration has not yet approved a total ceramic hip; approval for at least one of the hips could come late in 2000.
The MCGHealth Joint Replacement Center physicians see patients throughout the Augusta area and the Southeast. Drs. R. Scott Corpe and Timothy Young are co-directors of the center which replaces hips, knees and shoulders. The vast majority of their patients experience relief from their pain and a dramatic change in their quality of life.
For more information or to make an appointment, call the MCGHealth Care Referral Center at 706-721-CARE or 1-800-736-CARE.
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