ARTHRITIS: FAKE JOINTS, REAL ANSWERS
New information on replacement-joint infection sources
BY:MYRA DEMBROW
New thoughts are being flexed when it comes to understanding the source of infection in surgical prostheses—artificial hips and knees, for instance—used in some arthritis cases. And since there are about 750,000 such surgeries each year just in the U.S., those thoughts have a lot of impact.
Researchers from the Mayo Clinic discovered a more accurate diagnostic test to detect bacteria on artificial joints, sampling bacteria that adhere to the replacement joint itself rather than on the tissues around it. The new procedure also eliminates the need for multiple tissue samples and reduces the likelihood of mistaken results.
The scientists studied 331 cases in which artificial hips or knees were being replaced because of infections or other causes. Analyzing samples of bacteria that stuck to the prosthesis itself identified 78.5 percent of infections, whereas conventional tissue sampling detected only 60.8 percent.
"The problem with the conventional method is that you need multiple tissue specimens because the sensitivity of a single specimen is not good [and] the infection might be missed with just one sample," says study leader Robin Patel, MD, a Mayo Clinic professor of medicine. Samples from the artificial joints were not only more sensitive to testing, but also were cleaner. "Bacteria normally found on the skin can be picked up on the tissue specimen as it is extracted and passes through the skin, yielding a false-positive result," she explains.
The study, reported in the New England Journal of Medicine, detected many different types of bacteria, allowing doctors to be more effective. "It is ideal for the doctors to know what type of infection they are dealing with in order determine what type of antibiotic to give and, in some cases, what type of surgery to perform," Dr. Patel says.