Diagnostic Test Detects Infection of Prosthetic Joints

A new, more accurate diagnostic test has been developed to detect infection of prosthetic joints, potentially leading to better treatment options and patient outcomes.

The method involves sampling microorganisms in biofilms adhering to the prosthetic surface rather than culturing the tissue around the joint as in conventional tests.

Surgeons remove the prosthetic joint, place it in a special container, and send it to the laboratory. In the laboratory, a solution is added to the container and then the container subjected to a combination of vortexing and sonication to remove the biofilm bacteria. The bacteria, now in the solution, can be quantitatively cultured.

A team from the Mayo Clinic (Rochester, MN, USA) tested 331 patients with prosthetic hip or knee joints who were having their prosthetic joints removed for infection or another cause. The new diagnostic test detected more of the infected cases (78.5%) than did the conventional approach (60.8%). The study was published in the August 16, 2007, issue of the New England Journal of Medicine.

"The problem with the conventional method is that you need multiple tissue specimens, because the sensitivity of a single specimen is not good--in other words, the infection might be missed with just one sample,” explained Robin Patel, M.D., Mayo Clinic professor of medicine, who led the multidisciplinary team of orthopedic surgeons, infectious diseases physicians, and laboratory researchers.

"We found a wide variety of different types of bacteria,” added Dr. Patel. "This is important to recognize, because it is ideal for the doctors to know what type of infection they are dealing with in order to treat it properly--this determines what type of antibiotic to give, and in some cases, what type of surgery to perform.”


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