New Test for Detecting Infection in Prosthetic Joints

A new diagnostic test to detect infection of prosthetic joints by sampling bacteria that adhere to the prosthetic surface, could potentially lead to better treatment options and patient outcomes.

Researchers at 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 other causes. The new test involves removing the prosthetic joint, placing it in a special container, and sending it to the laboratory. In the laboratory, a solution is added to the container, which is then subjected to a combination of vortexing (shaking) and sonication (exposure to ultrasound), which has been shown to remove biofilm bacteria. The bacteria in the solution are then quantitatively cultured. The new diagnostic test detected more of the infected cases (78.5%) than did the conventional approach (60.8%), which samples tissue around the prosthetic joint at the time of surgery. The study was published in the August 16, 2007, issue of the New England Journal of Medicine (NEJM).

"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,” said lead author Prof. Robin Patel, M.D. "Another issue is that 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. These same bacteria may actually cause the infection, so doctors can't always tell just by the type of bacteria detected whether the patient has an infection or not. If multiple specimens are positive for the bacteria, then this indicates that the bacteria are causing the infection.”


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