A New Test to Identify Total Knee Replacement Infection

March 12, 2008 – Every year, hundreds of thousands of individuals undergo a total knee replacement, also known as total knee arthroplasty. And every year, some of these joints become infected…or do they? Sometimes, doctors can’t really tell.

However, progress is being made. The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) recently developed a test to prevent both false-negatives and false-positives when checking for infection.

If infection is suspected, surgeons insert a needle into the joint space and withdraw fluid.  This fluid is then cultured in a laboratory and examined for bacteria growth.  The problem was that sometimes the fluid failed to grow bacteria even when it was present (referred to as a false-negative), a situation that occurred between 27 to 50 percent of the time.

The new process reported by NIAMS uses a technology that polymerase chain reaction (PCR) to detect the messenger RNA of the bacteria and converts it into DNA that can be measured. With this new advancement, physicians will be able to determine if bacteria sampled from the knee is truly causing an infection.  If an infection is present, the surgeon can immediately take steps to treat the infection—likely removing the infected prosthetic knee. If an infection is not present, patients are spared an unnecessary and expensive treatment.

For further information: “Simulated joint infection assessment by rapid detection of live bacteria with real-time reverse transcription polymerase chain reaction,” Patrick Birmingham, MD, Jeannine M. Helm, Paul A. Manner, MD, and Rocky S. Tuan, PhD, Journal of Bone and Joint Surgery, vol 90, no 3, March 2008.