December 4, 1997
Media Contact: Karen Infeld
Phone: (410)955-1534

People who have total knee replacements and later undergo extensive dental work may be susceptible to knee infections years after their initial surgery, according to a study by Johns Hopkins physicians.

The infections are caused by bacteria introduced to the bloodstream during dental work on sensitive, blood-rich gum tissue. Bacteria can travel and infect the tissue surrounding prosthetic devices.

The study's results, published in an October issue of the Journal of Clinical Orthopedics and Related Research, suggest that antibiotics, taken one hour before extensive dental procedures and again eight hours afterward, might provide the best defense against infection.

While many patients with infected total knee replacements can be treated successfully, the authors note, they are at increased risk for potential loss of function, loss of range of motion, mechanical problems and in rare cases, sepsis or death.

"Patients who have had a total knee replacement and who are scheduled for extensive dental procedures may benefit from prophylactic antibiotics, especially if they have other conditions that predispose them to infection, such as diabetes or rheumatoid arthritis," says Michael A. Mont, M.D., an author of the study and an associate professor of orthopedic surgery.

The dental procedures associated with the infections included tooth extractions, root canals, periodontal surgeries and benign tumor removals. The average length of time between the dental procedure and the onset of knee symptoms (pain) was seven days.

"The potential for infection may be increased in more extensive oral procedures, such as tooth extraction, yet people should be aware that even routine dental procedures can result in bacteria flowing through the body for up to 30 minutes," Mont says. However, routine procedures may not require prophylaxis, he says.

Of 3,490 Hopkins patients studied who had total knee replacement operations between 1982 and 1993, 62 developed joint infections. In seven patients, the infections were closely linked to a dental procedure, and emerged as long as eight years after their knee replacements. These seven cases represented 11 percent of the identified infections or 0.2 percent of the total knee replacement procedures performed during this period.

In addition, among 12 patients referred from outside institutions for infections, two had infections associated with a dental procedure. Average age for all patients studied was 65. The study's other authors were Barry J. Waldman, M.D., and David S. Hungerford, M.D.

-- JHMI --
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