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AAOS Now

Published 1/1/2009
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Annie Hayashi

Patient characteristics, surgical choice influence infection rates

Study identifies factors that elevate TJR infection rates

“Total joint replacement (TJR) infection is a complication that negatively affects outcomes,” said Robert A. Malinzak, MD. “Iden­tifying ways to minimize this com­plication will improve out­comes for surgeons and their pa­tients as well as minimize societal costs.”

To identify factors that influence TJR infection rates, Dr. Malinzak and his colleagues conducted a retrospective review of 8,484 patients who had total knee replacements (TKR) or total hip replacements (THR).

From the study population, 43 patients (0.51 percent) developed a deep infection—30 patients with TKR and 13 patients with THR. The average age of patients in the “infected group” was 64.3 years old (+/-12.9 years); in the “non-infected group,” the average age of patients was 68.4 years old (+/-10.0 years).

Obesity, diabetes increase risk
Morbidly obese patients with a body mass index (BMI) greater than 50 had a significant risk for deep infection. Odds of infection for patients whose BMI was greater than 40 were 3.2 times greater than for patients with a BMI under 40 (p=.0041).

Diabetes was also a strong indicator for infection; 8 of the 43 patients (18.6 percent) who developed infections also had diabetes. Those with diabetes had 3.1 odds of infection when compared to their nondiabetic counterparts (p=0.0027).

Although patients with osteo­necrosis and rheumatoid arthritis did demonstrate a trend towards a higher infection rate than those with osteoarthritis, the trends were not statistically significant.

Patients who had simultaneous bilateral joint replacement were less likely to develop a deep infection than those who had unilateral TJR.

“Risk factor analysis will further enable us to develop strategies to prevent surgical complication,” Dr. Malinzak concluded.

Dr. Malinzak presented the study, “Morbid obesity, diabetes, younger age and unilateral surgery elevate total joint replacement infection rates” at the 2008 annual meeting of the American Assoc­iation of Hip and Knee Surgeons.

The authors report the following disclosures: Dr. Malinzak—Biomet, Zimmer, Stryker; Merrill A. Ritter, MD—Biomet; Michael E. Berend, MD—Biomet, MCS, Journal of Arthroplasty; John B. Meding, MD—Biomet, Stryker, Zimmer. Emily M. Olberding, MS, and Kenneth E. Davis, MS, reported no conflicts.

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org