Morbid obesity negatively affects TKA outcomes - Academy News at the 2007 AAOS Annual Meeting

Morbid obesity negatively affects TKA outcomes

By Peter Pollack

Increasing rates of obesity can have major implications for health care, particularly in joint replacement. According to poster exhibit P174, morbidly obese patients are likely to suffer negative clinical outcomes following total knee arthroplasty (TKA), including lower functional scores.

During the past 20 years there has been a dramatic increase in obesity in the United States. The latest data from the National Center for Health Statistics show that 30 percent of U.S. adults 20 years of age and older—more than 60 million people—are obese. Because the relationship between morbid obesity and TKA outcome has previously been inconclusive, researchers examined the records (including preoperative and one-year postoperative Western Ontario and McMaster Universities [WOMAC] scores) of 550 patients who had TKA.

Patients were excluded from the study if they had a diagnosis other than osteoarthritis, if they had another TKA during the follow-up period of the index knee arthroplasty, or if their body mass index (BMI) was less than 18.5. Researchers then stratified the remaining patients into a morbidly obese group (as defined by the World Health Organization as having a BMI of greater than 40), and a group consisting of all remaining patients.

Researchers performed two analyses: an independent t-test, to determine if there were any differences between the preoperative and one-year postoperative WOMAC scores of morbidly obese and all other patients; and a multi-variable linear regression, to determine the relationship between morbid obesity and the WOMAC scores.

The t-test showed that morbidly obese patients had significantly lower preoperative and one-year postoperative WOMAC scores (both p < 0.001). Through regression analysis, researchers found that morbid obesity was a negative influence on preoperative (p < 0.05) and postoperative (p < 0.05) WOMAC scores.

The lead researcher for poster exhibit P174 is Vaishnav Rajgopal, MD. Additional researchers include Robert B. Bourne, MD; Bert M. Chesworth, PhD; Steven J. MacDonald, MD; Richard W. McCalden, MD, and Cecil H. Rorabeck, MD—all of London, Ont., Canada. The authors report no conflicts of interest.

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