TKA does not result in weight loss for obese patients - Academy News 2007 AAOS Annual Meeting

TKA does not result in weight loss for obese patients

By Jennie McKee

A study of obese patients who underwent primary total knee arthroplasty (TKA) showed that their mean weight did not change two years after their surgery, despite an apparent increase in physical activity. This finding of podium presentation 294, “Weight and activity change in obese patients after primary TKA,” has important implications for patient expectations and preoperative counseling.

“Overweight and obese patients often claim they are unable to lose weight because pain from severe arthritis of the knee limits their activity and thus their ability to expend calories,” noted the authors. “These patients often believe that TKA will permit an increase in their physical activity and enable them to lose weight.” Based on the results of this study, however, overweight and obese patients should not expect TKA alone to result in weight loss.

Before and after results

This prospective study measured changes in patient weight, body mass index (BMI) and physical activity over two years in 188 consecutive overweight or obese patients (BMI greater than 25 kg/m2). The lead author assessed weight and BMI preoperatively (188 patients) and at one year (165 patients) and two years (152 patients) postoperatively.

Patients used the Lower Extremity Activity Scale (LEAS), a self-assessment instrument, to report physical activity. Multiple linear regression was used to examine the relationship between preoperative LEAS score and weight/BMI at two-year follow-up.

Weight and BMI data were available for 152 patients (81 percent) at two years postoperatively. No significant mean weight change was found (p = 0.80), but mean BMI increased by 0.46 kg/m2 (p = 0.049). The two-year postoperative mean LEAS score (96 patients) increased significantly (p < 0.001).

Pre- and postoperative weight changes were also measured; 17 per-cent of patients had lost more than 5 percent of their body weight, 23 percent had gained more than 5 percent of their body weight and 60 percent showed a weight change less than 5 percent of their body weight. Preoperative LEAS score was not associated with weight (p = 0.40) or BMI (p = 0.51) when measured two years after surgery.

“Two years after primary TKA, this cohort of overweight and obese patients experienced no change in mean weight, but an increase in BMI, despite an apparent increase in physical activity,” said the researchers. “BMI increased significantly among overweight patients, but not among obese patients.”

The researchers for Paper 294 include Anne M. Lachiewicz, MPH, and Paul F. Lachiewicz, MD, both of Chapel Hill, N.C. Dr. Lachiewicz serves as a consultant to Zimmer.

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