Preoperative weight loss may not affect outcomes for patients with obesity undergoing TKA
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Key takeaways:
- Preoperative weight loss did not affect outcomes for knee arthroplasty patients with class II and class III obesity.
- Weight loss at 1 year and 6 months before surgery did not impact revision or infection rates.
Results published in the Journal of Arthroplasty showed patients with class II and class III obesity do not benefit or harm from preoperative weight loss prior to total knee arthroplasty.
Researchers performed a retrospective study of 2,110 patients who underwent primary TKA from 2015 to 2020. Researchers calculated BMI 1 year before surgery, 6 months before surgery and on the day of surgery. Other outcomes included revision surgery and prosthetic joint infection (PJI), according to the study.
Researchers found a preoperative decrease in BMI of more than 5% at 1 year before surgery and 6 months before surgery had no effect on incidences of revision or PJI for patients with class II obesity (BMI of 35 kg/m2 to 39.9 kg/m2) and class III obesity (BMI of > 40 kg/m2). They also noted patients with class I obesity (BMI of 30 kg/m2 to 34.9 kg/m2) who had 6-month weight loss had greater odds of complications compared with matched patients who had 1-year weight loss.
“This study does not show significant benefit or harm to patients who had obesity class II and III losing weight preoperatively with respect to PJI or revision,” the researchers wrote. “For patients who have obesity class I or lower pursuing TKA, future research should consider potential risks associated with weight loss.”
Perspective
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BMI is a frequently targeted modifiable risk factor for preoperative optimization, with a goal of decreasing postoperative adverse events, specifically periprosthetic joint infection. While this paper demonstrates a neutral effect of weight loss, the benefits of losing weight remain obvious in terms of overall health and should not be discounted. Furthermore, the patients most likely undergoing weight loss are those who are already obese and have been urged to lose weight to attempt optimization for surgery; therefore, these higher risk patients may inherently have a higher infection rate than patients who are normal weight. In addition, a 5% BMI decrease is arbitrary and may not represent a clinically significant amount (ie, 200 pounds to 190 pounds). A future strategy would be to look at change in BMI, or change in weight, as a continuous variable for a dose-response relationship. Lastly, there are confounders that have not been evaluated in this study: 1) weight loss does not translate to good nutrition and studies have shown that malnutrition may lead to adverse events; and 2) patients were not stratified by whether they had bariatric surgery, which has mixed results in the literature regarding postoperative outcomes.
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