Preoperative Weight Loss Among Morbidly Obese Patients Undergoing Total Knee Arthroplasty: It May Not Affect Outcomes

The increasing obesity rate among total knee arthroplasty (TKA) patients presents a growing issue regarding surgical decision-making. Given the association between morbid obesity (MO, body mass index [BMI] ≥ 40) and postoperative complications, as well as the technical and physical challenges of performing TKA in MO patients, many professional associations and institutions have adopted guidelines for preoperative weight loss in MO patients undergoing TKA.

Morbidly obese patients who underwent TKA from 2019 to 2021 were identified. Patients who had < 90 days between their initial appointment and the date of surgery (time before surgery) were excluded. Preoperative characteristics and intraoperative and postoperative outcomes were compared between patients who achieved meaningful (≥ 5%) or target (≥ 10%) preoperative weight loss and those who did not. Multiple logistic regression was performed to identify independent predictors of weight loss.

Among all 115 patients, 13 (7.8%) gained meaningful weight (≥ 5% BMI increase), 59 (51.3%) did not experience meaningful weight change, and 47 (40.9%) lost meaningful weight, among whom 25 (21.7% of the full cohort) achieved target weight loss. Patients who achieved meaningful/target weight loss had higher preoperative BMI, more time before surgery, and lower proportions of Black patients, Hispanic/Latino patients, and patients undergoing revision surgery (P ≤ 0.038). There were no substantial differences in intraoperative or postoperative outcomes. In multiple logistic regression, higher preoperative BMI, more time before surgery, and non-Black race were independent predictors of weight loss (P ≤ 0.044).

A minority of MO patients achieve meaningful/target weight loss before TKA; however, preoperative weight loss does not appear to affect outcomes. Surgeons should provide more time for MO patients to lose weight preoperatively and more resources to patients (racial and ethnic minorities and those undergoing revision surgery) who may be at greater risk of not achieving meaningful/target weight loss.