Timing Matters: Optimizing the Timeframe for Preoperative Weight Loss to Mitigate Postoperative Infection Risks in Total Knee Arthroplasty

We explore the incidence of periprosthetic infections post-total knee arthroplasty (TKA) in morbidly obese patients who achieved weight loss. Current American Academy of Orthopaedic Surgeons guidelines suggest a preoperative body mass index (BMI) below 40 for TKA. This study assesses infection risks in patients initially who had a BMI of 40-50 who reduced their BMI to under 35 at varying intervals prior to surgery.We reviewed a national, all-payer database, PearlDiver, for patients undergoing primary TKA. Patients were stratified based on initial BMI of 40 to 50 and reduction of BMI to less than 35 at three-months (n=1,932), three to six-months (n=794), six to nine-months (n=2,233), and nine to twelve-months (n=1,194) prior to TKA, as well as patients who had a BMI between 40 to 50 (n=41,632) on the day of surgery. The non-obese group comprised of patients who had a BMI between 20 and 30 (n=33,294). Multivariate analyses was performed at one-year follow-up.We found an increased risk of PJI for patients who had achieved BMI reduction less than nine months prior to TKA, compared to the BMI 20 to 30 cohort at the one-year follow-up (p < 0.001). Patients achieved BMI reduction nine to twelve-months prior to TKA showed no significant difference in PJI risk compared to the matching non-obese cohort at one-year follow-up (p = 0.400).In conclusion, our results suggest that weight loss should be achieved at least nine months before TKA to decrease infection risks. These findings have significant implications for surgical considerations in obese patients undergoing TKA.