Preoperative and Postoperative Weight Change has Minimal Influence on Healthcare Utilization and Patient Reported Outcomes Following Total Knee Arthroplasty

Introduction: As obesity becomes more prevalent, more patients are at risk of lower extremity osteoarthritis and subsequent total knee arthroplasty (TKA). This study aimed to test 1) the association of preoperative weight change with healthcare utilization; and 2) the association of pre- and postoperative weight changes with failure to achieve satisfaction and minimal clinically important difference (MCID) in Knee injury and Osteoarthritis Outcome Score for pain (KOOS-Pain) and function (KOOS-PS) 1-year after TKA. Methods: Prospectively collected monocentric data on patients who underwent primary TKA was retrospectively reviewed. Multivariable logistic regression assessed the influence of BMI and weight change on outcomes while controlling for confounding variables. Outcomes included prolonged length of stay (LOS >3 days), non-home discharge, 90-day readmission rate, satisfaction, and achievement of MCID for KOOS-Pain and KOOS-PS. Results: Preoperative weight change had no impact on prolonged LOS (gain, p=0.173; loss, p=0.599). Preoperative weight loss was associated with increased risk of non-home discharge (OR 1.47, p=0.003). There was also increased risk of 90-day readmission with preoperative weight gain (OR 1.27, p=0.047) and decreased risk with weight loss (OR 0.73, p=0.033). There was increased risk of non-home discharge with obesity class II (OR 1.6, p=0.016) and III (OR 2.21, p<0.001). Weight change was not associated with failure to achieve satisfaction, MCID in KOOS-Pain, or MCID in KOOS-PS. Obesity class III patients had decreased risk of failure to reach MCID in KOOS-Pain (OR 0.43, p=0.005) and KOOS-PS (OR 0.7, p=0.007). Conclusion: Pre- and postoperative weight change has little impact on the achievement of satisfaction and clinically relevant differences in pain and function at 1-year. However, preoperative weight gain was associated with a higher risk of 90-day readmissions after TKA. Furthermore, patients categorized in Class III obesity were at increased risk of non-home discharge but experienced a greater likelihood of achieving MCID in KOOS-Pain and KOOS-PS. Our results raise awareness of the dangers of using weight changes and BMI alone as a measure of TKA eligibility.