Abstract
INTRODUCTION: The rising prevalence of obesity has increased the demand for total knee arthroplasty (TKA), but the impact on outcomes, particularly in Class I and II obesity, remains inconclusive. This study aimed to compare early in-hospital post-TKA outcomes in older patients with Class I (BMI 30-34.9 kg/m²) and Class II obesity (BMI 35-39.9 kg/m²). MATERIALS AND METHODS: Using data from the Nationwide Inpatient Sample (2016-2019), patients aged 65 and above who underwent TKA were categorized into Class I (n = 133,425) and Class II obesity groups (n = 122,432). Propensity score matching balanced baseline characteristics. Primary outcomes included in-hospital mortality and early postoperative complications. RESULTS: Post-matching, a higher prevalence of type 2 diabetes was found in the Class II obesity group (32.5% vs. 29.5%, P = 0.001). The Class II group had a significantly higher risk of in-hospital mortality (9.004-fold, 95% CI: 3.57-22.68, P < 0.001), acute kidney injury (45.8% increase, 95% CI: 1.383-1.537, P < 0.001), and postoperative pneumonia (32.5% increase, 95% CI: 1.095-1.604, P = 0.004). The risk of blood loss anemia was 3.3% lower in the Class II group (95% CI: 0.946-0.988, P = 0.002). No significant differences were found in heart failure, acute coronary artery disease, pulmonary edema, venous thromboembolism, pulmonary embolism, and blood transfusion. CONCLUSIONS: More intensive monitoring and preventive measures may be necessary for patients with Class II obesity to mitigate the heightened risks associated with TKA compared to those with Class I obesity.