Safety and early outcomes of simultaneous bilateral TKA in patients with BMI > 40: A retrospective comparative study

Introduction: Simultaneous bilateral total knee arthroplasties (SBTKA) are common in Asia, but surgeons may have a body mass index (BMI) threshold for performing these procedures. However, no guidelines regarding patient weight and SBTKA exist in the literature. We hypothesized that SBTKA can be performed safely and efficiently for morbidly obese patients. We aimed to compare 1) the rate of complications within one year after surgery, 2) operative time, blood loss, and length of stay, and 3) clinical outcomes at one year after SBTKA in patients with BMI < 30 versus 30 < BMI < 40 and BMI > 40. Methods: In this retrospective comparative matched (age, ASA score) study, we evaluated 113 patients who underwent SBTKA (posterior stabilized cemented TKA), between 2019 and 2022. The patient population was grouped based on their BMI: BMI < 30 (33 patients), 30 < BMI < 40 (43 patients), and BMI > 40 (37 patients). A complication was defined as an event that could be classified as a grade > 3 according to the Clavien-Dindo classification within one year of surgery. Data on complication rate, operation time, blood loss, and preoperative and post-operative function KSS at one year were compared. Results: No significant difference in the occurrence of early complications between the three groups was observed. One patient was readmitted for periprosthetic fracture in the BMI < 30 group. There was no significant difference in operative time, blood loss, and KSS score at one year between the three groups. A significant functional improvement was observed in all three groups at the one-year follow-up. Discussion: This study suggests that SBTKA in patients with a BMI > 40 is safe, with no increased complications, similar surgical time, and blood loss. Significant functional improvement was observed at one year postoperatively. While promising, further multi-center studies are needed to confirm these findings and evaluate long-term outcomes.