Disparate postoperative results in the first and second knees on simultaneous bilateral total knee arthroplasty.

We hypothesized that the circumstances of the two consecutive operations of a simultaneous bilateral total knee arthroplasty (TKA) are different, and could lead to different outcomes of overlapping bilateral TKAs. Both knees of 420 subjects were evaluated in the current study. In the second TKA, there were more incidence rates of outlier in mechanical femoro-tibial angle (16.2% vs. 9.0%), more blood loss (735 vs. 656 mL), and longer operation time (61, 58 minutes respectively), as compared to the first TKA, while no significant differences in clinical outcomes. In conclusion, there were no significant differences in the clinical outcomes even though few distinct outcomes due to different circumstances of the surgery. Awareness of these findings can help the continued success of bilateral TKA in an increasing patient population.