Comparison of time courses in postoperative functional outcomes between simultaneous bilateral and unilateral total knee arthroplasty with propensity score matching

Abstract

Abstract Background: No consensus has been reached on which is better in terms of functional outcomes between simultaneous bilateral and unilateral total knee arthroplasty (TKA). As patient characteristics, such as age, sex, and body mass index, have significant effects on functional outcomes after TKA, we should match these factors before making comparisons. This study aimed to compare time courses in functional outcomes between simultaneous bilateral TKA and unilateral TKA after matching the patient characteristics. Methods: In this retrospective study, we reviewed the clinical records of patients admitted to our hospital. After excluding the patients who did not meet the criteria, 43 underwent simultaneous bilateral TKA and 382 underwent unilateral TKA were included in this study. We performed propensity score matching for age, sex, and body mass index between simultaneous bilateral and unilateral TKA patients. We measured pain intensity, knee extensor strength, and knee-specific functional outcomes using the new knee society score, including total score, symptoms, patient satisfaction, patient expectations, and functional activities preoperatively and at 3 and 12 months postoperatively. Two-way repeated analysis of variance was performed to compare the time courses in functional outcomes between simultaneous bilateral and unilateral TKA. Results: After propensity score matching, 40 patients each for underwent bilateral TKA and unilateral TKA were selected. Knee extensor strength in simultaneous bilateral TKA patients was significantly lower than that in unilateral TKA patients at 3 months postoperatively (p = 0.04). A significant interaction was observed between the effects of time and group on knee extensor strength (F [1, 78] = 3.338; interaction: p = 0.042; η2 = 0.052). No significant interactions were found among the other variables measured. Conclusions: Patients who underwent simultaneous bilateral TKA showed delayed recovery in knee extensor strength at 3 months postoperatively, but recovered to the same level at 12 months postoperatively. Patients who underwent simultaneous bilateral TKA should undergo postoperative rehabilitation focused on alleviating delayed recovery in knee extensor strength during the acute phase.