No Difference in Postoperative Complications Between Simultaneous and Staged, Bilateral Unicompartmental Knee Arthroplasty

Background The optimal timing of contralateral surgery following unicompartmental knee arthroplasty (UKA) remains unknown. Therefore, the objective of this study was to examine the differences in postoperative complications in patients undergoing unilateral, simultaneous and staged bilateral UKA. Methods The PearlDiver administrative claims database was queried for patients undergoing UKA between 2015-2020. Patients undergoing unilateral UKA were matched in a 1:1 fashion based on age, gender, Elixhauser Comorbidity Index (ECI), obesity, diabetes and smoking status to patients undergoing simultaneous bilateral UKA, bilateral UKA staged 1-90 days and bilateral UKA staged 91-365 days. Univariate and multivariate analyses were performed to examine the impact of timing of bilateral procedures on 90-day postoperative complications relative to patients who underwent unilateral UKA. Outcomes were considered significant at p<0.05. Results A total of 9,638 patients undergoing UKA were included in the final analysis, of which 5,672 (58.9%) were unilateral, 396 (4.1%) were simultaneous bilateral, 1,496 (15.5%) were bilateral staged between 1-90 days and 2,074 (21.5%) were bilateral staged between 91-365 days. Univariate analysis identified no significant differences in complications between matched groups except for an increased incidence of wound dehiscence amongst patients who underwent simultaneous bilateral UKA (2.1% vs. 0.0%, p=0.040) compared to unilateral UKA. However, multivariate analysis demonstrated that simultaneous or staged bilateral UKA at either time point did not increase the risk of any postoperative complication relative to unilateral surgery. Conclusion Bilateral UKA can be performed simultaneously or in a staged fashion without increasing the risk of 90-day complications relative to unilateral UKA.