The effects of the COVID-19 pandemic on elective unicompartmental knee arthroplasty in the USA: further evidence that outpatient arthroplasty is safe and effective.

Purpose: In response to COVID-19, elective surgeries including unicompartmental knee arthroplasties (UKA) decreased. We aimed to quantify and compare temporal trends in utilization and complications in the calendar year 2019 (pre-pandemic) to 2020 in the USA.

Methods: The 2019 to 2020 ACS-NSQIP database was queried for patients undergoing elective UKA. Patients prior to COVID-19 (2019 and 2020 Q1) were compared to those after (2020 Q2-Q4). Case volumes, patient demographics, complications, and lengths of stay (LOS) were compared between years. Pearson's chi-square test was used to compare patient demographics. Linear regression was conducted to evaluate the change in case volumes. P values less than 0.05 were significant.

Results: In total, 3361 patients underwent UKA: 1880 in 2019 and 1481 in 2020. The number of outpatient UKAs increased (56.4% vs. 65.6%; p < 0.001). There was no significant difference in the volume of cases in 2019Q1 through 2020Q1 (p = 0.424). Case volumes fell by 60% in 2020Q2 compared with the average quarterly volume in 2019. Comparing 2019 to 2020, there was no significant difference in rates of total complications (2.1% vs. 2.2%; p = 0.843), minor complications (1.2% vs. 0.9%; p = 0.529), major complications (1.1% vs. 1.4%; p = 0.447), infection complications (1.0% vs. 0.8%; p = 0.652), wound complications (0.1% vs. 0.1%; p = 1.0), cardiac complications (0.0% vs. 0.1%; p = 0.111), pulmonary complications (0.1% vs. 0.2%; p = 0.473), hematology complications (0.1% vs. 0.1%; p = 1.0), renal complications (0.1% vs. 0.0%; p = 1.0), and Clavien-Dindo IV complications (0.1% vs. 0.4%; p = 0.177).

Conclusion: UKA case volumes declined during the second quarter of 2020. A significant proportion of surgeries were transitioned outpatient, despite no change in complication rates.