Major National Shifts to Outpatient Total Knee Arthroplasties in the United States: A 10-Year Trends Analysis of Procedure Volumes, Complications, and Healthcare Utilizations (2010 to 2020)

Background: The removal of total knee arthroplasty (TKA) from inpatient-only lists accelerated changes in orthopaedic surgical practices across the United States. This study aimed to (1) quantify the annual volume of inpatient/outpatient primary TKAs; (2) compare patient characteristics before/after the year 2018; and (3) compare annual trends in 30-day readmissions, 30-day complications, and healthcare utilization parameters for inpatient/outpatient TKAs. Methods: The National Surgical Quality Improvement Program was reviewed (January 2010 to December 2020) for patients who underwent primary TKA (n = 470,456). The primary outcome was annual volumes of inpatient/outpatient TKA. Secondary outcomes included 30-day readmissions, 30-day reoperations, and 30-day major/minor complications. Demographic characteristics and healthcare utilization parameters (hospital lengths of stay and discharge dispositions) were compared between cohorts via Chi-square goodness-of-fit tests. Results: Overall, 89% had inpatient TKA (n = 416,972) and 11% had outpatient TKA (n = 53,854). Between 2017 and 2020, annual volumes of outpatient TKA increased by 1,925 (1,019 to 20,633), while inpatient TKA decreased by 53% (61,874 to 29,280). Patients who had outpatient TKA after 2018 were older (P < .001), predominantly males (P < .001), more commonly White (P < .001), and had a greater proportion of American Society of Anesthesiologists class III (P < .001). The inpatient cohort had higher rates of 30-day readmissions, reoperations, and complications. Average length of stay and nonhome discharges decreased for both cohorts. Conclusion: Outpatient TKA increased 20-fold at NSQIP hospitals. The changes in comorbidity profiles and the increase in volumes of outpatient TKA were not associated with a rise in cumulative 30-day readmissions and complications. Further research and policy endeavors should focus on identifying patients who still require or benefit from inpatient TKA.