Trends in Outpatient Total Knee Arthroplasty From 2012 to 2020.

BACKGROUND: Trends over the past decade suggest a steady increase in the proportion of total knee arthroplasty (TKA) performed on an outpatient basis. However, the optimal patient selection criteria for outpatient TKA remain unclear. We aimed to describe longitudinal trends in patients selected for outpatient TKA and identify risk factors for 30-day morbidity following inpatient and outpatient TKA. METHODS: We identified 379,959 primary TKA patients, 17,170 (4.5%) of whom underwent outpatient surgery from 2012 to 2020 within a large national database. We used regression models to evaluate trends in outpatient TKA, factors associated with undergoing outpatient (versus inpatient) TKA and 30-day morbidity following outpatient and inpatient TKA. We used receiver operating curves to examine cutoff points for continuous risk factors. RESULTS: The proportion of patients undergoing outpatient TKA increased from 0.4% in 2012 to 14.1% in 2020. Younger age, male sex, lower body mass index (BMI), higher hematocrit, and fewer comorbidities were associated with receiving outpatient (versus inpatient) TKA. Variables associated with 30-day morbidity in the outpatient group included older age, chronic dyspnea, chronic obstructive pulmonary disease, and higher BMI. The receiver operating curves indicated outpatients aged 68 years and older, or with a BMI of 31.4 or higher were more likely to experience 30-day complications. CONCLUSION: The proportion of patients undergoing outpatient TKA has been increasing since 2012. Older age (≥68 years), a higher BMI (≥31.4), and comorbidities such as chronic dyspnea, chronic obstructive pulmonary disease, diabetes, and hypertension were associated with an increased odd of 30-day morbidity following outpatient TKA.