Centers for Medicare & Medicaid Services' 2018 Removal of Total Knee Arthroplasty From the Inpatient-only List Led to Broad Changes in Hospital Length of Stays.

Introduction: Centers for Medicare & Medicaid Services (CMS) removed total knee arthroplasty (TKA) from the "inpatient-only" list from January 1, 2018. The impact of this change on actual hospital length of stay (LOS) and patient coding is of interest.

Methods: Patients undergoing TKA were abstracted from the 2015 to 2018 National Surgical Quality Improvement Program database. Patient characterization as "inpatient" or "outpatient" and actual LOS were assessed. Ordinal and categorical data comparisons were done with Pearson chi-squared tests. Continuous variables were tested for normality, and nonparametric analyses were conducted using the Mann-Whitney test. Significance was set at P < 0.05.

Results: In total, 125,613 TKA patients from 2017 to 2018 were identified (232,269 TKA patients from 2015 to 2018). Most patients undergoing TKA were of Medicare eligibility (≥65 years old; 60.78% in 2017 and 62.42% in 2018). Overall, LOS decreased significantly from 2017 to 2018 (2.31 ± 1.56 days versus 2.05 ± 1.57 days; P < 0.001), and more patients were discharged the same day (5.09% versus 2.28%; P < 0.001). In 2017, patients were coded as "outpatient" 1.66% of the time (those with LOS = 0 days were 22.85%, LOS = 1 day were 1.80%, LOS = 2 days were 0.79%, and LOS ≥3 days were 0.85%). In 2018, patients were coded as "outpatient" 17.14% of the time (those with LOS = 0 days were 78.2%, LOS = 1 day were 29.75%, LOS = 2 days were 6.96%, and LOS ≥3 days were 3.05%). This represented a significant change for each LOS day (P < 0.001). These results remained true when stratifying by Medicare eligibility (P < 0.001 for those <65 years old and those ≥65 years old).

Discussion: After the 2018 removal of TKA from the CMS "inpatient-only" list, patients were more likely to be discharged the same day and be considered "outpatients." Patients with more prolonged LOS and those younger than 65 years were more likely to have been coded as "outpatient" in 2018 compared with 2017. These data demonstrate that national changes in CMS policies can have broad impact on overall practice patterns.

Level Of Evidence: Retrospective cohort study.