Inconsistent Classification of "Outpatient" Surgeries Leads to Different Outcomes Following Total Hip Arthroplasty in Medicare Beneficiaries: A Critical Analysis.

Background: With rising utilization of outpatient total hip arthroplasty (THA) in older patients including Medicare beneficiaries, the objective was to compare differences in definition including (1) patient demographics; (2) lengths of stay (LOS); and (3) outcomes of "outpatient" (stated status) versus "same-day discharge" (SDD) (actual LOS = 0 days) utilizing a nationwide database.

Methods: A national database from 2015 to 2019 was queried for Medicare-aged patients undergoing outpatient THA. Total outpatient THAs (N = 6,072) were defined in one of 2 ways: either "outpatient" by the hospital (N = 2,003) or LOS = 0 days (N = 4,069). Demographics, LOS, discharge destinations, and complications were compared between groups. Logistic regression models computed odds ratios (ORs) for factors leading to complications, readmissions, and nonhome discharges. P values < .008 were significant.

Results: Women (OR: 1.19, P = .002), diabetes mellitus (OR: 1.31, P = .003), general anesthesia (OR: 1.24, P = .001), and longer operative times (≥95 minutes) (OR: 1.82, P < .001) were associated with 'outpatient' designation versus SDD. Within the hospital-defined 'outpatient' cohort, 49.1% (983 of 2,003) were discharged the same day (LOS = 0 days), and 21.8% had LOS 2 or more days. The hospital-defined 'outpatient' cohort had greater odds of nonhome discharges (6.3 versus 2.8%; OR: 1.88, P < .001) compared to SDD surgeries. The incidence was higher for any complication among hospital-defined 'outpatient' designated patients compared to SDD (5.5 versus 3.9%, P = .007).

Conclusions: Outpatient surgeries may be misleading and often do not correlate with SDD, as over 20% remain in the hospital 2 or more days. Investigators should quantitatively define the "outpatient" status by actual LOS to allow standardization and results comparison.

Level Of Evidence: III.