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.
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 non-home discharges. P values <0.008 were significant.
Women (OR:1.19,P=0.002), diabetes mellitus (OR:1.31,P=0.003), general anesthesia (OR:1.24, P=0.001), and longer operative times (≥95 minutes) (OR:1.82,P<0.001) 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 lengths of stay 2 or more days. The hospital-defined 'Outpatient' cohort had greater odds of non-home discharges (6.3 vs 2.8%;OR: 1.88,P<0.001) compared to SDD surgeries. The incidence was higher for any complication among hospital-defined 'Outpatient' designated patients compared to SDD (5.5 vs. 3.9%,P=0.007).
Outpatient surgeries may be misleading and often do not correlate with same day discharge, as over 20% remain in the hospital 2 or more days. Investigators should quantitatively define the “Outpatient” status by actual lengths of stay to allow standardization and results comparison.

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