Rates and Causes of 90-day Complications and Readmissions Following Outpatient Hip and Knee Arthroplasty: A Retrospective Analysis of 525 Patients in a Single Institution.

Background: Outpatient joint arthroplasty (OJA) has gained increasing popularity and success in a well-defined population. Safety concerns, in terms of complications and readmissions, however still exist.

Patients And Methods: This retrospective study included 525 patients (90 primary THAs, 277 primary TKAs, and 158 primary UKAs), initially planned for OJA. All complications and readmissions were evaluated for timing and cause (surgical vs medical) within a 90-day followup. Complications and readmissions were compared by the length of stay (LOS): same-day discharge (SDD) vs ≥1 day. Differences were assessed by the log-rank test. Complications and readmission risk were assessed using multivariable logistic regression analysis.

Results: The complication rate was 9.9% at 30 days and 15% at 90 days. The readmission rate was 2.5% at 30 days and 4.2% at 90 days. The majority of surgical complications and readmissions were the result of wound discharge (43% and 56%, respectively). Overall, we did not observe different rates between SDD and LOS ≥1. Following THA, but not TKA or UKA, the 90-day complication rate was significantly lower in patients that underwent SDD compared with LOS ≥1. The risk of complications was positively associated with TKA (vs THA and UKA), ASA III (vs ASA I), and Charnley C (vs Charnley A). The risk of readmissions was negatively associated with a BMI ranging from 25-29.9 kg/m2 (vs BMI <25 kg/m2).

Conclusion: SDD following OJA did not result in more complications and hospital readmissions compared to a prolonged hospital stay. The majority of complications and readmissions were due to noninfected wound discharge.