Contemporary Outpatient Arthroplasty Is Safe Compared with Inpatient Surgery: A Propensity Score-Matched Analysis of 574,375 Procedures

Background:

Outpatient joint arthroplasty is a potential modality for increased case throughput and is rising in demand. However, we are aware of no study that has compared outcomes between risk-matched outpatient and inpatient procedures within the last 7 years. The aims of this study were to compare matched patient cohorts who underwent outpatient or inpatient joint arthroplasty in terms of 30-day adverse events and readmission rates.

Methods:

From the National Surgical Quality Improvement Program database, we identified patients who underwent primary total hip arthroplasty (THA), primary total knee arthroplasty (TKA), and primary unicompartmental knee arthroplasty (UKA) from 2009 to 2018. Using 10 perioperative variables, patients who underwent an outpatient procedure were 1:4 propensity score-matched with patients who underwent an inpatient procedure. The rates of 30-day adverse events and readmission were compared using the McNemar test. The risk factors for adverse events and readmissions were identified using multivariate regression.

Results:

Of 574,375 patients identified, 21,506 (3.74%) underwent an outpatient procedure. After propensity score matching, an outpatient joint arthroplasty was associated with a lower rate of adverse events (3.18% compared with 7.45%; p < 0.001). When assessed individually, outpatient TKA (3.15% compared with 8.11%; p < 0.001), THA (4.94% compared with 10.05%; p < 0.001), and UKA (1.78% compared with 3.39%; p < 0.001) were all associated with fewer adverse events overall and there was no difference in the rate of 30-day readmission, when compared with inpatient analogs. Outpatient joint arthroplasty was an independent factor for lower adverse events (odds ratio [OR], 0.407 [95% confidence interval (CI), 0.369 to 0.449]; p < 0.001), with no increase in the risk of readmission (OR, 1.004 [95% CI, 0.878 to 1.148]; p = 0.951).

Conclusions:

Contemporary outpatient joint arthroplasty demonstrated lower rates of adverse events with no increased rate of 30-day readmission when compared with risk-matched inpatient counterparts. Although multiple factors should guide the decision for the site of care, outpatient arthroplasty may be a safe alternative to inpatient arthroplasty.

Level of Evidence:

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.