Outpatient Revision TKA Does Not Increase Incidence of Repeat Revision or Medical and Surgical Complications Compared With Inpatient Revision TKA
Authors: Plancher Kevin D. , Mannina Carlo , Schwartz Elias , Briggs Karen K. , Petterson Stephanie C. 
Published: February 2025

Background
The incidence of revision TKA is escalating. The safety and efficacy of performing revision TKA in an outpatient setting is important given this increased demand.

Questions/purposes
(1) Are patients who undergo revision TKA in an outpatient setting more likely to undergo a repeat revision within 1 year compared with patients undergoing revision TKA in an inpatient setting? (2) Are patients who undergo outpatient revision TKA more likely to have increased hospital readmissions, manipulation under anesthesia (MUA), and medical complications compared with patients undergoing revision TKA in an inpatient setting?

Methods
Patients who underwent single-component revision TKA in either an outpatient or inpatient setting were identified in the PearlDiver Mariner database using Current Procedural Terminology codes or ICD-9 and ICD-10 diagnosis codes. The PearlDiver database is a for-fee insurance patient records database that contains > 165 million individual patient records from 2010 to 2022 and allows patients to be tracked over time. Groups were propensity score–matched to minimize the risk of selection bias that patients with greater comorbidities would be treated in an inpatient setting. Propensity matching was performed using a 1:4 ratio by age, gender, and Elixhauser Comorbidity Index (ECI). After propensity matching, a total of 30,924 patients who underwent single-component revision TKA were included in the inpatient group and 7731 patients were included in the outpatient group. Outcome measures included rates of repeat revision at 1 year, hospital readmission at 90 days, and complications including deep vein thrombosis, pulmonary embolus, blood transfusion, wound complications, periprosthetic joint infection, and MUA at 90 days. Chi-square analyses were used to compare categorical variables, and independent samples t-tests were used to compare continuous variables. Because any observed differences favoring outpatient revision TKA were likely due to selection bias with no biologically plausible explanation for outpatient surgery resulting in fewer medical or surgical complications, the findings were interpreted as a noninferiority analysis, indicating that outpatient revision TKA is not inferior to inpatient revision TKA even if the data indicated a potential advantage for outpatient revision TKA over inpatient revision TKA.

Results
The 1-year incidence of repeat revision was no higher in the outpatient group than the inpatient group (5% [359 of 7731] versus 5% [1606 of 30,924]; p = 0.05). The incidence of 90-day hospital readmission was no higher in the outpatient revision TKA group compared with the inpatient revision TKA group (8% [643 of 7731] versus 15% [4561 of 30,924]; p < 0.001). The incidence of all medical and surgical complications investigated was no higher in the outpatient revision TKA group compared with the inpatient revision TKA group.

Conclusion
In this study, outpatient revision TKA did not have a higher incidence of repeat revision, hospital readmission, and medical or surgical complications compared with performing revision TKA in an inpatient setting. However, we do not suggest that revision TKA in the outpatient setting is appropriate for all patients or that it is safer than in the inpatient setting, as there was some unmeasured confounding despite propensity matching in this large data set. Our findings suggest that with careful patient selection, complication and revision rates can be comparable to those seen with inpatient revision surgery while also freeing up inpatient resources for patients who would benefit from them. When determining the appropriate setting for revision TKA, it is crucial to consider the patient’s overall health and medical comorbidities. Future studies should explore patient selection criteria and outcomes including patient satisfaction, pain scores, and cost savings of outpatient versus inpatient revision TKA to refine best practices and guide clinical decision-making.

Level of Evidence
Level III, therapeutic study.