Outpatient Simultaneous Bilateral Unicompartmental Knee Arthroplasties: Safe with Positive Patient-Reported Outcomes.

Background: Bilateral unicompartmental knee arthroplasty (bUKA) done on the same day (simultaneous) (sbUKA) has been shown to be safe and cost-effective in hospital settings. Given the popularity and increased use of ambulatory surgery centers (ASC), the purpose of this study was to compare safety and patient-reported outcome measures (PROMs) of sbUKA done at the hospital versus ASC.

Methods: Consecutive primary sbUKAs over 5 years done by a single surgeon were retrospectively collected. Surgeries were done at a hospital or ASC. Baseline demographics, intraoperative and postoperative results, and Knee injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-jr) patient-reported outcome scores were collected between the two groups. Groups were compared utilizing Student's unpaired t-tests for continuous variables and χ2 tests for categorical variables.

Results: Of 146 patients (292 knees) who underwent sbUKA, 90 were done at a hospital, and 56 were done at an ASC. Length of stay was longer (53 versus five hours, P < 0.001), and operative time was longer (82 versus 68 minutes, P < 0.001) in the hospital group. In the hospital group, 11 (12.2%) were discharged to subacute rehab (SAR) and nine (10%) returned to the emergency department (ED) within 120 days compared to zero patients in the ASC group (P = 0.007 and 0.015, respectively). There was no significant difference in the final range of motion nor KOOS-jr scores postoperatively.

Conclusion: Outpatient SbUKA can safely be performed in selected patients. There is no difference in functional outcomes between outpatient and inpatient SbUKA.