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

Bilateral unicompartmental knee arthroplasty (bUKA) done on the same day (simultaneous bUKA [sbUKA]) has been shown to be safe and cost-effective in hospital settings. Given the popularity and increased use of ambulatory surgery centers (ASCs), the purpose of this study was to compare safety and patient-reported outcome measures of sbUKA done at the hospital versus ASC. Consecutive primary sbUKAs over five 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 patient-reported outcome scores were collected between the two groups. Groups were compared using Student’s unpaired t-tests for continuous variables and χ2 tests for categorical variables. 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 and nine (10%) returned to the emergency department 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 or Knee injury and Osteoarthritis Outcome Score for Joint Replacement scores postoperatively. Outpatient sbUKA can safely be performed in selected patients. There is no difference in functional outcomes between outpatient and inpatient sbUKA.