Reimbursement and Complications in Outpatient vs Inpatient Unicompartmental Arthroplasty

Increasing utilization of unicompartmental knee arthroplasty (UKA) has driven a greater push for outpatient treatment and cost containment in the setting of bundled payments. The purpose of this study is to evaluate utilization trends of inpatient vs outpatient UKA, index episode and 90-day reimbursement, and any differences in medical or surgical complications. The PearlDiver database was employed to identify all inpatient and outpatient UKAs performed between 2007 and 2016 with 2-year follow-up. Patients were matched by age, gender, and Elixhauser Comorbidity Index. We tracked index procedure and global period reimbursement, 90-day medical and surgical complications, and 2-year surgical complications. The reimbursement and utilization cohort included 3181 outpatient and 5490 inpatient UKAs. Outpatient UKA and overall utilization of UKA increased over the study period. Mean index reimbursement of inpatient UKA was $2486.16 higher per procedure (P < .001) while mean global period reimbursement was $2782.13 higher per inpatient procedure (P < .001). Ninety-day medical complications including postoperative anemia (P < .001), transfusion (P = .024), and arrhythmia (P = .004) were more common with inpatient UKAs, whereas surgical wound complications (P = .001) and operative debridement (P = .028) were more common among outpatient UKAs. Outpatient UKA was not associated with an increased risk of periprosthetic joint infection (P > .05), aseptic loosening (P > .05), or revision surgery (P > .05) when compared to inpatient UKA. Outpatient UKA utilization is increasing and is associated with decreased reimbursement compared to inpatient UKA without increased risk of major medical complications, although it is associated with increased risk of wound complication and need for operative debridement at 90 days.