Hospital Outpatient Department versus Ambulatory Surgical Center Outcomes in Lumbar Spine Surgery - A Propensity Matched Analysis by the Michigan Spine Surgery Improvement Collaborative (MSSIC)

Introduction: There has been a shift to performing elective surgical procedures at ambulatory surgery centers (ASC) to minimize costs, and spine surgery is no exception. However, there is a paucity of literature with direct comparisons between hospital outpatient department (HOPD) and ASC spine procedures within a multi-center study. We aim to compare post-operative outcomes for elective lumbar spine surgery between propensity matched patients undergoing surgery at HOPDs versus ASCs.

Methods: The Michigan Spine Surgery Improvement Collaborative (MSSIC) database was queried for patients who underwent outpatient lumbar decompression surgery from January 2021 to June 2023. Patients in the HOPD and ASC cohorts underwent propensity score matching based on BMI, ASA, and number of levels. Subsequent multivariate analysis was then performed to further control for confounding variables. Outcomes measured included adverse events, timing and disposition of discharge, readmissions, and ED presentations.

Results: 3,333 patients were included in this analysis. ASCs had a higher risk of any complication compared to HOPDs (IRR = 1.50; CI: 1.17-1.92, p=0.001) which was driven primarily by an increased risk in return to OR (IRR = 2.30; CI: 1.44-3.68, p < 0.001). Differences in risk of re-operation were driven by an increased incidence of recurrent disc herniations in the ASC setting (3.27% versus 1.01%). There was no significant difference in the risk of surgical site infection, post-operative ED visit, or 30- and 90-day readmission.

Conclusion : Though the utilization of ASCs may provide benefits in cost, surgical outcomes within health systems must be analyzed. There may be a higher risk of complications and reoperations for patients undergoing surgery at ASCs when compared to an outpatient surgery performed in a hospital setting.