Healthcare Utilization and Costs of Inpatient versus Outpatient Interspinous Process Device Placement: A National Claims Database Study

Purpose: As healthcare costs rise, lumbar spine procedures are increasingly performed in outpatient settings. Interspinous process devices (IPDs) were developed as motion-preserving alternatives to lumbar fusion and are more frequently utilized in ambulatory centers. This study compared complications, healthcare utilization, and costs of IPD placement in inpatient and outpatient settings. Methods: This retrospective cohort study identified patients who underwent single-level IPD placement with concurrent open decompression between 2017 and 2022 in the PearlDiver database. Patients were matched 1:4 on age, sex, and the Elixhauser Comorbidity Index to create inpatient and outpatient cohorts. Outcomes included perioperative complications, 30-day and 90-day emergency department (ED) visits and readmissions, day-of-surgery reimbursement, and 90-day global reimbursement. Descriptive statistics and Chi-squared tests were performed for between-group comparisons. Results: 1587 patients with outpatient procedures were matched with 412 patients with inpatient procedures. There were no significant differences in intraoperative or postoperative complications, or in rates of postoperative ED visits and readmissions. Outpatient procedures were associated with significantly lower costs, both on the day of surgery (mean ± SD; inpatient: $2505 ± $4804 vs. outpatient: $1976 ± $3391; p < 0.001) and within 90 days postoperatively (mean ± SD; inpatient: $5234 ± $6539 vs. outpatient: $4197 ± $5514; p < 0.001). Although total IPD procedure volume declined over the study period, the ambulatory proportion increased. Conclusion: Outpatient single-level IPD insertion with decompression is associated with lower costs with no significant differences in complications, ED visits, or readmissions. These findings may inform site-of-service decisions in appropriately selected patients.