Comparative Analysis of Inpatient and Outpatient Interspinous Process Device Placement for Lumbar Spinal Stenosis

Abstract

Purpose: To compare reoperations, health care utilization, and costs in lumbar spinal stenosis (LSS) patients undergoing interspinous process (ISP) device placement in an inpatient versus outpatient setting.

Methods: The MarketScan database (2007-2009) was queried for adults with LSS undergoing ISP device placement as a primary procedure. Reoperations, health care utilization, and costs in patients with at least 18 months of follow-up were analyzed. Chi-square and Student t tests were used to assess the differences in characteristics and outcomes between patients treated in the inpatient and outpatient setting.

Results: A total of 411 patients who underwent ISP device placement were identified; the mean age was 72 years, 51% were female, and most patients were insured by Medicare (73.7%). The average postoperative follow-up was 24.9 months. A subset of 182 patients (44.3%) had inpatient procedures; 229 (55.7%) underwent outpatient ISP device placements. The overall reoperation rate was 20.4%. ISP reoperation rates between inpatient and outpatient cohorts were comparable (23.1% versus 18.3%; p = 0.24). Inpatients accrued significantly higher index procedural costs compared with outpatients ($17,432 versus $8854; p = 0.0001), however, the outpatient cohort utilized more postoperative outpatient services (143 versus 112; p = 0.09) and higher outpatient service costs ($25,376 versus $15,481; p = 0.01). Consequently, cumulative overall cost was similar among the two cohorts ($51,059 versus $51,778; p = 0.94).

Conclusions: Long-term reoperation rates following ISP device placement are comparable in the inpatient and outpatient setting. Upfront cost savings may be achieved with outpatient ISP device placement, but this benefit is lost by 18 months following initial surgery.