Does patient selection account for the perceived cost savings in outpatient spine surgery? A meta-analysis of current evidence and analysis from an administrative database

Objective: From 1994 to 2006 outpatient spinal surgery increased 5-fold. The perceived cost savings with outcomes comparable to or better than those achieved with inpatient admission for the same procedures are desirable in an era where health expenditures are scrutinized. The increase in outpatient spine surgery is also driven by the proliferation of ambulatory surgery centers. In this study, the authors hypothesized that the total savings in outpatient spine surgery is largely driven by patient selection and biases toward healthier patients. Methods: A meta-analysis assessed patient selection factors and outcomes associated with outpatient spine procedures. Pooled odds ratios and mean differences were calculated using a Bayesian random-effects model. The authors extended this analysis in a novel way by using the results of the meta-analysis to examine cost data from an administrative database of academically affiliated hospitals. A Bayesian approach with priors informed by the meta-analysis was used to compare costs for inpatient and outpatient performance of anterior cervical discectomy and fusion (ACDF) and lumbar laminectomy. Results: Sixteen studies with a total of 370,195 patients met the inclusion criteria. Outpatient procedures were associated with younger patient age (mean difference [MD] -2.34, 95% credible interval [CrI] -4.39 to -0.34) and no diabetes diagnosis (odds ratio [OR] 0.78, 95% CrI 0.54-0.97). Outpatient procedures were associated with a lower likelihood of reoperation (OR 0.42, 95% CrI 0.16-0.80), 30-day readmission (OR 0.39, 95% CrI 0.16-0.74), and complications (OR 0.29, 95% CrI 0.15-0.50) and with lower overall costs (MD -$121,392.72, 95% CrI -$216,824.81 to -$23,632.92). Additional analysis of the national administrative data revealed more modest cost savings than those found in the meta-analysis for outpatient spine surgeries relative to inpatient spine surgeries. Estimated cost savings for both younger patients ($555 for those age 30-35 years [95% CrI -$733 to -$374]) and older patients ($7290 for those age 65-70 years [95% CrI -$7380 to -$7190]) were less than the overall cost savings found in the meta-analysis. Conclusions: Compared to inpatient spine surgery, outpatient spine surgery was associated with better short-term outcomes and an initial reduction in direct costs. A selection bias for outpatient procedures toward younger, healthier patients may confound these results. The additional analysis of the national database suggests that cost savings in the outpatient setting may be less than previously reported and a result of outpatient procedures being offered more frequently to younger and healthier individuals.