Understanding the value of minimally invasive procedures for the treatment of lumbar spinal stenosis: the case of interspinous spacer devices

Publication date: Available online 25 August 2017
Source:The Spine Journal
Author(s): Stephanie J. Tapp, Brook I. Martin, Tor D. Tosteson, Jon D. Lurie, Milton C. Weinstein, Richard A. Deyo, Sohail K. Mirza, Anna N.A. Tosteson
Background ContextMinimally invasive lumbar spinal stenosis procedures have uncertain long-term value.PurposeThis study sought to characterize factors affecting the long-term cost-effectiveness of such procedures using interspinous spacer devices ("spacers") relative to decompression surgery as a case study.Study DesignModel-based cost-effectiveness analysis.Patient SampleThe Medicare Provider Analysis and Review database for the years 2005-2009 was used to model a group of 65-year-old patients with spinal stenosis who had no previous spine surgery and no contraindications to decompression surgery.Outcome MeasuresCosts, quality-adjusted life years, and cost per quality-adjusted life year gained.MethodsA Markov model tracked health utility and costs over 10 years for a 65-year-old cohort under three care strategies: conservative care, spacer surgery, and decompression surgery. Incremental cost-effectiveness ratios (ICER) reported as cost per quality-adjusted life year (QALY) gained included direct medical costs for surgery. Medicare claims data were used to estimate complication rates, reoperation and related costs within 3 years. Utilities and long-term reoperation rates for decompression were derived from published studies. Spacer failure requiring reoperation beyond 3 years and post-spacer health utilities are uncertain and were evaluated through sensitivity analyses. In the base-case, the spacer failure rate was held constant for years 4-10 (cumulative failure: 47%). In a "worst-case" analysis, the 10-year cumulative reoperation rate was increased steeply (to 90%). Threshold analyses were performed to determine the impact of failure and post-spacer health utility on the cost-effectiveness of spacer surgery.ResultsThe spacer strategy had an ICER of $89,500/QALY gained under base-case assumptions, and remained under $100,000 as long as the 10-yr cumulative probability of reoperation did not exceed 54%. Under worst-case assumptions, the spacer ICER was $482,000/QALY and fell below $100,000 only if post-spacer utility was 0.01 greater than post-decompression utility or the cost of spacer surgery was $1,600 less than the cost of decompression surgery.ConclusionsSpacers may provide a reasonably cost-effective initial treatment option for patients with lumbar spinal stenosis. Their value is expected to improve if procedure costs are lower in outpatient settings where these procedures are increasingly being done. Decision analysis is useful for characterizing the long-term cost-effectiveness potential for minimally invasive spinal stenosis treatments and highlights the importance of complication rates and prospective health utility assessment.



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