Interspinous process devices versus standard conventional surgical decompression for lumbar spinal stenosis: cost-utility analysis.

BACKGROUND CONTEXT: In the 1980s, a new implant was developed to treat patients with intermittent neurogenic claudication caused by lumbar spinal stenosis (LSS). This implant is now widely used.

PURPOSE: The objective of this study is to determine whether a favorable cost-effectiveness for interspinous process devices (IPDs) compared with conventional bony decompression is attained.

STUDY DESIGN/SETTING: Cost-utility analysis was performed alongside a double-blind randomized controlled trial. Five neurosurgical centers (including one academic and four secondary level care centers) included participants for this study.

PATIENT SAMPLE: One hundred fifty-nine patients with LSS were treated with the implantation of IPD and with bony decompression. Eighty participants received an IPD, and seventy-nine participants underwent spinal bony decompression.

OUTCOME MEASURES: Outcome measures were quality-adjusted life-years (QALYs) and societal costs in the first year (estimated per quarter), estimated from patient-reported utilities (US and The Netherlands EuroQol 5D [EQ-5D] and EuroQol visual analog scale) and diaries on costs (health-care costs, patient costs, and productivity costs).

METHODS: All analyses followed the intention-to-treat principle. Given the statistical uncertainty of differences between costs and QALYs, cost-effectiveness acceptability curves graph the probability that a strategy is cost effective, as a function of willingness to pay. Paradigm Spine funded this trial but did not have any part in data analysis or the design and preparation of this article.

RESULTS: According to the EQ-5D, the valuation of quality of life after IPD and decompression was not different. Mean utilities during all four quarters were, not significantly, less favorable after IPD according to the EQ-5D with a decrease in QALYs according to the US EQ-5D of 0.024 (95% confidence interval, -0.031 to 0.079). From a health-care perspective, the costs of IPD treatment were higher (difference €3,030 per patient, 95% confidence interval, €561-€5,498). This significant difference is mainly because of additional cost of implants of €2,350 apiece. From a societal perspective, a nonsignificant difference of €2,762 (95% confidence interval, -€1,572 to €7,095) in favor of conventional bony decompression was found.

CONCLUSIONS: Implantation of IPD as indirect decompressing device is highly unlikely to be cost effective compared with bony decompression for patients with intermittent neurogenic claudication caused by LSS.

TRIAL REGISTRATION: Dutch Trial Register Number: NTR1307.