Cost-effectiveness of interspinous process device implantation “highly unlikely”

M Elske van den Akker-van Marle
Elske van den Akker-van Marle

A Dutch cost-utility study published in The Spine Journal argues that implantation of interspinous process devices as an indirect decompressing measure is “highly unlikely to be cost-effective compared with bony decompression for patients with intermittent neurogenic claudication caused by lumbar spinal stenosis”.

In 1984, interspinous process devices were developed to indirectly decompress the lumbar spinal by being placed between the spinous processes. When using these devices, procedure time was proposed to be shorter with less bony destruction, and the technique was meant to accustom day surgery protocols, resulting in a shorter rehabilitation period after surgery. Elske van den Akker-van Marle, Leiden University Medical Center, Leiden, The Netherlands, and colleagues write, “Despite the high costs of the implants and the high rate of implantations of interspinous process devices, clinical trials comparing them with the gold standard (bony decompression) were not performed. The scientific evidence published up to 2004 showed that the use of interspinous process devices was superior compared only with conservative (non-intervention) treatment.”

Van den Akker-van Marle and colleagues cite their previous research as indicating that the use of interspinous implants compared with conventional decompression did not result in the better outcomes or shorter recovery times hypothesised, while reoperation rate was “significantly higher” in the patients who had received an interspinous process device. “The higher costs of interspinous process devices in combination with the comparable results after one year and the higher reoperation rate do not seem to support the use of such devices from an economical point of view,” the authors write. “However, quality of life estimates and a complete cost overview could lead to another conclusion.”

In this investigation, cost-utility analysis was performed alongside a double-blind randomised controlled trial. Five neurosurgical centres (including one academic and four secondary level care centres) included participants. One hundred and fifty-nine patients with lumbar spinal stenosis were treated; 80 with an interspinous process device (X-STOP, Medtronic) and 79 participants with spinal bony decompression.

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 Dutch EuroQol 5D [EQ-5D] and EuroQol visual analogue scale) and diaries on costs (healthcare costs, patient costs, and productivity costs).

The authors report that, according to the EQ-5D, the valuation of quality of life after interspinous process device implantation and decompression was no different. Mean utilities during all four quarters were less favourable after interspinous device implantation 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), although this difference was not significant. From a health-care perspective, the costs of interspinous process device treatment were higher (difference of €2,302 per patient, 95% CI, €1,857–2,747). “This significant difference is mainly because of additional cost of implants of €2,350 apiece,” van den Akker-van Marle et al explain. In the first year after treatment, 21% of the interspinous process device patients underwent reoperation in comparison with 6% of the patients in the decompression group, resulting in (non-significant) higher costs of reoperation for interspinous process device patients of €198 per patient (€112–507). In total, mean healthcare costs per patient in the first year were €10,210 for interspinous process device and €7,180 for decompression patients. This difference of €3,030, the authors note, is significant (95% CI, €561–5,498).

“From a societal perspective, a nonsignificant difference of €2,762 (95% CI, €1,572–7,095) in favour of conventional bony decompression was found,” the authors continue; total societal costs were found to be €13,858 per interspinous process device patient and €11,096 per decompression patient in the first year after treatment.”

Using these findings for a cost-utility analysis, van den Akker-van Marle et al report that “The combination of (non-significant) higher societal costs and less favourable QALY outcomes (not significant) after interspinous process device implantation results in a small probability that it is more cost-effective compared with decompression. For any value of the willingness to pay for a QALY, the probability that interspinous process devices are more cost-effective than decompression is far below 50%.” The authors further note that these results hold for all outcome measures. They continue, “From a health-care perspective in which interspinous process devices are significantly more costly, the superiority of decompression is even clearer. This leads to the overall result that simple decompression is more cost-effective than interspinous process devices.”

In conclusion, van der Akker-van Marle told Spinal News International, “Implants are more expensive from a health care perspective compared with usual bony decompression without benefit.”


  1. Unfortunately the authors of this article do not understand the difference between posterior decompression devices and posterior interspinous stabilization devices for minimally invasive stabilization for fusions. They are two different devices for different uses. It is a well known fact that instomentation without fusion is set up for failure the posterior stabilization devices such as the Stabllink device can give the advantage of rods and screws for fusion without the wide dissection or risk associated with rods and screws. These need to be differentiated