The use of surgical interspinous implants has been a controversial subject. Wouter A Moojen writes that the efficacy of such devices should be challenged in order to adhere to medical ethical standards and protect patients.
The clinical introduction of novel medical implants, particularly high-risk spine implants, often occurs with relatively little oversight and regulation.1 This is in contrast with the strong regulatory requirements that are in place for the introduction of novel pharmaceuticals. As a consequence, the safety, efficacy and long-term effects of medical implant devices are often insufficiently known before they are used in patients.1,2
Surgical interspinous implants have been used to treat intermittent neurogenic claudication in patients with lumbar spinal stenosis. Some evidence has suggested it provides better outcomes compared with no (conservative) treatment.3 In 2011, >30% of spine centres used implants,4 though no clinical trial had previously been conducted to compare the efficacy of surgical interspinous implants with the gold-standard of spinal bony compression.
At the Annual Meeting of the North American Spine Society (12–15 November 2014, San Francisco, USA), I presented the two-year results of the “Surgical interspinous implant versus conventional decompression for lumbar spinal stenosis trial,”5 which compared surgical interspinous implants to conventional decompression for patients with one- or two-level lumbar spinal stenosis.
In this multicentre controlled, double-blinded trial, my colleagues and I randomised 159 patients with one- or two-level lumbar spinal stenosis for whom conservative treatment had failed, to an interspinous implant (n=80) or bony decompression (n=79) group.
The baseline characteristics, incision size, and postoperative care were similar in both groups. Surgery was performed on two levels in 18% of patients in the decompression group and 26% in the implant group. The visual analogue scale (VAS) leg-pain score was between 52 and 58, and the VAS back pain score was between 60 and 49.
We evaluated symptom severity, physical function, and patient satisfaction at eight weeks using the Zurich Claudication Questionnaire and found no difference between the two groups at one or two years (Figure 1). Further, no difference was found between the two groups at eight weeks, one year, or two years for back pain as measured with the VAS score. The analyses were intention-to-treat.
For patients treated with implants, our study found a significantly higher rate of re-operations compared with the bony decompression group (33% vs 8%; p value not reported). The rate of successful recovery after re-operation was lower than after the first operation.
Our study found that clinical outcomes were similar with surgical interspinous implants and conventional bony decompression at two years. Back pain, as measured by the VAS score, was not reduced with surgical interspinous implants. Further, it was associated with the need for additional surgery. Similar results were obtained in other clinical trials of implants in this setting.6 These studies and our own suggest that surgical interspinous implants confer no advantage over conventional bony decompression in patients with lumbar spinal stenosis, and, as such, conventional decompression should remain the standard for treatment.
These studies and results underscore the need to reconsider how innovation in medical devices can adhere to sound ethical standards without inhibiting surgical research and development. The two measures for improvement that are most feasible in the short term are to demand prospective studies before device introduction and to develop registries to monitor and evaluate new medical devices.
Wouter A Moojen is a neurosurgeon at Leiden University Medical Center and The Hague Medical Center, the Netherlands
1 World Health Organization; 2010.
2 Bredenoord AL, Giesbertz NA, van Delden JJ. Public Health Ethics 2013; 6: 226–9
3 Moojen WA et al. Eur Spine J 2011
4 Overdevest GM, Moojen WA, et al. Acta Neurochirurgica (Wien) 2014; 156(11): 2139–45
5 NASS 2014; abstract 121
6 Davis RJ. Spine 2013; Strömqvist BH. Spine (Phila Pa 1976) 2013; Richter A. Eur Spine J 2010