BMJ 2015;350:h1664 doi: 10.1136/bmj.h1664 (Published 1 April 2015)

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EDITORIALS Minimally invasive surgery for lumbar spinal stenosis As good as open laminectomy, but no better 12

Wouter A Moojen neurosurgeon-epidemiologist , Wilco C Peul neurosurgeon-epidemiologist


HAGA Medical Center, Leyweg 275, 2545 CH, The Hague, Netherlands; 2Neurosurgical Cooperative Holland, Medical Center The Hague and Leiden University MC, Leiden, Netherlands 1

Recent trends in spine surgery, such as endoscopic and other “micro” techniques, promised less invasive procedures and better outcomes compared with conventional open techniques for decompressing nerves. Minimally invasive techniques are popular with patients, promoted by industry, and increasingly used by surgeons.1 However, recent studies have failed to report any clear benefits for patients.2 Is our hunger for new techniques based on little more than a gut feeling that new and smaller is always better and, if so, is it ethically justifiable to “test” these new techniques on patients? In a linked paper (doi:10.1136/bmj. h1603) Nerland and colleagues provide some hard evidence to help inform these important debates.3 Their study compares the “old” standard surgical treatment for spinal stenosis (open laminectomy) with a newer and less invasive alternative (microdecompression). Microdecompression is a procedure to decompress the lumbar nerves by removing a minimal amount of bone and the ligamentum flavum but leaving the spinous process and the supraspinous and interspinous ligaments intact. The authors analyse data from a large, well organised and comprehensive national registry in Norway (the Norwegian Registry for Spine Surgery, NORspine). Thirty six out of 40 centres performing lumbar spine surgery in Norway record data prospectively in NORspine, making it a unique national resource for spine research.4 Nerland and colleagues identified 885 eligible patients (out of 2745 screened), and 81% completed the one year follow-up. Microdecompression and laminectomy were associated with similar improvements in disability scores and quality of life over one year, and the two techniques were statistically equivalent. In predefined subgroup analyses, microdecompression and laminectomy were also equivalent in older people and those with obesity. However, patients treated with laminectomy had more complications than those treated with microdecompression, and the difference was significant in one of the two main analyses (15.0% v 9.8%, P=0.018). Patients treated with microdecompression had significantly shorter hospital stays (1.9 v 3.4 days). The authors concluded that patients with stenosis of the lumbar spine should be treated with microdecompression to prevent instability and because

treatment with microdecompression leads to shorter hospital stays and fewer complications.

The authors mention that microdecompression may also induce less postoperative instability. They did not, however, report any reduction in instability associated with microdecompression, and there is no solid evidence that more invasive surgery causes greater instability or that less invasive surgery causes a better clinical recovery.5

As the authors claim, large clinical registries allow the effectiveness and safety of widely used procedures to be monitored and evaluated. Cautious interpretation of observational data from registries is, however, always advisable. Clinical outcomes in this study were equivalent in both treatment groups despite the small differences in complication rates and lengths of hospital stay and despite the large patient sample. Interpreting small differences in outcomes can be difficult when data are obtained from big registries. The risk of confounding by patient selection is high in non-randomised studies: small differences in results can be due to variations in case mix between the groups, along with differences in management or different postoperative regimens. Laminectomy is considered a more old fashioned treatment, but it could still be used in centres where fast track surgery is not available. It is even questionable whether patients with large bony decompressions really do need a longer hospital stay than those requiring less invasive surgery. When a provider switches to microdecompression as the preferred option, the mindset also shifts into the “less is better” paradigm: patients will be admitted on the day of surgery instead of the day before, and discharged the next day instead of two days later.

Surprisingly, the authors chose an “equivalence” design and powered their study accordingly, judging that the two options would be equivalent if the outcome difference between them after one year was eight points or less on the Oswestry disability index. A superiority design is more usual and arguably more useful for evaluations of alternatives to traditional laminectomy,6 and a clearer justification for the authors’ choice would have been helpful. The larger sample required for a superiority study was likely available in the NORspine registry.

Correspondence to: Wouter A Moojen [email protected] For personal use only: See rights and reprints


BMJ 2015;350:h1664 doi: 10.1136/bmj.h1664 (Published 1 April 2015)

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Ideally, registry based research should be confined to comparisons of treatments that are both known to be safe, because many patients have been treated by the time results are available from this kind of study. As Nerland and colleagues mention, minimally invasive surgery for spinal stenosis was accepted and used widely with minimal supporting evidence, and before safety was fully established. Nevertheless, big data studies such as theirs are useful because patients in registries are more typical of real world practice than the over-selected patients usually included in randomised controlled trials. Registry based research will be an important contributor to long term evaluations of surgical treatments and has already proved useful—for example, in evaluating the long term side effects of drugs: 50% of all new drugs have important side effects discovered only after approval and marketing.7 In conclusion, Nerland and colleagues’ study nicely demonstrates the potential benefits of registering patient outcomes associated with daily clinical practice. Studies of big data are clearly useful for evaluating surgical treatments and add a different dimension to the results of more selective randomised trials. In this case, however, we still have no evidence that minimally invasive surgery works any better in the long term for patients than more traditional open decompression techniques. In concordance with the IDEAL framework phase 3, all new surgical techniques must be evaluated more robustly in the future, starting with high quality

randomised trials and cost effectiveness analysis,8 followed by good long term follow-up using registries such as NORspine.9 Competing interests: We have read and understood the BMJ policy on declaration of interests and declare the following: none. Provenance and peer review: Commissioned; not externally peer reviewed. 1 2 3 4 5 6 7 8 9

Deyo RA, Mirza SK, Martin BI, et al. Trends, major medical complications, and charges associated with surgery for lumbar spinal stenosis in older adults. JAMA 2010;303:1259-65. Arts MP, Brand R, van den Akker ME, et al. Tubular diskectomy vs conventional microdiskectomy for sciatica: a randomized controlled trial. JAMA 2009;302:149-58. Nerland US, Jakola AS, Solheim O, et al. Minimally invasive decompression versus open laminectomy for central stenosis of the lumbar spine: pragmatic comparative effectiveness study. BMJ 2015;350:h1603. Thomé C, Zevgaridis D, Leheta O, et al. Outcome after less-invasive decompression of lumbar spinal stenosis: a randomized comparison of unilateral laminotomy, bilateral laminotomy, and laminectomy. J Neurosurg Spine 2005;3:129-41. Försth P, Michaëlsson K, Sandén B. Does fusion improve the outcome after decompressive surgery for lumbar spinal stenosis?: a two-year follow-up study involving 5390 patients. Bone Joint J 2013;95-B(7):960-5. Moojen WA, Bredenoord AL, Viergever RF, et al. Scientific evaluation of spinal implants: an ethical necessity. Spine (Phila Pa 1976) 2014;39:2115-8. Carragee EJ, Deyo RA, Kovacs FM, et al. Clinical research: is the spine field a mine field? Spine (Phila Pa 1976) 2009;34:423-30. Van den Akker-van Marle ME, Moojen WA, Arts MP, et al. Interspinous process devices versus standard conventional surgical decompression for lumbar spinal stenosis: cost utility analysis. Spine J 2014; published online 23 Oct. Cook JA, McCulloch P, Blazeby JM, et al. IDEAL framework for surgical innovation 3: randomised controlled trials in the assessment stage and evaluations in the long term study stage. BMJ 2013;346:f2820.

Cite this as: BMJ 2015;350:h1664 © BMJ Publishing Group Ltd 2015

For personal use only: See rights and reprints


Minimally invasive surgery for lumbar spinal stenosis.

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