Effectiveness of posterior decompression techniques compared with conventional laminectomy for lumbar stenosis

The gold standard treatment for symptomatic lumbar stenosis refractory to conservative management is a facet-preserving laminectomy. New techniques of posterior decompression have been developed to preserve spinal integrity and to minimise tissue damage by limiting bony decompression and avoiding removal of the midline structures (i.e. spinous process, vertebral arch and interspinous and supraspinous ligaments).

To compare the effectiveness of techniques of posterior decompression that limit the extent of bony decompression or avoid removal of posterior midline structures of the lumbar spine versus conventional facet-preserving laminectomy for the treatment of patients with degenerative lumbar stenosis.

An experienced librarian conducted a comprehensive electronic search of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Web of Science, and the clinical trials registries ClinicalTrials.gov and World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) for relevant literature up to June 2014.

We included prospective controlled studies comparing conventional facet-preserving laminectomy versus a posterior decompressive technique that avoids removal of posterior midline structures or a technique involving only partial resection of the vertebral arch. We excluded studies describing techniques of decompression by means of interspinous process devices or concomitant (instrumented) fusion procedures. Participants included individuals with symptomatic degenerative lumbar stenosis only.

Two review authors independently assessed risk of bias using the Cochrane Back Review Group criteria for randomised controlled trials (RCTs) and the Newcastle-Ottawa Scale for non-randomised studies. We extracted data regarding demographics, intervention details and outcome measures.

A total of four high-quality RCTs and six low-quality RCTs met the search criteria of this review. These studies included a total of 733 participants. Investigators compared three different posterior decompression techniques versus conventional laminectomy. Three studies (173 participants) compared unilateral laminotomy for bilateral decompression versus conventional laminectomy. Four studies (382 participants) compared bilateral laminotomy versus conventional laminectomy (one study included three treatment groups and compared unilateral and bilateral laminotomy vs conventional laminectomy). Finally, four studies (218 participants) compared a split-spinous process laminotomy versus conventional laminectomy.Evidence of low or very low quality suggests that different techniques of posterior decompression and conventional laminectomy have similar effects on functional disability and leg pain. Only perceived recovery at final follow-up was better in people who underwent bilateral laminotomy compared with conventional laminectomy (two RCTs, 223 participants, odds ratio 5.69, 95% confidence interval (CI) 2.55 to 12.71).Among the secondary outcome measures, unilateral laminotomy for bilateral decompression and bilateral laminotomy resulted in numerically fewer cases of iatrogenic instability, although in both cases, the incidence of instability was low (three RCTs, 166 participants, odds ratio 0.28, 95% CI 0.07 to 1.15; three RCTs, 294 participants, odds ratio 0.10, 95% CI 0.02 to 0.55, respectively). The difference in severity of postoperative low back pain following bilateral laminotomy (two RCTs, 223 participants, mean difference -0.51, 95% CI -0.80 to -0.23) and split-spinous process laminotomy compared with conventional laminectomy (two RCTs, 97 participants, mean difference -1.07, 95% CI -2.15 to -0.00) was significantly less, but was too small to be clinically important. A quantitative comparison between unilateral laminotomy and conventional laminectomy was not possible because of different reporting of outcome measures. We found no evidence to show that the incidence of complications, length of the procedure, length of hospital stay and postoperative walking distance differed between techniques of posterior decompression.

The evidence provided by this systematic review for the effects of unilateral laminotomy for bilateral decompression, bilateral laminotomy and split-spinous process laminotomy compared with conventional laminectomy on functional disability, perceived recovery and leg pain is of low or very low quality. Therefore, further research is necessary to establish whether these techniques provide a safe and effective alternative for conventional laminectomy. Proposed advantages of these techniques regarding the incidence of iatrogenic instability and postoperative back pain are plausible, but definitive conclusions are limited by poor methodology and poor reporting of outcome measures among included studies. Future research is necessary to establish the incidence of iatrogenic instability using standardised definitions of radiological and clinical instability at comparable follow-up intervals. Long-term results with these techniques are currently lacking.