Abstract: 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.

Plain-language summary: This review comprises published research studies current through June 2014. A total of 10 randomised controlled trials (RCTs), or studies comparing one treatment to another, were included in the final analysis. In total, the included studies looked at 733 participants. In this review, review authors compared conventional laminectomy versus three other surgical techniques for low back stenosis. Here's the breakdown: Three studies - involving a total of 173 patients - compared conventional laminectomy with one-sided laminotomy. Four studies - involving 382 patients total - compared conventional laminectomy with two-sided laminotomy (one study included three treatment groups and compared conventional laminectomy with one-sided and two-sided laminotomy). And finally, four studies - involving 218 patients total - compared conventional laminectomy with a split-spinous process laminotomy. The Cochrane review authors did not receive outside funding. This review found that each of the three newer techniques of surgery for low back stenosis delivered results no different from those of conventional laminectomy regarding self-care abilities and leg pain. Only perceived recovery of symptoms favoured patients who underwent bilateral laminotomy compared with conventional laminectomy, but the difference between unilateral laminotomy and split-spinous process laminotomy was not significant. The quality of evidence was low or very low according to Grades of Recommendation, Assessment, Development and Evaluation (GRADE) recommendations. This was due to the limited number of studies available for review and to poor study designs. Included studies were not designed in such a way as to yield reliable information about surgical outcomes. Before high-quality, evidence-based recommendations can be made about techniques of decompression for lumbar spinal stenosis, more rigorous studies should be done.