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Lumbar Spinal Stenosis Associated with Degenerative Lumbar Spondylolisthesis: A Systematic Review and Meta-analysis of Secondary Fusion Rates following Open vs. Minimally Invasive Decompression

Introduction Decompression surgery plus instrumented fusion is the gold standard in patients with lumbar spinal stenosis (LSS) associated with degenerative spondylolisthesis (DS) when conservative treatment has failed. Open laminectomy (OL) alone is an option in patients with stable low-grade DS, but progressive instability contributes to significant secondary fusion rates and compromises patient outcome. A minimally invasive unilateral laminotomy (MIL) for “over the top” decompression is a potentially less destabilizing alternative. The aim of our systematic review and meta-analysis was to analyze secondary fusion rates after open laminectomy and minimally invasive laminotomy in patients with LSS associated with DS. Material and Methods We performed a systematic literature search in the National Center for Biotechnology Information Database (Pubmed/MEDLINE) using the keywords “lumbar spondylolisthesis” and “decompression surgery.” All studies that separately reported the outcome of patients with LSS associated with DS that were treated by decompression surgery only were included. The accepted decompression techniques were 1.) open laminectomy and 2.) microsurgical transmuscular or subperiosteal unilateral laminotomy with “over the top” decompression. The primary end point was secondary fusion rate. Secondary end points were total reoperation, complications, postoperative progression of listhetic slip, and patient satisfaction. Results We identified 37 studies with a total number of 1156 patients that were published between 1983 and 2015. 19 studies reported the outcome after OL, and 18 after MIL. There were two randomized controlled trials, 8 prospective, and 24 retrospective cohort studies or case series. In two trials the study design was unclear. None of the trials compared OL to MIL. The pooled secondary fusion rates were 12.8% in the OL cohort, and 3.3% in the MIL cohort; the pooled total reoperation rates were 16.3% after OL, and 5.8% after MIL. The complication rate ranged from 0–5.4% in the OL cohort, and from 0–8.1% in the MIL cohort. Surgery-related deaths, major permanent complications, or medical complications were not reported by the studies. In the OL cohort 72% of the studies displayed a slip progression compared with 0% in the MIL cohort, respectively. After OL the pooled analysis of satisfactory outcome was 62.7% compared with 76% after MIL. Conclusion In patients with LSS associated with DS a minimally invasive laminotomy is associated with lower reoperation and fusion rates, less slip progression and greater patient satisfaction than open surgery. Better quality studies are needed to corroborate these results. These results also indicate that routine fusion may not be necessary in all patients with LSS and DS.