Interspinous process devices for treatment of degenerative lumbar spine stenosis: A systematic review and meta-analysis

Background Degenerative lumbar spinal stenosis is a condition related to aging in which structural changes cause narrowing of the central canal and intervertebral foramen. It is currently the leading cause for spinal surgery in patients over 65 years. Interspinous process devices (IPDs) were introduced as a less invasive surgical alternative, but questions regarding safety, efficacy, and cost-effectiveness are still unanswered. Objectives The aim of this study was to provide complete and reliable information regarding benefits and harms of IPDs when compared to conservative treatment or decompression surgery and suggest directions for forthcoming RCTs. Methods We searched MEDLINE, EMBASE, Cochrane Library, Scopus, and LILACS for randomized and quasi-randomized trials, without language or period restrictions, comparing IPDs to conservative treatment or decompressive surgery in adults with symptomatic degenerative lumbar spine stenosis. Data extraction and analysis were conducted following the Cochrane Handbook. Primary outcomes were pain assessment, functional impairment, Zurich Claudication Questionnaire, and reoperation rates. Secondary outcomes were quality of life, complications, and cost-effectiveness. This systematic review was registered at Prospero (International prospective register of systematic reviews) under number 42015023604. Results The search strategy resulted in 17 potentially eligible reports. At the end, nine reports were included and eight were excluded. Overall quality of evidence was low. One trial compared IPDs to conservative treatment: IPDs presented better pain, functional status, quality of life outcomes, and higher complication risk. Five trials compared IPDs to decompressive surgery: pain, functional status, and quality of life had similar outcomes. IPD implant presented a significantly higher risk of reoperation. We found low-quality evidence that IPDs resulted in similar outcomes when compared to standard decompression surgery. Primary and secondary outcomes were not measured in all studies and were often published in incomplete form. Subgroup analysis was not feasible. Difficulty in contacting authors may have prevented us of including data in quantitative analysis. Conclusions Patients submitted to IPD implants had significantly higher rates of reoperation, with lower cost-effectiveness. Future trials should improve in design quality and data reporting, with longer follow-up periods.