Demographic, Surgical, and Radiographic Risk Factors for Symptomatic Adjacent Segment Disease After Lumbar Fusion: A Systematic Review and Meta-Analysis.

Background Although multiple studies have investigated risk factors for symptomatic adjacent segment disease (ASD) after lumbar fusion, their findings were diverse and inconsistent. This review aimed to summarize risk factors for ASD in order to guide the management of ASD and future research. Methods Six electronic databases were systematically searched from inception to December 2019. Two reviewers independently screened titles, abstracts, and full-text articles to identify studies investigating risk factors for ASD after lumbar fusion in humans. The methodological quality of the included studies and the strength of evidence regarding risk factors were evaluated. Results Sixteen studies involving 3,553 patients were included. Meta-analyses revealed that high body mass index, facet joint violation, anterior shift of the preoperative and postoperative lumbosacral sagittal plumb line, decreased preoperative and postoperative lumbar lordosis, preoperative adjacent disc degeneration, decreased preoperative adjacent disc height, increased postoperative lumbopelvic mismatch, postoperative pelvic incidence, and postoperative pelvic tilt were significantly related to ASD. Conclusions This meta-analysis addressed the limitations of prior reviews and summarized evidence with regard to risk factors for ASD following lumbar fusion. Future prospective studies should investigate whether modification of these risk factors can reduce the ASD development. Level of evidence Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.