Perioperative Outcomes and Adverse Events of Minimally Invasive versus Open Posterior Lumbar Fusion: Meta-Analysis

OBJECT The objective of this study was to determine the clinical comparative effectiveness and adverse event rates of posterior minimally invasive surgery (MIS) compared with open transforaminal or posterior lumbar interbody fusion (TLIF/PLIF). METHODS A systematic review of the Medline, EMBASE, PubMed, Web of Science, and Cochrane databases was performed. A hand search of reference lists was conducted. Studies were reviewed by 2 independent assessors to identify randomized controlled trials (RCTs) or comparative cohort studies including at least 10 patients undergoing MIS or open TLIF/PLIF for degenerative lumbar spinal disorders and reporting at least 1 of the following: clinical outcome measure, perioperative clinical or process measure, radiographic outcome, or adverse events. Study quality was assessed using the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) protocol. When appropriate, a meta-analysis of outcomes data was conducted. RESULTS The systematic review and reference list search identified 3301 articles, with 26 meeting study inclusion criteria. All studies, including 1 RCT, were of low or very low quality. No significant difference regarding age, sex, surgical levels, or diagnosis was identified between the 2 cohorts (856 patients in the MIS cohort, 806 patients in the open cohort). The meta-analysis revealed changes in the perioperative outcomes of mean estimated blood loss, time to ambulation, and length of stay favoring an MIS approach by 260 ml (p < 0.00001), 3.5 days (p = 0.0006), and 2.9 days (p < 0.00001), respectively. Operative time was not significantly different between the surgical techniques (p = 0.78). There was no significant difference in surgical adverse events (p = 0.97), but MIS cases were significantly less likely to experience medical adverse events (risk ratio [MIS vs open] = 0.39, 95% confidence interval 0.23-0.69, p = 0.001). No difference in nonunion (p = 0.97) or reoperation rates (p = 0.97) was observed. Mean Oswestry Disability Index scores were slightly better in the patients undergoing MIS (n = 346) versus open TLIF/PLIF (n = 346) at a median follow-up time of 24 months (mean difference [MIS - open] = 3.32, p = 0.001). CONCLUSIONS The result of this quantitative systematic review of clinical comparative effectiveness research examining MIS versus open TLIF/PLIF for degenerative lumbar pathology suggests equipoise in patient-reported clinical outcomes. Furthermore, a meta-analysis of adverse event data suggests equivalent rates of surgical complications with lower rates of medical complications in patients undergoing minimally invasive TLIF/PLIF compared with open surgery. The quality of the current comparative evidence is low to very low, with significant inherent bias.