Systematic reviews and meta-analyses in spine surgery, neurosurgery and orthopedics: guidelines for the surgeon scientist

Abstract

The research evidence in the realm of surgery is expanding at a rapid pace, and thus corresponds with an increasing need to critically appraise and synthesize the available literature. Particularly in fields such as spine surgery, neurosurgery and orthopedics which traditionally have little Class I randomized clinical data, reviews are important to pool the available evidence on clinical questions which are otherwise difficult to answer. Whilst systematic reviews and meta-analyses have the potential to provide critical and updated surgical evidence to guide clinical decisions, poorly performed analyses and misinterpretation of such reviews may have a detrimental effect on patient care and outcomes. We present a summary of the critical steps in performing a systematic review and meta-analysis, allowing the surgeon scientist to better interpret and perform their own systematic reviews and meta-analyses.

Keywords: Systematic review; academic surgery; clinical outcomes; evidence; forest plot; heterogeneity; meta-analysis; spine; surgery.

Figure 1

Example of forest plot, comparing anterior lumbar interbody fusion (ALIF) and transforaminal lumbar interbody fusion (TLIF) in terms of dural injury, neurological deficit, blood vessel injury, and infection rates. The blue square represents the effect size of the adjacent study, whilst the horizontal line represents the 95% confidence interval (CI). These effect sizes were pooled to produce an overall effect size, represented by the black diamond in the lowest row. When the black diamond is completely on either side of the midline, this indicates a statistically significant difference (e.g., dural injury pooled effect size). The width of the diamond represents the 95% CI of the pooled data. Heterogeneity analysis is determined as per I² test, where heterogeneity I²>50% is considered statistically significant.

Figure 2

Example of funnel plot of total complications, in a meta-analysis comparing minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) versus open-TLIF (O-TLIF). No significant asymmetry or publication bias was detected using Begg’s and Egger’s tests. RR, relative risk.