Figure 2.

Forest plot of the meta-analysis of the NDI score comparing hybrid surgery with ACDF by a random effects model. Seven studies with high heterogeneity (I² = 72.8%) were analyzed to calculate the summary risk ratio with corresponding 95% CI. The SMD was −0.552 for the NDI (P = 0.038, the diamond locates on the left of the null line), indicating that hybrid surgery showed lower NDI than ACDF at 2-year follow-up. ACDF = anterior cervical discectomy and fusion, CI = confidence interval, NDI = neck disability index, SMD = standardized mean difference.