Abstract Background Degenerative spondylolisthesis affects approximately 39 million patients worldwide. While consensus supports decompression with fusion for single-level pathology, optimal surgical approaches for multi-level disease remain disputed. Despite the frequency of this clinical presentation, evidence comparing outcomes between Single-Level versus Multi-Level interbody fusion procedures is surprisingly scarce. This study aims to determine how the level of interbody fusion extent impacts outcomes in patients undergoing lumbar fusion for degenerative spondylolisthesis. Methods Our systematic review methodology involved comprehensive database searches (Web of Science, Scopus, PubMed, and Cochrane Library) from inception through April 2025. Two independent reviewers performed article screening, data extraction, and quality assessment. Statistical analyses used R software (v4.4.2), with outcomes reported as risk ratios for categorical variables and mean differences for continuous measures (95% CI). The certainty of evidence was assessed using the GRADE approach. Results Our meta-analysis evaluated 10 studies ( N = 1430 patients; 971 Single-Level, 366 Double-Level, 198 Multi-Level fusions). Single-Level procedures demonstrated 41% lower revision rates (RR = 0.59 0.40–0.86, p = 0.007). Operative advantages included reduced surgical time (−60.73 min − 80.89 to − 40.57, p < 0.001), blood loss (-286.99mL − 496.71 to − 77.27, p = 0.007), and hospitalization (−1.22 days − 2.09 to − 0.34, p = 0.006). Oswestry Disability Index (ODI) scores showed borderline improvement (-3.90 − 7.89 to 0.10, p = 0.06). Screw loosening decreased by 84% (RR = 0.16 0.08–0.34, p < 0.001). We observed no significant differences in lumbar lordosis (-0.01 − 1.75 to 1.72, p = 0.99), infection rates (RR = 0.49 0.19–1.25, p = 0.13), adjacent segment deterioration, vascular injuries, or dural tears. The certainty of evidence ranged from low to very low, and high heterogeneity was observed in perioperative outcomes. Conclusions Single-level fusion may offer a more favorable perioperative profile than double- or multi-level constructs, including lower revision risk, shorter operative time, reduced blood loss, shorter hospitalization, and fewer screw loosening events in pooled analyses. However, complications did not differ significantly between groups. Given substantial heterogeneity for perioperative outcomes and generally low to very low certainty of evidence, these findings should be interpreted cautiously and individualized to patient pathology and surgical context.
Alharbi et al. (Sat,) studied this question.