Single-bundle versus double-bundle anterior cruciate ligament reconstruction in clinical and functional outcomes: an umbrella review and meta-meta-analysis

Background: Anterior cruciate ligament (ACL) tears are common injuries, that often lead to long-term knee instability and complications. Anterior cruciate ligament reconstruction can be performed using either single-bundle (SB) or double-bundle (DB) techniques. This study aimed to systematically compare clinical, functional, and complication outcomes between the two techniques through an umbrella review and meta-meta-analysis. Materials and Methods: Our study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and included meta-analyses published in PubMed, Embase, Cochrane, and Web of Science up to January 2025. Data on knee stability, functional scores, complications (graft failure, osteoarthritis incidence, knee extension/flexion deficits), and clinical outcomes were extracted, and quality was assessed using the A Measurement Tool to Assess Systematic Reviews 2 and Grading of Recommendations Assessment, Development, and Evaluation systems. Continuous outcomes were synthesized using the Mean Difference (MD) and Standardized Mean Difference (SMD). Results: A total of 22 meta-analyses were analyzed. The results of our meta-meta-analysis showed no statistically significant differences in objective knee joint stability between DB and SB reconstruction on the pivot shift test, KT 1000/2000 arthrometer, and Lachman test. Clinical outcomes favored the DB technique, which showed statistically superior Lysholm scores (MD = 0.82, P = 0.02) and better subjective IKDC scores (MD = 1.42, P = 0.007); however, these differences did not reach the minimum clinically important difference. There were also no significant differences in complication rates, including graft failure, incidence of osteoarthritis, and knee extension/flexion deficits. Conclusion: This meta-meta-analysis indicates no definitive superiority for either DB or SB anterior cruciate ligament reconstruction. We found no significant differences in knee joint stability or complication rates. While minor statistical differences in clinical outcomes were observed—favoring DB for both Lysholm and subjective IKDC scores—these were not clinically meaningful.