Hamstring Autograft Size Can Be Predicted and Is a Potential Risk Factor for Anterior Cruciate Ligament Reconstruction Failure

Purpose: The purposes of this systematic review were (1) to determine whether there is a minimum hamstring autograft size for anterior cruciate ligament (ACL) reconstruction that significantly decreases the risk of failure and (2) to evaluate the methods to accurately and reliably predict the size of hamstring grafts. Methods: We performed a systematic review of Level III and IV studies using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. All studies assessing failure of quadrupled-strand autograft hamstring ACL reconstruction as a function of graft diameter with at least 1 year of follow-up and those that assessed the use of imaging or anthropometric patient-specific factors to predict hamstring autograft size were included. Results: We identified 4 clinical studies that directly compared graft size and failure rate. These correlated with a 6.8 times greater relative risk of failure if the graft diameter was equal to or less than 8 mm (P = .008). All 9 anthropometric-based prediction studies were able to significantly correlate at least 1 parameter with intraoperative graft size. Height was the most common correlation, with r = 0.45 (P < .00001). Five of 6 imaging-based prediction studies showed signification correlation, with r = 0.66 (P < .00001), between cross-sectional area and graft size. The most common method of imaging prediction was magnetic resonance imaging-derived cross-sectional area of both the semitendinosus and gracilis tendons. Conclusions: On the basis of the available evidence, ACL reconstruction with a quadrupled-strand hamstring autograft with a diameter equal to or larger than 8 mm decreases failure rates. In addition, grafts larger than 8 mm decrease failure rates in patients aged younger than 20 years, a group identified to be at increased risk of failure. Both patient height and magnetic resonance imaging-derived cross-sectional area of the hamstring tendons can be used preoperatively to reliably predict the hamstring autograft diameter.