Can Preoperative MRI Predict Intra-operative Hamstring Graft Size in Double Bundle Anterior Cruciate Ligament Reconstruction?

Background: Hamstring tendon graft diameters < 8 mm are considered a risk factor for graft failure. There is a lack of data regarding the prediction of double-bundle (DB) hamstring graft diameter using magnetic resonance imaging (MRI). This study aimed to evaluate whether preoperative MRI can be a predictor of DB hamstring graft diameter and to determine the minimum hamstring tendon cross-sectional area (CSA) on MRI required to produce a hamstring graft equivalent to 8 mm of a single-bundle (SB) graft, in the case of a DB graft.Methods: A retrospective study was performed on patients who underwent anterior cruciate ligament (ACL) reconstruction between 2017 and 2020. The inclusion criteria were (1) patients aged 20 years or older and (2) operation with DB reconstruction. The exclusion criteria were (1) multiple ligament injuries, (2) previous hamstring injury, and (3) patients who underwent revision surgery. The correlation between preoperative MRI CSA and anthropometric data and graft size was calculated, and the factors most associated with graft size were calculated using multiple regression analysis. The receiver operating characteristic (ROC) curve was also used to calculate the threshold for creating a thicker DB graft.Results: Based on the inclusion and exclusion criteria, we selected 69 patients for this study. There was a positive correlation between intra-operative graft size and height (r = 0.590, P < 0.001), weight (r = 0.485, P < 0.001) and preoperative MRI semitendinosus tendon + gracilis tendon CSA (r = 0.591, P < 0.001). Multiple regression analysis showed that preoperative MRI CSA was the most influential factor on intra-operative graft size (β = 0.366, 95% CI 0.237-0.946, P = 0.001). Based on the ROC analysis, the optimal cut-off value of MRI CSA for determining the CSA of DB graft corresponding to an SB diameter of 8 mm was 19.1 mm2 (sensitivity 96.3%, specificity 80.0%).Conclusions: MRI CSA was found to be the most relevant factor for graft size. The ability to predict graft diameter by preoperative MRI is beneficial for surgical planning and graft selection and may reduce the risk of failure.Level of Evidence: Level IV, case series