Personalizing the Quadriceps Tendon Graft in Anterior Cruciate Ligament Reconstruction: A Novel, Continuous Method to Predict Graft Size Using Preoperative MRI.

Background: The quadriceps tendon (QT) graft is increasingly popular in primary anterior cruciate ligament reconstruction (ACLR). However, postoperative quadriceps strength can be significantly weakened after use of a QT graft, compared to using hamstring tendon or bone-patellar tendon-bone grafts. There currently exists no continuous method to predict QT graft size based on preoperative magnetic resonance imaging (MRI) measurements; only dichotomous methods exist at limited cutoff values. Purpose: To (1) assess the accuracy of preoperative MRI QT thickness in predicting graft size dichotomously (<10 mm vs ≥10 mm), (2) assess the accuracy of the formula 2 ×√( Study Design: Cross-sectional study; Level of evidence, 3. Methods: This is a retrospective review of 130 patients who underwent primary ACLR with full-thickness QT autografts at a single tertiary institution from January 1, 2022, to July 17, 2025. A novel, reproducible method to measure QT thickness on the MRI sagittal view at the most proximal patellar attachment site was developed. Two blinded reviewers independently measured QT thickness. Receiver operating characteristic (ROC) analysis was performed to determine the optimal threshold for predicting a final graft diameter <10 mm, with area under the curve (AUC) as the primary measure of discriminative ability. Sensitivity and specificity at the optimal threshold were additionally reported given their direct clinical relevance to intraoperative decision-making at a fixed cutoff. Results: The mean age was 16.4 years (95% CI, 15.9-16.9 years), with 59 females and 71 males. ROC analysis identified a preoperative QT thickness <8.3 mm as the optimal threshold for predicting a final graft diameter <10 mm, with an AUC of 0.818, a sensitivity of 98.2%, and a specificity of 39.1%. The authors applied the formula 2 ×√( Conclusion: The authors present a novel, numerically continuous way of predicting harvested quadriceps graft size. A preoperative QT thickness <8.3 mm is 98.2% sensitive and 39.1% specific in predicting a final graft diameter <10 mm. Personalizing the width of the harvested QT according to patient's tendon thickness and surgeon's desired graft size may be considered to minimize unnecessary over- or underharvesting of QT in the future.