Comparing Ultrasound and MRI Evaluations of the Hamstring Tendon for Predicting Autograft Size in Anterior Cruciate Ligament Reconstruction

Background: Adequate graft size and length are crucial factors in anterior cruciate ligament (ACL) reconstruction. Accurate identification of patients who may be at risk for an insufficient length or size of the hamstring tendon (HT) can aid surgeons in preoperative planning.Purpose: To evaluate whether magnetic resonance imaging (MRI) or ultrasound could more accurately predict the size of the semitendinosus tendon (ST) and gracilis tendon (GT) and to investigate the correlation between anthropometry, graft size, and imaging measurements to find a predictive formula.Study Design: Cross-sectional study; Level of evidence, 3.Methods: Included in the study were 36 patients who underwent ACL reconstruction with HT autograft at our institution between July 2021 and May 2022. Anthropometric data and MRI and ultrasound measurements were collected preoperatively. The length and diameter of the HT were recorded intraoperatively. Correlations between anthropometry, graft size, and imaging measurements were analyzed. Linear regression analysis was performed to construct a prediction formula.Results: The intraoperative graft diameters of the ST and GT were weakly to moderately associated with their cross-sectional areas as measured by MRI and ultrasound. MRI and ultrasound interpreted 11.9% to 15.7% and 18.4% to 41.7% of the variation in the graft diameter of the HT, with an accuracy of 50.0% to 55.6% and 69.4% to 86.1%, respectively. The intraoperative lengths of the ST and GT were both associated with patient height and tendon lengths as measured by ultrasound. Additionally, intraoperative GT length was associated with patient weight. Four formulas combining relevant anthropometric parameters and imaging measurements were calculated from multilinear regression analysis, explaining up to 46.3% of the variance in the size of HT.Conclusion: Ultrasound and MRI alone showed limited ability to predict the graft diameter of the ST and GT, while ultrasound could more accurately predict the graft size than MRI. Among the different anthropometric variables, height was the most influential in predicting tendon length.