Preoperative MRI Assessment of Hamstring Tendons to Predict the Quadruple Hamstring Graft Diameter in Anterior Cruciate Ligament Reconstruction

Abstract

Introduction The cross-sectional area (CSA) and length of an individual's hamstring tendons are both variable, making it challenging for the operating surgeon to generate an ideal size graft during arthroscopic anterior cruciate ligament (ACL) reconstruction surgery. If we can predict the hamstring graft diameter using MRI (a routine radiological investigation used to diagnose knee pathology), this information, if obtained before surgery rather than after the harvesting of the hamstring tendons, may influence the graft choice and allow us to successfully perform ACL reconstruction with sufficient graft diameter. Aims The aims of this study were to determine the reliability and accuracy of 3T MRI in predicting quadruple hamstring graft diameter for ACL reconstruction, to determine the statistical correlation between the CSA of hamstring tendons on MRI and intraoperative quadruple hamstring graft diameter, and to find out the minimum CSA of hamstring tendons (ST+GR) required for an 8 mm quadruple hamstring graft diameter. Methods This prospective diagnostic study included 50 patients diagnosed with complete ACL rupture. On MRI, we assessed the CSA of the semitendinosus and gracilis tendons at two levels: one at the joint line and the other at the level where the anteroposterior (AP) diameter of the medial femoral condyle is longest. The quadruple ST+GR graft was passed through 0.5 mm increments of holes in the block (Biotek (Winooski, Vermont) or Smith & Nephew, London, United Kingdom) intraoperatively, and the diameter of the hole that permitted smooth passage of the whole graft was taken as the quadruple graft diameter. The cutoff CSA required for a graft of sufficient size was calculated using simple logistic regression analysis. The correlation between CSA measurements on MRI and intraoperative quadruple hamstring graft diameter was determined using Pearson's rank correlation coefficient. Results The mean ST+GR CSA on MRI was 18.9 mm², the minimum CSA was 14.45 mm², and the maximum CSA was 23.8 mm². Pearson's correlation between the intraoperative quadruple hamstring graft diameter (mm) and ST+GR CSA on MRI was 0.838. The minimum ST+GR CSA required for an 8 mm quadruple hamstring graft diameter is 17.5 mm². Conclusion A strong statistical correlation between ST+GR CSA on MRI and intraoperative quadruple hamstring graft diameter was found (Pearson's correlation = 0.838, p-value = 0.000). Thus, MRI is a reliable radiological investigation that can be used to predict the quadruple hamstring graft diameter. This method can help orthopedic surgeons successfully perform ACL reconstruction surgery without any graft complications.

Keywords: acl reconstruction; gracilis; mri; preoperative assessment; quadruple hamstring graft diameter; semitendinosus.

Figure 1. MRI scans showing (A) a sagittal view of the right knee joint; (B) an axial view of the right knee joint at the joint line, displaying the cross-sectional area of the semitendinosus and gracilis

🟦 denotes semitendinosus tendon; 🔴 denotes gracilis tendon

Figure 2. MRI scans showing (A) a sagittal view of the right knee joint; B) an axial view of the right knee joint at a level where the AP diameter of the medial femoral condyle is longest

🟦 denotes semitendinosus tendon; 🔴 denotes gracilis tendon

Figure 3. The intraoperative diameter of the quadruple hamstring graft was measured with the help of a sizing cylinder

Figure 4. Bar chart showing age and gender distribution of patients included in this study (n = 50)

Figure 5. Pie chart showing the side of injury of patients included in this study (n = 50)

Figure 6. Pie chart showing the mode of injury of patients included in this study (n = 50)

Figure 7. Scatter plot showing the correlation between the CSA of hamstring tendons (ST+GR) on MRI and the intraoperative quadruple hamstring graft diameter

CSA: cross-sectional area; ST: semitendinosus; GR: gracilis; MRI: magnetic resonance imaging