Summary

The evaluation of graft isometry and tunnel enlargement after anatomic single bundle ACL reconstruction with dynamic computed tomography

Abstract

Purpose

The purpose of this study was to evaluate the isometry of the graft and tunnel enlargement after anatomic single bundle anterior cruciate ligament (ACL) reconstruction with dynamic computed tomography throughout the knee range of motion. Method: A total of 17 patients, after single bundle ACL reconstruction using an accessory anteromedial (AM) portal technique, underwent dynamic computed tomography during a cycle of knee extension to ?exion at a mean follow up of 6 months. 3D bone models of each patient’s knee at different flexion positions (0°, 30°, 60°, 90°, and 120°) were reconstructed from the images. The graft length change and the tunnel enlargement were measured. The clinical outcomes were measured by the International Knee Documentation Committee (IKDC) scores, the Lachman test and pivot-shift test. Results: There was a decrease in graft length from 0° to 90° of knee ?exion and an increase from 90° to 120°. The length reduction was greater in early ?exion from 0° to 30°. Tunnel enlargement greater than 2 mm was observed in 29.4% of the femoral tunnels (5 of 17) and in 17.6% of the tibial tunnels (3 of 17). The graft length change was correlated to the tibial tunnel enlargement. There was no correlation between the clinical outcomes and graft isometry. Conclusion: The graft length change was not isometric and could affect tibial tunnel enlargement after anatomic single bundle ACL reconstruction. The graft should be fixed near 30° of flexion in anatomic single bundle ACL reconstruction.