Dynamic computed tomography evaluation of graft isometry after anatomic single bundle reconstruction of anterior cruciate ligament / 中华创伤骨科杂志

ABSTRACT

Objective To evaluate graft isometry after anatomic single bundle reconstruction of anterior cruciate ligament (ACL) using dynamic computed tomography (CT).Methods A retrospective study was conducted of the 14 patients who had undergone single bundle ACL reconstruction from June to August 2015.They were all men,with an average age of 28.6 years (range,from 18 to 39 years).At 6 months after operation,they received dynamic CT scanning during a cycle of knee extension to flexion.3D bone models representing the knee at different flexion positions (0°,30°,60°,90°,and 120°) in each patient were reconstructed from the CT images.The grid method was used to locate the positions of the central footprints of the tibial and femoral tunnels.The lengths between the entries of the femoral and tibial tunnels were measured from each tunnel entry to reflect the graft length change.Furthermore,we measured the isometry at the over-the-top position of the femur and at the anatomic tibial position.Results All the tunnel entries were located at the central area of the ACL anatomic attachment.The reconstructed ACL was the longest when the knee was in full extension.The length was gradually shortened between the femoral and tibial tunnels during flexion of the knee from 0° to 90°.The anatomic position showed an average of 4.82 mm shortening and the over-the-top position an average of 3.28 mm shortening.The length excursion increased in early flexion from 0° to 30° (2.91 ±0.91 mm on average) and reduced in later flexion from 90° to 120° (2.98 ± 1.41 mm on average).Conclusions None of the reconstructed ACL was isometric.A graft length may be the longest when the knee is in full extension and decrease gradually during the flexion from 0° to 90° and increase gradually during the flexion of 90° to 120°.The graft should be fixed when the knee is in the flexion of 30°.