Intraoperative Graft Isometry in Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction

PURPOSE: Little is known about the isometry of anatomic single-bundle anterior cruciate ligament (ACL) tunnel positions in vivo although it is closely related to graft tension throughout the range of motion. The purpose of this study was to evaluate intraoperative graft isometry in anatomic single-bundle ACL reconstruction in vivo. MATERIALS AND METHODS: Graft length changes were assessed before bio-screw fixation in the tibial tunnel by pulling the graft with tensions of 20 lbs and 30 lbs in full extension at flexion angles of 30°, 60°, 90°, and 120°. RESULTS: At the flexion angle of 30°, 20 lbs and 30 lbs of tension showed −0.4 mm and −0.6 mm length changes, respectively. The greater the flexion angle of the knee, the shorter the graft length in the joint. At the flexion angles of 90° and 120°, there was significant difference in the graft length change between 20 lbs and 30 lbs of tension. CONCLUSIONS: Anatomic single-bundle ACL reconstruction was non-isometric. The graft length was the longest in full extension. The tension of graft became loose in flexion. At the flexion angles of 90° and 120°, there was significant difference in the graft length change between 20 lbs and 30 lbs of tension.