Variation in Graft Bending Angle During Range of Motion in Single-Bundle Posterior Cruciate Ligament Reconstruction: A 3-Dimensional Computed Tomography Analysis of 2 Techniques

Abstract

To compare variations in femoral graft bending angle during range of motion (ROM) of the knee between inside-out (IO) and retro-socket outside-in (OI) techniques in posterior cruciate ligament (PCL) reconstruction using invivo 3-dimensional (3D) computed tomography analysis. Ten patients underwent PCL reconstruction by the IO technique (5 patients) or the retro-socket OI technique (5 patients) for suspensory femoral fixation. After PCL reconstruction, 3D computed tomography was performed in 0° extension and 90° flexion to reconstruct 3D femur and tibia bone models using Mimics software. Positions of femur and tibia at 30°, 45°, and 60° flexion were reproduced by determining the kinematic factors of anteroposterior translation, mediolateral translation, and internal-external rotation angle of each patient based on previously measured kinematic data. Variation in graft bending angle according to the flexion range of the knee was calculated by the difference in graft angulation measured at each flexion angle. The results were compared between the 2 techniques. There was significant difference in variation of femoral graft bending angle between IO and retro-socket OI techniques from 0° to 90° flexion of the knee (P= .008). Significant difference was also noticed at 30° to 45° (P= .008), 45° to 60° (P= .008), and 60° to 90° (P= .016) ROM of the knee between the 2 groups. The retro-socket OI technique resulted in less variation in femoral graft bending angle compared with the IO technique during knee ROM. We recommend the retro-socket OI technique for femoral tunnel placement to reduce the graft motion at the intra-articular femoral tunnel aperture. The retro-socket OI technique produces significantly less variation in femoral graft bending angle when compared with the IO technique. Such reduction in variation of femoral graft bending angle might be related to lower stress at the femoral tunnel aperture.