Influence of knee flexion angle and transverse drill angle on creation of femoral tunnels in double-bundle anterior cruciate ligament reconstruction using the transportal technique: Three-dimensional computed tomography simulation analysis

Abstract

BACKGROUND: The purpose of this study was to find appropriate flexion angle and transverse drill angle for optimal femoral tunnels of anteromedial (AM) bundle and posterolateral (PL) bundle in double-bundle ACL reconstruction using transportal technique. METHODS: Thirty three-dimensional knee models were reconstructed. Knee flexion angles were altered from 100 degrees to 130 degrees at intervals of 10 degrees . Maximum transverse drill angle (MTA), MTA minus 10 degrees and 20 degrees were set up. Twelve different tunnels were determined by four flexion angles and three transverse drill angles for each bundle. Tunnel length, wall breakage, inter-tunnel communication and graft-bending angle were assessed. RESULTS: Mean tunnel length of AM bundle was >30mm at 120 degrees and 130 degrees of flexion in all transverse drill angles. Mean tunnel length of PL bundle was >30mm during every condition. There were >/=1 cases of wall breakage except at 120 degrees and 130 degrees of flexion with MTA for AM bundle. There was no case of wall breakage for PL bundle. Considering inter-tunnel gap of >2mm without communication and obtuse graft-bending angle, 120 degrees of flexion and MTA could be recommended as optimal condition for femoral tunnels of AM and PL bundles. CONCLUSION: Flexion angle and transverse drill angle had combined effect on femoral tunnel in double-bundle ACL reconstruction using transportal technique. Achieving flexion angle of 120 degrees and transverse drill angle close to the medial femoral condyle could be recommended as optimal condition for femoral tunnels of AM and PL bundles to avoid insufficient tunnel length, wall breakage, inter-tunnel communication and acute graft-bending angle.