High risk of tunnel convergence during combined anterior cruciate ligament and anterolateral ligament reconstruction.

Purpose: To assess the risk of femoral tunnel convergence in combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstructions. The hypothesis was that a more proximal and anterior orientation of the ALL femoral tunnel should reduce the risk of convergence with the ACL femoral tunnel.

Methods: 15 fresh-frozen cadaver knees were examined. An anatomic ACL femoral tunnel was drilled arthroscopically in each specimen and ALL tunnels were made in two directions: (1) 0° coronal angulation and 20° axial angulation, (2) 30° coronal angulation and 30° axial angulation. Computed tomography scans were performed to investigate tunnel convergence and to measure the minimal distance between tunnels, tunnel length and the LFC width.

Results: Tunnel convergence occurred in 20 of 30 cases (67%). Convergence was significantly reduced when tunnels were drilled at 30° coronal and 30° axial angulation (p < 0.05). The mean length of the ALL tunnel was 15.9 mm [95% CI (13.6; 18.1)] and was independent of ALL tunnel angulation. The mean minimal distance between the ALL and ACL tunnel was 3.1 mm [95% CI (2.1; 4.1)]. The odds ratio for tunnel convergence was 3.5 for small LFC, relative to large LFC (n.s.) CONCLUSION: A high risk of tunnel convergence was observed when performing combined ACL and ALL reconstructions. The clinical relevance of this work is that the occurrence of tunnel conflicts can be reduced by aiming the ALL tunnel in a more proximal and anterior direction. Surgeons should be aware of this, since tunnel convergence could jeopardize the ACL reconstruction and fixation.