Safe drilling angles avoid femoral tunnel complications during combined anterolateral ligament and anterior cruciate ligament reconstruction

Purpose To determine the best angle to drill the femoral tunnels of an anterolateral ligament (ALL) anatomic reconstruction combined with a single-bundle anterior cruciate ligament (ACL) reconstruction to avoid tunnel collisions and cortical disruption. Methods Ten cadaveric knees were studied. Single-bundle anatomic ACL femoral tunnels were arthroscopically drilled. The starting point of the ALL femoral tunnel was located posterior and superior to the lateral epicondyle. ALL tunnels were drilled at four different angulations: (1) 0 degrees axial/0 degrees coronal, (2) 0 degrees axial/30 degrees coronal superior, (3) 30 degrees axial anterior/0 degrees coronal, and (4) 30 degrees axial anterior 30 degrees coronal superior. Specimens were scanned by computed tomography to measure the relations of each trajectory with the ACL socket and the nearest cortical bone. Results None of the four trajectories studied presented risk of collision with the ACL. The tunnel at 30 degrees anterior/30 degrees proximal presented the safest distance to the ACL socket (P = 0.01) [mean distance 18.6 mm (SD +/- 6.7)]. However, both tunnels angled at 0 degrees in the axial plane presented a high risk of posterior femoral cortex disruption (P = 0.01), either by close proximity or direct contact in some specimens (mean distance 3.1 mm (SD +/- 2.8) at 0 degrees axial/0 degrees coronal and 3.7 mm (SD +/- 2.2) at 0 degrees axial/30 degrees coronal). Conclusions When performing simultaneous ACL and ALL ligament reconstruction, the ALL femoral tunnel should be drilled with an angle of 30 degrees anterior in the axial plane and 30 degrees proximal in the coronal plane. Tunnels with an angle of 0 degrees in the axial plane showed high risk of contact and disruption of the posterior femoral cortex; thus, these angles should be avoided. The clinical relevance of this work is that an ALL anatomical reconstruction does not represent a risk when performing a simultaneous ACL reconstruction as long as the ALL tunnel is reamed with a proximal and anterior angulation.