Risk analysis of tunnel collision in combined anterior cruciate ligament and anterolateral ligament reconstructions

Abstract

Background: To assess the risk of tunnel collision in combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstructions. Methods: Three-dimensional (3D) CT reconstructions of 32 knees after transtibial (TT) (N = 16) or anteromedial portal (AMP) (N = 16) ACL reconstruction were used to simulate potential tunnel collision of, the femoral ACL tunnel if combined with a virtual ALL reconstruction. The minimal distance between tunnels, the ALL tunnel length, and the lateral femoral condyle (LFC) width were measured. Moreover, the relationship between the ALL tunnel and the intercondylar notch, trochlear groove and posterior femoral cortex was determined. Results: The highest rate of tunnel collision (81%) was observed when the ALL tunnel was aimed at 20 degrees in the coronal plane and 0 degrees in the axial plane. However, by aiming the ALL tunnel at 0 degrees coronal and 40 degrees axial angulation, collision was avoided in all patients and no violation of the trochlea was observed. Tunnel collision rate was significantly higher (P = 0.002) when the ACL tunnel was drilled by the AMP technique. Conclusions: Risk of tunnel collision was significantly increased when the tunnel was drilled at 0 degrees in the axial plane. Tunnel collision was avoided by aiming the ALL tunnel 40 degrees anteriorly and perpendicular to the anatomical axis of the femur. A more horizontal orientation of the ACL with the AMP technique is a risk factor for tunnel conflicts.