Femoral bone tunnel placement

Identification of the anatomical anterior cruciate ligament (ACL) footprint is essential in femoral tunnel preparation. The lateral intercondylar ridge (LIR), which is termed the anterior border of the femoral ACL footprint, can be used as a landmark during surgery. The entire ACL footprint consists of the direct insertion of the ACL located behind the LIR and the attachment of fanlike extension fibers extended to the posterior cartilage margin. The lateral bifurcate ridge can be observed between the attached anteromedial (AM) and posterolateral (PL) bundles in 80% of cases. Options for drilling the femoral tunnel consist of the trans-tibial tunnel technique, the transmedial portal technique, and the outside-in technique. Although it is sometimes difficult to drill the desired point when using the conventional transtibial technique, modifications, such as using of a special angle guide, applying an external rotation and varus force to the tibia, or drilling the femoral AM tunnel through the tibial PL tunnel, enable consistent creation of the tunnels at the anatomical position. The transmedial portal technique requires deep knee flexion during drilling to avoid posterior wall blowout. Both the knee flexion angle and location of the working portal affect the location of the tunnel outlet on the lateral femoral surface. Retrograde reaming devices for the outside-in technique enable the use of the cortical fixation buttons for any diameter grafts. The tunnel direction relative to the cortical surface affects the shape and size of tunnel apertures at both outlets on the ACL footprint side and lateral femoral side.