Anterior cruciate ligament reconstruction: drilling a femoral posterolateral tunnel cannot be accomplished using an over-the-top step-off drill guide.

The objective of this study was to evaluate the position of a K-wire drilled into the lowest and most shallow position possible in the femoral footprint of the anterior cruciate ligament (ACL) with an over-the-top drill guide and to compare this position in relation to the total length of the femoral footprint. In eight specimens, the K-wire was drilled through the guide from the medial side to mimic the anteromedial portal used during arthroscopy. The distances between the K-wire and the farthest points of the anteromedial (AM) and posterolateral (PL) end of the ACL footprint were measured. The median ACL footprint was 15 mm (range 14-18). The median distance from the K-wire was 5 mm (range 3-8) to the AM end of the footprint and 10 mm (range 9-15) to the PL end of the footprint. The K-wire did not reach the middle of the ACL footprint length in any of the specimens. The posterior border of the articular cartilage on the lateral femoral condyle prevented the drill guide from being placed in a lower and more shallow position. The results of this study showed that a tunnel drilled using an over-the-top drill guide and placed in the lowest and most shallow position possible within the ACL footprint is almost exclusively situated in the AM bundle origin.