Influence of the different anteromedial portal on femoral tunnel orientation during anatomic ACL reconstruction

Abstract

Objective: The purpose of this study was to evaluate the effect of femoral tunnel orientation, drilledthrough the accessory anteromedial (AAM) portal or the high AM portal in anatomic anterior cruciateligament (ACL) reconstruction.Methods: In 16 cadaver knees, using o'clock method, centers of the ACL femoral footprint were drilledwith an 8-mm reamer via an AAM portal (eight knees) or a high AM portal (eight knees). Computedtomography (CT) scans were taken of each knee. Three-dimensional (3D) models were constructed toidentify the femoral tunnel orientation and to create femoral tunnel virtual cylinders for measuringtunnel angles and length.Results: In two of the 16 specimens, we observed a posterior femoral cortex blowout (PFCB) whendrilling through a high AM portal. When drilled through the high AM portal, the femoral tunnel lengthwas signiŞcantly shorter than when using an AAM portal (30.3 ± 3.8 mm and 38.2 ± 3.1 mm, p < 0.001).The femoral tunnel length was signiŞcantly shorter in the group with PFCB compared to the group withno PFCB (25.9± 0.6 mm and 35.5 ± 4.5 mm, p ¼ 0.011). The axial obliquity of the high AM portal wassigniŞcantly higher than that of the AAM portal (52.2 ± 5.9and 43.0± 2.3, p¼ 0.003).Conclusions: In anatomic ACL reconstruction, a mal-positioned AM portal can cause abnormal tunnelorientation, which may lead to mechanical failure during ACL reconstruction. Therefore, it is important toselect accurate AM portal positioning, and possibly using an AAM portal by measuring an accurate position when drilling a femoral tunnel in anatomic ACL reconstruction.