The Safe Zone for TransFix Fixation in Anterior Cruciate Ligament Reconstruction Using the Anteromedial Portal Technique

Abstract

The risk of neurovascular injury is inherent to cross-pin femoral fixation for anterior cruciate ligament reconstruction and has not been evaluated using the anteromedial portal technique; therefore, we determined a safe zone of cross-pin drill angles. Five cadaveric midthigh to midknee specimens underwent anterior cruciate ligament reconstruction by use of the anteromedial portal to drill the femoral tunnel and a cross-pin femoral fixation system. Guide pins were passed through the femur at -40°, -20°, 0°, and +20°, with 0° being the coronal plane bisecting the femoral shaft, negative angles when the guide pin started posteriorly, and positive angles when the guide pin started anteriorly. Distances between the guide pin and saphenous nerve, femoral artery, and peroneal nerve were measured. The neurovascular structures were considered safe if the guide pin did not pass within 10 mm of the structures. The mean distance from pin to saphenous nerve was 74, 61, 21, and 24 mm at -40°, -20°, 0°, and +20°, respectively; pin to femoral artery was 100, 85, 59, and 51 mm, respectively; and pin to peroneal nerve was 40, 50, 65, and 76 mm, respectively. The safe zone for the saphenous nerve was violated at 0° and +20° in 2 of 5 knees, and the safe zone for the femoral artery was violated at +20° in 2 of 5 knees. We have shown that a 20° safe zone of rotational angles about the axis of the femoral tunnel, from -40° to -20°, minimizes the risk of damage to the saphenous nerve, femoral artery, and peroneal nerve. Intraoperative guide-pin angle measurement can be made in reference to the coronal plane of the femur to guide safe drilling of the TransFix guide pin (Arthrex, Naples, FL).