Comparison Between Rigid and Flexible Systems for Drilling the Femoral Tunnel Through an Anteromedial Portal in Anterior Cruciate Ligament Reconstruction

Purpose: The purpose of this study was to compare the differences in femoral tunnel length and distance to the lateral anatomic structures when using standard and flexible guide pins for anterior cruciate ligament (ACL) femoral tunnel drilling through a medial portal. Methods: Using a medial arthroscopic portal in 10 cadaveric knees, we sequentially drilled straight and flexible guide pins into the center of the ACL femoral footprint using the same starting point. We recorded the interosseous length and distances to the peroneal nerve and the femoral origin of the lateral collateral ligament (LCL) for each pin. Results: The mean interosseous length was 43.5 mm for the flexible pin and 37.1 mm for the straight pin (P = .01). The mean distance to the peroneal nerve was 42.3 mm for the flexible pin and 37.8 mm for the straight pin (P = .33). The mean distance to the femoral origin of the LCL was 26.1 mm for the flexible pin and 13.4 mm for the straight pin (P = .003). Conclusions: The use of commercially available flexible reamers and 42 femoral guides results in longer femoral interosseous tunnel length than can be achieved with a straight guide pin. Femoral interosseous length consistently of 40 mm can be achieved with this technique and cannot be replicated with a rigid straight pin. This is advantageous for femoral tunnel drilling in an anatomic ACL reconstruction that uses suspensory fixation devices. There is minimal risk to the peroneal nerve and the femoral origin of the LCL unless lateral femoral wall blowout occurs. Clinical Relevance: Flexible pins allow longer femoral tunnels and safer distances from the LCL by use of a medial portal technique.