The Effect of Femoral Tunnel Starting Position on Tunnel Length in Anterior Cruciate Ligament Reconstruction: A Cadaveric Study

Purpose: The purpose of this cadaveric study was to evaluate the effect of femoral tunnel starting position on femoral tunnel length and to evaluate the effect of tibial tunnel starting position on femoral tunnel starting position in anterior cruciate ligament (ACL) reconstruction. Methods: Seven fresh-frozen cadaver knees were studied. Tibial tunnels were placed at each of 3 different locations: anterior placement, far medial placement, and midway between the anterior and far medial placements. Femoral guidewires were placed using a 5-mm offset guide at each of 4 different locations: 1 from each of the 3 tibial tunnels and 1 from the anteromedial arthroscopic portal. The depth of the resultant femoral tunnels and the clock face location of each tunnel were measured. Results: The mean clock position (o'clock) and length (mm) of the femoral tunnel versus tibial starting position were as follows. Anterior tibia: 11:30 o'clock and 61 mm. Midpoint tibia: 10:50 o'clock and 44 mm. Far medial tibia: 10:17 o'clock and 37 mm. Medial arthroscopy portal: 9:35 o'clock and 23 mm. The differences in tunnel length between starting positions were statistically significant, and the differences in femoral starting position between tibial starting positions were statistically significant. Conclusions: Tunnel length greater than 2 cm and 10:30 o'clock starting position can be achieved by medial placement of the tibial tunnel. Placement from the medial arthroscopy portal can result in femoral tunnels more lateral than 10 o'clock, but they may be shorter than 2 cm. Clinical Relevance: Tibial starting position affects femoral starting position in the intercondylar notch. Femoral starting position affects femoral tunnel length. Femoral starting position and tunnel length are important considerations in clinical ACL reconstruction.