Femoral Tunnel Placement in Single-Bundle Anterior Cruciate Ligament Reconstruction

Abstract

Background: There is controversy regarding the necessity of reconstructing both the posterolateral and anteromedial bundles of the anterior cruciate ligament.Hypothesis: A laterally oriented transtibial drilled femoral tunnel replaces portions of the femoral footprints of the anteromedial and posterolateral bundles of the anterior cruciate ligament.Study Design: Descriptive laboratory study.Methods: Footprints of the anteromedial and posterolateral bundles of the anterior cruciate ligament were preserved on 7 matched pairs (5 female, 2 male) of fresh-frozen human cadaveric femurs (14 femurs total). Each femur was anatomically oriented and secured in a custom size–appropriate, side-matched replica tibia model to simulate transtibial retrograde drilling of a 10-mm femoral tunnel in each specimen. The relationship of the tunnel relative to footprints of both bundles of the anterior cruciate ligament was recorded using a Microscribe MX digitizer. The angle of the femoral tunnel relative to the vertical 12-o'clock position was recorded for all 14 specimens; only 10 specimens were used for footprint measurements.Results: On average, the 10-mm femoral tunnel overlapped 50% of the anteromedial bundle (range, 2%–83%) and 51% of the posterolateral bundle (range, 16%–97%). The footprint of the anteromedial bundle occupied 32% (range, 3%–49%) of the area of the tunnel; the footprint of the posterolateral bundle contributed 26% (range, 7%–41%). The remainder of the area of the 10-mm tunnel did not overlap with the anterior cruciate ligament footprint. The mean absolute angle of the femoral tunnel as measured directly on the specimen was 48° (range, 42°–53°) from vertical, corresponding to approximately a 10:30 clock face position on a right knee.Conclusion: Anterior cruciate ligament reconstruction using a laterally oriented transtibial drilled femoral tunnel incorporates portions of the anteromedial and posterolateral bundle origins of the native anterior cruciate ligament.Clinical Relevance: A laterally oriented transtibial drilled femoral tunnel placed at the 10:30 position (1:30 for left knees) reconstructs portions of the anteromedial and posterolateral bundles of the anterior cruciate ligament.