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.