Femoral Tunnel Widening After Double-Bundle Anterior Cruciate Ligament Reconstruction With Hamstring Autograft Produces a Small Shift of the Tunnel Position in the Anterior and Distal Direction: Computed Tomography-Based Retrospective Cohort Analysis

Purpose: To determine whether the femoral tunnel position remains in an anatomical footprint after tunnel widening and shifting. Methods: Patients who underwent unilateral double-bundle anterior cruciate ligament reconstruction with hamstring autograft and performed computed tomography scan evaluation at the time of 5 days and 1 year postoperatively were included in this retrospective cohort study. Three-dimensional models of the femur and femoral tunnels were reconstructed from computed tomography scan data. The location of the tunnel center and tunnel margins in the anatomical coordinate system, and the mean shifting distance of tunnel center and margin were measured with image analysis software during the period. The change of tunnel center location in Bernard quadrant was confirmed if the tunnel center remained within the boundaries of anatomical position after tunnel widening. Results: A total of 56 patients satisfied the inclusion criteria. The mean shifting distance of AM and PL tunnel centers were 1.7 +/- 0.9 mm and 1.6 +/- 0.6 mm. The Tunnel margin of the anteromedial (AM) and posteromedial (PL) tunnels were shifted to 2.5 +/- 1.3 mm and 2.6 +/- 1.4 mm in the anterior direction, and 1.4 +/- 0.9 mm and 1.0 +/- 0.7 mm in the distal direction, respectively. Among the anatomical located tunnel, 97% (32/33) and 87.1% (27/31) of AM and PL tunnel centers remained in a range of anatomical footprint. The tunnel center was shifted from the anatomical position into a nonanatomical position in 3% (1/33) of the AM tunnel and 12.9% (4/31) of PL tunnel after tunnel widening. The tunnel location which shifted non anatomically were relatively anterior and distal position. Conclusions: Tunnel widening shifts the tunnel position to the anterior and distal direction, which could change the initial tunnel position. Nevertheless, the majority of tunnel positions remained in the anatomical position after tunnel widening and shifting.