Femoral tunnel widening after double-bundle ACL reconstruction with hamstring autograft produces a small shift of the tunnel position in the anterior and distal direction : CT based retrospective cohort analysis.

Abstract Purpose The purpose of this study is to confirm was to determine whether the femoral tunnel position after double-bundle ACL reconstruction remains in an anatomical position footprint after tunnel widening and shifting. Methods A patients who underwent unilateral double-bundle ACL reconstruction with hamstring autograft and performed CT 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 (CT) scan data. The location of the tunnel center and tunnel margins in the Anatomical coordinate system, 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 AM and 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 non-anatomical 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. Conclusion 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.