Observations on Bone Tunnel Enlargement After Double-Bundle Anterior Cruciate Ligament Reconstruction

Purpose: The purpose of this study was to determine the amount of tibial and femoral bone tunnel enlargement after double-bundle anterior cruciate ligament (ACL) reconstruction. Methods: Twenty-five consecutive patients undergoing primary double-bundle hamstring ACL reconstruction were included in a prospective case series. Femoral fixation was performed by means of 2 EndoButton CL devices (Smith & Nephew Endoscopy, Andover, MA), and tibial fixation was done with 2 bioresorbable interference screws. Magnetic resonance imaging (MRI) was performed in all patients at a mean of 12.3 months postoperatively. Tunnel enlargement was determined by digitally measuring the widths perpendicular to the long axis of the anteromedial (AM) and posterolateral (PL) tunnels on an oblique coronal and axial plane. The MRI measurements were compared with the intraoperative drill diameter. Results: The mean tibial AM bone tunnel diameter increased from 0.74 to 1.06 cm, and the mean PL diameter increased from 0.60 to 0.89 cm. The mean femoral AM bone tunnel diameter increased from 0.71 to 0.97 cm, and the mean PL diameter increased from 0.58 to 0.85 cm. Bone tunnel enlargement was 43% (P = .001) for both tibial tunnels and 35% (P = .001) versus 48% (P < .001) for the femoral AM bone tunnel versus the PL femoral bone tunnel. On the tibial side, communication of the bone tunnels occurred in 41% of patients. Conclusions: This study shows significant tibial and femoral bone tunnel enlargement on MRI after 4-tunnel double-bundle ACL reconstruction 1 year postoperatively. In 41% of patients separate tibial bone tunnel measurements were impossible because of tunnel communication caused by intraoperative bone tunnel drilling, screw contact, or postoperative bone tunnel enlargement. On the femoral side, no bone tunnel communication occurred. The short-term clinical results were good and were not influenced by tunnel communication. Level of Evidence: Level IV, therapeutic case series.

Key Words: Anterior cruciate ligament reconstruction, Double bundle, Anteromedial bundle, Posterolateral bundle, Hamstrings, Tunnel widening, Magnetic resonance imaging