Title:
Eccentric femoral tunnel widening in anatomic anterior cruciate ligament reconstruction.

Abstract:
The purpose of this study was to retrospectively evaluate femoral tunnel widening (TW) and migration of the femoral tunnel aperture after anatomic anterior cruciate ligament (ACL) reconstructions with hamstring grafts and bone-patellar tendon-bone (BPTB) grafts.
Of the 105 consecutive patients who underwent ACL reconstruction, the 52 patients who underwent isolated ACL reconstruction and in whom tunnel measurement could be obtained by computed tomography were included in this study. In 26 patients, double-bundle reconstruction (DBR) of the ACL using hamstring tendons was performed. These patients were compared with 26 patients in whom rectangular tunnel ACL reconstruction using BPTB grafts (BPTBR) was performed. Femoral tunnel aperture positioning and TW were investigated postoperatively using 3-dimensional computed tomographic images, which were performed a week and a year after surgery in all patients.
In DBR, the average diameter of the anteromedial (AM) femoral tunnel increased by 34.0% in the horizontal direction and 28.2% in the vertical direction, whereas that of the posterolateral (PL) femoral tunnel increased by 58.2% and 73.4%, respectively, at 1 year after surgery compared with 1 week after surgery. The percentage TW value of the PL tunnel was significantly greater than that of the AM tunnel. In BPTBR, the average diameter increased by 22.0% and 17.1%, respectively. The percentage TW value of the PL tunnel in DBR was significantly greater than that of the femoral tunnel in BPTBR. Each tunnel aperture migrated distally ("shallow") in the horizontal direction and high in the vertical direction. AM and PL tunnel apertures in DBR migrated in the vertical direction significantly more than they did in BPTBR. No significant differences between the 2 groups were found in clinical outcomes.
The femoral PL tunnel aperture in DBR showed significantly more widening than did the AM tunnel aperture in DBR and the femoral tunnel aperture in BPTBR. Also, greater migration of the femoral tunnel aperture in the vertical direction because of TW was observed in DBR than in BPTBR.
Level IV, therapeutic case series.