An in Vivo 3D Computed Tomographic Analysis of Femoral Tunnel Geometry and Aperture Morphology between Rigid and Flexible Systems in Double-Bundle Anterior Cruciate Ligament Reconstruction Using the Transportal Technique

Purpose The aim of this study was to compare femoral tunnel length, femoral graft-bending angle, posterior wall breakage, and femoral aperture morphologic characteristics between rigid and flexible systems after double-bundle (DB) anterior cruciate ligament (ACL) reconstruction using the transportal (TP) technique. Methods We evaluated 3-dimensional computed tomography (3D-CT) results for 54 patients who underwent DB ACL reconstruction using the TP technique with either a flexible system (n = 27) or a rigid system (n = 27). The femoral tunnel length, femoral graft-bending angle, posterior wall breakage, femoral tunnel aperture height to width (H:W) ratio, aperture axis angle, and femoral tunnel position were assessed using OsiriX Imaging Software and Geomagic Qualify 2012 (Geomagic, Cary, NC). Results The mean anteromedial (AM) femoral tunnel length of the flexible group was significantly longer than that of the rigid group (P =.009). The mean femoral graft-bending angles in the flexible group were significantly less acute than those in the rigid group (AM, P <.001; posterolateral [PL], P =.003]. Posterior wall breakage was observed in both groups (P = 1.00). The mean H:W ratios in the rigid group were significantly larger (more elliptical) than those of the flexible group (AM, P <.001; PL, P =.006). The mean aperture axis angle of the PL femoral tunnel in the rigid group was more parallel to the femoral shaft axis than that in the flexible group (P <.001). There were no significant differences in femoral tunnel position between the 2 groups. Conclusions The AM femoral tunnel length and the AM/PL femoral graft-bending angle of the flexible system were significantly longer and less acute than those of the rigid system. However, the aperture morphologic characteristics of the AM/PL femoral tunnel and the aperture axis angle of the PL femoral tunnel in the rigid system were significantly more elliptical and closer to parallel to the femoral shaft axis than those of the flexible system. Level of Evidence Level III, retrospective comparative study.