Intégration dans le tunnel fémoral du greffon dans les reconstructions du LCA : voie transportale versus technique outside-in

Abstract

Purpose Although the independent drilling techniques using transportal portal or outside-in approaches in ACL reconstruction have some advantages over the trans-tibial technique in placing the anatomical femoral tunnel, these techniques may make an acute graft-bending angle at the femoral tunnel entry or result in a short femoral tunnel length. However, there have been no reports on whether an acute graft-bending angle of an independent drilling technique might result in poor graft healing or negatively affecting clinical outcomes. The purpose of this study was to compare femoral tunnel geometry including tunnel position, length, and graft bending angle between the transportal and the outside-in techniques in ACL reconstruction and discover whether such differences in tunnel geometry could influence graft healing or clinical outcomes. Methods Sixty patients with anatomical single-bundle ACL reconstruction performed with use of either the transportal technique (32 patients) or the outside-in technique (28 patients) were included for this study. The femoral tunnel location, length and graft-bending angle at the femoral tunnel were analyzed on the 3D CT knee model, and we compared the location and length of the femoral tunnel, and graft-bending angle between the two techniques. Each group underwent MRI scans at least 1 year (range of 1–2 years) following the ACL reconstruction. We confirmed that all patients showed an intact ACL graft on the MRI images. On the oblique axial image taken after the ACL reconstruction, to determine graft healing at the femoral and tibial tunnels, and the intra-articular portion, the graft signal intensity ratio was calculated by dividing signal intensity (SI) of the reconstructed ACL by that of the posterior cruciate ligament (PCL) in the region-of-interest (ROI). We also compared the clinical outcomes in terms of Tegner activity scores, the International Knee Documentation Committee (IKDC) scores and Lachman and pivot-shift test results. Results While the location of femoral tunnel was similar in both groups, the femoral tunnel length was a little bit longer in the outside-in technique (37 vs. 32 mm, P = 0.07). Meanwhile, the outside-in technique showed a more significant acute graft tunnel angle than the transportal technique (100 vs. 113, P = 0.04). However, the signal intensity ratios of the grafts (compared with SI of PCL) were similar in femoral tunnel, tibial tunnel or intrarticular portions. Moreover, there were no significant statistical differences between the two groups in terms of IKDC scores (86.1 vs. 91.0, P = 0.32) and Tegner activity scores (6.5 vs. 6.8, P = 0.79). We also could not find any significant differences in the results of Lachman and pivot-shift tests. Conclusions Even though the outside-in technique in ACL reconstruction created a more acute femoral graft bending angle and a longer femoral tunnel length than the transportal technique, these had no negative effects in graft healing. In addition, the transportal and outside-in techniques in ACL reconstruction showed similar femoral tunnel positions, and no significant differences in clinical outcome. Therefore, the outside-in ACL reconstruction can be considered as the more effective method for surgeons to overcome the weakness of the traditional transportal technique.