How the Aperture of Femoral Tunnel Affected in ACL Reconstruction Performed with AM Portal Technique?

PURPOSE OF THE STUDY The purpose of this study was to evaluate the position of tibial tunnel (TT) and femoral tunnels (FT) performed by using the anteromedial (AM) portal technique and its effect on the aperture of FT. MATERIAL AND METHODS A total 44 patients operated for anterior cruciate ligament (ACL) rupture by AM portal technique between January 2013 and July 2015, were included in this study. They were subjected to a magnetic resonance imaging of the knee to assess the FT, dimensions of the FT aperture and TT. The location of the ACL graft within the joint was compared with the intact ACL of healthy individuals. The patients were also evaluated using Lysholm and IKDC subjective scores for functional outcome. RESULTS The mean FT angle on both the coronal plane (42.88°±5.83°) and the sagittal plane (68.47°±9.57°) was significantly different from the intra-articular part of the hamstring autograft angles (74.93°±7.27° and 58.74°±4.88°, respectively) (p<0.0001). The mean distance of the FT aperture was 13.18 (±2.49) mm on vertical axis, 10.97 (±1.50) mm on the sagittal axis (p<0.0001). The difference between TT axis and the axis of the intra-articular part of autograft on both coronal (72.78°±4.67° and 74.93°±7.27°, respectively) and sagittal planes (60.12°±5.53° and 58.74°±4.88°, respectively) were not significant (p>0.05). DISCUSSION Ilingrowth et al. claimed that the FT were scattered in the very large distance and some of them were placed outside of anatomical range in the series included the cases performed with transtibial and transtibial independent techniques. In this series, in which we used a femoral guide to drill the FT at lateral femoral condyle at 2 or 10 o'clock position depended upon the site of operation, we obtained a consistent FT which is comparable with the intra-articular part of native ACL. Amano et al. found that the FT aperture enlargement was significant in the series when hamstring tendons were used as autograft, over a 6-month period. We also found a significant difference between the narrowest part of the FT (7.01 ± 1.05 mm) and its aperture (10.97 ± 1.50 mm in sagittal, 13.18 ± 2.49 mm in vertical direction). The enlargement was mainly in the vertical direction, due to the fact that the loads resulting from daily life are mostly on the horizontal plane. CONCLUSIONS The direction of intra-articular part of the ACL graft in the cases operated with the AM portal technique is significantly different from the FT direction in both the coronal and sagittal planes. The enlargement of the FT aperture is larger in the vertical axis compared to the sagittal axis. Although the long-term clinical consequences of asymmetrical enlargement of the FT aperture are not known yet, to avoid this potential risk, a technique to approximate the direction of FT to the intra-articular part of the ACL without changing the FT entry site, can be used. Key words: knee, anterior cruciate ligament reconstruction, femoral tunnel, tibial tunnel, anteromedial portal.