Relationship between femoral tunnel location and graft bending angle in outside-in and transportal technique for ACL double bundle reconstruction in 3D-CT study.

Abstract

In anterior cruciate ligament (ACL) reconstruction, sharp angulation of the graft at tunnel aperture increases local strain to the graft. The purpose of this study is to investigate the relationship between femoral tunnel location and femoral graft bending angle after ACL double bundle reconstruction (ACL-DBR) with two different drilling techniques. In ACL-DBR, femoral tunnel was created by two techniques; outside-in technique (26 patients, group A) and transportal technique (25 patients, group B). CT scan was taken at 1week postoperatively. The position of femoral tunnel exit on the lateral femoral cortex, and intra-articular femoral and tibial tunnel aperture of the anteromedial bundle (AMB) and postero-lateral bundle (PLB) was measured using a rectangular frame on three-dimensional CT images. Femoral graft bending angle was measured using two-dimensional CT images. Femoral tunnel exits of AMB and PLB in group A were significantly anterior and proximal than those in group B (p<0.05), while there was no significant difference in intra-articular femoral and tibial tunnel apertures between group A and B. A mean femoral graft bending angle of AMB was 80.3° in group A and 69.2 degrees in group B, respectively (p<0.05). A mean femoral graft bending angle of PLB was 66.3° in group A and 64.6° in group B, respectively. In both groups, a significant (p<0.05) correlation (r<-0.4) was observed between the position of the femoral tunnel exit (anterior-posterior ratio from femoral anterior border line) and the femoral graft bending angle in AMB. Since the femoral tunnel exit in outside-in technique was located more anterior and proximal, femoral graft bending angle of AMB in outside-in technique was greater than that in transportal technique. Anterior position of the femoral tunnel exit in AMB increased femoral graft bending angle in outside-in and transportal techniques.