Comparisons of tunnel-graft angle and tunnel length and position between transtibial and transportal techniques in anterior cruciate ligament reconstruction

Purpose Our aim was to evaluate tunnel-graft angle, tunnel length and position and change in graft length between transtibial (30 patients) and anteromedial (30 patients) portal techniques using 3D knee models after anterior cruciate ligament (ACL) reconstruction. Methods The 3D angle between femoral or tibial tunnels and graft at 0 degrees and 90 degrees flexion were compared between groups. We measured tunnel lengths and positions and evaluated the change in graft length from 0 degrees to 90 degrees flexion. Results The 3D angle at the femoral tunnel with graft showed a significant difference between groups at 0 degrees flexion (p = 0.01) but not at 90 degrees flexion (p = 0.12). The 3D angle of the tibial tunnel showed no significant differences between groups. Femoral tunnel length in the transtibial group was significantly longer than in the transportal group (40.7 vs 34.7 mm,), but tibial tunnel length was not. The relative height of the lateral femoral condyle was significantly lower in the transportal than the transtibial group (24.1 % vs 34.4 %). No significant differences were found between groups in terms of tibial tunnel position. The change in graft length also showed no significant difference between groups. Conclusions Even though the transportal technique in ACL reconstruction can place the femoral tunnel in a better anatomical position than the transtibial technique, it has risks of a short femoral tunnel and acute angle at the femoral tunnel. Moreover, there was also no difference in the change of the graft length between groups.