Effect of tunnel position for anatomic single-bundle ACL reconstruction on knee biomechanics in a porcine model

Attention has been focused on the importance of anatomical tunnel placement in anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the effect of different tunnel positions for single-bundle (SB) ACL reconstruction on knee kinematics. Ten porcine knees were used for the following reconstruction techniques: three different anatomic SB [AM-AM (antero-medial), PL-PL (postero-lateral), and MID-MID] (n = 5 for each group), conventional SB (PL-high AM) (n = 5), and anatomic double-bundle (DB) (n = 5). Using a robotic/universal force-moment sensor testing system, an 89 N anterior load (simulated KT1000 test) at 30, 60, and 90A degrees of knee flexion and a combined internal rotation (4 N m) and valgus (7 N m) moment (simulated pivot-shift test) at 30 and 60A degrees were applied. Anterior tibial translation (ATT) (mm) and in situ forces (N) of reconstructed grafts were calculated. During simulated KT1000 test at 60A degrees of knee flexion, the PL-PL had significantly lower in situ force than the intact ACL (P < 0.01). In situ force of the MID-MID was higher than other SB reconstructions (at 30A degrees: 94.8 +/- A 2.5 N; at 60A degrees: 85.2 +/- A 5.3 N; and 90A degrees: 66.0 +/- A 8.7 N). At 30A degrees of knee flexion, the PL-high AM had the lowest in situ values (67.1 +/- A 19.3 N). At 60 and 90A degrees of knee flexion the PL-PL had the lowest in situ values (at 60A degrees: 60.8 +/- A 19.9 N; 90A degrees: 38.4 +/- A 19.2 N). The MID-MID and DB had no significant in situ force differences at 30 and 60A degrees of knee flexion. During simulated pivot-shift test at 60A degrees of knee flexion, the PL-PL and PL-high AM reconstructions had a significant lower in situ force than the intact ACL (P < 0.01). During simulated KT1000 test at 30, 60, and 90A degrees of knee flexion, the PL-PL and PL-high AM had significantly lower ATT than the intact ACL (P < 0.01). During simulated KT1000 test at 60 and 90A degrees, the MID-MID, AM-AM, and DB had significantly lower ATT than the ACL deficient knee (P < 0.01). During simulated KT1000 test at 90A degrees, every reconstructed knee had significantly higher ATT than the intact knee (P < 0.01). In conclusion, the MID-MID position provided the best stability among all anatomic SB reconstructions and more closely restored normal knee kinematics.