PurposeRecent reports have highlighted the importance of an anatomic tunnel placement for anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the effect of different tunnel positions for single-bundle ACL reconstruction on knee biomechanics.MethodsSixteen fresh-frozen cadaver knees were used. In one group (n = 8), the following techniques were used for knee surgery: (1) anteromedial (AM) bundle reconstruction (AM–AM), (2) posterolateral (PL) bundle reconstruction (PL–PL) and (3) conventional vertical single-bundle reconstruction (PL-high AM). In the other group (n = 8), anatomic mid-position single-bundle reconstruction (MID–MID) was performed. A robotic/universal force-moment sensor system was used to test the knees. An anterior load of 89 N was applied for anterior tibial translation (ATT) at 0°, 15°, 30° and 60° of knee flexion. Subsequently, a combined rotatory load (5 Nm internal rotation and 7 Nm valgus moment) was applied at 0°, 15°, 30° and 45° of knee flexion. The ATT and in situ forces during the application of the external loads were measured.ResultsCompared with the intact ACL, all reconstructed knees had a higher ATT under anterior load at all flexion angles and a lower in situ force during the anterior load at 60° of knee flexion. In the case of combined rotatory loading, the highest ATT was achieved with PL-high AM; the in situ force was most closely restored with MIDMID, and the in situ force was the highest AM–AM at each knee flexion angle.ConclusionAmong the techniques, AM–AM afforded the highest in situ force and the least ATT.

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 90 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 60 degrees were applied. Anterior tibial translation (ATT) (mm) and in situ forces (N) of reconstructed grafts were calculated. During simulated KT1000 test at 60 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 30 degrees : 94.8 +/- 2.5 N; at 60 degrees : 85.2 +/- 5.3 N; and 90 degrees: 66.0 +/- 8.7 N). At 30 degrees of knee flexion, the PL-high AM had the lowest in situ values (67.1 +/- 19.3 N). At 60 and 90 degrees of knee flexion the PL-PL had the lowest in situ values (at 60 degrees : 60.8 +/- 19.9 N; 90 degrees : 38.4 +/- 19.2 N). The MID-MID and DB had no significant in situ force differences at 30 and 60 degrees of knee flexion. During simulated pivot-shift test at 60 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 90 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 90 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 90 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.

Triaxial accelerometer could serve as a quantitative evaluation of rotational instability. The present study demonstrated that PL bundle has the most important contribution for rotational instability (80.4%) when compared to IM bundle (0.01%) and AM bundle (19.5%) in porcine knee model.