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

Abstract

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.

Anatomic Anterior Cruciate Ligament Reconstruction Utilizing the Double-Bundle Technique

“…Most studies that reported graft failure after ACL reconstruction included patients who underwent nonanatomic ACL reconstruction. However, after anatomic ACL reconstruction, a higher graft failure rate may be expected because, as demonstrated by Kato et al, 45 the forces in an anatomically placed graft will be greater (comparable to the native ACL) than those in a nonanatomically placed graft (less force than the native ACL due to the nonanatomic position of the graft). Therefore, rehabilitation and return to sport after anatomic ACL reconstruction may need to be progressed slower than after a traditional, nonanatomic ACL reconstruction.…”

“…Another concern is that, based on biomechanical studies, graft forces are greater when the graft is anatomically positioned. 45 For this reason, functional activities that place a high load on the graft, such as jumping, cutting, pivoting, and return to sport, are more gradually initiated and progressed after anatomic ACL reconstruction.…”

“…45 Although increased loading of the graft may protect other structures in the knee from progressive degeneration, the higher load on the graft must be considered during postoperative recovery and rehabilitation while the graft is still healing and maturing. Because of the higher graft loads after anatomic ACL reconstruction, we recommend that rehabilitation be progressed more carefully.…”

Assessment of foot print of femoral tunnel placement with commercially available off set guide in arthroscopic ACL reconstruction

“…Biomechanical studies have shown that a vertically oriented ACL graft may resist the motion of anterior tibial translation, but may fail to control the combined motions of anterior tibial translation and internal rotation which occurs during the pivot shift phenomenon. 12 This may result in patient experiencing continued symptoms of instability and giving away episodes due to the pivot shift phenomenon. Still many surgeons prefer trans-tibial technique of femoral drill.…”

Anatomic Anterior Cruciate Ligament Reconstruction With a Flexible Reamer System and 70° Arthroscope

“…On the basis of a number of published biomechanical studies, accurate anatomic tunnel placement for graft positioning is a key component in improving ACL reconstruction outcomes. 1 Nonanatomic tibial and/or femoral tunnel placement remains one of the most common reasons for failure after ACL reconstruction. 2 A variety of techniques have been developed to facilitate accurate, reproducible anatomic tunnel placement during ACL reconstruction, including use of femoral independent drilling through accessory portals, use of an outside-in femoral drilling technique, creation of a wide notchplasty, and visualization of the femoral anatomy by use of an anteromedial (AM) portal, among others.…”