Two-Bundle ACLs

Abstract & Commentary

Synopsis: Anatomic 2-bundle reconstruction may produce a better biomechanical outcome than single-bundle reconstruction.

Source: Yagi M, et al. Biomechanical analysis of an anatomic anterior cruciate ligament reconstruction. Am J Sports Med. 2002;30(5):660-666.

Replacement of the anteromedial bundle, not the posterolateral bundle, is the focus of most anterior cruciate ligament reconstructions. The present study evaluates an anatomic reconstruction that approximates both functional bundles of the ACL. In this controlled laboratory study, 10 fresh-frozen cadaveric knees were subjected to various external loading conditions: 134-N anterior tibial load at 0°, 30°, 60°, and 90° of knee flexion, and combined rotary load of 5 nm internal tibial torque and 10 nm valgus torque at 15° and 30° of knee flexion to reproduce a pivot shift force. Through the use of a robotic/universal force-moment sensor testing system, highly accurate measurements of knee kinematics and in situ forces in grafts were taken for knees that were intact, ACL deficient, single-bundle reconstructed, and (anatomically) reconstructed with 2 bundles.

Under the 134-N anterior tibial load, anterior tibial translation for the anatomic reconstruction was significantly (P < 0.05) closer to that of the intact knee than was the single-bundle reconstruction. The magnitude of the in situ force in the ACL and the ACL graft for the anatomic reconstruction did not differ significantly from the intact ACL at all flexion angles and was significantly higher than those for the single-bundle reconstruction (P < 0.05). The in situ force normalized to the intact ACL for the anatomic reconstruction was 97% ± 9%, whereas the single-bundle reconstruction was only 89% ± 13%.

Under the combined rotary load, the coupled anterior tibial translation of the anatomic reconstruction was significantly greater than that of the intact knee but significantly less than that of single-bundle reconstruction. The forces on the graft itself were greatest in the intact knee, followed by the 2-bundle and then the single-bundle reconstructions (P < 0.05). The normalized in situ force for the single-bundle and anatomic reconstructions at 30° of flexion was 66% and 91%, respectively.

Comment by Brian J. Cole, MD, and Nina Shervin

Surgical reconstruction of the ACL is a common procedure to restore knee stability with good-to-excellent clinical results and high success rates. Most ACL reconstruction procedures have focused only on replacing the anteromedial bundle; however, recent reports describe the outcomes of more anatomically correct ACL reconstructions designed to reconstruct both the anteromedial and posterolateral bundles of the ACL.1,2 The findings of this study suggest that anatomic reconstruction may produce a better biomechanical outcome than does single-bundle reconstruction, especially during rotary loads. It appears as though anatomic ACL reconstruction more closely restores normal knee kinematics and more closely resembles the in situ forces seen in an intact ACL than single-bundle reconstruction. The use of the robotic/universal force-moment sensor testing system allowed Yagi and colleagues to obtain measurements directly from the same specimen, thereby minimizing the interspecimen variation and increasing the statistical power. Despite the promising results of this study, as noted by Yagi et al, further investigation and long-term clinical trials are required to determine the potential functional advantages of anatomic ACL reconstruction procedures.

Dr. Cole, Assistant Professor, Orthopaedic Surgery, Rush Presbyterian Medical Center, Midwest Orthopaedics, Chicago, IL, is Associate Editor of Sports Medicine Reports.

References

1. Muneta T, et al. Two-bundle reconstruction of the anterior cruciate ligament using semitendinosus tendon with endobuttons: Operative technique and preliminary results. Arthroscopy. 1999;15:618-624.

2. Pederzini L, et al. Double tibial tunnel using quadriceps tendon in anterior cruciate ligament reconstruction. Arthroscopy. 2000;16:E9.