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Document Title: Zantop-AJSM-Feb07.shtml
Article Title: The Role of the Anteromedial and Posterolateral Bundles of the Anterior Cruciate Ligament in Anterior Tibial Translation and Internal Rotation
Authors: Thore Zantop, MD, Mirko Herbort, MD, Michael J. Raschke, MD, Freddie H. Fu, MD and Wolf Petersen, MD
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: February 2007
Volume 35, pages 223-227
Keywords: Knee biomechanics, kinematics, kinetics, anterior cruciate ligament, rotational stability, double bundle ACL graft.
(Reference-denoting numbers appear in the same font and point size as the document text. As with all Knee Library documents, this article is provided in full-text form, complete with all figures and tables.)
Comments: This brilliantly perceptive, eye-opening article discusses the intricate double-bundle (anteromedial and posterolateral) structure of the natural ACL. The authors clearly show that the only hope of reproducing the complex functioning of the natural ACL is with a double-bundle graft. While it would be biomechanically wonderful if all knee-involved orthopedists were to perform double-bundle ACL grafts, the problem is that double-bundle grafting is technically far more complicated than single-bundle ACL grafting (which in itself is already technically very demanding). This means that double-bundle grafting, while kinematically far superior to single-bundle ACL grafting, would introduce a greater risk of surgeon error. Hopefully, improvements and standardization in ACL-grafting techniques, combined perhaps with technological enhancements (tools and perhaps electronic tunnel-drilling guidance systems), will make double-bundle ACL grafting feasible for mass implementation.
ABSTRACT
Background: A rupture of the entire fibers of the anterior cruciate ligament leads to knee instability due to increased anterior tibial translation and increased internal tibial rotation. The influence of isolated deficiency of the anteromedial or posterolateral bundle of the anterior cruciate ligament on the resulting knee kinematics have not yet been reported.
Hypothesis: Transection of the anteromedial bundle will lead to increased anterior tibial translation at 90°. Transection of the posterolateral bundle will show an increased anterior tibial translation as well as a combined rotatory instability at 30°.
Study Design: Controlled laboratory study.
Methods: Kinematics of the intact knee were determined in response to a 134-N anterior tibial load and a combined rotatory load of 10 N·m valgus and 4 N·m internal tibial rotation using a robotic/universal force moment sensor testing system. Subsequently, the fibers of the anteromedial and posterolateral bundle were resected in an alternating order and the new translation in response to the same external loading conditions measured. Statistical analysis was performed using a 2-way ANOVA test.
Results: Transection of the anteromedial bundle increased anterior tibial translation at 60° and 90° of knee flexion significantly. Isolated transsection of the posterolateral bundle increased anterior tibial translation in response to 134-N anterior load at 30° of knee flexion significantly and resulted in a significant increase in combined rotation at 0° and 30° in response to a combined rotatory load compared with the intact knee and isolated resection of the anteromedial bundle.
Conclusion: The anteromedial and posterolateral bundles stabilize the knee joint in response to anterior tibial loads and combined rotatory loads in a synergistic way.
Clinical Relevance: The results of the current study suggest that, from a biomechanical point of view, it may be beneficial to reconstruct both bundles of the anterior cruciate ligament to better restore normal anterior tibial translation and combined rotation.
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