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Scientific Articles   |    
Effect of ACL Transection on Internal Tibial Rotation in an in Vitro Simulated Pivot Landing
Youkeun K. Oh, MS1; Jennifer L. Kreinbrink, BS2; James A. Ashton-Miller, PhD1; Edward M. Wojtys, MD2
1 Biomechanics Research Laboratory, Department of Mechanical Engineering, University of Michigan, G.G. Brown 3204 (Y.K.O.) and 3208 (J.A.A.-M.), Ann Arbor, MI 48109-2125. E-mail address for Y.K. Oh: youkeun@umich.edu. E-mail address for J.A. Ashton-Miller: jaam@umich.edu
2 MedSport, University of Michigan, 24 Frank Lloyd Wright Drive, Ann Arbor, MI 48106. E-mail address for J.L. Kreinbrink: kreinbri@umich.edu. E-mail address for: E.M. Wojtys: edwojtys@umich.edu
View Disclosures and Other Information
Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from the National Institutes of Health (R01-AR054821). Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

Investigation performed at MedSport, Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan

Copyright © 2011 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2011 Feb 16;93(4):372-380. doi: 10.2106/JBJS.J.00262
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Abstract

Background: 

The amount of resistance provided by the ACL (anterior cruciate ligament) to axial tibial rotation remains controversial. The goal of this study was to test the primary hypotheses that ACL transection would not significantly affect tibial rotation under the large impulsive loads associated with a simulated pivot landing but would increase anterior tibial translation.

Methods: 

Twelve cadaveric knees (mean age of donors [and standard deviation] at the time of death, 65.0 ± 10.5 years) were mounted in a custom testing apparatus to simulate a single-leg pivot landing. A compound impulsive load was applied to the distal part of the tibia with compression (~800 N), flexion moment (~40 N-m), and axial tibial torque (~17 N-m) in the presence of five trans-knee muscle forces. A differential variable reluctance transducer mounted on the anteromedial aspect of the ACL measured relative strain. With the knee initially in 15° of flexion, and after five combined compression and flexion moment (baseline) loading trials, six trials were conducted with the addition of either internal or external tibial torque (internal or external loading), and then six baseline trials were performed. The ACL was then sectioned, six baseline trials were repeated, and then six trials of either the internal or the external loading condition, whichever had initially resulted in the larger relative ACL strain, were carried out. Tibiofemoral kinematics were measured optoelectronically. The results were analyzed with a nonparametric Wilcoxon signed-rank test.

Results: 

Following ACL transection, the increase in the normalized internal tibial rotation was significant but small (0.7°/N-m ± 0.3°/N-m to 0.8°/N-m ± 0.3°/N-m, p = 0.012), while anterior tibial translation increased significantly (3.8 ± 2.9 to 7.0 ± 2.9 mm, p = 0.017).

Conclusions: 

ACL transection leads to a small increase in internal tibial rotation, equivalent to a 13% decrease in the dynamic rotational resistance, under the large forces associated with a simulated pivot landing, but it leads to a significant increase in anterior tibial translation.

Clinical Relevance: 

An ACL reconstruction that restores both ligament orientation and stiffness will provide major resistance to anterior tibial translation while providing minor resistance to axial tibial rotation.

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    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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