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Background: Although anatomical double-bundle anterior cruciate ligament reconstruction can successfully restore normal knee biomechanics for knees with typical varus-valgus alignment, the efficacy of the same reconstruction method for knees after a valgus high tibial osteotomy is unclear. Hypothesis: Anatomical double-bundle anterior cruciate ligament reconstruction for valgus knees after a high tibial osteotomy cannot restore normal knee kinematics and can result in abnormally high in situ forces in the ligament graft. Study Design: Controlled laboratory study. Methods: Ten cadaveric knees were subjected to valgus high tibial osteotomy followed by an anatomical double-bundle anterior cruciate ligament reconstruction. The valgus knees were tested using a robotic/universal force-moment sensor system before and after the ligament reconstruction. The knee kinematics in response to anterior tibial load and combined rotatory loads, as well as the corresponding in situ forces of the anterior cruciate ligament bundles and grafts, were compared between the ligament-intact and ligament-reconstructed valgus knees. Results: After reconstruction, the anterior tibial translation and internal tibial rotation for the valgus knee decreased approximately 2 mm and 2°, respectively, at low flexion angles compared with those of the anterior cruciate ligament-intact knee (P < .05). The in situ forces in the posterolateral graft became 56% to 200% higher than those in the posterolateral bundle of the intact anterior cruciate ligament (P < .05). Conclusion: Performing an anatomical double-bundle anterior cruciate ligament reconstruction on knees after valgus high tibial osteotomy may overconstrain the knee and result in high forces in the posterolateral graft, which could predispose it to failure. Clinical Relevance: Modifications of anterior cruciate ligament reconstruction procedures to reduce posterolateral graft force may be needed for valgus knees after a high tibial osteotomy. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effect of the iliotibial band (ITB) on the kinematics of anterior cruciate ligament (ACL) intact and deficient knees and also on the in situ force in the ACL during a simulated pivot shift test. A combination of 10 N-m valgus and 5 N-m internal tibial torques was applied to 10 human cadaveric knees at 15°, 30°, 45°, and 60° of flexion using a robotic/universal force-moment sensor testing system. ITB forces of 0, 22, 44, and 88 N were also applied. An 88 N ITB force significantly decreased coupled anterior tibial translation of ACL deficient knees by 32%-45% at high flexion angles, but did not have a significant effect at low flexion angles. Further, an 88 N ITB force significantly decreased in situ forces in the ACL at all flexion angles by 23%-40%. These results indicate that during the pivot shift test, the ITB can improve tibial reduction at high flexion angles while not affecting subluxation at low flexion angles. Additionally, the action of the ITB as an ACL agonist suggests that its use as an ACL graft might hinder knee stability in response to rotatory load. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [ABSTRACT FROM AUTHOR]

Injury of the anterior cruciate ligament (ACL) can lead to knee instability associated with damage to other knee structures and the increased risk of osteoarthritis. Thus, surgeons have turned to the use of autografts as ACL replacements to restore knee function and expedite the patient's return to sports, as well as avoid the long-term complications associated with chronic knee instability. However, retrospective and prospective clinical studies conducted at short- and long-term follow-up have revealed that 15% to 25% of patients have less than satisfactory results. Whereas there can be numerous factors that contribute to this outcome, biomechanical studies have helped to gain a new perspective of the complex function of the ACL that these replacement grafts failed to restore. In this article, the readers are provided with a brief review of the experimental methodology used to evaluate the biomechanical properties and function of the ACL and its replacements. Specifically, the use of tensile tests to measure the structural properties of the graft tissue and graft-fixations constructs is described. Tensile testing has allowed for comparison of different graft materials, fixation methods, as well as provided insight into changes in mechanical behavior of the graft construct throughout graft remodeling and incorporation. A unique testing system utilizing a six degrees of freedom robotic manipulator and universal force-moment sensor (UFS) has been developed such that the knee measurements can be made in a non-contact fashion while allowing a series of experiments to be performed on the same knee. Using this robotic/UFS testing system, it has been possible to quantitatively assess the crucial roles of the ACL and their respective bundles in maintaining normal knee stability, especially under rotatory loading. The effects of several variables for reconstruction (graft selection, femoral tunnel positioning, anatomic “double bundle” reconstruction, and initial graft tension) on knee kinematics are then reviewed. To close, directions for future research that could potentially further improve the outcome of reconstructions are provided. [ABSTRACT FROM AUTHOR]