Document Title: Tashman-AJSM-Jun04.shtml
Article Title: Abnormal Rotational Knee Motion During Running After Anterior Cruciate Ligament Reconstruction
Authors: Scott Tashman, PhD, David Collon, MD, Kyle Anderson, MD, Patricia Kolowich, MD and William Anderst, MS
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: June 2004
Volume 32, pages 975-983
Keywords: tibiofemoral motion, kinematics, biomechanics, three-dimensional, ACL reconstruction.

(Figures included. Reference-denoting numbers appear in the same point size as the document text.)

This article makes clear the need for ongoing refinements and enhancements to ACL-reconstruction techniques. Although the current method (entailing implantation of a single sliver of pilfered tendon) certainly brings good results in terms of restoring knee stability, the motion (kinematics) of the reconstructed knee still leaves something to be desired. The problem is that the natural ACL has a multifascicular structure (two or three bundles, depending on the reference source consulted), an attribute which explains the complex three-dimensional movement of the natural knee. (The knee flexes and extends in the anterior-posterior direction, hence in the sagittal plane; this movement itself is a combination of roll and glide. And, to facilitate locking during standing, the knee also twists slightly at full extension; this is movement in the transverse plane. And, the knee effectively becomes slightly knock-kneed at full extension; this valgus-type movement occurs in the frontal plane [also known as the coronal plane].) In an ACL-reconstructed knee, the movement is detectably different from that of a never-injured knee, particularly when dynamic, high-kinetic-energy movements are involved. (Note that kinetic energy increases with speed squared, and so running at thrice the speed of walking translates into nine times as much kinetic energy which the knee is forced to deal with when changing direction or accelerating/decelerating.) The authors note that further research is needed in order to ascertain whether the lingering abnormalities in the movement of the reconstructed knee are a harbinger of premature osteoarthritis. (Keep in mind that about 85% of ACL injuries are accompanied by bone-bruising [articular-cartilage damage], and that such damage itself leaves permanent aftereffects. Meniscal-cartilage damage is also a common accompaniment to ACL tearing. Because all types of joint-cartilage damage leads to early-onset arthritic degeneration, it is not easy to determine whether joint deterioration is a consequence of cartilage damage from the initial injury [or from subsequent giving-way incidents that may have occurred prior to reconstruction] or whether it arises as a result of abnormal knee motion. Also note that the motion of a completely-ACL-deficient-but-non-reconstructed knee is far more abnormal than that of an ACL-reconstructed knee.) The authors note that double-bundle ACL grafts might be a future possibility.

ABSTRACT

Background: The effectiveness of anterior cruciate ligament reconstruction for restoring normal knee kinematics is largely unknown, particularly during sports movements generating large, rapidly applied forces.

Hypothesis: Under dynamic in vivo loading, significant differences in 3-dimensional kinematics exist between anterior cruciate ligament–reconstructed knees and the contralateral, uninjured knees.

Study Design: Prospective, in vivo laboratory study.

Methods: Kinematics of anterior cruciate ligament–reconstructed and contralateral (uninjured) knees were evaluated for 6 subjects during downhill running 4 to 12 months after anterior cruciate ligament reconstruction, using a 250 frame/s stereoradiographic system. Anatomical reference axes were determined from computed tomography scans. Kinematic differences between the uninjured and reconstructed limbs were evaluated with a repeated-measures analysis of variance.

Results: Anterior tibial translation was similar for the reconstructed and uninjured limbs. However, reconstructed knees were more externally rotated on average by 3.8 ± 2.3°across all subjects and time points (P = .0011). Reconstructed knees were also more adducted, by an average of 2.8 ± 1.6°(P = .0091). Although differences were small, they were consistent in all subjects.

Conclusions: Anterior cruciate ligament reconstruction failed to restore normal rotational knee kinematics during dynamic loading.

Clinical Relevance: Although further study is required, these abnormal motions may contribute to long-term joint degeneration associated with anterior cruciate ligament injury/reconstruction.

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