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, 14 (3), 298-306

In Vivo Anterior Cruciate Ligament Elongation in Response to Axial Tibial Loads

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In Vivo Anterior Cruciate Ligament Elongation in Response to Axial Tibial Loads

Ali Hosseini et al. J Orthop Sci.

Abstract

Background: The knowledge of in vivo anterior cruciate ligament (ACL) deformation is fundamental for understanding ACL injury mechanisms and for improving surgical reconstruction of the injured ACL. This study investigated the relative elongation of the ACL when the knee is subject to no load (<10 N) and then to full body weight (axial tibial load) at various flexion angles using a combined dual fluoroscopic and magnetic resonance imaging (MRI) technique.

Methods: Nine healthy subjects were scanned with MRI and imaged when one knee was subject to no load and then to full body weight using a dual fluoroscopic system (0 degrees-45 degrees flexion angles). The ACL was analyzed using three models: a single central bundle; an anteromedial and posterolateral (double functional) bundle; and multiple (eight) surface fiber bundles.

Results: The anteromedial bundle had a peak relative elongation of 4.4% +/- 3.4% at 30 degrees and that of the posterolateral bundle was 5.9% +/- 3.4% at 15 degrees. The ACL surface fiber bundles at the posterior portion of the ACL were shorter in length than those at the anterior portion. However, the peak relative elongation of one posterolateral fiber bundle reached more than 13% whereas one anteromedial fiber bundle reached a peak relative elongation of only about 3% at 30 degrees of flexion by increasing the axial tibial load from no load to full body weight.

Conclusions: The data quantitatively demonstrated that under external loading the ACL experiences nonhomogeneous elongation, with the posterior fiber bundles stretching more than the anterior fiber bundles.

Figures

Fig. 1
Fig. 1
Magnetic resonance (MR) images of a knee in the sagittal and coronal planes and construction of a three-dimensional (3D) knee model using magnetic resonance imaging (MRI)
Fig. 2
Fig. 2
A Three-dimensional anterior cruciate ligament (ACL) model constructed from MR images. B ACL configuration of a cadaveric knee. C Definition of ACL surface fiber bundles. PL, posterolateral; AM, anteromedial
Fig. 3
Fig. 3
A Dual fluoroscopic system for measuring joint position in space and a subject during a lunge activity. (From Jordan et al., with permission) B Virtual dual fluoroscopic system constructed for reproducing the in vivo knee position in space
Fig. 4
Fig. 4
A Length of the ACL central bundle when the knee is under no load and under full body load at various flexion angles. BW, body weight. B Relative elongation of the ACL central bundle in response to full body weight
Fig. 5
Fig. 5
Lengths of the (A) anteromedial bundle (AMB) and (B) posterolateral bundle (PLB) when the knee is under no load and at full body load at various flexion angles. C Relative elongation of the AM and PL bundles in response to full body weight
Fig. 6
Fig. 6
Lengths of the anterior surface bundle 4 and the pos- elongation of the eight ACL surface fiber bundles in response terior surface bundle 7 when the knee is under (A) no load to full body weight and (B) full body load at various flexion angles. C Relative elongation of the eight ACL surface fi ber bundles in response to full body weight

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