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Document Title: DeFrate-AJSM-Dec04.shtml
Article Title: In Vivo Function of the Posterior Cruciate Ligament During Weightbearing Knee Flexion
Authors: Louis E. DeFrate, MS, Thomas J. Gill, MD and Guoan Li, PhD
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: December 2004
Volume 32, pages 1923-1928
Keywords: posterior cruciate ligament (PCL), in vivo knee biomechanics, kinematics, magnetic resonance imaging, MRI, NMR.
(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 article will be of interest to anyone who has a PCL injury, and especially anyone who is exploring surgical treatments. The importance of reproducing the knee biomechanics as closely as possible is made clear. (The double-bundle method of PCL reconstruction is far superior to the single-bundle method, since it better reproduces the multifascicular structure of the natural PCL. Articles delving into the double-bundle method in detail can be found in the PCL Injuries and Reconstructive Surgeries section.)
ABSTRACT
Background: Current knowledge of posterior cruciate ligament function is mainly based on in vitro cadaveric studies. There are few studies on the in vivo function of the posterior cruciate ligament. The objective of the study was to quantify the multidimensional deformation of the posterior cruciate ligament.
Hypothesis: During in vivo weightbearing flexion, the posterior cruciate ligament undergoes complex 3-dimensional deformations, including elongation, twist, and changes in orientation.
Study Design: In vivo biomechanical study.
Methods: Magnetic resonance images of 5 human knees were used to create 3-dimensional computer models of each subject’s knee, including the insertion areas of the posterior cruciate ligament. Orthogonal fluoroscopic images of each subject’s knee were acquired as a quasi-static lunge was performed. The images and computer models were used to reproduce the in vivo motion of the knee. The relative motion of the femoral and tibial insertions was described in terms of elongation, twist, elevation (the angle between the tibial plateau and posterior cruciate ligament, measured in the sagittal plane), and deviation (mediolateral orientation, measured in plane of tibial plateau).
Results: The length of the posterior cruciate ligament increased significantly with increasing flexion. It twisted almost 80° as the knee flexed from 0° to 90°. The elevation angle remained relatively constant at 50°. The deviation angle was medially oriented by 20° at full extension, then decreased to approximately 10° at 30° through 90° of flexion.
Conclusion: The posterior cruciate ligament undergoes a complex twisting motion as it elongates with flexion.
Clinical Relevance: During reconstruction, the tunnels and graft may need to be placed such that the multidimensional deformation of the intact posterior cruciate ligament is reproduced.
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