Quantification of patellar tracking using kinematic MRI

Authors

  • Christopher M. Powers PhD, PT,

    Corresponding author
    1. Department of Biokinesiology and Physical Therapy, University of Southern California, 1540 East Alcazar Street, CHP 155, Los Angeles, CA 90033
    • Department of Biokinesiology and Physical Therapy, University of Southern California, 1540 East Alcazar Street, CHP 155, Los Angeles, CA 90033
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  • Frank G. Shellock PhD,

    1. Future Diagnostics, Los Angeles, CA
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  • Martin Pfaff PhD

    1. Intuitive Software Technology, West Hills, CA
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Abstract

The purpose of this study was to describe a method to quantify dynamic patellar tracking using kinematic MRI (KMRI). Twelve normal females and three patients with patellofemoral pain participated. Imaging was performed with a 1.5-T/64-MHz MR system using a fast spoiled gradient-recalled acquisition in the steady state (GRASS) pulse sequence. A nonferromagnetic positioning device permitted active, bilateral knee extension against resistance (15% bwt) from 45° knee flexion to full extension. Subjects were instructed to extend their knees at a rate of 9° per second, which allowed images to be obtained at 45°, 36°, 27°, 18°, 9°, and 0°. All images were assessed for medial/lateral patellar displacement, patellar tilt, and sulcus angle using a computer-aided system. Normal patellar motion was characterized by medial movement from 45° to 18°, followed by a reversal toward lateral displacement from 18° to full extension. The results for patellar tilt revealed a tendency toward decreasing lateral tilt as the knee extended. Sulcus angle measurements indicated that the patella was moving to a more shallow portion of the trochlear groove (superiorly) during extension.

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