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Technical Briefs

Analysis Techniques for Congruence of the Patellofemoral Joint

[+] Author and Article Information
K. D. Connolly

Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive Northwest, Calgary, AB, T2N 1N4, Canada; Human Performance Laboratory, Roger Jackson Center for Health and Wellness Research, Faculty of Kinesiology, University of Calgary, 2500 University Drive Northwest, Calgary, AB, T2N 1N4, Canadaconnollykd@hotmail.com

J. L. Ronsky1

Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive Northwest, Calgary, AB, T2N 1N4, Canada; Human Performance Laboratory, Roger Jackson Center for Health and Wellness Research, Faculty of Kinesiology, University of Calgary, 2500 University Drive Northwest, Calgary, AB, T2N 1N4, Canadajlronsky@ucalgary.ca

L. M. Westover

Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive Northwest, Calgary, AB, T2N 1N4, Canada; Human Performance Laboratory, Roger Jackson Center for Health and Wellness Research, Faculty of Kinesiology, University of Calgary, 2500 University Drive Northwest, Calgary, AB, T2N 1N4, Canadalmwestov@ucalgary.ca

J. C. Küpper

Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive Northwest, Calgary, AB, T2N 1N4, Canada; Human Performance Laboratory, Roger Jackson Center for Health and Wellness Research, Faculty of Kinesiology, University of Calgary, 2500 University Drive Northwest, Calgary, AB, T2N 1N4, Canadajohnsojc@ucalgary.ca

R. Frayne

Departments of Radiology and Clinical Neurosciences, University of Calgary, 2500 University Drive Northwest, Calgary, AB, T2N 1N4, Canada; Seaman Family MR Research Centre, Foothills Medical Centre, Calgary Health Region, 1403 29 Street Northwest, Calgary, AB, T2N 2T9, Canadarfrayne@ucalgary.ca

1

Corresponding author.

J Biomech Eng 131(12), 124503 (Nov 04, 2009) (7 pages) doi:10.1115/1.3212111 History: Received September 30, 2008; Revised May 18, 2009; Published November 04, 2009; Online November 04, 2009

Quantifying joint congruence may help to understand the relationship between joint function and health. In previous studies, a congruence index (CI) has been used to define subject-specific joint congruence. However, the sensitivity of the CI algorithm to surface representation was unknown. The purpose of this study was to assess the effects of applying five modifications (M1–M5) to the CI algorithm to determine whether the magnitude and variability of the patellofemoral CI is dependent on the surface representation used. The five modifications focused on calculating the CI based on the principal curvature (M1) at the centroid of the contact region, (M2) using an root mean square value for the contact region, (M3) using a mean value for the contact region, (M4) using all digitized points of the patellar surface, and (M5) using all digitized points in contact. The CI found using the contact area (M1, M2, M3, and M5) provides a local measure for congruence, which was shown to increase (decreasing CI) with increasing joint angle. In ten healthy subjects measured with magnetic resonance (MR) images, the patellofemoral joint became significantly more congruent as the knee angle increased from 15 deg to 45 deg using method M5. The magnitude and variability of the patellofemoral CI was dependent on the surface representation used, suggesting that standardization of the surface representation is important to provide a consistent measure. Specifically, M5 provides a local measure of joint congruence, which can account for joint position and orientation. M5 balances the ability to detect differences in congruence between knee angles without introducing high variability.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

(a) Knee loading apparatus during MR imaging and (b) schematic showing the force model, where FA is the applied force, FP is the force through patellar tendon, FR is the reaction force at knee, FM is the forces through hamstrings muscles, W is the limb weight, and FS is the support force (assumed to act at the center of gravity CG), which offsets the limb weight

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Figure 2

Description of the various modifications (M1–M5) to the patellar and femoral surface representations in the CI calculation

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Figure 3

The average CI found using the five variations to the algorithm at the three knee angles studied. The error bars show one standard deviation from the mean for each method (corresponding symbols indicate significance at Bonferroni adjusted p<0.017 between knee angles).

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