Research Papers

The Effects of Femoral Fixed Body Coordinate System Definition on Knee Kinematic Description

[+] Author and Article Information
Nathaniel M. Lenz, Amitkumar Mane, Nicholas A. Morton

Department of Mechanical Engineering, University of Kansas, 1530 W 15th Street, Learned Hall, Room 3138, Lawrence, KS 66045

Lorin P. Maletsky

Department of Mechanical Engineering, University of Kansas, 1530 W 15th Street, Learned Hall, Room 3138, Lawrence, KS 66045maletsky@ku.edu

J Biomech Eng 130(2), 021014 (Apr 03, 2008) (7 pages) doi:10.1115/1.2898713 History: Received February 06, 2006; Revised October 25, 2007; Published April 03, 2008

Understanding the differences in knee kinematic descriptions is important for comparing data from different laboratories and observing small but important changes within a set of knees. The purpose of this study was to identify how differences in fixed body femoral coordinate systems affect the described tibiofemoral and patellofemoral kinematics for cadaveric knee studies with no hip present. Different methods for describing kinematics were evaluated on a set of seven cadaveric knees during walking in a dynamic knee simulator. Three anatomical landmark coordinate systems, a partial helical axis, and an experimental setup-based system were examined. The results showed that flexion-extension was insensitive to differences in the kinematic systems tested, internal-external rotation was similar for most femoral coordinate systems although there were changes in absolute position, varus-valgus was the most sensitive to variations in flexion axis direction, and anterior-posterior motion was most sensitive to femoral origin location. Femoral coordinate systems that define the sagittal plane using anatomical landmarks and locate the flexion axis perpendicular to the femur’s mechanical axis in the frontal plane were typically similar and described kinematics most consistently.

Copyright © 2008 by American Society of Mechanical Engineers
Topics: Kinematics , Motion , Knee , Rotation
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Figure 1

Location of anatomical landmarks listed in Table 2, which were used to construct body-fixed coordinate systems

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Figure 2

Average of seven knees in five different FCSs described using a three-cylindric open chain. Average standard deviations of the seven knees over the gait cycle in each FCS are listed in the legend.

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Figure 3

Knee 2 compared to the average kinematics of all the knees where the description in each of the five FCSs is relative to the average in that FCS. Kinematics were aligned by offsetting the average position to zero. The differences between FCSs are representative of the set of knees.

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Figure 4

Absolute knee position. Comparing the standard deviation over seven knees of the within knee average of five FCSs (Variation b/n knees) to the mean over seven knees of the within knee standard deviation of five FCSs (Variation b/n FCSs).

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Figure 5

Average kinematics of seven knees using GS, PC, and HE FCS. TF Var/Val and Ant/Post motions are shown with TF Int/Ext showing the same trend as Var/Val. PC FCS is presented with both the PC origin and the GS origin while GS and HE use the GS origin. The origin used is indicated by the subscript. Average standard deviations of the FCS over the gait cycle are listed in the legend.




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