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RESEARCH PAPERS

In Vitro Measurement of the Tracking Pattern of the Human Patella

[+] Author and Article Information
A. M. Ahmed, N. A. Duncan

Department of Mechanical Engineering, McGill University, Montreal, Québec, Canada

M. Tanzer

Department of Orthopaedic Surgery, McGill University, Montreal, Québec, Canada

J Biomech Eng 121(2), 222-228 (Apr 01, 1999) (7 pages) doi:10.1115/1.2835107 History: Received July 23, 1998; Revised December 01, 1998; Online January 23, 2008

Abstract

This study sought to determine whether a general pattern describing the three-dimensional tracking characteristics of the human patella could be established, and if not, then to determine the extent and nature of interspecimen variations in the characteristics in a normal population. Using 32 fresh-frozen knees subjected to extensor moment magnitudes similar to those in “static-lifting” and “leg-raising against resistance” maneuvers, patellar displacements were measured in the knee extension range 120 to 0 deg. For static-lifting, a constant foot-floor reaction of 334 N was applied. For leg-raising, a constant net quadriceps tension of 668 N was used throughout the extension range. Measurements were taken with a calibrated six-degree-of-freedom electromechanical goniometer and a displacement coordinate system referenced to the geometry of individual specinens. The three patellar displacements in the plane of knee extension/flexion (extension rotation, and anterior and proximal translations) consistently demonstrated the same pattern in the entire knee extension range with an average coefficient of variation of 13 percent. For knee angles greater than 45 deg, the three other displacements (medial lateral translation, and rotations about the anterior–posterior and proximal–distal axes) followed a general pattern. However, for knee angles less than 45 deg, these displacements differed considerably between specimens for each loading condition, both in terms of magnitude (average coefficient of variation: 70 percent), and direction.

Copyright © 1999 by The American Society of Mechanical Engineers
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