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Applied Bionics and Biomechanics
Volume 7, Issue 3, Pages 177-186
http://dx.doi.org/10.1080/11762322.2010.490043

Photoelastic Measurements of Polymer Insert Stress in the Knee Prostheses Designed for High/Deep Flexion

A. Lawi,1 J. Takiguchi,1 M. Hasegawa,1 S. Hirokawa,1 M. Todo,2 and T. Hotokebuchi3

1Faculty of Engineering, Kyushu University, Fukuoka, Japan
2Research Institute of Applied Mechanics, Kyushu University, Fukuoka, Japan
3School of Medicine, Saga University, Saga, Japan

Received 31 March 2010

Copyright © 2010 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper presents the experimental results of photoelasticity for determining the magnitude and distribution of stresses on the polyethylene insert of the knee prostheses designed for high/deep knee flexion. The prostheses used in our experiment were a conventional posterior stabiliser knee, Scorpio NRG (Non-Restricted Geometry, Stryker Co., USA) and CFK (Complete Flexion Knee, Japan Medical Material Co., Japan), which we have developed to enable the patient to make a complete knee flexion (i.e. seiza in Japanese). Prior to the photoelastic experiment, we had introduced the forces exerted on the knee joint during ascending from deep knee flexion. Here we took squatting as an example of deep knee flexion instead of seiza because ascending from seiza contains complex modalities. The introduced data in terms of knee angles and joint forces were applied to the photoelastic models. The results demonstrated that after the knee angle became larger than 90°, the shear stresses on the post and cam of NRG were higher than those on the ball and socket of CFK. We conclude that the design and the configuration of CFK is acceptable at deep knee flexion from a load-bearing viewpoint.