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International Journal of Rheumatology
Volume 2012, Article ID 607872, 7 pages
http://dx.doi.org/10.1155/2012/607872
Research Article

The Influence of Partial Knee Replacement Designs on Tensile Strain at Implant-Bone Interface

1Biomechanics Laboratory, School of Physical Education, Sport, and Exercise Science, Ball State University, Muncie, IN 47306, USA
2Henry County Center for Orthopedics Surgery & Sports Medicine, New Castle, IN 47362, USA

Received 17 January 2012; Revised 8 March 2012; Accepted 15 March 2012

Academic Editor: Snežana Todorovic-Tomasevic

Copyright © 2012 He Wang and Lindsey Rolston. 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

Partial knee replacement (PKR) results in fast recovery and good knee mechanics and is ideal to treat medial knee osteoarthritis. Cementless PKR depends on bone growing into the implant surface for long-term fixation. Implant loosening may occur due to high tensile strain resulted from large mechanical loads during rehab exercises. The purpose of this study is to investigate whether external fixations such as superior screw and frontal flange could reduce the tensile strain at the implant-bone interface. Three medial PKRs were designed. The first PKR had no external fixations. A superior screw and a frontal flange were then added to the first PKR to form the second and third PKR designs, respectively. Finite element analysis was performed to examine the tensile strain at the implant-bone interface during weight-bearing exercises. The PKR with no external fixations exhibited high tensile strain at the anterior implant-bone interface. Both the screwed and flanged PKRs effectively reduced the tensile strain at the anterior implant-bone interface. Furthermore, the flanged PKR resulted in a more uniform reduction of the tensile strain than the screwed PKR. In conclusion, external fixations are necessary to alleviate tensile strain at the implant-bone interface during knee rehab exercises.