0
TECHNICAL PAPERS: Bone/Orthopedics

Cortical Bone Viscoelasticity and Fixation Strength of Press-Fit Femoral Stems: An In-Vitro Model

[+] Author and Article Information
T. L. Norman1

Department of Engineering, Cedarville University, 251 N. Main Street, Cedarville, OH 45314tnorman@cedarville.edu

E. S. Ackerman

Programme d’Orthopedie Edouard-Samson, Hospital du Sacre-Coeur, 5400 boul. Gouin Quest, Bureau G-2000, Montreal (Quebec) H4J1C5, Canada

T. S. Smith

 DePuy, A Johnson and Johnson Co., 700 Orthopaedic Drive, Warsaw, IN 46581-0988

T. A. Gruen

 Zonal Concepts, 31153 Shaker Circle, Wesley Chapel, FL 33543

A. J. Yates

 UPMC Orthopedic Surgery, Shadyside Medical Bldg., Suite 415, 5200 Centre Avenue, Pittsburgh, PA

J. D. Blaha

Department of Orthopedics, University of Michigan, Ann Arbor, MI 48109

V. L. Kish

Department of Orthopedics, Musculoskeletal Research Center, West Virginia University, Morgantown, WV 26506-9196

1

To whom correspondence should be addressed.

J Biomech Eng 128(1), 13-17 (May 06, 2005) (5 pages) doi:10.1115/1.2133766 History: Received July 20, 2004; Revised May 06, 2005

Cementless total hip femoral components rely on press-fit for initial stability and bone healing and remodeling for secondary fixation. However, the determinants of satisfactory press-fit are not well understood. In previous studies, human cortical bone loaded circumferentially to simulate press-fit exhibited viscoelastic, or time dependent, behavior. The effect of bone viscoelastic behavior on the initial stability of press-fit stems is not known. Therefore, in the current study, push-out loads of cylindrical stems press-fit into reamed cadaver diaphyseal femoral specimens were measured immediately after assembly and 24h with stem-bone diametral interference and stem surface treatment as independent variables. It was hypothesized that stem-bone interference would result in a viscoelastic response of bone that would decrease push-out load thereby impairing initial press-fit stability. Results showed that push-out load significantly decreased over a 24h period due to bone viscoelasticity. It was also found that high and low push-out loads occurred at relatively small amounts of stem-bone interference, but a relationship between stem-bone interference and push-out load could not be determined due to variability among specimens. On the basis of this model, it was concluded that press-fit fixation can occur at relatively low levels of diametral interference and that stem-bone interference elicits viscoelastic response that reduces stem stability over time. From a clinical perspective, these results suggest that there could be large variations in initial press-fit fixation among patients.

FIGURES IN THIS ARTICLE
<>
Copyright © 2006 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Push-out test configuration

Grahic Jump Location
Figure 2

Push-out load vs interference at t=0h

Grahic Jump Location
Figure 3

Push-out load vs interference at t=24h

Grahic Jump Location
Figure 4

Load ratio plotted against stem-bone interference. A significant quadratic relationship exists.

Grahic Jump Location
Figure 5

Push-out loads for each coating at 0 and 24h. The asterisk indicates significant differences at P<0.05.

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In