This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Letters to the Editor: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when Letters to the Editor are posted
Right arrow Alert me if a correction is posted
Services
Right arrow E-mail this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My File Cabinet
Right arrow Download to citation manager
Right arrow Rights and Permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Harrington, M. A.
Right arrow Articles by Harris, W. H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Harrington, M. A., Jr.
Right arrow Articles by Harris, W. H.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us   Add to Facebook   Add to Technorati   Add to Twitter  
What's this?
The Journal of Bone and Joint Surgery (American) 84:573-579 (2002)
© 2002 The Journal of Bone and Joint Surgery, Inc.

Scientific Article

Effects of Femoral Neck Length, Stem Size, and Body Weight on Strains in the Proximal Cement Mantle

Melvyn A. Harrington, Jr., MD, Daniel O. O'Connor, AS, Andrew J. Lozynsky, BS, Ian Kovach, MD and William H. Harris, MD

Investigation performed at the Orthopaedic Biomechanics and Biomaterials Laboratory and the Adult Reconstructive Unit of the Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, Massachusetts

Melvyn A. Harrington Jr., MD
Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, Maywood, IL 60153

Daniel O. O'Connor, AS
Andrew J. Lozynsky, BS
William H. Harris, MD
Orthopaedic Biomechanics and Biomaterials Laboratory, GrJ 1126, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114. E-mail address for W.H. Harris: wharris.obbl{at}partners.org

Ian Kovach, MD
Hertzler Clinic, 327 Chestnut Street, Halstead, KS 67056

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from Zimmer, Incorporated. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. A commercial entity (Massachusetts General Hospital) paid or directed, or agreed to pay or direct, benefits to a research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Background: Several studies have shown that certain cemented total hip replacement femoral stems have been associated with the complications of early debonding, loosening, and osteolysis. Some authors have suggested that these failures may be related to the surface finish of the stems. We developed an in vitro biomechanical experiment characterized by simulated stair-climbing to investigate the multiple factors involved in loosening of cemented femoral stems. In this study, we measured the effects of stem neck length, body weight, stem size, and calcar-collar contact on the torsional stability, as reflected by the strains in the proximal cement mantle, of one design of cemented femoral stem.

Methods: Eight Centralign femoral stems (Zimmer, Warsaw, Indiana) were cemented into eight cadaver femora with use of contemporary cementing techniques. Prior to insertion, fifteen strain-gauge rosettes were mounted around the proximal portion of the stem. The stems were loaded on a jig that simulated static peak loading during stair-climbing. Loading was repeated for each stem with three different joint reaction forces and for three different neck lengths. Calcar loading by the collar was then eliminated by removing a 0.5-mm slice of bone beneath the collar, and all loadings were then repeated.

Results: The peak principal tensile strains in the proximal cement increased linearly with both body weight (r 2 > 0.95) and neck length (r 2 > 0.75). Increasing body weight affected the peak cement strains far more than did increasing neck length. During simulated stair-climbing, calcar-collar contact reduced peak strains in the proximal cement by a factor of 1.5 to two. Peak principal tensile strains in the proximal cement often exceeded 1000 me when the smaller stems were used.

Conclusions: In this stair-climbing test model, the peak proximal cement strains were increased more by changes in body weight than they were by changes in neck length. Even during stair-climbing, calcar-collar contact reduced peak cement strains.

Clinical Relevance: Many cemented femoral stems that become loose do so by rotating into retroversion. In this study of one design of a cemented femoral component during simulated stair-climbing, the peak strain magnitudes in the proximal cement mantle were increased more by changes in body weight than by changes in the length of the neck of the stem. The strong effect of stem size on the cement strains suggests that cemented femoral stems should not be used in heavy patients with small medullary canals that require a small cemented stem.


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Facebook Facebook   Add to Technorati Technorati   Add to Twitter Twitter    What's this?