The Journal of Bone and Joint Surgery (American) 85:421-427 (2003)
© 2003 The Journal of Bone and Joint Surgery, Inc.
Effects of Preheating of Hip Prostheses on the Stem-Cement Interface
Kazuho Iesaka, MD,
William L. Jaffe, MD and
Frederick J. Kummer, PhD
Investigation performed at the Department of Orthopaedic Surgery, Musculoskeletal Research Center, New York University-Hospital for Joint Diseases, New York, NY
Kazuho Iesaka, MDWilliam L. Jaffe, MD
Frederick J. Kummer, PhD
Musculoskeletal Research Center, Hospital for Joint Diseases, 301 East 17th Street, Room 1500, New York, NY 10003. E-mail address for K. Iesaka: kazuho{at}biomech.org
In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from Stryker-Howmedica-Osteonics. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
A commentary is available with the electronic versions of this article, on our web site (www.jbjs.org) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM).
Background: Debonding of the cement from metal implants has been implicated in the loosening of cemented total hip prostheses. Strengthening of the stem-cement interface has been suggested as a way to prevent loosening of the component. Previously, it was reported that preheating the stem to 44°C reduced the porosity of the cement at the stem-cement interface. The purpose of this study was to determine the effect of stem preheating on the characteristics of the stem-cement interface.
Methods: The effects of stem preheating, at temperatures of 37°C, 44°C, and 50°C, on the stem-cement interface were studied in a test model and a preparation that closely simulated the clinical situation. Static interface strength was determined initially and after the stems had been kept in isotonic saline solution at 37°C for two weeks. Fatigue lifetimes were measured, and the nature and extent of porosity at the interface were quantified.
Results: Stem preheating had significant effects on the stem-cement interface. Stems preheated to 37°C had greater interface shear strength than stems at room temperature both initially (53% greater strength) and after simulated aging (155% greater strength). Fatigue lifetimes were also improved, and there was a >99% decrease in interface porosity. The setting time of the cement decreased 12%, and the maximum temperature at the cement-bone interface increased 6°C. Similar effects were found after preheating to 44°C and 50°C.
Conclusions: Stem preheating had significant effects on the stem-cement interface, with significant improvements in the shear strength and cement porosity of the interface. Also, polymerization temperatures at the cement-bone interface increased. The possible biological effects of these increased interface temperatures at the cement-bone interface require further study.

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