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Materials Science and Engineering Distinguished Alumni Seminar

Engineering the Natural History of Total Joint Replacements

Clare M. Rimnac, Ph.D.
Wilbert J. Austin Professor of Engineering
Departments of Mechanical and Aerospace Engineering and Orthopaedics
Case Western Reserve University, Cleveland, OH

Friday, September 26, 2008 --- 2:00 p.m. – WH 303
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Abstract

Total joint replacements for the hip and knee are typically composed of a metallic component articulating against a plastic (ultra high molecular weight polyethylene) component.  A significant long-term complication in total joint replacement is loosening, which has been linked to the biological response invoked by debris generated from wear of the polyethylene component. New, highly crosslinked formulations of polyethylene that are very resistant to the generation of wear debris have been introduced into clinical use. Clinical findings support that wear is greatly reduced in total hip replacements using highly crosslinked polyethylenes.  However, structural fracture of these devices is a concern, due to a reduction in ductility and static and cyclic fracture resistance of these materials. Thus, there is a need to be able to prospectively predict the propensity for fracture for current and new component total hip and total knee replacement designs that make use of both traditional and highly crosslinked polyethylene formulations.

We have taken a comprehensive approach to determining and influencing the “natural history” of polyethylene components in total joint replacements, through: 1) evaluation of in vivo performance of retrieved polyethylene components to identify factors affecting wear damage and fracture; 2) identification of failure mechanisms leading to wear damage; 3) determination of static and cyclic mechanical properties of polyethylene; and, 4) prediction of the effects of changes in design variables on structural performance. Progress and findings in these on-going areas of investigation will be presented.       

Biography

Clare Rimnac received a B.S. in Metallurgy and Materials Science from Carnegie-Mellon University in 1978, and an M.S. in 1980 and a Ph.D. in 1983 in Metallurgy and Materials Engineering from Lehigh University.  In 1983, she was a Research Fellow and from 1984 until 1996 she was a Scientist in the Department of Biomechanics at The Hospital for Special Surgery in New York City.  In 1996, Professor Rimnac joined the faculty of the School of Engineering at Case Western Reserve University where she is currently the Wilbert J. Austin Professor of Engineering and Chair of the Department of Mechanical and Aerospace Engineering.  She holds secondary appointments in Biomedical Engineering and Orthopaedics.  Professor Rimnac’s research is primarily funded by the NIH and is directed towards orthopaedic biomechanics, with a focus on implant retrieval analysis, mechanical behavior and modeling of materials used in total joint replacements, and damage and fracture behavior of bone tissue. She has published more than 90 peer-reviewed articles and book chapters. She is a Deputy Editor for Research for the Journal of Bone and Joint Surgery and is in the Presidential Line of the Orthopaedic Research Society.  Professor Rimnac is the recipient of an AAOS Kappa Delta Award, two Hip Society Awards, and a Knee Society Award.