© 2008 the American Academy of Orthopaedic Surgeons How do alternative bearing surfaces influence wear behavior?Dr. Clarke is Professor in Research, Peterson Research Center, Loma Linda University, Loma Linda, CA. Dr. Manley is Academic Director, Homer Stryker Center, Mahwah, NJ. *The Implant Wear Symposium 2007 Engineering Work Group included Donald L. Bartel, PhD, Thomas D. Brown, PhD, Ian C. Clarke, PhD, Roy D. Crowninshield, PhD, Darryl DLima, MD, PhD, A. Seth Greenwald, DPhil(Oxon), Steven M. Kurtz, PhD, Jack Lemons, PhD, Michael T. Manley, PhD, Harry A. McKellop, PhD, Orhun K. Muratoglu, PhD, Ebru Oral, PhD, Lisa Pruitt, PhD, Clare Rimnac, PhD, Peter S. Walker, PhD, and Timothy Wright, PhD. Dr. Clarke or a member of his immediate family has received research or institutional support from Amedica, Biomet, CeramTec, Encore, Global, Smith & Nephew, Stryker, and Zimmer, and has received miscellaneous nonincome support from Biomet, Encore, and Stryker. Dr. Manley or a member of his immediate family has received research or institutional support from Stryker Orthopaedics, holds stock or stock options in Stryker, and is an employee of Stryker Orthopaedics. Metal, ceramic, and polyethylene liners represent contemporary bearing choices for total joint replacement. Each has limitations in terms of design, sensitivity to manufacturing, and surgical placement. With polyethylene, larger femoral heads represent a design restriction and a potential wear issue. One side benefit is that polyethylene does not click, squeak, or create stripe wear. The attraction of hard-on-hard bearings (metal-on-metal, ceramic-on-ceramic) is that their typically ultra-low wear alleviates concerns with large femoral head designs. However, hard-on-hard bearings produce stripe wear due to the effects of the rigid liner edge. Slight subluxation (microseparation) during swing phase of gait can result in stripe wear on the ball and liner rim. In addition, high levels of implant wear with vertically placed cups can be anticipated. Currently, only alumina-on-alumina bearings can claim virtually no biologic risk. Thus, the role of laboratory studies is to isolate relevant aspects of performance by cup design and to predict the risk-benefit ratios in patients requiring total hip replacement.
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