title: (v) Simulation and measurement of wear in metal-on-metal bearings in vitro- understanding the reasons for increased wear.
abstract: A new Stratified Approach For Enhanced Reliability (SAFER) pre-clinical simulation testing of joint prostheses has been described in a preceding paper in this volume. The application of SAFER in vitro simulation and testing to metal-on-metal bearings is described in this review paper. The review aims to provide further understanding of the reasons for, and causes of, increased wear in metal-on-metal hips in a proportion of patients. Variation in positioning (mal-positioning) of the head and cup in hip prostheses results in the head contacting the rim of the cup and producing increased wear. Variation in both translational and rotational positioning has been investigated. Variation in translational positioning of the centres of the head and cup, which is not detected on radiographs, is a frequent occurrence clinically and can result in a substantial increase in wear rate. The variation in translational positioning acts synergistically with variation in rotational positioning to produce substantial increases in wear. These recent findings are consistent with the wear mechanisms and formation of stripe wear reported for ceramic-on-ceramic bearings over a decade ago, and provide insight into the reasons for the variation and increases in the wear rate found clinically in metal-on-metal hips in specific patients, which may cause premature failure.
authors: Professor, Institute of Medical and Biological Engineering iMBE, University of Leeds, Leeds, UK and Leeds Musculoskeletal Biomedical Research Unit, Leeds Teaching Hospital Trust, Leeds, UK.
authors: John
authors: J
authors: Fisher
authors: Mazen
authors: M
authors: Al Hajjar
authors: Sophie
authors: S
authors: Williams
authors: Joanne
authors: J
authors: Tipper
authors: Eileen
authors: E
authors: Ingham
authors: Louise
authors: L
authors: Jennings