1.1 The objective of this guide is to advise researchers on the possible high-demand wear test features that should be included in evaluation of hard-on-hard articulations. This guide makes suggestions of what high-demand test features may need to be added to an overall high-demand wear test regime. Device-articulating components manufactured from other metallic alloys, ceramics, or with coated or elementally modified surfaces could possibly be evaluated with this guide. However, such materials may include risks and failure mechanisms that are not adressed in this guide. 1.2 Hard-on-hard hip-bearing systems include metal-on-metal, ceramic-on-ceramic, ceramic-on-metal, or any other bearing systems in which both the head and cup components have high-surface hardness. An argument has been made that the hard-on-hard total hip replacement (THR) articulation may be better for younger more active patients. These younger patients may be more physically fit and expect to be able to perform more energetic activities. Consequently, new designs of hard-on-hard THR articulations may have some implantations subjected to more demanding and longer wear performance requirements. 1.3 THR with metal-on-metal articulations have been used clinically for more than 50 years. Early designs had mixed clinical results. Eventually, they were eclipsed by THR systems using metal-on-polyethylene articulations. In the 1990s, the metal-on-metal articulation again became popular with more modern designs, including surface replacement. 1.4 In the 1970s, the first ceramic-on-ceramic THR articulations were used. In general, the early results were not satisfactory. Improvement in alumina and new designs in the 1990s improved the results for ceramic-on-ceramic articulations. 1.5 The values stated in SI units are to be regarded as the standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Currently, there is no test method to test metal-on-metal hip articulations in regimes beyond a simple walking cycle. Work needs to start on developing a standard. This guide will promote standardization while it helps to guide the development of appropriate methods. Eventually, it should be adopted by the US FDA.
Keywordshigh-demand wear; metal-on-metal; ceramic-on-ceramic; hard-on-hard; hip simulator testing; third-body wear; insert/shell angle
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top
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