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538 Advances in Biomaterials Science and Biomedical Applications

Total hip replacement (THR) surgery has been available for several decades and is now a relatively common procedure. Since the introduction of the Charnley metal-on-ultra-high molecular weight polyethylene (UHMWPE) hip prosthesis, THR is seen as one of the most successful orthopaedic operations available today. There are currently over 80,000 hip re‐ placement procedures carried out in England and Wales [1] each year and THR has now be‐ come more popular with the younger, more active patient. This is shown in the statistics reported in the National Joint Registry; 12% of the patients who undergo THR are under the age of 55 and 85% of these are recorded as being either fit and healthy (16%) or with mild disease that is not incapacitating (69%) [1]. However, failure of these artificial joints does oc‐ cur, leading to the need for revision surgery; approximately 10% of the THR procedures re‐ ported are revision operations [1].

Failure, in many cases, is due to aseptic loosening [1, 2]. With the conventional metal-on-UHMWPE joint this has been shown to be due to wear particle induced osteolyisis [3]. Al‐ though 90% of these joints are operating well 15 years after implantation [2] this wear particle induced osteolysis may lead to repetitive revision requirements for the younger, more active patient.

An alternative to the conventional metal-on-UHMWPE type of hip joint is to use ceramicon-ceramic joints. Ceramic-on-ceramic joints were first introduced in the early 1970s but of‐ ten resulted in poor performance due to fixation problems, poor quality alumina as a result of inadequately controlled grain size and other material properties (leading to catastrophic wear), and sub optimal design parameters such as too large a clearance. The work of many people over the years, including material scientists and engineers, has improved the quality of these ceramics. Therefore, since the introduction of the standard for ceramic production

© 2013 Scholes and Joyce; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

(ISO 6474:1981 (second-generation ceramics), which was replaced with ISO 6474:1994 (thirdgeneration ceramics) and has now been replaced by ISO 6474-1:2010 (fourth-generation ce‐ ramics)) the performance of these all ceramic bearings has been greatly improved [4, 5]. The third and fourth-generation alumina ceramics are manufactured using hot isostatic pressing. This produces a material that is highly pure with a small grain size (≤ 2.5 μm and many manufacturers produce ceramics with even smaller grain sizes) that provides material strength and minimises the risk of fracture. The majority of the ceramic-on-ceramic joints discussed in this chapter were produced using third-generation ceramics.

Ceramic-on-ceramic hip prosthesis performance will be reviewed in this chapter (*in vitro* and *in vivo*) along with a discussion of the concerns with ceramic-on-ceramic joints that hap‐ pen in a minority of cases such as joint "squeaking" and component fracture. The majority of articles reviewed discuss the performance of alumina-on-alumina joints. There are, how‐ ever, other ceramic materials available on the market today for use in orthopaedic surgery, for example BIOLOX® delta (an alumina matrix composite containing 72.5% alumina, 25.5% zirconia, and 2% mixed oxides). The reader will be made aware when joints made from this material are discussed.
