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Improving Bearing Surfaces of Artificial Joints
Author(s) -
Willmann G.
Publication year - 2001
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/1527-2648(200103)3:3<135::aid-adem135>3.0.co;2-b
Subject(s) - materials science , tribology , ceramic , composite material , bearing (navigation) , fracture toughness , bearing surface , cubic zirconia , corrosion , toughness , lubrication , cartography , geography
The requirements for materials to be used for bearing surfaces in joint replacement are corrosion resistance in the body environment, reliability, hardness, and stiffness. Most important is coverage of the bearing surface with a stable oxide layer, so that the articulating surfaces can be lubricated by the synovial fluid. The synovial fluid, being a protein, can degenerate during frictional heating. This can be avoided if the materials used for wear couples have very good thermal conductivity. Bioceramics for joint replacement have been used since the 1970s. Alumina ceramics reduce the wear rate and solve the problem of implant loosening (osteolysis). Although the in vivo fracture rate for alumina parts is very small, further improved reliability is demanded. Alternative materials may be non‐oxide ceramics, zirconia ceramics, or hard coatings on metals. Advanced non‐oxide ceramics, such as SiC and Si 3 N 4 , are not suitable for bearing surfaces in knee‐ and hip‐joint replacement because the surface oxide formed is SiO 2 , which chips off. Y‐TZP zirconia does not have adequate phase stability. All hard coatings tried hitherto (TiN, DLC) have not been good enough. Alumina matrix composite (AMC) is a new type of bioceramics. AMC offers excellent tribological properties, no frictional heating, improved mechanical strength and fracture toughness, thus more in vivo reliability. So far test results have been very promising.