Abstract
The choice to use alumina in the manufacture of a low-wear THR bearing made by Boutin and its co-workers has proven its effectiveness in almost 35 years of clinical use. A continuous development process aimed to improve mechanical properties led to today’s materials that exhibit extreme high reliability. The recent introduction in clinical use of an alumina matrix composite developed by CeramTec and available under the trade name Biolox®Delta represents the latest evolution of alumina. This material allow new design in ceramic components thanks to its equilibrium among high hardness, high toughness, and high bending strength.
Composites obtained introducing zirconia in the alumina matrix, known as Zirconia Toughened Alumina (ZTA) are candidate for use in THA bearings from a long time. A real breakthrough was represented by alumina ceramics toughened both by phase transformation both by platelets nucleated in-situ during sintering. Optimised processing and quality control led to optimised material behaviour.
The chemical composition and the microstructure of Biolox®Delta were optimised to achieve a ceramic material joining strength of more than 1200 MPa, Vickers hardness 1975, fracture toughness of 6,5 MPam-1/2, and extremely low wear also in the most severe simulator tests performed in microseparation mode.
The paper reviews the improvements introduced in the technology of ceramic for arthoplasty, and their effects on the microstructural properties and on the performances of the past and actual generation of ceramic for THR bearings, and summarise the results obtained in the development of alumina matrix composite Biolox® Delta.
Correspondence should be addressed to Richard Komistek, PhD, International Society for Technology in Arthroplasty, PO Box 6564, Auburn, CA 95604, USA. E-mail: ista@pacbell.net
