A NEW CERAMIC COMPOSITE FOR USE IN TOTAL HIP ARTHROPLASTY

Abstract

Demand for ceramic bearings is increasing rapidly because of excellent clinical results. Alumina offers advantages such as chemical resistance, excellent bio-inertness and tribology. However, alumina has limited strength, therefore the applications are restricted to certain designs. Zirconia materials have been used clinically for ten years, they reveal problems due to poor hydrothermal stability. Thus, there is a strong need for new bearing material that combine strength and stability.

The new ceramic named Alumina Matrix Composite (AMC) uses the following principle of transformation toughening: Firstly, the dispersing of small particles of Y-TZP Zirconia in the alumina matrix and secondly the reinforcement by introduction of an anisotropic crystal like whiskers. This process dissipates the crack energy that is associated with an increase of strength. The examination of the tribological situation of AMC, especially under challenging conditions of hydrothermal ageing and under severe micro separation, shows the aptitude of this material in wear applications.

Alumina Matrix Composite offers a better mechanical resistance than alumina while maintaining the structural stability and equivalent tribological qualities. This is a material that has been very thoroughly evaluated and tested as a permanent implant material for the last 9 years. The results of this evaluation and testing process have been included in the manufacturer’s Master File at the Food and Drug Administration and approved.

The substantial improvement in mechanical properties and the excellent wear behaviour, even under severe microseparation conditions, make this material a promising new addition to the orthopaedic surgical community and a possible solution to the longevity problems seen with many total joint systems in young and active patients. No complications have been reported yet at six-year follow-up, with more than 310,000 components (heads and inserts) implanted. Additionally, due to the enhanced mechanical behaviour, new applications in orthopaedics are possible.