Bernard MASSON, Scientific Consultant MSc.Ph.
Demand for ceramic bearings is increasing rapidly because of excellent clinical results. Alumina offers advantages such as chemical resistance, excellent bioinertness and tribology. However, alumina has limited strength, therefore the applications are restricted to certain designs. Zirconia materials have been used clinically but reveal problems due to poor hydrothermal stability. Thus, there is a strong need for new bearing material that combines strength and stability.
The 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 ceramic composite will enable new application possibilities to be offered in orthopaedics.
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. Its first clinical use in the United States was in June of 2001. Since its introduction, the Alumina Matrix Composite more than 200,000 ball heads has been implanted around the world.