Advanced testing of ceramic femoral knee components

Abstract

For over 35 years, ceramics in joint replacement are known for their excellent biocompatibility, extremely low wear rates and excellent wettability. Ceramic on ceramic bearings have shown excellent survival rates. Also in hard on soft bearings, i. e. ceramic ball head against (highly crosslinked) polyethylene, a reduction in wear rate compared to metal on (highly crosslinked) polyethylene was shown in-vitro as well as in-vivo. In knee arthroplasty a ceramic component has several advantages: First of all, there is no ion release implying no risk for potential allergies. Secondly, the extreme hardness of the material leads to a scratch resistance surface and less PE wear over time. In the past, ceramic femoral components in knee applications were limited in the variety of design possibilities due to necessary thickness of the component resulting from the associated fracture risk of ceramics. By the development of an alumina matrix composite material with increased mechanical properties it is possible to develop a ceramic femoral component which has nearly the same design as a metal component and uses the same surgical approach as well as instruments. This offers the surgeon the opportunity to choose intraoperatively between metal or ceramic femoral components. Extensive in-vitro testing derived from in-vivo loading situations has shown that ceramic femoral components achieve execellent superior mechanical test results. The reliability of the components is build on testing of the design by two burst tests and a fatigue test to evaluate the design of the ceramic component. A proof test which is performed on each individual component before release for sale ensures highest quality of the ceramic knee components.