INVESTIGATION OF THE WEAR BEHAVIOUR OF A CERAMIC KNEE CONCEPT WITH FLOATING MENISCAL BEARING

Abstract

The first Ceramic knee implant in a human patient was used by Dr. G. Langer of the Orthopedic Clinic at the University of Jena, Germany in 1972 [1]. In 1980, Drs. Oonishi and Hasegave began using an Alumina femoral component on a polyethylene tibial component [2]. These early attempts all involve the search for solutions to the wear and degradation problems. The application of ceramics was limited by the demand of thin components. In the present feasibility study the in vitro wear behavior of a knee concept with a novel Alumina Matrix Composite (AMC) Ceramic was examined [3,4].

The wear behaviour of the Ceramic components for the knee system were tested in accordance to ISO/WD 14243-3 for 5*106 cycles. Six samples were tested. The lubricant was calf serum diluted with deionized water. All tests have been performed with components made of the novel AMC Ceramic. The wear test performed showed an average gravimetric wear rate below 1 mg/1*106 cycles on each of the six components. A change of geometry was not measurable after 5 million cycles. No significant change of the surface structure was detectable with a conventional surface tracer. SEM and AFM pictures show traces of ultra mild abrasive wear at the surface.

The performed investigation on the novel knee concept shows the following potential benefits for a Ceramic knee bearing:

1. approx. 500 times lower volumetric wear

2. low risk of tribologically induced failure

3. no PE particle induced osteolysis

The novel AMC Ceramic offers a solution to minimize the allergic and wear related problems of knee implants. New concepts on the basis of hard on hard combination are to be realized. The use of knee endoprosthesis with Ceramic on Ceramic combination is an option for ”zero” wear bearings in the knee. These first results motivate to start further R& D on Ceramic on Ceramic bearings for total knee implants.