SURVIVAL RATE AND RELIABILITY OF CERAMIC FEMORAL HEADS FOR TOTAL HIP-ARTHROPLASTY

Femoral heads and sockets made of alumina ceramics are successfully us ed in total hip replacement. The in vivo fracture rate of Biolox: head s is lower than 0.02 %. An extremely high load (e. g. accident) can in itiate subcritical crack growth causing fracturing. 107 retrieved Biol ox heads were investigated. When measuring their fracture load no fati gue was detected. This result can be explained by the relation between crack velocity and stress intensity (v-K-diagram). The stress intensi ty of ceramic heads when loaded with standard conditions (e. g. walkin g, max. load 3 kN) is in the order of 0.6 MPa m(1/2). Stress intensiti es like that are below alumina's fatigue limit K-lo which is in the or der on I MPa m(1/2). Biolox alumina heads are examples for engineering ceramics that are reliable despite tensile stress over very long pero ds of time.