Damage evaluations in Supporting Porous Components using Infrared Thermography and Acoustic Emission and their Effects on Loosening Behaviour of Acetabular Cup

Abstract

This study aims at experimentally revealing the effect of accumulated damages in supporting porous components on loosening behaviour using Infrared thermography(IR) and Acoustic emission(AE). Aseptic loosening is occurred due to degradation of fixing force of acetabular cups by biological effects or mechanical loading. However, effects of mechanical loading on loosening behaviors have not been observed yet. An integrated assembly of hip joint components, which is composed of stems and acetabular cups was set in distilled water in order to apply cyclic load in vitro. We developed the simulation system of loosening behaviour of acetabular cups by cyclic loading using cantilever. Damage evaluations on interface between the acetabular cup, HAp coating and supporting porous components (we call it " simulated bone ", which has similar Young ’ s modulus and density for those of cancellous bone) using AE. Additionally inelastic damage behaviour in simulated bone was simultaneously observed using IR. IR could successfully observed dissipation energy by inelastic damage accumulated during cyclic loading, which indicate its fatigue strength within shorter cyclic loading. Cyclic loading test for 1 million revealed that both lateral and angular displacement of the acetabular cup can be associated with the progress of damages in delamination of Hap coating or inelastic compression of simulated bone Loosening mechanism of the acetabular cup by cyclic loading can be considered by the contribution of both damages at the interface and in the simulated bone.