臼蓋カップのゆるみ挙動に及ぼす界面損傷のAE法およびIR法の組合せ評価

抄録

In this study, we aim at revealing the damage behavior of HAp sprayed coating on the surface of acetabular cup subjected to cyclic loading using AE (Acoustic Emission) method and IR (Infrared thermography) methods. Loosening of acetabular cups, a major cause of revision surgery of total hip joint, can be attributed to the delamination or wear of plasma sprayed HAp coating on the surface of Ti alloy substrate. However, complex relationships between damages in several places with the extent of displacement of the acetabular cup were not experimentally unveiled. Fatigue test was conducted in SBF(simulated body fluid), and the displacement of acetabular cup embedded in simulated bone was measured by two cantilever pairs. Acoustic emissions from delamination or wear of HAp coating were also measured by AE method, and the temperature change due to friction and wear near the top was measured by IR method. The noise of AE waveform can be removed by DWT (Discrete Wavelet transform), and the measured AE signals were then analyzed its frequency after FFT (Fast Fourier Transform). The analyzed result could estimate the process in which delamination occurs in the initial stage of test and then friction and wear occur. The rotation displacement of acetabular cup could be associated with cracking or delamination of the HAp sprayed coating, friction and wear at the interfaces between simulated bone and acetabular cup. The subsidence displacement of acetabular cup can be caused by collapse of the simulated bone accompanied by an increase in AE energy as well as an increase in dissipated energy. Combined analyses using AE method and IR method clarified that the inelastic damages in simulated bone at the top of acetabular cups could lead the acceleration of both normal and rotational displacement of the acetabular cup whereas interface damages also attributed to exaggerate the displacement by deteriorated fixation.