Tissue Attenuation Characteristics of Acoustic Emission Signals for Wear and Degradation of Total Hip Arthroplasty Implants

Recent research has investigated the use of Acoustic Emission (AE) monitoring of patients with Total Joint Replacement (TJR) implants. This technique involves using a set of four passive ultrasonic receivers to monitor the acoustic events that are created when a TJR implant is articulated through a range of motion. Both in-vitro and in-vivo monitoring of implants is possible. The soft-tissue attenuation characteristics are a very important aspect of how these two signal types are related as the aim of AE monitoring is to provide in-vivo diagnosis of implant degradation. This manuscript presents the results of in-vivo monitoring of patients with Total Hip Replacement (THR) implants. The corresponding Bode plots are presented to approximate the soft tissue attenuation characteristics. Overall averages are taken across 45 patient data sets and each of the four sensors, located against the skin surface, from the greater trochanter to mid-femur. Each sensor set is also analysed individually to delineate different tissues attenuation at the different locations. These results of this research can be used to determine the maximum likely frequency of interest present on the skin surface during AE monitoring, even if higher frequencies may be observed in-vitro.