Evaluating the dynamic behaviour of bone anchored hearing aids using a finite element model and its applications to implant stability assessment

Abstract

The dynamic behavior of osseointegrated implants can be used for the non-invasive evaluation of the condition of the bone-implant-interface (BII). The Advanced System for Implant Stability Testing (ASIST) is a vibration measurement system that relies on an impact technique and an analytical model to compute the interface stiffness and the ASIST stability coefficient ([Formula: see text]). The objective of this work is to develop a finite element (FE) model capable of capturing the dynamic behaviour of the bone-anchored hearing aid under the ASIST loading condition. The model was validated with previously collected in vitro and in vivo data which were compared to the model's acceleration responses and [Formula: see text] scores. Similar acceleration responses were obtained, and the maximum absolute differences in [Formula: see text] scores between the FE model and the in vitro and in vivo data were 1.15% and 5.48% respectively. The model was then used to show the existence of a relationship between the rod's acceleration response and the BII stress field. Finally, the model was used to interpret the factors that affect the stiffness parameters of the ASIST analytical model. The interface stiffness and the system's dynamic properties were more influenced ([Formula: see text]) by the BII material and friction coefficient compared to the implant geometry. In this work, a finite element model of the bone anchored hearing aid was used to simulate the dynamic behaviour of the bone-implant system under the ASIST's loading conditions. The model was first validated with previously collected experimental and clinical results. The validated model was then used to study the relationship between the impact rod's acceleration response and the response at the bone implant interface. Finally, the model was used to formulate a better understanding on the influencing factors on the interface stiffness.

Keywords: Finite element modelling; Implant dynamic response; Implant stability; Osseointegration.