The influence of ventilation tube design on the magnitude of stress imposed at the implant/tympanic membrane interface

Abstract

The design of ventilation tubes or grommets is thought to have a considerable influence on their performance. A computational model (finite element method) was used to investigate the significance of four design parameters of a commonly-used design of ventilation tube. The design parameters were: the length of the shaft, the diameter of the flanges, the thickness of the flanges, and the material type. A statistical analysis technique, known as a factorial analysis of variance, was used to examine the importance of the four design parameters on the dynamical behaviour of the middle-ear with the implant in situ and on the magnitude of stress induced at the implant/tympanic membrane interface. We predicted that the ventilation tube alters the frequency response of the middle ear; specifically the shaft length and the thickness of the flanges were found to have a significant effect upon the vibratory pattern at the umbo. A reduced length of tube and an increased size of flange were also found to be significant for minimising membrane stress (both with P < 0.001). Thus design parameters of critical influence on optimising performance were identified.