Modelagem do ouvido na otosclerose

Abstract

Introduction: Otosclerosis is a hereditary disease that affects from about 0.5 to 1% of the population. It is bilateral in most of cases. A major symptom is hearing loss. Biomechanical studies that simulate otosclerosis are poorly described in the literature. Objective: Simulate otosclerosis using a one-dimensional mass-spring model and create one tridimensional geometric model of the ear. Methods: The one-dimensional mass-spring model consists of six masses (air volume of the external ear canal, eardrum, malleus, incus, stapes and cochlear fluid), plus springs and dashpots simulating the ligaments and muscles supporting. In this study, we simulated otosclerosis by an increase of 10 to 100 times of the stapedial annulus ligament stiffness and an increase by 5 times of the stapes mass. The three-dimensional model was contructed using a sample of three ear bones, malleus, incus and stapes, originated from the Institute of Biological Sciences, UFMG. The ear bones were taken to the laboratory and Ceramic Materials UFMG for conducting a test image using the X-ray SkyScan 1172. The images obtained from the three bones were imported into an image processing program, Simpleware ®, which digitally reconstructed three ear bones resulting in a three-dimensional geometric model for each of them. The geometric models of the bones were imported into Rapidform software XOR / Redesign which is capable of producing solid models with a smaller amount of data. The tympanic membrane and the ligaments were inserted along with geometric models of the bones, using SolidWorks 19.4, computer aided design software, according to the anatomical parameters found in the literature. Results: In the one-dimensional model stapes displacement were reduced at lower frequencies with increasing stiffness of the stapedial annulus ligament and reducing the displacement of the stapes in high frequencies with increased its mass. The increase of stapedial annulus ligament stiffness may be related to the initial stage of the disease, from the viewpoint audiometric, while increased bone tissue volume suggests a progression of the disease. In the three-dimensional model was possible to obtain a geometry compatible with the anatomy of the middle ear. Conclusion: The results of the one-dimensional model met the audiological findings that suggest the disease and the need for early diagnosis of the annular ligament of the stapes in order to detect as soon as the hearing loss caused by your changes. The tridimensional geometric model of the ear can be used to simulate dynamic behavior using finite-element method to understand the normal hearing, pathology and tratament.