Nueva prótesis de maleovestibulopexia. Diseño y análisis experimental en un modelo computarizado 3D basado en elementos finitos / Design and experimental analysis of a new malleovestibulopexy prosthesis using a finite element model of the human middle ear

Introducción: Existen numerosas prótesis diseñadas con el fin de sustituir elementos osiculares en el oído medio. En este trabajo presentamos el diseño de una nueva prótesis de sustitución osicular total anclada en el mango del martillo y analizamos su comportamiento mecanoacústico teórico. Métodos: Para el diseño de la prótesis hemos utilizado el método de los elementos finitos (FEM) basándonos en un modelo computarizado 3D dinámico del oído medio humano, analizando su comportamiento mecánico. Resultados: La prótesis resultante presenta un comportamiento mecanoacústico teórico superponible al del oído humano sano. Posee, además, otras ventajas biológicas como son estabilidad y la facilidad de implantación. Conclusiones: La simulación computarizada puede ser utilizada para diseñar y optimizar las características vibroacústicas de prótesis implantables en el oído medio. Mostramos la eficiencia mecanoacústica de un nuevo diseño de prótesis de maleovestibulopexia útil en la reconstrucción de la cadena osicular (AU)

Introduction and Objective: Many designs of prostheses are available for middle ear surgery. In this study we propose a design for a new prosthesis, which optimises mechanical performance in the human middle ear and improves some deficiencies in the prostheses currently available. Our objective was to design and assess the theoretical acoustic-mechanical behaviour of this new total ossicular replacement prosthesis. Methods: The design of this new prosthesis was based on an animal model (an iguana). For the modelling and mechanical analysis of the new prosthesis, we used a dynamic 3D computer model of the human middle ear, based on the finite elements method (FEM). Results: The new malleovestibulopexy prosthesis design demonstrates an acoustical-mechanical performance similar to that of the healthy human middle ear. This new design also has additional advantages, such as ease of implantation and stability in the middle ear. Conclusions: This study shows that computer simulation can be used to design and optimise the vibroacoustic characteristics of middle ear implants and demonstrates the effectiveness of a new malleovestibulopexy prosthesis in reconstructing the ossicular chain (AU)

A surgical technique for implantation of the vibrant soundbridge middle ear implant in dogs.

OBJECTIVE: To report a surgical implantation of the Vibrant Soundbridge (VSB) middle ear implant in dogs. STUDY DESIGN: Pilot study. ANIMALS: Dogs (n=3). METHODS: A lateral approach to the tympanic bulla was used to insert the floating mass transducer of the VSB into the tympanic bulla. Using microscopic guidance the transducer was moved to and inserted into the round window niche by manipulation through the acoustic bony meatus, after reflection of the tympanic membrane. VSB position was confirmed by computed tomography (CT) imaging. RESULTS: No intraoperative complications occurred and CT images confirmed correct placement of the VSB. CONCLUSIONS: A VSB can be safely implanted in the middle of dogs.

Treatment of age-related hearing loss in dogs with the vibrant soundbridge middle ear implant: short-term results in 3 dogs.

BACKGROUND: Age-related hearing loss (ARHL), or presbycusis, is the most common form of acquired hearing loss in dogs. Middle ear implants have been used successfully in people with ARHL who cannot benefit from conventional hearing aids. HYPOTHESIS: Audibility improves in dogs with ARHL after implantation of the Vibrant Soundbridge (VSB) middle ear implant. ANIMALS: Three Beagle dogs with ARHL, mean age 11.1 years. METHODS: The dogs were assessed pre- and postoperatively by brainstem-evoked response audiometry (BERA), otoscopy, and computed tomography scans of the ears. A VSB middle ear implant was implanted unilaterally. Three months later the functionality of the implants was assessed by auditory steady-state responses (ASSRs), after which the dogs were euthanized for histopathological examination. RESULTS: The VSB was implanted successfully in all dogs. Recovery from surgery was uneventful, except for transient facial nerve paralysis in 2 dogs. ASSRs showed that hearing improved after activation of the implants with a mean of 20.7, 13, and 16.3 dB at 1, 2, and 4 kHz, respectively. The implantation procedure did not affect residual hearing (with inactive implants) as measured by BERA. CONCLUSIONS AND CLINICAL IMPORTANCE: Implantation of the VSB resulted in lower ASSR thresholds, but only at the higher gain settings of the audioprocessor. As in humans, a more powerful audioprocessor is required to treat sensorineural hearing loss exceeding 20 dB in dogs. A substantial improvement in patient-owner communication will have to be demonstrated in future studies before the procedure can be recommended in clinical practice.

Sympathetic auricular chondritis in rats: a model of autoimmune disease?

Following the unilateral implantation of metal ear tags in female Crl:CD(SD)BR-rats, chronic inflammatory lesions were observed in both auricles in 7% and 24% of the animals after 30 and 60 weeks, respectively. Involvement of the collateral auricles was identified only after diffuse inflammation of the ear tag-marked pinnae had developed. Histological examination revealed a multifocal granulomatous chondritis, characterized by progressive destruction of the cartilaginous plate and excessive regeneration of cartilaginous tissue. IgG and complement deposits were present in the matrix of the marginal area of regenerating cartilage and at the destruction sites of autochthonous cartilage. It is likely that the pinally-restricted chondritis was due to an autoimmune response initiated by a chronic inflammatory process at the insertion site of the ear tag. Since the response was not due to immunity to type II collagen, this pathologic phenomenon in rats may provide a useful animal model to study autoimmunity involving other cartilaginous matrix molecules.