Читать книгу Advances in Hearing Rehabilitation - Группа авторов - Страница 32

Predictable hearing results after ossicular reconstruction are very difficult to achieve, with wide variations in reported results [1]. In its usual form, the ossicular prosthesis acts simply as a connector between the tympanic membrane (TM) and ultimately the cochlear fluids. Many factors outside of the prosthesis design affect its performance. Poor ventilation can result in TM retraction and movement of the prosthesis, scarring can damp its vibrations, and sudden TM movements can dislodge it. Some prostheses also affect host biological responses, such as inflammation (resulting in biocompatibility concerns).

Very often, the reason for hearing loss is because some underlying pathology has upset the normal physiology of the ear, and even if the ossicular connections are re-established, the underlying physiologic mechanisms of the ear are still disrupted, for example, by TM perforations, fluid, or ossicular fixation. Ideally, the prosthesis also helps restore the middle ear function, for instance, by maintaining a middle ear space. This reversal of pathology aspect is rarely considered in prosthesis design.

The host factors dominate the hearing results; an ear with poor ventilation and excessive scarring will not predictably achieve good hearing results regardless of surgical technique. In an ear with a more favorable starting state, the surgical technique and prosthesis design become more important in achieving predictable results; here, it is likely the surgical technique predominates.

Further details regarding the mechanics of middle ear reconstruction have been published by Bance and Adamson [2]. Most of the data presented in this chapter come from fresh cadaveric temporal bone models of ossiculoplasty, where individual factors can be carefully controlled.