gms | German Medical Science

79. Jahresversammlung der Deutschen Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie e. V.

Deutsche Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie e. V.

30.04. - 04.05.2008, Bonn

Effects of the Nonlinear Properties of the Ossicular Chain Coupled with an Active Implant

Meeting Abstract

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  • corresponding author Albrecht Eiber - Institute of Engineering and Computational Mechanics, University of Stuttgart, Stuttgart, Germany
  • author Hans-Peter Zenner - Department of Otolaryngology, Head and Neck Surgery, University of Tübingen, Tübingen, Germany
  • author Michael Lauxmann - Institute of Engineering and Computational Mechanics, University of Stuttgart, Stuttgart, Germany

German Society of Oto-Rhino-Laryngology, Head and Neck Surgery. 79th Annual Meeting of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery. Bonn, 30.04.-04.05.2008. Düsseldorf, Köln: German Medical Science; 2008. Doc08hno47

Die elektronische Version dieses Artikels ist vollständig und ist verfügbar unter: http://www.egms.de/de/meetings/hno2008/08hno47.shtml

Veröffentlicht: 8. Juli 2008

© 2008 Eiber et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielf&aauml;ltigt, verbreitet und &oauml;ffentlich zug&aauml;nglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Sound transfer depends strongly on the coupling of the prosthesis to the ossicles. An actuator pressed against the incus, leads to unilateral coupling. To assure permanent contact, a sufficient preload is necessary which is chosen by the surgeon via the angle φ of an adjusting screw. Due to nonlinear properties of the ossicular chain and the coupling region, the actual motion of the actuator as well as the corresponding motion of the ossicles depends strongly on the preload imposed between the active implant and the ossicle but likewise on the individual stiffness of the ossicular chain.

On the basis of measurements on human cadaveric temporal bones and computer-aided simulations with nonlinear mechanical models, the effects of preload on sound transfer, distortion, feedback and ligament forces were studied. Optimal coupling is only achieved within an individually different range of preload depending mainly on the individual stiffness properties of the ossicular chain. Applying too less preload will result in distorted sound transfer due to unilateral contact with loose coupling and to high sensitivity against static pressure variations. In contrast, too high preload shifts the working position of the ossicular chain into the nonlinear region so that stapes displacement decreases even in the case of high actuator forces which involves risk of feedback due to sound radiation from the ear drum. Further distortion and high static forces in specific ligaments occur. By reason of ligament relaxation the latter may lead in the long term to an undetermined change of sound transfer and to an increasing loose coupling which entails distortion.

Nonlinear models enable the description of the discussed effects and allow deriving important advices for the clinical practice.

Figure 1 [Fig. 1]