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A three-dimensional finite element model of round window membrane vibration before and after stapedotomy surgery.

Kwacz M, Marek P, Borkowski P, Mrówka M - Biomech Model Mechanobiol (2013)

Bottom Line: The overclosure effect described by the majority of researchers affects mainly low and medium frequencies, and a large number of patients report a lack of satisfactory results for frequencies above 2 kHz.A satisfactory agreement between the FE model and the experimental data was found.The new prosthesis caused an increase of 20-30 dB in the RW displacement amplitude compared with the 0.4-mm piston prosthesis.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Mechatronics, Institute of Micromechanics and Photonics, Warsaw University of Technology, ul. św. A. Boboli 8, 02-525 , Warsaw, Poland, m.kwacz@mchtr.pw.edu.pl.

ABSTRACT
Piston stapes prostheses are implanted in patients with refractory conductive or mixed hearing loss due to stapes otosclerosis to stimulate the perilymph with varying degrees of success. The overclosure effect described by the majority of researchers affects mainly low and medium frequencies, and a large number of patients report a lack of satisfactory results for frequencies above 2 kHz. The mechanics of perilymph stimulation with the piston have not been studied in a systematic manner. The objective of this study was to assess the influence of stapedotomy surgery on round window membrane vibration and to estimate the postoperative outcomes using the finite element (FE) method. The study hypothesis is that the three-dimensional FE model developed of the human inner ear, which simulates the round window (RW) membrane vibration, can be used to assess the influence of stapedotomy on auditory outcomes achieved after the surgical procedure. An additional objective of the study was to enable the simulation of RW membrane vibration after stapedotomy using a new type of stapes prosthesis currently under investigation at Warsaw University of Technology. A three-dimensional finite element (FE) model of the human inner ear was developed and validated using experimental data. The model was then used to simulate the round window membrane vibration before and after stapedotomy surgery. Functional alterations of the RW membrane vibration were derived from the model and compared with the results of experimental measurements from temporal bones of a human cadaver. Piston stapes prosthesis implantation causes an approximately fivefold (14 dB) lower amplitude of the RW membrane vibrations compared with normal anatomical conditions. A satisfactory agreement between the FE model and the experimental data was found. The new prosthesis caused an increase of 20-30 dB in the RW displacement amplitude compared with the 0.4-mm piston prosthesis. In all frequencies, the FE model predicted a RW displacement curve that was above the experimental curves for the normal ear. The stapedotomy can be well simulated by the FE model to predict the auditory outcomes achieved following this otosurgery procedure. The 3D FE model developed in this study may be used to optimize the geometry of a new type of stapes prosthesis in order to achieve a similar sound transmission through the inner ear as for a normal middle ear. This should provide better auditory outcomes for patients with stapedial otosclerosis.

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Related in: MedlinePlus

The structure of the simplified cochlear model in the post-stapedotomy state. The geometry, boundary conditions, and FE meshes of the other elements of the post-stapedotomy model were left the same as in the pre-stapedotomy model. a 3D schematic view showing the shape and the location of the piston stapes prosthesis (green) in the stapes footplate (blue), b 3D view of the stapes footplate and the piston of the prosthesis showing the dimensions, the FE mesh, and the mechanical properties of the piston and the modified FE mesh of the stapes footplate
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Fig2: The structure of the simplified cochlear model in the post-stapedotomy state. The geometry, boundary conditions, and FE meshes of the other elements of the post-stapedotomy model were left the same as in the pre-stapedotomy model. a 3D schematic view showing the shape and the location of the piston stapes prosthesis (green) in the stapes footplate (blue), b 3D view of the stapes footplate and the piston of the prosthesis showing the dimensions, the FE mesh, and the mechanical properties of the piston and the modified FE mesh of the stapes footplate

Mentions: To assess the effect of stapedotomy on sound transmission into the inner ear, the pre-stapedotomy model was modified as follows: the SF was immobilized by complete fixation of the AL nodes, a hole with a diameter of 0.4 mm was made in the center of the SF, and the piston of the stapes prosthesis with the same diameter was placed into the hole. The piston of the stapes prosthesis was assumed as a cylinder with a diameter of 0.4 mm and a length of 2.2 mm (Fig. 2). The piston was meshed by 192 eight-node 3D hexahedral solid elements (Solid45 in ANSYS). The geometry, boundary conditions, and FE meshes of the other elements of the post-stapedotomy model were left the same as in the pre-stapedotomy model.


A three-dimensional finite element model of round window membrane vibration before and after stapedotomy surgery.

Kwacz M, Marek P, Borkowski P, Mrówka M - Biomech Model Mechanobiol (2013)

The structure of the simplified cochlear model in the post-stapedotomy state. The geometry, boundary conditions, and FE meshes of the other elements of the post-stapedotomy model were left the same as in the pre-stapedotomy model. a 3D schematic view showing the shape and the location of the piston stapes prosthesis (green) in the stapes footplate (blue), b 3D view of the stapes footplate and the piston of the prosthesis showing the dimensions, the FE mesh, and the mechanical properties of the piston and the modified FE mesh of the stapes footplate
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3824605&req=5

Fig2: The structure of the simplified cochlear model in the post-stapedotomy state. The geometry, boundary conditions, and FE meshes of the other elements of the post-stapedotomy model were left the same as in the pre-stapedotomy model. a 3D schematic view showing the shape and the location of the piston stapes prosthesis (green) in the stapes footplate (blue), b 3D view of the stapes footplate and the piston of the prosthesis showing the dimensions, the FE mesh, and the mechanical properties of the piston and the modified FE mesh of the stapes footplate
Mentions: To assess the effect of stapedotomy on sound transmission into the inner ear, the pre-stapedotomy model was modified as follows: the SF was immobilized by complete fixation of the AL nodes, a hole with a diameter of 0.4 mm was made in the center of the SF, and the piston of the stapes prosthesis with the same diameter was placed into the hole. The piston of the stapes prosthesis was assumed as a cylinder with a diameter of 0.4 mm and a length of 2.2 mm (Fig. 2). The piston was meshed by 192 eight-node 3D hexahedral solid elements (Solid45 in ANSYS). The geometry, boundary conditions, and FE meshes of the other elements of the post-stapedotomy model were left the same as in the pre-stapedotomy model.

Bottom Line: The overclosure effect described by the majority of researchers affects mainly low and medium frequencies, and a large number of patients report a lack of satisfactory results for frequencies above 2 kHz.A satisfactory agreement between the FE model and the experimental data was found.The new prosthesis caused an increase of 20-30 dB in the RW displacement amplitude compared with the 0.4-mm piston prosthesis.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Mechatronics, Institute of Micromechanics and Photonics, Warsaw University of Technology, ul. św. A. Boboli 8, 02-525 , Warsaw, Poland, m.kwacz@mchtr.pw.edu.pl.

ABSTRACT
Piston stapes prostheses are implanted in patients with refractory conductive or mixed hearing loss due to stapes otosclerosis to stimulate the perilymph with varying degrees of success. The overclosure effect described by the majority of researchers affects mainly low and medium frequencies, and a large number of patients report a lack of satisfactory results for frequencies above 2 kHz. The mechanics of perilymph stimulation with the piston have not been studied in a systematic manner. The objective of this study was to assess the influence of stapedotomy surgery on round window membrane vibration and to estimate the postoperative outcomes using the finite element (FE) method. The study hypothesis is that the three-dimensional FE model developed of the human inner ear, which simulates the round window (RW) membrane vibration, can be used to assess the influence of stapedotomy on auditory outcomes achieved after the surgical procedure. An additional objective of the study was to enable the simulation of RW membrane vibration after stapedotomy using a new type of stapes prosthesis currently under investigation at Warsaw University of Technology. A three-dimensional finite element (FE) model of the human inner ear was developed and validated using experimental data. The model was then used to simulate the round window membrane vibration before and after stapedotomy surgery. Functional alterations of the RW membrane vibration were derived from the model and compared with the results of experimental measurements from temporal bones of a human cadaver. Piston stapes prosthesis implantation causes an approximately fivefold (14 dB) lower amplitude of the RW membrane vibrations compared with normal anatomical conditions. A satisfactory agreement between the FE model and the experimental data was found. The new prosthesis caused an increase of 20-30 dB in the RW displacement amplitude compared with the 0.4-mm piston prosthesis. In all frequencies, the FE model predicted a RW displacement curve that was above the experimental curves for the normal ear. The stapedotomy can be well simulated by the FE model to predict the auditory outcomes achieved following this otosurgery procedure. The 3D FE model developed in this study may be used to optimize the geometry of a new type of stapes prosthesis in order to achieve a similar sound transmission through the inner ear as for a normal middle ear. This should provide better auditory outcomes for patients with stapedial otosclerosis.

Show MeSH
Related in: MedlinePlus