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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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The structure of the simplified cochlear model with detailed dimensions and FE meshes of the anatomical structures in the pre-stapedotomy FE state. a 3D schematic view of the uncoiled cochlea showing the overall dimensions of the scala vestibule (SV) and the scala tympani (ST), b 3D view of the basilar membrane (BM) and the supported structures of the BM with detailed dimensions of the BM, c 3D view of the uncoiled cochlea showing the FE mesh of both the SV and the ST with the mechanical properties assumed in the FE model, d 3D view of the BM with the mechanical properties assumed in the FE model, 1—at the base, 2—in the middle, 3—at the apex, e 3D view of the stapes footplate (SF, blue), the annular ligament (AL, pink), and the round window membrane (RW, violet) showing the detailed dimensions, the FE meshes, and the mechanical properties of these three structures
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Fig1: The structure of the simplified cochlear model with detailed dimensions and FE meshes of the anatomical structures in the pre-stapedotomy FE state. a 3D schematic view of the uncoiled cochlea showing the overall dimensions of the scala vestibule (SV) and the scala tympani (ST), b 3D view of the basilar membrane (BM) and the supported structures of the BM with detailed dimensions of the BM, c 3D view of the uncoiled cochlea showing the FE mesh of both the SV and the ST with the mechanical properties assumed in the FE model, d 3D view of the BM with the mechanical properties assumed in the FE model, 1—at the base, 2—in the middle, 3—at the apex, e 3D view of the stapes footplate (SF, blue), the annular ligament (AL, pink), and the round window membrane (RW, violet) showing the detailed dimensions, the FE meshes, and the mechanical properties of these three structures

Mentions: The geometry of the inner ear structures was adopted according to dimensions published in the literature (Gan et al. 2007), similar to the real coiled geometry of the cochlea. Our FE model was constructed based on the information given by Gan’s group, but these two models differ from each other. The main differences are the geometry of the stapes footplate, the annular ligament, the RW membrane, the variable height of both SV and ST, the finite element mesh and number of finite elements for the individual structures, the material properties of the stapes footplate and the annular ligament, except density of the AL. The geometry was then meshed in ANSYS 13.0 (Ansys, Inc., Canonsburg, PA). Figure 1 shows the structure of the simplified cochlear model with detailed dimensions and FE meshes of the anatomical structures.


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 with detailed dimensions and FE meshes of the anatomical structures in the pre-stapedotomy FE state. a 3D schematic view of the uncoiled cochlea showing the overall dimensions of the scala vestibule (SV) and the scala tympani (ST), b 3D view of the basilar membrane (BM) and the supported structures of the BM with detailed dimensions of the BM, c 3D view of the uncoiled cochlea showing the FE mesh of both the SV and the ST with the mechanical properties assumed in the FE model, d 3D view of the BM with the mechanical properties assumed in the FE model, 1—at the base, 2—in the middle, 3—at the apex, e 3D view of the stapes footplate (SF, blue), the annular ligament (AL, pink), and the round window membrane (RW, violet) showing the detailed dimensions, the FE meshes, and the mechanical properties of these three structures
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig1: The structure of the simplified cochlear model with detailed dimensions and FE meshes of the anatomical structures in the pre-stapedotomy FE state. a 3D schematic view of the uncoiled cochlea showing the overall dimensions of the scala vestibule (SV) and the scala tympani (ST), b 3D view of the basilar membrane (BM) and the supported structures of the BM with detailed dimensions of the BM, c 3D view of the uncoiled cochlea showing the FE mesh of both the SV and the ST with the mechanical properties assumed in the FE model, d 3D view of the BM with the mechanical properties assumed in the FE model, 1—at the base, 2—in the middle, 3—at the apex, e 3D view of the stapes footplate (SF, blue), the annular ligament (AL, pink), and the round window membrane (RW, violet) showing the detailed dimensions, the FE meshes, and the mechanical properties of these three structures
Mentions: The geometry of the inner ear structures was adopted according to dimensions published in the literature (Gan et al. 2007), similar to the real coiled geometry of the cochlea. Our FE model was constructed based on the information given by Gan’s group, but these two models differ from each other. The main differences are the geometry of the stapes footplate, the annular ligament, the RW membrane, the variable height of both SV and ST, the finite element mesh and number of finite elements for the individual structures, the material properties of the stapes footplate and the annular ligament, except density of the AL. The geometry was then meshed in ANSYS 13.0 (Ansys, Inc., Canonsburg, PA). Figure 1 shows the structure of the simplified cochlear model with detailed dimensions and FE meshes of the anatomical structures.

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