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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

a Post-stapedotomy amplitude frequency profiles of the RW membrane displacement (Arw) while the 0.4-mm piston stapes prosthesis was inserted into the oval window. The figure presents the model-derived frequency response curve (MODEL post-stapedotomy, thick, black, solid curve line, white squares) while the amplitudes of the harmonic displacement excitations are given in Table 2 (A_in post-stapedotomy) in comparison with the corresponding curves (EX post SPECIMEN, thin, colored, dashed curve lines) obtained from four temporal bone specimens in the post-stapedotomy state when 90 dB SPL pure tones were applied in the external ear canal, and the values of average displacement amplitude of four points for all specimens (EXPERIMENT post(mean), thick, red, solid curve line). The model-derived pre-stapedotomy amplitude frequency profile of the RW membrane displacement (MODEL pre-stapedotomy, thick, black, solid curve line, black circles) was shown to compare with the post-stapedotomy profiles. b Changes in the model-derived RW membrane displacement amplitude (Arw, where the magnitude of Arw equals 20*log[Arw/Arw]) induced by the 0.4-mm piston stapes prosthesis (MODEL piston 0.4 mm, black, solid curve line), the 0.6-mm piston stapes prosthesis (MODEL piston 0.6 mm, gray, solid curve line) and measured before and after experimental stapedotomy with the 0.4-mm piston prosthesis (EXPERIMENT piston 0.4 mm, red, solid curve line). For the model curves, the amplitudes of the harmonic displacement excitations are given in Table 2
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Fig7: a Post-stapedotomy amplitude frequency profiles of the RW membrane displacement (Arw) while the 0.4-mm piston stapes prosthesis was inserted into the oval window. The figure presents the model-derived frequency response curve (MODEL post-stapedotomy, thick, black, solid curve line, white squares) while the amplitudes of the harmonic displacement excitations are given in Table 2 (A_in post-stapedotomy) in comparison with the corresponding curves (EX post SPECIMEN, thin, colored, dashed curve lines) obtained from four temporal bone specimens in the post-stapedotomy state when 90 dB SPL pure tones were applied in the external ear canal, and the values of average displacement amplitude of four points for all specimens (EXPERIMENT post(mean), thick, red, solid curve line). The model-derived pre-stapedotomy amplitude frequency profile of the RW membrane displacement (MODEL pre-stapedotomy, thick, black, solid curve line, black circles) was shown to compare with the post-stapedotomy profiles. b Changes in the model-derived RW membrane displacement amplitude (Arw, where the magnitude of Arw equals 20*log[Arw/Arw]) induced by the 0.4-mm piston stapes prosthesis (MODEL piston 0.4 mm, black, solid curve line), the 0.6-mm piston stapes prosthesis (MODEL piston 0.6 mm, gray, solid curve line) and measured before and after experimental stapedotomy with the 0.4-mm piston prosthesis (EXPERIMENT piston 0.4 mm, red, solid curve line). For the model curves, the amplitudes of the harmonic displacement excitations are given in Table 2

Mentions: Firstly, a piston prosthesis with a diameter of 0.4 mm was considered. Figure 7a shows the frequency response curves of the RW membrane displacement derived from the FE post-stapedotomy model (Arw_postM0.4) and control experimental curves measured from the human temporal bones following the stapedotomy surgery (Arw_postE0.4) compared to the curve for the FE pre-stapedotomy model. As can be seen, the FE model shows a maximum reduction in RW membrane displacement amplitude for the post-stapedotomy state within the 4–8 kHz frequency range. The post-stapedotomy FE model displacement amplitude curve (Arw_postM0.4) falls well within the range of the four temporal bone control experimental curves for frequencies above 1.25 kHz. Compared with the control experimental curves, the post-stapedotomy FE model showed higher values for the RW membrane displacement amplitudes for frequencies from 0.5 to 1.0 kHz. However, in general, the simulation from the post-stapedotomy FE model shows a pattern similar to the mean experimental curve.


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)

a Post-stapedotomy amplitude frequency profiles of the RW membrane displacement (Arw) while the 0.4-mm piston stapes prosthesis was inserted into the oval window. The figure presents the model-derived frequency response curve (MODEL post-stapedotomy, thick, black, solid curve line, white squares) while the amplitudes of the harmonic displacement excitations are given in Table 2 (A_in post-stapedotomy) in comparison with the corresponding curves (EX post SPECIMEN, thin, colored, dashed curve lines) obtained from four temporal bone specimens in the post-stapedotomy state when 90 dB SPL pure tones were applied in the external ear canal, and the values of average displacement amplitude of four points for all specimens (EXPERIMENT post(mean), thick, red, solid curve line). The model-derived pre-stapedotomy amplitude frequency profile of the RW membrane displacement (MODEL pre-stapedotomy, thick, black, solid curve line, black circles) was shown to compare with the post-stapedotomy profiles. b Changes in the model-derived RW membrane displacement amplitude (Arw, where the magnitude of Arw equals 20*log[Arw/Arw]) induced by the 0.4-mm piston stapes prosthesis (MODEL piston 0.4 mm, black, solid curve line), the 0.6-mm piston stapes prosthesis (MODEL piston 0.6 mm, gray, solid curve line) and measured before and after experimental stapedotomy with the 0.4-mm piston prosthesis (EXPERIMENT piston 0.4 mm, red, solid curve line). For the model curves, the amplitudes of the harmonic displacement excitations are given in Table 2
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig7: a Post-stapedotomy amplitude frequency profiles of the RW membrane displacement (Arw) while the 0.4-mm piston stapes prosthesis was inserted into the oval window. The figure presents the model-derived frequency response curve (MODEL post-stapedotomy, thick, black, solid curve line, white squares) while the amplitudes of the harmonic displacement excitations are given in Table 2 (A_in post-stapedotomy) in comparison with the corresponding curves (EX post SPECIMEN, thin, colored, dashed curve lines) obtained from four temporal bone specimens in the post-stapedotomy state when 90 dB SPL pure tones were applied in the external ear canal, and the values of average displacement amplitude of four points for all specimens (EXPERIMENT post(mean), thick, red, solid curve line). The model-derived pre-stapedotomy amplitude frequency profile of the RW membrane displacement (MODEL pre-stapedotomy, thick, black, solid curve line, black circles) was shown to compare with the post-stapedotomy profiles. b Changes in the model-derived RW membrane displacement amplitude (Arw, where the magnitude of Arw equals 20*log[Arw/Arw]) induced by the 0.4-mm piston stapes prosthesis (MODEL piston 0.4 mm, black, solid curve line), the 0.6-mm piston stapes prosthesis (MODEL piston 0.6 mm, gray, solid curve line) and measured before and after experimental stapedotomy with the 0.4-mm piston prosthesis (EXPERIMENT piston 0.4 mm, red, solid curve line). For the model curves, the amplitudes of the harmonic displacement excitations are given in Table 2
Mentions: Firstly, a piston prosthesis with a diameter of 0.4 mm was considered. Figure 7a shows the frequency response curves of the RW membrane displacement derived from the FE post-stapedotomy model (Arw_postM0.4) and control experimental curves measured from the human temporal bones following the stapedotomy surgery (Arw_postE0.4) compared to the curve for the FE pre-stapedotomy model. As can be seen, the FE model shows a maximum reduction in RW membrane displacement amplitude for the post-stapedotomy state within the 4–8 kHz frequency range. The post-stapedotomy FE model displacement amplitude curve (Arw_postM0.4) falls well within the range of the four temporal bone control experimental curves for frequencies above 1.25 kHz. Compared with the control experimental curves, the post-stapedotomy FE model showed higher values for the RW membrane displacement amplitudes for frequencies from 0.5 to 1.0 kHz. However, in general, the simulation from the post-stapedotomy FE model shows a pattern similar to the mean experimental curve.

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