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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

Comparison of stapes displacement amplitudes between Asai et al. (1999, 80 dB SPL at the TM), Huber et al. (2003 and 2006, 80 dB SPL at the TM), Stenfelt et al. (2004a, 80 dB SPL at the TM), and the present study (90 dB SPL at the TM). The velocity amplitudes reported by Stenfelt et al. (2004a) were recalculated to obtain the displacement amplitudes according to the formula A = A/cos(2*3.14* where A—velocity amplitude, —frequency
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Fig9: Comparison of stapes displacement amplitudes between Asai et al. (1999, 80 dB SPL at the TM), Huber et al. (2003 and 2006, 80 dB SPL at the TM), Stenfelt et al. (2004a, 80 dB SPL at the TM), and the present study (90 dB SPL at the TM). The velocity amplitudes reported by Stenfelt et al. (2004a) were recalculated to obtain the displacement amplitudes according to the formula A = A/cos(2*3.14* where A—velocity amplitude, —frequency

Mentions: The results of our modeling and experimental studies showed the differences in the RW vibrations between physiological conditions and following stapedotomy. The motion of the RW membrane has been used to determine the efficiency of the transfer of acoustic energy to the inner ear and to predict hearing results following some types of middle ear reconstructions (Asai et al. 1999; Mehta et al. 2003; Stenfelt et al. 2004b; Chien et al. 2007). This justifies the experimental and modeling investigations of the RW vibration in the case of stapedotomy surgery. To develop an appropriate simulation model of cochlear macromechanics, knowledge of the vibration parameters has been required, based on the experimental measurements. We used the LDV technique to find the displacement amplitude of the SF, the piston of the stapes prosthesis, and the RW membrane from fresh cadaver temporal bone specimens. We do not publish the phase data because our data differ substantially from the earlier studies (e.g., Stenfelt et al. 2004a). We suspect that the experimental phase data obtained by us are not correlated in time with the sound signal supplied to the external ear canal. Therefore, the analysis of the phase data without repeating the measurements is impossible. Nevertheless, our measurement results of the displacement amplitudes were comparable with other researchers’ studies (Asai et al. 1999; Huber et al. 2003, 2006; Stenfelt et al. 2004a, b). Figure 9 compares our measurement results of the stapes displacement amplitude to Fig. 5 of Asai et al. (1999), Fig. 6C of Huber et al. (2003), Fig. 2 of Huber et al. (2006), and Fig. 4a of Stenfelt et al. (2004a). Stenfelt et al. (2004a) reported the velocity amplitude of points on the stapes footplate. We recalculated these data to obtain the displacement amplitude (Asf) according to the formula Asf = Vsf/cos(2*3.14*) where Vsf—velocity amplitude, —frequency. Asai et al. (1999), Huber et al. (2003, 2006), and Stenfelt et al. (2004a) performed the experiments when a sound stimulation of 80 dB SPL was presented at the tympanic membrane. Because we measured the stapes displacement at 90 dB SPL, our measurement results are slightly higher compared to others. Figure 10 shows comparison of the RW displacement amplitude for the pre-stapedotomy state between (Asai et al. 1999, Fig. 5, center of the RW), Stenfelt et al. (2004a, Fig. 4c, the highest curve), Stenfelt et al. (2004b, Fig. 3a, the highest curve), and the present study. All curves are similar, but it should be noted that our measurement was made with 90 dB SPL. However, because complicated vibration patterns of the RW, comparing the RW membrane vibration at a single point, can give erroneous results. To our knowledge, only Stenfelt et al. (2004b) measured the RW vibration for the post-stapedotomy state. Stenfelt et al. made their measurement for a 0.6-mm piston stapes prosthesis with a sound pressure level at the tympanic membrane of 80 dB SPL. The results from nine target positions closed to the center of the RW membrane were presented as relative measures (Fig. 6, Stenfelt et al. 2004b). Therefore, it is difficult to compare our measurement results of the RW displacement amplitude (Arw) for a 0.4-mm piston stapes prosthesis and 90 dB SPL to the measurement results reported by Stenfelt et al. (2004b). In our measurement, the piston prosthesis substantially changed the vibration pattern of the RW membrane for the entire frequency range 0.5–10 kHz (Wysocki et al. 2011). Similar results were recorded by Stenfelt et al. (2004b). This suggests that the fluid volume displacement at the RW should be calculated to estimate the stimulation of the cochlea, especially in the case of stapedotomy surgery.


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)

Comparison of stapes displacement amplitudes between Asai et al. (1999, 80 dB SPL at the TM), Huber et al. (2003 and 2006, 80 dB SPL at the TM), Stenfelt et al. (2004a, 80 dB SPL at the TM), and the present study (90 dB SPL at the TM). The velocity amplitudes reported by Stenfelt et al. (2004a) were recalculated to obtain the displacement amplitudes according to the formula A = A/cos(2*3.14* where A—velocity amplitude, —frequency
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig9: Comparison of stapes displacement amplitudes between Asai et al. (1999, 80 dB SPL at the TM), Huber et al. (2003 and 2006, 80 dB SPL at the TM), Stenfelt et al. (2004a, 80 dB SPL at the TM), and the present study (90 dB SPL at the TM). The velocity amplitudes reported by Stenfelt et al. (2004a) were recalculated to obtain the displacement amplitudes according to the formula A = A/cos(2*3.14* where A—velocity amplitude, —frequency
Mentions: The results of our modeling and experimental studies showed the differences in the RW vibrations between physiological conditions and following stapedotomy. The motion of the RW membrane has been used to determine the efficiency of the transfer of acoustic energy to the inner ear and to predict hearing results following some types of middle ear reconstructions (Asai et al. 1999; Mehta et al. 2003; Stenfelt et al. 2004b; Chien et al. 2007). This justifies the experimental and modeling investigations of the RW vibration in the case of stapedotomy surgery. To develop an appropriate simulation model of cochlear macromechanics, knowledge of the vibration parameters has been required, based on the experimental measurements. We used the LDV technique to find the displacement amplitude of the SF, the piston of the stapes prosthesis, and the RW membrane from fresh cadaver temporal bone specimens. We do not publish the phase data because our data differ substantially from the earlier studies (e.g., Stenfelt et al. 2004a). We suspect that the experimental phase data obtained by us are not correlated in time with the sound signal supplied to the external ear canal. Therefore, the analysis of the phase data without repeating the measurements is impossible. Nevertheless, our measurement results of the displacement amplitudes were comparable with other researchers’ studies (Asai et al. 1999; Huber et al. 2003, 2006; Stenfelt et al. 2004a, b). Figure 9 compares our measurement results of the stapes displacement amplitude to Fig. 5 of Asai et al. (1999), Fig. 6C of Huber et al. (2003), Fig. 2 of Huber et al. (2006), and Fig. 4a of Stenfelt et al. (2004a). Stenfelt et al. (2004a) reported the velocity amplitude of points on the stapes footplate. We recalculated these data to obtain the displacement amplitude (Asf) according to the formula Asf = Vsf/cos(2*3.14*) where Vsf—velocity amplitude, —frequency. Asai et al. (1999), Huber et al. (2003, 2006), and Stenfelt et al. (2004a) performed the experiments when a sound stimulation of 80 dB SPL was presented at the tympanic membrane. Because we measured the stapes displacement at 90 dB SPL, our measurement results are slightly higher compared to others. Figure 10 shows comparison of the RW displacement amplitude for the pre-stapedotomy state between (Asai et al. 1999, Fig. 5, center of the RW), Stenfelt et al. (2004a, Fig. 4c, the highest curve), Stenfelt et al. (2004b, Fig. 3a, the highest curve), and the present study. All curves are similar, but it should be noted that our measurement was made with 90 dB SPL. However, because complicated vibration patterns of the RW, comparing the RW membrane vibration at a single point, can give erroneous results. To our knowledge, only Stenfelt et al. (2004b) measured the RW vibration for the post-stapedotomy state. Stenfelt et al. made their measurement for a 0.6-mm piston stapes prosthesis with a sound pressure level at the tympanic membrane of 80 dB SPL. The results from nine target positions closed to the center of the RW membrane were presented as relative measures (Fig. 6, Stenfelt et al. 2004b). Therefore, it is difficult to compare our measurement results of the RW displacement amplitude (Arw) for a 0.4-mm piston stapes prosthesis and 90 dB SPL to the measurement results reported by Stenfelt et al. (2004b). In our measurement, the piston prosthesis substantially changed the vibration pattern of the RW membrane for the entire frequency range 0.5–10 kHz (Wysocki et al. 2011). Similar results were recorded by Stenfelt et al. (2004b). This suggests that the fluid volume displacement at the RW should be calculated to estimate the stimulation of the cochlea, especially in the case of stapedotomy surgery.

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