Three-dimensional stapes footplate motion in human temporal bones

Effect of electromagnetic middle-ear implant simulating sites on the stapes spatial motion: A finite element analysis

The electromagnetic middle-ear implant (MEI) is a new type of hearing device for addressing sensorineural and mixed hearing loss. The hearing compensation effect of the MEI varies depending on the transducer stimulation sites. This paper investigates the impact of transducer stimulation sites on MEI performance by analyzing stapes spatial motion. Firstly, we constructed a human-ear finite element model based on micro-CT scanning and inverse molding techniques. This model was validated by comparing its predictions of stapes spatial motion and cochlear response with experimental data. Then, stimulation force was applied at four common sites: umbo, incus body, incus long process and stapes to simulate the electromagnetic transducer. Results show that at low and middle frequencies, stapes-stimulating and incus-long-process-stimulating produce similar spatial motion to normal hearing; at high frequencies, incus-body-stimulating produces similar results to normal hearing. The equivalent sound pressure level generated by the stapes piston motion is less sensitive to the stimulation direction than that deduced by the stapes rocking motion.

Dynamic X-ray Microtomography vs. Laser-Doppler Vibrometry: A Comparative Study

Purpose

There are challenges in understanding the biomechanics of the human middle ear, and established methods for studying this system show significant limitations. In this study, we evaluate a novel dynamic imaging technique based on synchrotron X-ray microtomography designed to assess the biomechanical properties of the human middle ear by comparing it to laser-Doppler vibrometry (LDV).

Methods

We examined three fresh-frozen temporal bones (TB) using dynamic synchrotron-based X-ray microtomography for 256 Hz and 512 Hz, stimulated at 110 dB and 120 dB SPL. In addition, we performed measurements on these TBs using 1D LDV, a well-established method.

Results

The normalized displacement values (μm/Pa) at the umbo and the posterior crus of the stapes are consistent or within 5-10 dB differences between all LDV and dynamic microtomography measurements and previously reported literature references. In general, the overall behavior is similar between the two measurement techniques.

Conclusion

In conclusion, our results demonstrate the suitability of dynamic synchrotron-based X-ray microtomography in studying the middle ear's biomechanics. However, this study shows that better standardization regarding acoustic stimulation and measurement points is needed to better compare the two measurement techniques.

Semi-automatic algorithm to build finite element numerical models of the human hearing system from Micro-CT data

Finite Element modeling has been an extended methodology to build numerical model to simulate the behavior of the hearing system. Due to the complexity of the system and the difficulties to reduce the uncertainties of the geometric data, they result in computationally expensive models, sometimes generic, representative of average geometries. It makes it difficult to validate the model with direct experimental data from the same specimen or to establish a patient-oriented modeling strategy. In the present paper, a first attempt to automatize the process of model building is made. The source information is geometrical information obtained from CT of the different elements that compose the system. Importing that data, we have designed the complete procedure to build a model including tympanic membrane, ossicular chain and cavities. The methodology includes the proper coupling of all the elements and the generation of the corresponding finite element model. The whole automatic procedure is not complete, as we need to make some human-assisted decisions; however, the model development time is reduced from 4 weeks to approximately 3 days. The goal of the modeling algorithm is to build a Finite Element Model with a limited computational cost. Several tasks as contour identification or model decimation are designed and integrated in order to follow a semi-automated process that allows generating a patient-oriented model.

Audiologic Outcomes After Vestibulotomy in Patients With Congenital Absence of the Oval Window

OBJECTIVE

To examine the clinical features and surgical outcomes in patients with congenital absence of the oval window (CAOW), and to investigate the potential factors that affect audiologic results.

STUDY DESIGN

A retrospective chart review.

SETTING

A tertiary academic center.

PATIENTS AND INTERVENTION

A total of 17 ears among 16 patients were confirmed to have CAOW. Among them, 13 ears underwent vestibulotomy for hearing reconstruction. Clinical parameters associated with the hearing outcomes were analyzed.

MAIN OUTCOME MEASURES

A mean air-bone gap (ABG) after 6-month and long-term follow-up was compared with preoperative measurements.

RESULTS

Intraoperative findings showed that anomalies of the malleus or incus were observed in 11 ears (64.7%), stapes anomalies were present in all ears (100%), and facial nerve anomalies were present in 10 ears (58.8%). Because of unfavorable facial nerve anomalies, hearing reconstruction was aborted in four cases (23.5%). In the hearing reconstruction group, the mean ABG at 6 months postoperation was significantly reduced after compared with the preoperative value (44.0 ± 8.4 dB versus 58.8 ± 9.1 dB, p = 0.006). After dividing ears into a success subgroup (ABG ≤ 30 dB, seven ears) and non-success subgroup (ABG > 30 dB, six ears), the use of a drill during vestibulotomy was significantly related to a poor hearing outcome (100% versus 16.7%, p = 0.015). The long-term follow-up result (mean, 60 mo) revealed no deterioration compared with the 6-month postoperative result. Five ears (29.4%) underwent revision surgery, and three of them showed ABG improvements. No serious complications were reported.

CONCLUSION

Vestibulotomy is an effective and safe option for hearing restoration in patients with CAOW, particularly when the use of a drill is not required. The long-term audiologic outcome is also reliable.

Influence of inner ear impedance on middle ear sound transfer functions

Introduction

For experimental studies on sound transfer in the middle ear, it may be advantageous to perform the measurements without the inner ear. In this case, it is important to know the influence of inner ear impedance on the middle ear transfer function (METF). Previous studies provide contradictory results in this regard. With the current study, we investigate the influence of inner ear impedance in more detail and find possible reasons for deviations in the previous studies.

Methods

11 fresh frozen temporal bones were prepared in our study. The factors related to inner ear impedance, including round window membrane stiffness, cochleostomy, cochlea fluid and cochlea destruction were involved in the experimental design. After measuring in the intact specimen as a reference (step 1), the round window membrane was punctured (step 2), then completely removed (step 3). The cochleostomy was performed (step 4) before the cochlear fluid was carefully suctioned through scala tympani (step 5) and scala vestibuli (step 6). Finally, cochlea was destroyed by drilling (step 7). Translational and rotational movement of the stapes footplate were measured and calculated at each step. The results of the steps were compared to quantify the effect of inner ear impedance changing related to the process of cochlear drainage.

Results

As the inner ear impedance decreases from step 1 to 7, the amplitudes of the METF curves at each frequency gradually increase in general. From step 6 on, the measured METF are significantly different with respect to the intact group at high frequencies above 3 kHz. The differences are frequency dependent. However, the significant decrement of rotational motion appears at the frequencies above 4.5 kHz from the step 5.

Conclusion

This study confirms the influence of inner ear impedance on METF only at higher frequencies (≥3 kHz). The rotational motions are more sensitive to the drainage of fluid at the higher frequency. Study results that found no influence of cochlea impedance may be due to incomplete drainage of the cochlea.

Mammalian middle ear mechanics: A review

The middle ear is part of the ear in all terrestrial vertebrates. It provides an interface between two media, air and fluid. How does it work? In mammals, the middle ear is traditionally described as increasing gain due to Helmholtz's hydraulic analogy and the lever action of the malleus-incus complex: in effect, an impedance transformer. The conical shape of the eardrum and a frequency-dependent synovial joint function for the ossicles suggest a greater complexity of function than the traditional view. Here we review acoustico-mechanical measurements of middle ear function and the development of middle ear models based on these measurements. We observe that an impedance-matching mechanism (reducing reflection) rather than an impedance transformer (providing gain) best explains experimental findings. We conclude by considering some outstanding questions about middle ear function, recognizing that we are still learning how the middle ear works.

Contribution of the flexible incudo-malleal joint to middle-ear sound transmission under static pressure loads

The incudo-malleal joint (IMJ) in the human middle ear is a true diarthrodial joint and it has been known that the flexibility of this joint does not contribute to better middle-ear sound transmission. Previous studies have proposed that a gliding motion between the malleus and the incus at this joint prevents the transmission of large displacements of the malleus to the incus and stapes and thus contributes to the protection of the inner ear as an immediate response against large static pressure changes. However, dynamic behavior of this joint under static pressure changes has not been fully revealed. In this study, effects of the flexibility of the IMJ on middle-ear sound transmission under static pressure difference between the middle-ear cavity and the environment were investigated. Experiments were performed in human cadaveric temporal bones with static pressures in the range of +/- 2 kPa being applied to the ear canal (relative to middle-ear cavity). Vibrational motions of the umbo and the stapes footplate center in response to acoustic stimulation (0.2-8 kHz) were measured using a 3D-Laser Doppler vibrometer for (1) the natural IMJ and (2) the IMJ with experimentally-reduced flexibility. With the natural condition of the IMJ, vibrations of the umbo and the stapes footplate center under static pressure loads were attenuated at low frequencies below the middle-ear resonance frequency as observed in previous studies. After the flexibility of the IMJ was reduced, additional attenuations of vibrational motion were observed for the umbo under positive static pressures in the ear canal (EC) and the stapes footplate center under both positive and negative static EC pressures. The additional attenuation of vibration reached 4~7 dB for the umbo under positive static EC pressures and the stapes footplate center under negative EC pressures, and 7~11 dB for the stapes footplate center under positive EC pressures. The results of this study indicate an adaptive mechanism of the flexible IMJ in the human middle ear to changes of static EC pressure by reducing the attenuation of the middle-ear sound transmission. Such results are expected to be used for diagnosis of the IMJ stiffening and to be applied to design of middle-ear prostheses.

Mechanical Energy Dissipation Through the Ossicular Chain and Inner Ear Using Laser Doppler Vibrometer Measurement of Round Window Velocity

HYPOTHESIS

Round window velocity measurements should correlate closely with vibration measurements taken at proximal points along an intact chain over a set frequency range. These round window vibration measurements should be similar to the vibration measurements taken of the ossicles if mechanical energy is conserved through the vestibular organ.

BACKGROUND

To date there has not been a study which compares vibratory velocity measurements through an intact ossicular chain to the level of the round window. This study attempted to quantify the degree of mechanical energy transmission and suspected dissipation through the ossicular chain and vestibular organ through incus, stapes, and round window velocity measurements in response to sound stimulus.

METHODS

Five thawed human temporal bones with intact ossicular chain and tympanic membrane underwent complete mastoidectomy and a facial recess approach. A laser Doppler vibrometer (LDV) was mounted on the operating microscope to measure vibration of incus, stapes, and round window in response to a sound stimulus within the external auditory canal. Sound stimulus frequencies ranged from 0.5 to 4 kHz at 90 dB SPL.

RESULTS

Vibration velocity was measured across the frequency range for each incus, stapes, and round window. Vibration velocity curves obtained over the frequency range were similar for each of the bones with a notable resonant frequency around 2 kHz. The incus and stapes curve amplitudes were nearly identical with similar maximum velocity and frequency at which this maximal velocity was noted. Round window vibration velocity demonstrated a unique peak velocity. Transfer function measurements of the stapes and round window demonstrated markedly similar curves. The variation in velocity between temporal bones in response to the standardized stimulus was more dramatic in the round window measurements when compared with the incus and stapes.

CONCLUSIONS

This study supports the concept that round window transfer function is equivalent to stapes footplate transfer function when subjected to the same acoustic stimuli. This study also demonstrates that the round window is a much more difficult target to measure when using LDV technology and improvements in experimental design are required to better understand round window physiology in relation to transfer of acoustic vibratory stimulus transferred throughout the middle ear. A complete and thorough understanding of the biophysical properties of the middle and inner ear are critical for optimal ossiculoplasty outcomes and the development of future ossicular prosthetics.

Forward and Reverse Middle Ear Transmission in Gerbil with a Normal or Spontaneously Healed Tympanic Membrane

Tympanic membranes (TM) that have healed spontaneously after perforation present abnormalities in their structural and mechanical properties; i.e., they are thickened and abnormally dense. These changes result in a deterioration of middle ear (ME) sound transmission, which is clinically presented as a conductive hearing loss (CHL). To fully understand the ME sound transmission under TM pathological conditions, we created a gerbil model with a controlled 50% pars tensa perforation, which was left to heal spontaneously for up to 4 weeks (TM perforations had fully sealed after 2 weeks). After the recovery period, the ME sound transmission, both in the forward and reverse directions, was directly measured with two-tone stimulation. Measurements were performed at the input, the ossicular chain, and output of the ME system, i.e., at the TM, umbo, and scala vestibuli (SV) next to the stapes. We found that variations in ME transmission in forward and reverse directions were not symmetric. In the forward direction, the ME pressure gain decreased in a frequency-dependent manner, with smaller loss (within 10 dB) at low frequencies and more dramatic loss at high frequency regions. The loss pattern was mainly from the less efficient acoustical to mechanical coupling between the TM and umbo, with little changes along the ossicular chain. In the reverse direction, the variations in these ears are relatively smaller. Our results provide detailed functional observations that explain CHL seen in clinical patients with abnormal TM, e.g., caused by otitis media, that have healed spontaneously after perforation or post-tympanoplasty, especially at high frequencies. In addition, our data demonstrate that changes in distortion product otoacoustic emissions (DPOAEs) result from altered ME transmission in both the forward and reverse direction by a reduction of the effective stimulus levels and less efficient transfer of DPs from the ME into the ear canal. This confirms that DPOAEs can be used to assess both the health of the cochlea and the middle ear.

[Laser Doppler vibrometric measurements on human temporal bones]

Laser Doppler vibrometric (LDV) measurements on human temporal bones represent the standard method for predicting the performance of active middle ear implants (AMEI) and are used as preclinical tests in the development, approval process, and indication expansion of AMEI. The quality of the coupling of the floating mass transducer to the mobile structures of the middle ear is decisive for the performance of the implant and patients' hearing perception. The cochlea can be stimulated via the oval window (forward stimulation) or the round window (reverse stimulation). For forward stimulation, the ASTM standard F2504-05 defines a method to ensure physiologically normal properties of the temporal bones used in the experiments. For reverse stimulation, which depends even more critically on the quality of the temporal bone, a comparable standard method is lacking. Appropriate preparation and storage of the human petrous bone as well as suitable LDV test setups with respect to calibration and reproducibility of measuring positions and angles provide results that allow a comparison of different types of coupling and also correlate well with clinical data.

Vibration direction sensitivity of the cochlea with bone conduction stimulation in guinea pigs

Sound and vibrations that cause the skull bone to vibrate can be heard as ordinary sounds and this is termed hearing by bone conduction (BC). Not all mechanisms that causes a skull vibration to result in BC hearing are known, and one such unknown is how the direction of the vibration influences BC hearing. This direction sensitivity was investigated by providing BC stimulation in five different directions at the vertex of the guinea pig skull. The hearing thresholds for BC stimulation was obtained in the frequency range of 2 to 20 kHz by measurements of compound action potential. During the stimulation by BC, the vibration of the cochlear promontory was measured with a three-dimensional laser Doppler vibrometer resulting in a set of unique three-dimensional velocity magnitude combinations for each threshold estimation. The sets of three-dimensional velocity magnitude at threshold were used to investigate nine different predictors of BC hearing based on cochlear promontory velocity magnitudes, six single direction (x, y and z directions in isolation, the normal to the stapes footplate, the oval to round window direction, and the cochlear base to apex direction), one linear combination of the three dimension velocity magnitudes, one square-rooted sum of the squared velocity magnitudes, and one sum of the weighted three dimensional velocity magnitudes based on a restricted minimum square error (MSE) estimation. The MSE gave the best predictions of the hearing threshold based on the cochlear promontory velocity magnitudes while using only a single direction gave the worst predictions of the hearing thresholds overall. According to the MSE estimation, at frequencies up to 8 kHz the vibration direction between the right and left side gave the greatest contribution to BC hearing in the guinea pig while at the highest frequencies measured, 16 and 20 kHz, the anteroposterior direction of the guinea pig head gave the greatest contribution.

Rapid imaging of tympanic membrane vibrations in humans

Functional imaging of the human ear is an extremely challenging task because of its minute anatomic structures and nanometer-scale motion in response to sound. Here, we demonstrate noninvasive in vivo functional imaging of the human tympanic membrane under various acoustic excitations, and identify unique vibration patterns that vary between human subjects. By combining spectrally encoded imaging with phase-sensitive spectral-domain interferometry, our system attains high-resolution functional imaging of the two-dimensional membrane surface, within a fraction of a second, through a handheld imaging probe. The detailed physiological data acquired by the system would allow measuring a wide range of clinically relevant parameters for patient diagnosis, and provide a powerful new tool for studying middle and inner ear physiology.

Middle Ear Actuator Performance Determined From Intracochlear Pressure Measurements in a Single Cochlear Scala

HYPOTHESIS

Intracochlear pressure measurements in one cochlear scala are sufficient as reference to determine the output of an active middle ear implant (AMEI) in terms of "equivalent sound pressure level" (eqSPL).

BACKGROUND

The performance of AMEIs is commonly calculated from stapes velocities or intracochlear pressure differences (PDiff). However, there are scenarios where measuring stapes velocities or PDiff may not be feasible, for example when access to the stapes or one of the scalae is impractical.

METHODS

We reanalyzed data from a previous study of our group that investigated the performance of an AMEI coupled to the incus in 10 human temporal bones. We calculated eqSPL based on stapes velocities according to the ASTM standard F2504-05 and based on intracochlear pressures in scala vestibuli, scala tympani, and PDiff.

RESULTS

The AMEI produced eqSPL of ∼100 to 120 dB at 1 Vrms. No significant differences were found between using intracochlear pressures in scala vestibuli, scala tympani, or PDiff as a reference. The actuator performance calculated from stapes displacements predicted slightly higher eqSPLs at frequencies above 1000 Hz, but these differences were not statistically significant.

CONCLUSION

Our findings show that pressure measurements in one scala can be sufficient to evaluate the performance of an AMEI coupled to the incus. The method may be extended to other stimulation modalities of the middle ear or cochlea when access to the stapes or one of the scalae is not possible.

Investigation of Mechanisms in Bone Conduction Hyperacusis With Third Window Pathologies Based on Model Predictions

A lumped element impedance model of the inner ear with sources based on wave propagation in the skull bone was used to investigate the mechanisms of hearing sensitivity changes with semi-circular canal dehiscence (SSCD) and alterations of the size of the vestibular aqueduct. The model was able to replicate clinical and experimental findings reported in the literature. For air conduction, the reduction in cochlear impedance due to a SSCD reduces the intra-cochlear pressure at low frequencies resulting in a reduced hearing sensation. For bone conduction, the reduced impedance in the vestibular side due to the SSCD facilitates volume velocity caused by inner ear fluid inertia, and this effect dominates BC hearing with a third window opening on the vestibular side. The SSCD effect is generally greater for BC than for AC. Moreover, the effect increases with increased area of the dehiscence, but areas more than the cross section area of the semi-circular canal itself leads to small alterations. The model-predicted air-bone gap for a SSCD of 1 mm² is 30 dB at 100 Hz that decreases with frequency and become non-existent at frequencies above 1 kHz. According to the model, this air-bone gap is similar to the air-bone gap of an early stage otosclerosis. The normal variation of the size of the vestibular aqueduct do not affect air conduction hearing, but can vary bone conduction sensitivity by up to 15 dB at low frequencies. Reinforcement of the OW to mitigate hyperacusis with SSCD is inefficient while a RW reinforcement can reset the bone conduction sensitivity to near normal.

Analysis of the Human Middle Ear Dynamics Through Multibody Modeling

The dynamics of the human middle ear (ME) has been studied in the past using several computational and experimental approaches in order to observe the effect on hearing of different conditions, such as conductive disease, corrective surgery, or implantation of a middle ear prosthesis. Multibody (MB) models combine the analysis of flexible structures with rigid body dynamics, involving fewer degrees-of-freedom (DOF) than finite element (FE) models, but a more detailed description than traditional 1D lumped parameter (LP) models. This study describes the reduction of a reference FE model of the human middle ear to a MB model and compares the results obtained considering different levels of model simplification. All models are compared by means of the frequency response of the stapes velocity versus sound pressure at the tympanic membrane (TM), as well as the system natural frequencies and mode shapes. It can be seen that the flexibility of the ossicles has a limited impact on the system frequency response function (FRF) and modes, and the stiffness of the tendons and ligaments only plays a role when above certain levels. On the other hand, the restriction of the stapes footplate movement to a piston-like behavior can considerably affect the vibrational modes, while constraints to the incudomalleolar joint (IMJ) and incudostapedial joint (ISJ) can have a strong impact on the system FRF.

Comparison of sheep and human middle-ear ossicles: anatomy and inertial properties

The sheep middle ear has been used in training to prepare physicians to perform surgeries and to test new ways of surgical access. This study aimed to (1) collect anatomical data and inertial properties of the sheep middle-ear ossicles and (2) explore effects of these features on sound transmission, in comparison to those of the human. Characteristic dimensions and inertial properties of the middle-ear ossicles of White-Alpine sheep (n = 11) were measured from high-resolution micro-CT data, and were assessed in comparison with the corresponding values of the human middle ear. The sheep middle-ear ossicles differed from those of human in several ways: anteroinferior orientation of the malleus handle, relatively small size of the incus with a relatively short distance to the lenticular process, a large area of the articular surfaces at the incudostapedial joint, and a relatively small moment of inertia along the anterior-posterior axis. Analysis in this study suggests that structure and orientation of the middle-ear ossicles in the sheep are conducive to an increase in the hinge-like ossicular-lever-action around the anterior-posterior axis. Considering the substantial anatomical differences, outcomes of middle-ear surgeries would presumably be difficult to assess from experiments using the sheep middle ear.

Optimum Coupling of an Active Middle Ear Actuator: Effect of Loading Forces on Actuator Output and Conductive Losses

Introduction:

The desired outcome of the implantation of active middle ear implants is maximum coupling efficiency and a minimum of conductive loss. It has not been investigated yet, which loading forces are applied during the process of coupling, which forces lead to an optimum actuator performance and which forces occur when manufacturer guidelines for coupling are followed.

Methods:

Actuator output was measured by laser Doppler vibrometry of stapes motion while the actuator was advanced in 20 μm steps against the incus body while monitoring static contact force. The occurrence of conductive losses was investigated by measuring changes in stapes motion in response to acoustic stimulation for each step of actuator displacement. Additionally, the electrical impedance of the actuator was measured over the whole frequency range at each actuator position.

Results:

Highest coupling efficiency was achieved at forces above 10 mN. Below 1 mN no efficient coupling could be achieved. At 30 mN loading force, which is typical when coupling according to manufacturer guidelines, conductive losses of more than 5 dB were observed in one out of nine TBs. The electrical impedance of the actuator showed a prominent resonance peak which vanished after coupling.

Conclusion:

A minimum coupling force of 10 mN is required for efficient coupling of the actuator to the incus. In most cases, coupling forces up to 100 mN will not result in clinically relevant conductive losses. The electrical impedance is a simple and reliable metric to indicate contact.

Effectiveness of Bone Conduction Stimulation Applied Directly to the Otic Capsule Measured at Promontory: Assessment in Cadavers

INTRODUCTION

The aims of this study included: (a) to develop a method of direct acoustic bone conduction (BC) stimulation applied directly to the otic capsule, (b) to investigate the effect of different stimulation sites on the promontory displacement amplitude, and (c) to find the best stimulation site (among 2 located directly on the otic capsule and 1 standard site approved for clinical use) that provides the greatest transmission of vibratory energy.

METHODS

Measurements were performed on 9 cadaveric whole human heads. A commercial scanning laser Doppler vibrometer was used. The promontory displacement was recorded in response to BC stimulation delivered by an implant at 3 sites: BC1 on the squamous part of the temporal bone, BC2 on the ampulla of the lateral semicircular canal, and BC3 between the semicircular canals. The displacement of the promontory was analyzed in detail.

RESULTS

The results show that BC1 caused an overall smaller promontory displacement than both sites BC2 and 3. BC3 stimulation is more efficient than that at BC2.

CONCLUSIONS

BC is an effective method of acoustic stimulus delivery into the inner ear, with the effectiveness increasing when approaching closer to the cochlea. Placing the implant directly on the labyrinth and thus applying vibrations directly to the otic capsule is possible and very effective as proved in this study. The results are encouraging and represent the potential of new stimulation sites that could be introduced in the field of BC hearing rehabilitation as the possible future locations for implantable BC hearing devices.

De novo topology optimization of total ossicular replacement prostheses

Conductive hearing loss, due to middle ear pathologies or traumas, affects more than 5% of the population worldwide. Passive prostheses to replace the ossicular chain mainly rely on piston-like titanium and/or hydroxyapatite devices, which in the long term suffer from extrusion. Although the basic shape of such devices always consists of a base for contact with the eardrum and a stem to have mechanical connection with the residual bony structures, a plethora of topologies have been proposed, mainly to help surgical positioning. In this work, we optimize the topology of a total ossicular replacement prosthesis, by maximizing the global stiffness and under the smallest possible volume constraint that ensures material continuity. This investigation optimizes the prosthesis topology in response to static displacement loads with amplitudes that normally occur during sound stimulation in a frequency range between 100 Hz and 10 kHz. Following earlier studies, we discuss how the presence and arrangement of holes on the surface of the prosthesis plate in contact with the umbo affect the overall geometry. Finally, we validate the designs through a finite-element model, in which we assess the prosthesis performance upon dynamic sound pressure loads by considering four different constitutive materials: titanium, cortical bone, silk, and collagen/hydroxyapatite. The results show that the selected prostheses present, almost independently of their constitutive material, a vibroacustic behavior close to that of the native ossicular chain, with a slight almost constant positive shift that reaches a maximum of ≈5 dB close to 1 kHz. This work represents a reference for the development of a new generation of middle ear prostheses with non-conventional topologies for fabrication via additive manufacturing technologies or ultraprecision machining in order to create patient-specific devices to recover from conductive hearing loss.

Sensor-actuator component for a Floating Mass Transducer-based fully implantable hearing aid

We propose a novel system based on the Floating Mass Transducer (FMT) to be used as the active component of a fully implantable, Vibrant Soundbridge-like middle ear implant. The new system replaces the external microphone used in the currently available design with an implantable piezoelectric sensor that is inserted into the incudostapedial joint and picks up the vibrations transmitted to the long process of the incus. The FMT is coupled to the round window of the cochlea. We characterize the system by measuring the gain in intracochlear sound pressure using laser Doppler vibrometry at a surgically installed "third window" into the cochlea of six temporal bones. Closed-loop feedback oscillations limit the system's available output. We show that using an adaptive control algorithm, a mean functional gain of up to 40 dB is achieved, which is similar to Soundbridge functional gain. The concept matches the FMT's one-point fixation philosophy and offers several advantages over other designs, namely an easy and time-efficient surgery, reversibility of implantation, and natural hearing for the prospective patient.

Static and dynamic forces in the incudostapedial joint gap

Dynamic pressure at the tympanic membrane is transformed and subsequently transferred through the ossicular chain in the form of forces and moments. The forces are primarily transferred to the inner ear. They are transferred partly to the stapedial annular ligament which exhibits non-linear behavior and stiffens for larger static forces. In unventilated middle ears, static pressure is additionally transferred to the ossicles. The purpose of this study was to measure the force inside the ossicular chain as a physiological parameter. We determined the forces which act for dynamic sound transmission and for static load on the ossicular chain. The study is the first one which introduces these forces. The static forces have direct impact on clinically relevant questions for middle ear reconstructions with passive or active prosthesis. The dynamic forces have an impact on the development of middle ear sensors. Quasi-static forces in the incudostapedial joint (ISJ) gap were measured with two different sensor types in 17 temporal bones. The sensing elements, a single crystal piezo and a strain gauge element for validation, were bonded to a thin flexible titanium plate and encapsulated in a titanium housing to allow the acquisition of the applied force signal inside the ossicular chain. Dynamic forces were measured in 11 temporal bones with the piezo sensor. We measured a static force of 23 mN in the ISJ after sensor insertion. The mean force for dynamic physiological acoustic excitation from 250 Hz to 6 kHz was 26 μN/Pa. If the tympanic membrane is loaded with a static pressure, the static force in the ISJ increases up to 1 N for a maximum static pressure load scenario of 30 kPa.

Multiphoton imaging for morphometry of the sandwich-beam structure of the human stapedial annular ligament

BACKGROUND

The annular ligament of the human stapes constitutes a compliant connection between the stapes footplate and the peripheral cochlear wall at the oval window. The cross section of the human annular ligament is characterized by a three-layered structure, which resembles a sandwich-shaped composite structure. As accurate and precise descriptions of the middle-ear behavior are constrained by lack of information on the complex geometry of the annular ligament, this study aims to obtain comprehensive geometrical data of the annular ligament via multiphoton imaging.

METHODS

The region of interest containing the stapes and annular ligament was harvested from a fresh-frozen human temporal bone of a 46-years old female. Multiphoton imaging of the unstained sample was performed by detecting the second-harmonic generation of collagen and the autofluorescence of elastin, which are constituents of the annular ligament. The multiphoton scans were conducted on the middle-ear side and cochlear side of the annular ligament to obtain accurate images of the face layers on both sides. The face layers of the annular ligament were manually segmented on both multiphoton scans, and then registered to high-resolution μCT images.

RESULTS

Multiphoton scans of the annular ligament revealed 1) relatively large thickness of the core layer compared to the face layers, 2) asymmetric geometry of the face layers between the middle-ear side and cochlear side, and variation of their thickness and width along the footplate boundary, 3) divergent relative alignment of the two face layers, and 4) different fiber composition of the face layers along the boundary with a collagen-reinforcement near the anterior pole on the middle-ear side.

CONCLUSION AND OUTLOOK

Multiphoton microscopy is a feasible approach to obtain the detailed three-dimensional features of the human stapedial annular ligament along its full boundary. The detailed description of the sandwich-shaped structures of the annular ligament is expected to contribute to modeling of the human middle ear for precise simulation of middle-ear behavior. Further, established methodology in this study may be applicable to imaging of other middle-ear structures.

Effects of tympanic membrane perforation on middle ear transmission in gerbil

Perforations of the tympanic membrane (TM) alter its structural and mechanical properties, thus resulting in a deterioration of sound transmission through the middle ear (ME), which presents itself clinically as a conductive hearing loss (CHL). The resulting CHL is proposed to be due to the loss of the pressure difference across the TM between the outer ear canal space and the ME cavity, a hypothesis which has been tested with both theoretical and experimental approaches. In the past, direct experimental observations had been either from the ME input (umbo) or the output of the stapes, and were focused mainly on the low frequency region. However, there was little documentation providing a thorough picture of the influence of systematically increasing sizes of TM perforations on ME sound transmission from the input (i.e., pressure at the TM or motion of the umbo) to the output (pressure produced by the motion of the stapes). Our study explored ME transmission in gerbil under conditions of a normal, intact TM followed by the placement of mechanically-induced TM perforations ranging from miniscule to complete removal of the pars tensa, leaving the other parts of ME intact. Testing up to 50 kHz, variations of ME transmission were characterized in simultaneously measured tone induced pressure responses at the TM (P_TM), pressure responses in the scala vestibuli next to the stapes (P_SV), and velocity measurements of the umbo (V_umbo), as well as by detailed descriptions of sound transmission from the TM to the stapes, i.e., the umbo transfer function (TF), the transfer of the sound stimulus along the ossicular chain as found from the ratio of cochlear pressure to umbo motion, and ME pressure gain (MEPG). Our results suggested that increasing the size of TM perforations led to a reduction in MEPG, which appeared to be primarily due to the reduction in the effective/initial mechanical drive to the umbo, with a relatively smaller decrease of sound transfer along the ossicular chain. Expansion of the perforation more than 25% appeared to drastically reduce sound transmission through the ME, especially for the higher frequencies.

Development of intra-operative assessment system for ossicular mobility and middle ear transfer function

Objective measurements of the ossicular mobility have not been commonly performed during the surgery, and the assessment of ossicular mobility is made by palpation in most cases. Palpation is inherently subjective and may not always be reliable, especially in milder degrees of ossicular fixation and in the case of multiple fixation. Although several devices have been developed to quantitatively measure the ossicular mobility during surgery, they have not been widely used. In this study, a new system with a hand-held probe which enables intraoperative quantitative measurements of ossicular mobility has been developed. This system not only measures the ossicular mobility, but also investigates "local" transmission characteristics of the middle ear by directly applying vibration to the ossicles and measuring cochlear microphonic. The basic performance of this system was confirmed by measuring the mobility of artificial ossicles and cochlear microphonics in an animal experiment. Our system may contribute to selection of a better surgical method and reducing the risks of revision surgery.

Impedances of the inner and middle ear estimated from intracochlear sound pressures in normal human temporal bones

For almost a decade, we have measured intracochlear sound pressures evoked by air conducted (AC) sound presented to the ear canal in many fresh human cadaveric specimens. Similar measurements were also obtained during round window (RW) mechanical stimulation in multiple specimens. In the present study, we use our accumulated data of intracochlear pressures and simultaneous velocity measurements of the stapes or RW to determine acoustic impedances of the cochlear partition, RW, and the leakage paths from scala vestibuli and scala tympani, as well as the reverse middle ear impedance. With these impedances, we develop a computational lumped-element model of the normal ear that illuminates fundamental mechanisms of sound transmission. To calculate the impedances for our model, we use data that passes strict inclusion criteria of: (a) normal middle-ear transfer function defined as the ratio of stapes velocity to ear-canal sound pressure, (b) no evidence of air within the inner ear, and (c) tight control of the pressure sensor sensitivity. After this strict screening, updated normal means, as well as individual representative data, of ossicular velocities and intracochlear pressures for AC and RW stimulation are used to calculate impedances. This work demonstrates the existence and the value of physiological acoustic leak impedances that can sometimes contribute significantly to sound transmission for some stimulation modalities. This model allows understanding of human sound transmission mechanisms for various sound stimulation methods such as AC, RW, and bone conduction, as well as sound transmission related to otoacoustic emissions.

Human ossicular-joint flexibility transforms the peak amplitude and width of impulsive acoustic stimuli

The role of the ossicular joints in the mammalian middle ear is still debated. This work tests the hypothesis that the two synovial joints filter potentially damaging impulsive stimuli by transforming both the peak amplitude and width of these impulses before they reach the cochlea. The three-dimensional (3D) velocity along the ossicular chain in unaltered cadaveric human temporal bones (N = 9), stimulated with acoustic impulses, is measured in the time domain using a Polytec (Waldbronn, Germany) CLV-3D laser Doppler vibrometer. The measurements are repeated after fusing one or both of the ossicular joints with dental cement. Sound transmission is characterized by measuring the amplitude, width, and delay of the impulsive velocity profile as it travels from the eardrum to the cochlea. On average, fusing both ossicular joints causes the stapes velocity amplitude and width to change by a factor of 1.77 (p = 0.0057) and 0.78 (p = 0.011), respectively. Fusing just the incudomalleolar joint has a larger effect on amplitude (a factor of 2.37), while fusing just the incudostapedial joint decreases the stapes velocity on average. The 3D motion of the ossicles is altered by fusing the joints. Finally, the ability of current computational models to predict this behavior is also evaluated.

Intracochlear pressure measurements during acoustic shock wave exposure

INTRODUCTION

Injuries to the peripheral auditory system are among the most common results of high intensity impulsive acoustic exposure. Prior studies of high intensity sound transmission by the ossicular chain have relied upon measurements in animal models, measurements at more moderate sound levels (i.e. < 130 dB SPL), and/or measured responses to steady-state noise. Here, we directly measure intracochlear pressure in human cadaveric temporal bones, with fiber optic pressure sensors placed in scala vestibuli (SV) and tympani (ST), during exposure to shock waves with peak positive pressures between ∼7 and 83 kPa.

METHODS

Eight full-cephalic human cadaver heads were exposed, face-on, to acoustic shock waves in a 45 cm diameter shock tube. Specimens were exposed to impulses with nominal peak overpressures of 7, 28, 55, & 83 kPa (171, 183, 189, & 192 dB pSPL), measured in the free field adjacent to the forehead. Specimens were prepared bilaterally by mastoidectomy and extended facial recess to expose the ossicular chain. Ear canal (EAC), middle ear, and intracochlear sound pressure levels were measured with fiber-optic pressure sensors. Surface-mounted sensors measured SPL and skull strain near the opening of each EAC and at the forehead.

RESULTS

Measurements on the forehead showed incident peak pressures approximately twice that measured by adjacent free-field and EAC entrance sensors, as expected based on the sensor orientation (normal vs tangential to the shock wave propagation). At 7 kPa, EAC pressure showed gain, calculated from the frequency spectra, consistent with the ear canal resonance, and gain in the intracochlear pressures (normalized to the EAC pressure) were consistent with (though somewhat lower than) previously reported middle ear transfer functions. Responses to higher intensity impulses tended to show lower intracochlear gain relative to EAC, suggesting sound transmission efficiency along the ossicular chain is reduced at high intensities. Tympanic membrane (TM) rupture was observed following nearly every exposure 55 kPa or higher.

CONCLUSIONS

Intracochlear pressures reveal lower middle-ear transfer function magnitudes (i.e. reduced gain relative to the ear canal) for high sound pressure levels, thus revealing lower than expected cochlear exposure based on extrapolation from cochlear pressures measured at more moderate sound levels. These results are consistent with lowered transmissivity of the ossicular chain at high intensities, and are consistent with our prior report measuring middle ear transfer functions in human cadaveric temporal bones with high intensity tone pips.

Analysis of the Mechanical Properties of the Human Tympanic Membrane and Its Influence on the Dynamic Behaviour of the Human Hearing System

The difficulty to estimate the mechanical properties of the tympanic membrane (TM) is a limitation to understand the sound transmission mechanism. In this paper, based on finite element calculations, the sensitivity of the human hearing system to these properties is evaluated. The parameters that define the bending stiffness properties of the membrane have been studied, specifically two key parameters: Young's modulus of the tympanic membrane and the thickness of the eardrum. Additionally, it has been completed with the evaluation of the presence of an initial prestrain inside the TM. Modal analysis is used to study the qualitative characteristics of the TM comparing with vibration patterns obtained by holography. Higher-order modes are shown as a tool to identify these properties. The results show that different combinations of elastic properties and prestrain provide similar responses. The presence of prestrain at the membrane adds more uncertainty, and it is pointed out as a source for the lack of agreement of some previous TM elastic modulus estimations.

[New clinical applications for laser Doppler vibrometry in otology]

BACKGROUND

An instrument to measure vibration in the middle ear needs to be sensitive enough to detect displacement on a nanometer scale, yet not affect the vibration itself. Numerous techniques have been described in the literature, but laser Doppler vibrometry (LDV) has nowadays become established as the standard method in hearing research.

OBJECTIVE

This article aims to present possible clinical applications of an LDV system in otology.

MATERIALS AND METHODS

A commercially available single-point vibrometer was used. Measurements were carried out both with the sensor head mounted on an operating microscope and as a handheld device with the sensor head manually inserted in the ear canal. For the latter, a custom-made unit containing an electrically tunable lens was attached to the sensor head. Middle ear vibrations were measured in a temporal bone model as well as in patients during and after implantation of a Vibrant Soundbridge (VSB; MED-EL Corp., Durham/NC, USA).

RESULTS

Different types of middle ear pathologies can be distinguished by the frequency response of the umbo. The LDV technique can be used for intraoperative quantification of the coupling quality of the VSB's Floating Mass Transducer (FMT; MED-EL) to the ossicle chain during VSB implantation. Postoperatively, the method serves as a follow-up testing tool if a deterioration in aided hearing threshold occurs. The measurement can reveal changes in the umbo transfer function, e. g., due to middle ear scarring or dislocation of the FMT.

CONCLUSION

Many clinical questions in otology can be addressed by LDV. However, due to the high acquisition costs of an LDV system, the relatively large instrumental setup, and the large inter-ear variability of middle-ear function, the technique has not (yet) become established in clinical routine.

Validation of methods for prediction of clinical output levels of active middle ear implants from measurements in human cadaveric ears

Today, the standard method to predict output levels of active middle ear implants (AMEIs) before clinical data are available is stapes vibration measurement in human cadaveric ears, according to ASTM standard F2504-05. Although this procedure is well established, the validity of the predicted output levels has never been demonstrated clinically. Furthermore, this procedure requires a mobile and visually accessible stapes and an AMEI stimulating the ossicular chain. Thus, an alternative method is needed to quantify the output level of AMEIs in all other stimulation modes, e.g. reverse stimulation of the round window. Intracochlear pressure difference (ICPD) is a good candidate for such a method as it correlates with evoked potentials in animals and it is measurable in cadaveric ears. To validate this method we correlated AMEI output levels calculated from ICPD and from stapes vibration in cadaveric ears with outputs levels determined from clinical data. Output levels calculated from ICPD were similar to output levels calculated from stapes vibration and almost identical to clinical data. Our results demonstrate that both ICPD and stapes vibration can be used as a measure to predict AMEI clinical output levels in cadaveric ears and that ICPD as reference provided even more accurate results.

Middle-Ear Sound Transmission Under Normal, Damaged, Repaired, and Reconstructed Conditions

HYPOTHESIS

We hypothesize that current clinical treatment strategies for the disarticulated or eroded incus have the effect of combining the incus and stapes of the human middle ear (ME) into one rigid structure, which, while capable of adequately transmitting lower-frequency sounds, fails for higher frequencies.

BACKGROUND

ME damage causes conductive hearing loss (CHL) and while great progress has been made in repairing or reconstructing damaged MEs, the outcomes are often far from ideal.

METHODS

Temporal bones (TBs) from human cadavers, a laser Doppler vibrometer (LDV), and a fiber-optic based micro-pressure sensor were used to characterize ME transmission under various ME conditions: normal; with a disarticulated incus; repaired using medical glue; or reconstructed using a partial ossicular replacement prosthesis (PORP).

RESULTS

Repairing the disarticulated incus using medical glue, or replacing the incus using a commercial PORP, provided similar restoration of ME function including almost perfect function at frequencies below 4 kHz, but with more than a 20-dB loss at higher frequencies. Associated phase responses under these conditions sometimes varied and seemed dependent on the degree of coupling of the PORP to the remaining ME structure. A new ME-prosthesis design may be required to allow the stapes to move in three-dimensional (3-D) space to correct this deficiency at higher frequencies.

CONCLUSIONS

Fixation of the incus to the stapes or ossicular reconstruction using a PORP limited the efficiency of sound transmission at high frequencies.

Stapes displacement and intracochlear pressure in response to very high level, low frequency sounds

The stapes is held in the oval window by the stapedial annular ligament (SAL), which restricts total peak-to-peak displacement of the stapes. Previous studies have suggested that for moderate (<130 dB SPL) sound levels intracochlear pressure (P_IC), measured at the base of the cochlea far from the basilar membrane, increases directly proportionally with stapes displacement (D_Stap), thus a current model of impulse noise exposure (the Auditory Hazard Assessment Algorithm for Humans, or AHAAH) predicts that peak P_IC will vary linearly with D_Stap up to some saturation point. However, no direct tests of D_Stap, or of the relationship with P_IC during such motion, have been performed during acoustic stimulation of the human ear. In order to examine the relationship between D_Stap and P_IC to very high level sounds, measurements of D_Stap and P_IC were made in cadaveric human temporal bones. Specimens were prepared by mastoidectomy and extended facial recess to expose the ossicular chain. Measurements of P_IC were made in scala vestibuli (P_SV) and scala tympani (P_ST), along with the SPL in the external auditory canal (P_EAC), concurrently with laser Doppler vibrometry (LDV) measurements of stapes velocity (V_Stap). Stimuli were moderate (∼100 dB SPL) to very high level (up to ∼170 dB SPL), low frequency tones (20-2560 Hz). Both D_Stap and P_SV increased proportionally with sound pressure level in the ear canal up to approximately ∼150 dB SPL, above which both D_Stap and P_SV showed a distinct deviation from proportionality with P_EAC. Both D_Stap and P_SV approached saturation: D_Stap at a value exceeding 150 μm, which is substantially higher than has been reported for small mammals, while P_SV showed substantial frequency dependence in the saturation point. The relationship between P_SV and D_Stap remained constant, and cochlear input impedance did not vary across the levels tested, consistent with prior measurements at lower sound levels. These results suggest that P_SV sound pressure holds constant relationship with D_Stap, described by the cochlear input impedance, at these, but perhaps not higher, stimulation levels. Additionally, these results indicate that the AHAAH model, which was developed using results from small animals, underestimates the sound pressure levels in the cochlea in response to high level sound stimulation, and must be revised.

Finite-Element Modelling of the Acoustic Input Admittance of the Newborn Ear Canal and Middle Ear

Admittance measurement is a promising tool for evaluating the status of the middle ear in newborns. However, the newborn ear is anatomically very different from the adult one, and the acoustic input admittance is different than in adults. To aid in understanding the differences, a finite-element model of the newborn ear canal and middle ear was developed and its behaviour was studied for frequencies up to 2000 Hz. Material properties were taken from previous measurements and estimates. The simulation results were within the range of clinical admittance measurements made in newborns. Sensitivity analyses of the material properties show that in the canal model, the maximum admittance and the frequency at which that maximum admittance occurs are affected mainly by the stiffness parameter; in the middle-ear model, the damping is as important as the stiffness in influencing the maximum admittance magnitude but its effect on the corresponding frequency is negligible. Scaling up the geometries increases the admittance magnitude and shifts the resonances to lower frequencies. The results suggest that admittance measurements can provide more information about the condition of the middle ear when made at multiple frequencies around its resonance.

Modelling the effect of round window stiffness on residual hearing after cochlear implantation

Preservation of residual hearing after cochlear implantation is now considered an important goal of surgery. However, studies indicate an average post-operative hearing loss of around 20 dB at low frequencies. One factor which may contribute to post-operative hearing loss, but which has received little attention in the literature to date, is the increased stiffness of the round window, due to the physical presence of the cochlear implant, and to its subsequent thickening or to bone growth around it. A finite element model was used to estimate that there is approximately a 100-fold increase in the round window stiffness due to a cochlear implant passing through it. A lumped element model was then developed to study the effects of this change in stiffness on the acoustic response of the cochlea. As the round window stiffness increases, the effects of the cochlear and vestibular aqueducts become more important. An increase of round window stiffness by a factor of 10 is predicted to have little effect on residual hearing, but increasing this stiffness by a factor of 100 reduces the acoustic sensitivity of the cochlea by about 20 dB, below 1 kHz, in reasonable agreement with the observed loss in residual hearing after implantation. It is also shown that the effect of this stiffening could be reduced by incorporating a small gas bubble within the cochlear implant.

Acoustic effects of the reconstructed lateral epitympanic wall in a temporal bone and clinical study

OBJECTIVE

Acoustic evaluation of reconstruction of the lateral epitympanic wall with bone or cartilage in a temporal bone study, and evaluation of audiometric data of patients who underwent cholesteatoma surgery with reconstruction of the lateral epitympanic wall with horseshoe-shaped cartilage.

STUDY DESIGN

Temporal bone study and retrospective chart review.

METHODS

Preparation of temporal bones included reconstruction of the epitympanic wall with fixated and loose cartilage and bone. The volume velocities of the stapes footplate were measured from the inner-ear side of the footplate by laser scanning doppler vibrometry following sound stimulation in the outer ear canal. Additionally, the audiometric data of 13 consecutive patients who underwent epitympanic cholesteatoma surgery, with an intact ossicular chain and reconstruction of the scutum with a horseshoe-shaped cartilage in contact with the malleus' neck, were evaluated retrospectively.

RESULTS

The experimental results showed similar volume velocities at the stapes footplate for the fixated and unfixated cartilage as well as for the unfixated bone. However, the fixated bone yielded significantly reduced volume velocities. Clinical data confirmed that the cartilaginous horseshoe- technique allowed for a stable reconstruction of the scutum with satisfying audiometric outcome.

CONCLUSION

In case of cholesteatoma surgery and the need for the reconstruction of the scutum, no adverse effects on hearing outcome are to be expected by using the malleus' neck as an anchoring point for cartilaginous scutum reconstruction.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:1427-1434, 2017.

Objective Measurements of Ossicular Chain Mobility Using a Palpating Instrument Intraoperatively

BACKGROUND

The judgment of a normal or impaired mobility of middle ear ossicles is based on palpation and depends highly on the surgeon's subjective experience. The aim of this study was to develop and test a palpating instrument recording force and vector and allowing to support the surgeon's subjective impression with objective measurement results.

STUDY DESIGN

Prospective recordings at surgery.

SETTING

Tertiary referral center.

PATIENTS AND METHODS

A fiberoptic force-sensing element allowing force measures in three orthogonal directions was integrated into a handheld 45 degree hook and tested in temporal bones. Clinical data series from patients with a functionally normal chain (e.g., cochlear implants (CI)) and impaired ossicles (otosclerosis) were collected. The ossicles were palpated until their first movements out of the resting stage were visualized, the applied force, and vector were recorded by an independent observer.

RESULTS

Four CI and 19 otosclerosis patients were further evaluated. The minimum detectable force change of the sensor was 0.2 gF (2 mN). In the otosclerosis patients the average force applied to move the malleus was 9.5 gF, on the incus 8.7 gF. These values were slightly lower after separation of the incudostapedial joint, reaching 8.5 gF and 6.9 gF, respectively. The fixed stapes showed a rigidity of 14.7 gF or higher. The values were lower in the CI group measuring 4.4 gF, 4.1 gF, and 3.3 gF on the three ossicles, respectively.

CONCLUSIONS

We were able to produce a disposable, easy-to-handle palpating probe that enables the otologist to record continuously tip contact forces in three dimensions during his standard palpation of each ossicle. Normative values were reproduced for each ossicle, as well as increased rates for stapes fixation in otosclerosis.

First results of a novel adjustable-length ossicular reconstruction prosthesis in temporal bones

OBJECTIVES/HYPOTHESIS

The performance of an ossicular replacement prosthesis (ORP) is influenced by its alignment and appropriate tension between the tympanic membrane and the stapes footplate. A novel ORP with a flexible element that potentially allows for length adjustment in situ is presented and tested for acoustic performance.

STUDY DESIGN

Laser Doppler vibrometry in fresh human cadaveric temporal bones was used to test the acoustic performance of the adjustable ORP relative to standard prostheses used for ossiculoplasty.

METHODS

The three-dimensional (3D) velocity of the stapes posterior crus was measured in the 0.2- to 20-kHz range using a Polytec CLV-3D laser Doppler vibrometer. The middle ear cavity was accessed through a facial recess approach. After measuring the normal response, the incus was removed and stapes velocity was measured in the disarticulated case, then after insertion of the new prosthesis, a conventional prosthesis (Kurz BELL Dusseldorf type), and a sculpted autologous incus prosthesis in each temporal bone. The 3D stapes velocity transfer function (SVTF) was calculated for each case and compared.

RESULTS

The novel ORP design restored stapes velocity to within 6 dB (on average) of the intact response. No significant differences in 3D-SVTF were found between the new, conventional, or autologous ORPs.

CONCLUSIONS

The inclusion of an in situ adjustable element into the ORP design did not adversely affect its acoustic performance. The adjustable element may increase the ease of achieving optimal ORP placement, especially through a facial recess approach.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:2559-2564, 2016.

Outcomes with gold wire and hydroxyapatite partial ossicular replacement prostheses in type 2 tympanoplasty: a preliminary study

OBJECTIVES

To compare the hearing results and graft take rates of the recently developed gold wire prosthesis with those of the hydroxyapatite partial ossicular replacement prosthesis in patients with chronic otitis media.

METHOD

This retrospective study examined patients who underwent type 2 tympanoplasty with a minimum follow up of one year. The study population consisted of 32 patients in the partial ossicular replacement prosthesis group and 26 patients in the gold wire group. The main outcome measures were the graft success rate and level of hearing improvement. Complications and extrusion rates were also noted.

RESULTS

The graft take rate was 90.6 per cent for the partial ossicular replacement prosthesis group and 92.3 per cent for the gold wire group (p = 0.848). Pre-operatively, there were no significant differences in the air or bone-conduction thresholds between groups. Post-operatively, the mean hearing gain was 18.5 ± 14.0 dB in the partial ossicular replacement prosthesis group and 16.5 ± 10.6 dB in the gold wire group (p = 0.555). The mean air-conduction thresholds were 26.6 ± 12.4 and 32.6 ± 10.5 dB, respectively (p = 0.027), and the mean bone-conduction thresholds were 9.7 ± 7.0 and 10.4 ± 6.4 dB, respectively (p = 0.687).

CONCLUSION

The success and complication rates provided by the gold wire prosthesis seem comparable to those of the hydroxyapatite partial ossicular replacement prosthesis.