Malleus-incus Complex Research Articles

Improved radiological imaging of congenital aural atresia using flat-panel volume CT. German version

Precise preoperative radiological evaluation of aural atresia is of utmost importance for surgical planning. Until now, multislice computed tomography (MSCT) has been used but it cannot adequately visualize small structures such as the stapes. Flat-panel volume CT (fpVCT) with its secondary reconstructions (fpVCTSECO) offers ahigh-resolution visualization of the middle ear. New otosurgical planning software also enables detailed 3D reconstruction of the middle ear anatomy. Evaluation of the use of fpVCTSECO in combination with an otosurgical planning software for amore accurate diagnosis and treatment of congenital aural atresia. Sevenpatients with congenital aural atresia underwent preoperative MSCT (600 µm slice thickness) and corresponding fpVCT (466 µm slice thickness). In addition, fpVCTSECO (99 µm slice thickness) were reconstructed. The Jahrsdoerfer and Siegert grading scores were determined and their applicability in the abovementioned imaging modalities was evaluated. In addition, the malleus incus complex was analyzed in 3D rendering. Imaging with fpVCTSECO enabled reliable visualization of the abnormalities, in particular the ossicular chain. Asignificant difference in the Siegert grading score was found. In addition, the malleus-incus complex could be visualized better in 3D. The introduction of new imaging techniques and surgical planning techniques into the diagnostic concept of aural atresia facilitates the identification of malformed anatomy and enables systematic analysis. This combination can also help to more accurately classify the pathology and thus increase the safety and success of the surgical procedure.

Analysis of medium and long term efficacy of ossicle chain bypass technique in treatment of tympanosclerosis

Objective:For tympanosclerosis patients with ossicular chain fixation, we use ossicular chain bypass technique and evaluate its long-term effects. Methods:From June 2017 to June 2019, 147 patients with tympanosclerosis who underwent middle ear surgery with otoscopy in Yinchuan First People's Hospital were reviewed. The subjects were divided into three groups according to the implemented operation plan, 51 cases in the ossicular chain mobilization group（OCM）, 56 cases in the ossicular chain bypass reconstruction group（OCB）, and 40 cases in the malleus-incus complex resection reconstruction group（MICR）. Through a three-year follow-up, the medium and long-term effects of different operation plans were compared and analyzed. Results:There was no significant difference among the three groups in the incidence of tympanic membrane perforation, delayed facial nerve palsy, and the dispatch and displacement of PORP. The incidence of tympanic membrane retraction pocket or cholesteatoma after operation in OCB group（0） was significantly lower than that in OCM group（11.76%） and MICR group（7.5%）（P<0.05）. At 12 months after operation, ΔABG of OCB group and MICR group were better than that in the OCM group（P<0.05）. At 36 months after operation, ΔABG of OCB group was better than that in the OCM group（P<0.05）, and there was no significant difference between OCB group and MICR group. The audiological performance of patients with epitympanic sclerosis（ETS） at 12, 24 and 36 months after operation was better than that of patients with posterior tympanosclerosis（PTS） and total tympanosclerosis（TTS）（P<0.05）. Conclusion:Compared with patients undergoing ossicular chain mobilization and malleus-incus complex resection for ossicular chain reconstruction, patients with tympanosclerosis undergoing bypass technique have better and stable hearing prognosis in medium and long term. This technique can effectively prevent the formation of retracted pocket and cholesteatoma in patients with tympanosclerosis after operation.

Three-dimensional quasi-static displacement of human middle-ear ossicles under static pressure loads: Measurement using a stereo camera system

The time delay and/or malfunctioning of the Eustachian tube may cause pressure differences across the tympanic membrane, resulting in quasi-static movements of the middle-ear ossicles. While quasi-static displacements of the human middle-ear ossicles have been measured one- or two-dimensionally in previous studies, this study presents an approach to trace three-dimensional movements of the human middle-ear ossicles under static pressure loads in the ear canal (EC). The three-dimensional quasi-static movements of the middle-ear ossicles were measured using a custom-made stereo camera system. Two cameras were assembled with a relative angle of 7° and then mounted onto a robot arm. Red fluorescent beads of a 106–125 µm diameter were placed on the middle-ear ossicles, and quasi-static position changes of the fluorescent beads under static pressure loads were traced by the stereo camera system. All the position changes of the ossicles were registered to the anatomical intrinsic frame based on the stapes footplate, which was obtained from µ-CT imaging. Under negative ear-canal pressures, a rotational movement around the anterior-posterior axis was dominant for the malleus-incus complex, with small relative movements between the two ossicles. The stapes showed translation toward the lateral direction and rotation around the long axis of the stapes footplate. Under positive EC pressures, relative motion between the malleus and the incus at the IMJ became larger, reducing movements of the incus and stapes considerably and thus performing a protection function for the inner-ear structures. Three-dimensional tracing of the middle-ear ossicular chain provides a better understanding of the protection function of the human middle ear under static pressured loads as immediate responses without time delay.

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.

Combined analysis of finite element model and audiometry provides insights into the pathogenesis of conductive hearing loss.

The middle ear transmits sound to the inner ear via vibrations in the eardrum and ossicles, and damage to the middle ear results in conductive hearing loss. Although conductive hearing loss can be corrected by surgery, the currently available clinical investigations cannot always diagnose the ossicular chain pathology underlying the conductive hearing loss, and even intraoperative findings can be equivocal. Acoustic analysis using finite element models (FEMs) can simulate the sound pressure change at an arbitrary site for each frequency. FEMs are used in acoustic engineering to simulate the frequency-dependent sound pressure distribution at discrete cells in a simulated model and analyze the effects of specific parameters on the audiogram. However, few reports have compared the numerical results obtained using FEMs with data from clinical cases. We used FEMs to simulate audiograms of the air-bone gap (ABG) for various ossicular chain defects and compared these with preoperative audiograms obtained from 44 patients with a normal tympanic membrane who had otosclerosis, middle ear malformations or traumatic ossicular disruption. The simulated audiograms for otosclerosis and attic fixation of the malleus-incus complex both exhibited an up-slope but could be distinguished from each other based on the ABG at 1000 Hz. The simulated audiogram for incudostapedial joint discontinuity exhibited a peak at around 750 Hz and a down-slope above 1000 Hz. In general, the simulated audiograms for otosclerosis, attic fixation and incudostapedial joint discontinuity were consistent with those obtained from clinical cases. Additional simulations indicated that changes in ossicular mass had relatively small effects on ABG. Furthermore, analyses of combination pathologies suggested that the effects of one defect on ABG were added to those of the other defect. These FEM-based findings provide insights into the pathogenesis of conductive hearing loss due to otosclerosis, middle ear malformations and traumatic injury.

The impact of tympanic membrane perforations on middle ear transfer function

PurposeInjury or inflammation of the middle ear often results in the persistent tympanic membrane (TM) perforations, leading to conductive hearing loss (HL). However, in some cases the magnitude of HL exceeds that attributable by the TM perforation alone. The aim of the study is to better understand the effects of location and size of TM perforations on the sound transmission properties of the middle ear.MethodsThe middle ear transfer functions (METF) of six human temporal bones (TB) were compared before and after perforating the TM at different locations (anterior or posterior lower quadrant) and to different degrees (1 mm, ¼ of the TM, ½ of the TM, and full ablation). The sound-induced velocity of the stapes footplate was measured using single-point laser-Doppler-vibrometry (LDV). The METF were correlated with a Finite Element (FE) model of the middle ear, in which similar alterations were simulated.ResultsThe measured and calculated METF showed frequency and perforation size dependent losses at all perforation locations. Starting at low frequencies, the loss expanded to higher frequencies with increased perforation size. In direct comparison, posterior TM perforations affected the transmission properties to a larger degree than anterior perforations. The asymmetry of the TM causes the malleus-incus complex to rotate and results in larger deflections in the posterior TM quadrants than in the anterior TM quadrants. Simulations in the FE model with a sealed cavity show that small perforations lead to a decrease in TM rigidity and thus to an increase in oscillation amplitude of the TM mainly above 1 kHz.ConclusionSize and location of TM perforations have a characteristic influence on the METF. The correlation of the experimental LDV measurements with an FE model contributes to a better understanding of the pathologic mechanisms of middle-ear diseases. If small perforations with significant HL are observed in daily clinical practice, additional middle ear pathologies should be considered. Further investigations on the loss of TM pretension due to perforations may be informative.

Exploring ancestral phenotypes and evolutionary development of the mammalian middle ear based on Early Cretaceous Jehol mammals.

We report a new Cretaceous multituberculate mammal with 3D auditory bones preserved. Along with other fossil and extant mammals, the unequivocal auditory bones display features potentially representing ancestral phenotypes of the mammalian middle ear. These phenotypes show that the ectotympanic and the malleus-incus complex changed notably during their retreating from the dentary at various evolutionary stages and suggest convergent evolution of some features to extant mammals. In contrast, the incudomalleolar joint was conservative in having a braced hinge configuration, which narrows the morphological gap between the quadroarticular jaw joint of non-mammalian cynodonts and the incudomalleolar articulations of extant mammals. The saddle-shaped and abutting malleus-incus complexes in therians and monotremes, respectively, could have evolved from the braced hinge joint independently. The evolutionary changes recorded in the Mesozoic mammals are largely consistent with the middle ear morphogenesis during the ontogeny of extant mammals, supporting the relation between evolution and development.

Predictive Factors for Hearing Outcomes After Canaloplasty in Patients With Congenital Aural Atresia.

The aim of this study was to determine the most important factors in preoperative imaging, including components of Jahrsdoefer score (J score), and favorable prognostic factors for postoperative hearing results after canaloplasty for congenital aural atresia. Retrospective review of medical records. One hundred eight patients who underwent canaloplasty by a single surgeon between January 2011 and July 2014 were included. The influence of the following factors on the success for restoring of hearing was evaluated by univariable and multivariable logistic regression analyses: sex, atretic side, total J score, each component of Jahrsdoerfer grading scale, incudostapedial joint angle, inferior displacement of the tegmen, middle ear height, and inner ear anomaly. Successful hearing outcome was defined as postoperative air conduction ≤40 dB at 3 months after surgery, and it was achieved in 74 of 108 ears (70.5%). Univariable analysis revealed that the total J score, course of the facial nerve, presence of the malleus-incus complex, pneumatization of the mastoid, and middle ear height were significant as favorable predictive factors. Multivariable analysis revealed that middle ear height and inferior displacement of the tegmen were significant as favorable predictive factors. Inferior displacement of the tegmen was the most significant factor by the stepwise selection method in the final model. Middle ear height and inferior displacement of the tegmen are useful factors in predicting favorable hearing results after canaloplasty for congenital aural atresia. These factors might have a useful prognostic value supplementary to the J score.

Results of VSB implantation at the short process of the incus in children with ear atresia

Objective(s)To describe a new and more simple surgical procedure for implanting the Vibrant Soundbridge (VSB) on the short process of the incus in children with ear atresia and atretic plate and present the audiometric results. MethodsSince 2014, pre- and post-operative audiometric tests with tonal and vocal audiometryat the maximal follow up, respectively 33, 22 and 12 months were performed after VSB implantation at the ENT department, Necker Enfants Malades Hospital, Paris, France. 3 children aged 11, 9 and 15 years with conductive hearing loss due to high grade ear atresia and absent ear canal were implanted. The malformed and fused malleus-incus complex was found to be immobile in two of the subjects, who then underwent a superior tympanotomy to carefully remobilize the malleus. Stapes were mobile in all cases. The FMT clip was customized and crimped on the short process, stabilized by the metallic wire. ResultsAt the maximum follow-up time, the bone conduction was unchanged, and the mean aided ACPTA was 21 dB, 29 dB and 30 dB, compared to 66 dB, 63 dB and 68 dB unaided, respectively. The word recognition score (WRS) at 65 dB SPL increased from 10%, 10% and 70% (unaided) respectively to 100% (aided). ConclusionsThe long process of the incus is usually very hypoplastic in patients with ear atresia with a fused malleus-incus complex lateral to the stapes. VSB coupling to the long process of the incus or the stapes may be challenging in small mastoids. Coupling to the short process of the incus is comparatively a simple procedure, since there is no need for posterior tympanotomy and has no proximity to the facial nerve. The results of this study are similar to other ear atresia cases in the literature with classic FMT placement on the stapes or long process of the incus. Outcomes should be confirmed in a larger number of patients.

A method to measure sound transmission via the malleus–incus complex

BackgroundThe malleus–incus complex (MIC) plays a crucial role in the hearing process as it transforms and transmits acoustically-induced motion of the tympanic membrane, through the stapes, into the inner-ear. However, the transfer function of the MIC under physiologically-relevant acoustic stimulation is still under debate, especially due to insufficient quantitative data of the vibrational behavior of the MIC. This study focuses on the investigation of the sound transformation through the MIC, based on measurements of three-dimensional motions of the malleus and incus with a full six degrees of freedom (6 DOF). MethodsThe motion of the MIC was measured in two cadaveric human temporal bones with intact middle-ear structures excited via a loudspeaker embedded in an artificial ear canal, in the frequency range of 0.5–5 kHz. Three-dimensional (3D) shapes of the middle-ear ossicles were obtained by sequent micro-CT imaging, and an intrinsic frame based on the middle-ear anatomy was defined. All data were registered into the intrinsic frame, and rigid body motions of the malleus and incus were calculated with full six degrees of freedom. Then, the transfer function of the MIC, defined as velocity of the incus lenticular process relative to velocity of the malleus umbo, was obtained and analyzed. ResultsBased on the transfer function of the MIC, the motion of the lenticularis relative to the umbo reduces with frequency, particularly in the 2–5 kHz range. Analysis of the individual motion components of the transfer function indicates a predominant medial-lateral component at frequencies below 1 kHz, with low but considerable anterior-posterior and superior-inferior components that become prominent in the 2–5 kHz range. ConclusionThe transfer function of the human MIC, based on motion of the umbo and lenticularis, has been visualized and analyzed. While the magnitude of the transfer function decreases with frequency, its spatio-temporal complexity increases significantly.

Manubrio-stapedioplasty: new surgical technique for malleus and incus fixation due to tympanosclerosis.

This paper reports the authors' technique of manubrio-stapedioplasty using glass ionomer cement for malleus and incus fixation due to tympanosclerosis. A retrospective case review was conducted of five patients with conductive hearing loss (mean pre-operative air-bone gap of 42.75 dB) treated in a tertiary referral centre. The hearing results of a manubrio-stapedial bone cement ossiculoplasty technique, utilised on the five patients, were analysed. All cases were Wielinga and Kerr tympanosclerosis classification type 2 (attic fixation of the malleus-incus complex with a mobile stapes). The incus and head of the malleus were removed in all patients, and the manubrium was directly connected to the head of the mobile stapes using glass ionomer cement. Patients were evaluated in terms of pre- and post-operative audiometric results; hearing gain and post-operative air-bone gap were the main outcome measures. Mean post-operative air-bone gap was 5.25 dB. Four patients had an air-bone gap of less than 10 dB; the remaining patient had an air-bone of 12.50 dB. Manubrio-stapedioplasty is an effective method for ossicular reconstruction in cases of malleus and incus fixation due to tympanosclerosis.

Anatomic Variants on Computed Tomography in Congenital Aural Atresia and Stenosis

ObjectivesTo quantitatively analyzing the anatomic variants on temporal computed tomography (CT) in congenital external auditory canal stenosis (EACS), congenital aural atresia (CAA), and normal ear structure.MethodsThrough a retrospective study, we analyzed 142 temporal high-resolution CT studies performed in 71 microtia patients. The following 6 parameters were compared among the three groups: Marx classification, medial canal diameter, vertical facial nerve (VFN) anterior displacement, tegmen mastoideum position, tympanic cavity volume, and malleus-incus joint or malleus-incus complex (MIC) area.ResultsThe results showed that the microtia distributions in the Marx classification in these three groups were significantly different, as 86% (31 of 35) of ears with major microtia (third-degree dysplasia) had an atresia, and in 54.8% (23 of 42) of the minor microtic (first-degree or second-degree) ears, the bony or cartilaginous part of the external auditory canal was stenotic. Measurement data also showed that the potential medial canal diameter of the atresia group was obviously shorter than that of the stenosis group. The VFN anterior displacement and temporomandibular joint backward-shift together lead to medial canal diameters in ears with atresic canals that is smaller than those with stenotic canals. The tegmen mastoideum position was not significantly different between the three groups.ConclusionThe mal-development of the external auditory canal is significantly associated with auricle and middle ear developmental anomalies. Compared with CAA ears, EACS have better development of the auricle, canal, tympanic cavity and MIC and relatively safer surgical operation except for the position of the tegmen mastoideum and the VFN.

Acoustics-structure interactions in the human middle ear produce variety of motion modes at the malleus-incus complex

We developed a 3D finite-element model to simulate the dynamics of the human middle ear, using COMSOL Multiphysics software to solve the resulting acoustics-structure interaction problem. We validated the model by comparing numerical results with experimental data measured in the ear canal, on the tympanic membrane (TM), at the umbo, and at the stapes footplate. The results show that at low frequencies (up to 500 Hz), the conventionally accepted hinge-like motion of the malleus-incus complex dominates the response, with the angle between the rotational axes of the malleus and incus staying below about 5 degrees. However, above 5 kHz, this angle becomes significantly larger, indicating that the malleus and incus rotate about different axes. Near the upper frequency limit of 20 kHz, the angle between the rotational axes of the malleus and incus approaches 90 degrees as the malleus adopts a lower-inertia twisting-like rotation about its first principal axis. The model is also used to explore the effects, on ossicular motion and overall pressure transfer from the ear canal to the cochlea, of alterations to the mechanical properties of the TM, to the flexibility of the malleus-incus joint, and to the mass of the ossicles. [Funded by NIDCD/NIH.]

Anatomic Variants on Computed Tomography in Congenital Aural Atresia

To report the prevalence of anatomic variants on computed tomography (CT) in congenital aural atresia (CAA) and external auditory canal stenosis (EACS). Anatomic variants included inferiorly displaced/obstructing tegmen mastoideum, malleus-incus complex (MIC) directly lateral to stapes, facial nerve obstruction of oval window (OW) or middle ear, and incudostapedial joint (ISJ) angle. Cross-sectional study. Tertiary care children's hospital. An anatomic analysis of 130 CT scans (98 children, 32 bilateral) of CAA/EACS, performed by a blinded neuroradiologist. Both Jahrsdoerfer's and new/modified anatomic considerations were graded in 32 atresiaplasty and 66 nonsurgical patients. Surgical data were analyzed for anatomic correlations related to surgical findings. Prevalence of anatomic variants was as follows: 13% of the ears had mild inferior displacement of tegmen, 4% had a significantly obstructing tegmen, and 24% had MIC directly lateral to stapes. The facial nerve obstructed access to OW in 41% and middle ear in 21%. Six atresiaplasty patients were reported to have a large MIC obstructing stapes access with increased intraoperative difficulty in viewing and assessing the integrity and mobility of the ISJ and stapes. Five of these 6 (83%) were noted on CT scan. The mean ISJ angle was 101° (range, 51°-155°). A large obstructing MIC increases difficulty of atresiaplasty. Awareness of the presence of these anatomic variants is an aid in teaching temporal bone anatomy and may possibly influence the decision regarding atresiaplasty.

Anatomic Variants on Congenital Computed Tomography in Congential Aural Atresia

Objective: Report incidence of anatomic variants in temporal bone CT scans with congenital aural atresia (CAA) or external auditory canal stenosis (EACS). Anatomic variants include: inferiorly displaced tegmen, malleus/incus complex (MIC) directly lateral to stapes, facial nerve obstruction at oval window (OW) and middle ear, middle ear area, incudostapedial (IS) joint angle. Method: Prospective anatomic study of 134 CT scans (102 children, 32 bilateral) of CAA/EACS, graded by a blinded neuroradiologist. Both Jahrsdoerfer and absence or presence of new/refined anatomic considerations were graded. There were 32 atresiaplasty and 70 nonsurgical patients. Surgical and audiological data were reviewed retrospectively for anatomic correlations related to outcomes. Results: Prevalence of anatomical variants: inferiorly displaced tegmen X (X%), MIC directly lateral to stapes Y (Y%), facial nerve obstructed access to oval window Z (Z%), and middle ear B (B%). Large MIC obstructing stapes access (5/7 patients) with increased intra-operative difficulty. Mean middle ear area DD (range, 0.07 to 0.86mm2) and mean IS joint angle FF (range, 50°-147°). Trend toward improved outcomes with: normal tegmen, facial nerve favorable to OW, or non-obstructing MIC. No statistically significant clinical correlations for anatomic factors including Jahrsdoerfer grading. Conclusion: Large obstructing MIC increases the difficulty of atresiaplasty. There is a trend showing improved outcomes with normal tegmen, facial nerve favorable to oval window, or nonobstructing MIC. A larger atresiaplasty cohort is needed since the number of cases was insufficient to demonstrate statistical significance. Nonetheless, the frequency of these new/refined anatomic variants has been more clearly delineated. The presence of these anatomic variants may possibly influence the decision for or against atresiaplasty.

Is There a “Biological Gear” in the Human Middle Ear?

Objective: A mammal’s ability to hear high-frequency sound is due to unique structures such as 3 distinct middle-ear (ME) ossicles. In larger mammals such as humans, the ME features a cylindrical malleus cross section, differing eardrum areas on each side of the malleus handle, and a mobile saddle-shaped malleus-incus joint (MIJ). Method: Based entirely on 3D reconstructions of micro-CT images, a finite element biocomputation model was constructed, which includes the ear canal, eardrum, ossicles, suspensory soft tissue attachments, and ME joints modeled as mobile and fluid-filled. Frequency responses of acoustics-structure interactions were calculated using COMSOL Multiphysics solvers. Results: Results indicate that at low frequencies, hinge-like motion is dominant as expected, and that the orthotropy of the eardrum boosts the ME gain due to increased peak displacement. However, at high frequencies we observe multi-resonance vibration modes at the eardrum and a bevel-gear-like motion at the MIJ, and the orthotropy of the eardrum makes the rotation axis of the malleus more coincident with its long axis. This supports the hypothesis that a “twisting” motion of the malleus and incus is required in larger mammals at high frequencies in order to compensate for larger moments-of-inertia of the larger ossicular masses. Conclusion: We argue that a new “twisting” gear-like motion is necessary for efficient high-frequency sound transmission in larger mammals, due to higher moments of inertia for hinge-like motion in these species. These features favor the existence of the twisting motion of the malleus-incus complex in addition to the classical hinge-like motion.

Diagnostic Value of Bent‐Lever Planes in Detecting Abnormality of the Malleus‐Incus Complex

To retrospectively investigate the diagnostic value of the bent-lever planes in detecting abnormality of the malleus-incus complex. Diagnostic test assessment. The study was conducted at the Shandong Medical Imaging Research Institute, Shandong University, Jinan, People's Republic of China. Eighty-five ears in 74 patients with surgically proved abnormality of the malleus-incus complex. The bent-lever planes and direct axial images were reviewed by 2 radiologists. The radiologists assigned a value of abnormality or continuity to different parts of the malleus-incus complex. Differences in categorical data were evaluated with the McNemar test. The sensitivity, specificity, Youden index, and interobserver agreement were calculated. There was no significant difference between bent-lever planes and direct axial images in identifying abnormality of the malleus-incus complex. The sensitivity ranged from 71.4% to 97.1%, and specificity ranged from 89.5% to 100.0%. The Youden index ranged from 0.609 to 0.971. The radiologists had almost perfect or substantial agreement in identifying the abnormality of different parts of the malleus-incus complex. The bent-lever planes do not add additional diagnostic value for experienced observers.

CT scan versus surgery: how reliable is the preoperative radiological assessment in patients with chronic otitis media?

The objective of the study was to evaluate the accuracy of the preoperative radiological assessment regarding 10 different middle ear structures in patients with chronic otitis media (COM). The setting of the prospective study was in a Tertiary university hospital. Fifty patients scheduled for a primary operation for COM. All patients underwent preoperative temporal bone high-resolution CT-scan (HRCT). AC(1)-statistics between the radiological report and the intra-operative findings were calculated. There was no correlation between the radiological assessment and the surgical findings in the scutum, attic area, and oval window. There was a poor or fair agreement on the condition of the malleus-incus complex, the status of the tympanic cavity, and the round window. There was a moderately strong agreement regarding the status of the lateral semicircular canal (LSCC) and tegmen tympani. This agreement was primarily observed, when no erosion/exposure was present in the LSCC or the dura. There was a very strong agreement in the mastoid air-cell complex and the sigmoid sinus, especially when the former was abnormal and the latter had no pathology. There are significant difficulties in radiological imaging for reliably assessing the middle ear in patients with chronic otitis media, using HRCT. The preoperative CT scan generally underestimates the actual pathology found by the surgeon in certain middle ear areas. The decision for surgical intervention should not be based on the radiological interpretation of certain middle ear structures, and ENT surgeons should be prepared to encounter conditions which are not reported by the radiologist preoperatively, and modify the operating strategy accordingly. EBM level: 2c.

A 3-D Force and Moment Motor for Small-Scale Biomechanics Experiments

The inability to identify 3-D force and moment components for actuators and sensors is a major limiting factor in the study of 3-D force interactions with small-scale biological structures. While recent advances have been made in the measurement of stimulating forces using load cells and atomic-force microscopy in experimental preparations of biological structures such as mammalian temporal bones, these techniques have mostly been limited to one or two dimensions. In this paper, a method is described for stimulating biological structures using a small magnet (2 mg Sm(2)Co(17)) and a nearby current-conducting coil (46 gauge, 50 turns), that allows the 3-D Lorentz forces and moments acting on the magnet to be calculated. To make these calculations possible, the dimensions and placements of the magnet and coil are accurately determined (within 10 μm for in vitro preparations) using high-resolution micro-CT imaging. This noncontact force motor method has been used to study the mechanics of the malleus-incus complex in the mammalian middle ear in addition to basilar membrane mechanics and fluid flow inside the cochlea, and it can also be applied to the study of other biomechanical structures.

Tympanic-membrane and malleus–incus-complex co-adaptations for high-frequency hearing in mammals

The development of the unique capacity for high-frequency hearing in many mammals was due in part to changes in the middle ear, such as the evolution of three distinct middle-ear bones and distinct radial and circumferential collagen fiber layers in the eardrum. Ossicular moment(s) of inertia (MOI) and principal rotational axes, as well as eardrum surface areas, were calculated from micro-CT-based 3-D reconstructions of human, cat, chinchilla, and guinea pig temporal bones. For guinea pig and chinchilla, the fused malleus–incus complex rotates about an anterior–posterior axis, due to the relatively lightweight ossicles and bilateral symmetry of the eardrum. For human and cat, however, the MOI calculated for the unfused malleus are 5–6 times smaller for rotations about an inferior–superior axis than for rotations about the other two orthogonal axes. It is argued that these preferred motions, along with the presence of a mobile malleus–incus joint and asymmetric eardrum, enable efficient high-frequency sound transmission in spite of the relatively large ossicular masses of these species. This work argues that the upper-frequency hearing limit of a given mammalian species can in part be understood in terms of morphological co-adaptations of the eardrum and ossicular chain.