Incudomalleolar Joint Research Articles

Middle Ear Ossicular Joint Changes in Type 2 Diabetes Mellitus: A Histopathological Study.

Although previous research has indicated inner ear changes in diabetes mellitus (DM) patients, no prior study has explored the middle ear, particularly the ossicles and their joints, in DM patients. This study aimed to investigate whether type 2 DM is associated with middle ear changes, specifically affecting the ossicular chain and joints. This study included 47 ears from 25 patients with DM (male = 13, female = 12, age: 51.0 ± 20.5) and age- and sex-matched controls (male = 10, female = 10, age: 54.8 ± 15.9) (sex; p = 1.000, Age; p = 0.991). Otopathological evaluations of the auditory ossicles and incudomalleolar joint (IMJ) were performed using light microscopy. In the IMJ of DM cases, malleus hyalinized cartilage (Malleus hC) and incus hyalinized cartilage (Incus hC) were significantly increased compared with control cases (Malleus hC; DM, 34.17 ± 9.71 μm vs. control 21.96 ± 4.16 μm, p < 0.001) (Incus hC; DM 35.11 ± 10.12 μm vs. control 22.42 ± 4.368 μm, p < 0.001). In addition, bone-line distance was significantly longer than in DM cases than control cases (DM 266.72 ± 59.11 μm vs. control 239.81 ± 35.56 μm p = 0.040). On the other hand, joint discus distance was longer in the control group than in DM cases (DM 96.84 ± 36.80 μm vs. Control 113.63 ± 23.81 μm, p = 0.001). This study reveals a notable increase in the hyalinized cartilage layer and bone-line distance accompanied by reducing joint discus distance within the IMJ in DM cases. These findings suggest that DM may influence microjoints, such as the IMJ, and potentially impact auditory function. N/A Laryngoscope, 134:2871-2878, 2024.

Post-traumatic Malleo-Incudal Complex Dislocation

A 27-year-old man undergoes otolaryngologic evaluation for blunt head trauma suffered in a vehicular accident. With regards to the right ear, pertinent otologic findings include an ear canal laceration and a delayed-onset facial nerve paresis. Tuning fork testing reveals an abnormal Rinne test on the right (AC&lt;BC). The radiologist’s interpretation of the computerized tomographic imaging study of the temporal bone indicated the presence of a longitudinal fracture of the right temporal bone with no disruption of the ossicular chain. (Figure 1) However, careful examination of the anatomy of the malleo-incudal complex in relation to the other structures in the epitympanum actually reveals findings indicative of a malleo-incudal complex dislocation. How can this discrepancy in the radiologic interpretation be accounted for? By what objective parameters can the presence of a malleoincudal complex dislocation be identified?&#x0D; &#x0D; Meriot et al.1 described five types of traumatic ossicular dislocation injury: incudomalleolar joint separation, incudostapedial joint separation, stapediovestibular dislocation, incus dislocation, and malleo-incudal complex dislocation. Of these, incudomalleolar joint separation would probably be the most easily identified, as it would manifest as a disruption in the distinctive ice-cream cone appearance of the malleus head and the body and short process of the incus visualized on axial CT imaging of the temporal bone. (Figure 2) In contrast, malleo-incudal complex dislocation would involve movement of both ossicles en-bloc within the tympanic cavity (usually into the mesotympanum), without disruption of the incudomalleolar joint.1 As such, the ice-cream cone configuration may be preserved in this type of injury. Proper identification of this type of injury would be based on identifying any discrepancy in the positional relationship between the ossicular complex and the other structures within the confines of the&#x0D; tympanic cavity.&#x0D; &#x0D; The malleus head and the body and short process of the incus are located in the most superior portion of the tympanic cavity, the pneumatised area called the epitympanum. Also known as the attic or&#x0D; epitympanic recess, this region is bordered superiorly by the tegmen tympani and inferiorly by the mesotympanum. The epitympanum is divided into two compartments: the anterior epitympanic space or&#x0D; recess, and the much larger posterior epitympanum, which houses the epitympanic portions of the malleus and incus. This division is created by a thin bony plate known as the cog, which projects downwards from the tegmen tympani and is located anterior to the malleus head.2 In the axial plane, the malleo-incudal complex is normally centered within the posterior epitympanum with the short process of the incus pointing into the incudal fossa. The position of the malleo-incudal complex may sometimes be slightly lateral, but is never medial in the normal situation.1&#x0D; &#x0D; Based on these broader anatomical relationships, it can be seen that in the imaging study under investigation (Figure 3), the malleo-incudal complex (the ice-cream cone) has actually shifted forward - the malleus head is located not posterior to the cog, but at the same level as the cog in the antero-posterior dimension. Additionally, the malleo-incudal complex is located more medially within the posterior epitympanum, and is much closer to the tympanic segment of the facial nerve than to the lateral bony margin (the scutum) of the epitympanum. These findings clearly and unequivocally demonstrate the presence of a malleo-incudal complex dislocation.&#x0D; &#x0D; In summary, one of the keys to the proper evaluation of post-traumatic ossicular injury is to look not only at the anatomical relationship between ossicles, but also at the relationship of the entire ossicular complex to the other structures that are also located within the confines of the tympanic cavity

ALADA Dose Optimization in the Computed Tomography of the Temporal Bone: The Diagnostic Potential of Different Low-Dose CT Protocols.

Objective: Repeated computed tomography (CT) is essential for diagnosis, surgical planning and follow-up in patients with middle and inner ear pathology. Dose reduction to “as low as diagnostically acceptable” (ALADA) is preferable but challenging. We aimed to compare the diagnostic quality of images of subtle temporal bone structures produced with low doses (LD) and reference protocols (RP). Methods: Two formalin-fixed human cadaver heads were scanned using a 64-slice CT scanner and cone-beam CT (CBCT). The protocols were: RP (120 kV, 250 mA, CTDIvol 83.72 mGy), LD1 (100 kV, 80 mA, CTDIvol 26.79 mGy), LD2 (100 kV, 35 mA, CTDIvol 7.66 mGy), LD3 (80 kV, 40 mA, CTDIvol 4.82 mGy), and CBCT standard protocol. Temporal bone structures were assessed using a 5-point scale. Results: A median score of ≥2 was achieved with protocols such as the tendons of m. tensor tympani (RP/LD1/LD2/CBCT) and m. stapedius (CBCT), the incudostapedial joint (RP/LD1/CBCT), the incudomalleolar joint (RP/LD1/LD2/CBCT), the stapes feet (RP/LD1/CBCT), the stapes head (RP/LD1/LD2/CBCT), the tympanic membrane (RP/LD1/LD2/CBCT), the lamina spiralis ossea (none), the chorda tympani (RP/LD1/CBCT), and the modiolus (RP/LD1/LD2/CBCT). Adaptive statistical iterative reconstructions did not show advantages over the filtered back projection. Conclusions: LD protocols using a CTDIvol of 7.66 mGy may be sufficient for the identification of temporal bone structures.

Conductive Hearing Loss with Age-A Histologic and Audiometric Evaluation.

A retrospective analysis to quantify age-related changes of the incudo-malleolar joint (IMJ) and incudo-stapedial joint (ISJ), and to analyse changes in the air-bone gap (ABG) with age, was performed. Defined histologic parameters of 153 IMJ and 106 ISJ from subjects aged from birth to 70 years were correlated to age. Additionally, audiograms of 1760 ears of 974 other subjects aged 20 to 80 years were retrospectively analysed and the ABG was correlated to age. The joint space (age group from 0 to 10 compared to 61 to 70 years) became significantly wider with age (IMJ: from a mean of 44 µm to 100 µm, p < 0.001; ISJ: from a mean of 28 µm to 69 µm, p < 0.009. The thickness of cartilage of the incus decreased in the first 20 years of life (IMJ, from a mean of 88 µm to 65 µm, p < 0.01; ISJ: from a mean of 44 µm to 35 µm, p < 0.01). The ABGs of younger ears (20–40 years) was significantly larger at 500 Hz compared to older ears (60–80 years) by 2–4 dB, while it was significantly smaller by 3–5 dB at 4000 Hz (p < 0.0017). Interindividual variations in all age groups were large for both analyses. The increased joint spaces could potentially reduce the stiffness in the joints and explain the increase in ABG at 4000 Hz and the drop at 500 Hz. While the average change is small and of minimal clinical relevance, a larger increase of ABG with age is seen in some subjects.

Histopathology of the Incudomalleolar Joint in Cases of "Indeterminate" Presbycusis.

Retrospective study.

Structural stiffening in the human middle ear due to static pressure: Finite-element analysis of combined static and dynamic middle-ear behavior

The vibration response of the middle ear (ME) to sound changes when static pressure gradients are applied across the tympanic membrane (TM). To date, it has not been well understood which mechanisms lead to these changes in ME vibration response. In this study, a 3D finite-element model of the human ME was developed that simulates the sound-induced ME vibration response when positive and negative static pressures of up to 4 kPa are applied to the TM. Hyperelasticity of the soft-tissue components was considered to simulate large deformations under static pressure. Some ME components were treated as viscoelastic materials to capture the difference between their static and dynamic stiffness, which was needed to replicate both static and dynamic ME behavior. The change in dynamic stiffness with static preload was simulated by linearization of the hyperelastic constitutive model around the predeformed state. For the preloaded harmonic response, we found that the statically deformed ME geometry introduced asymmetry in the vibration loss between positive and negative pressure, which was due to the TM cone shape. As opposed to previous assumptions, the prestress in the ME due to static pressure had a substantial impact on the vibration response. We also found that material nonlinearity led to a higher stiffening at the umbo but a less pronounced stiffening at the footplate compared to the linear elastic condition. The results suggest that flexibility of the incudomalleolar joint (IMJ) enhances the decoupling of static umbo and footplate displacements, and that viscosity and viscoelasticity of the IMJ could play a role in the transfer of sound-induced vibrations from the umbo to the footplate. The components of the incudostapedial joint had minimal effect on ME mechanical behavior.

Middle Cranial Fossa Approach: The Incudomalleolar Joint as a Reliable Landmark.

Introduction The middle cranial fossa approach is performed by fewer neurotologists owing to a reduced number of indications. Consistent landmarks are mandatory to guide the surgeon in a narrow field. Objectives We have evaluated the incus and malleus head and the incudomalleal joint (IMJ) as a key landmark for identifying the superior semicircular canal (SSC) and to get oriented along the floor of the middle cranial fossa. Methods A combination of 20 temporal bone dissections and CT imaging were utilized to test and describe these landmarks. Results The blue line of the SSC is consistently identified along the prolongation of a virtual line through the IMJ and the angulation toward the root of zygoma. The mean distance from the zygoma toward the IMJ ranged from 1.60 to 1.90cm. Once the IMJ was identified, the blue line of the SSC was consistently found along the virtual line through the IMJ within 5 to 9mm. Conclusions The IMJ is a safe and consistent anatomical marker in the surgical approach to the middle cranial fossa floor. Opening the tegmen 1.5 to 2cm medial to the root of the zygoma and identifying the joint allows to trace a virtual line toward the SSC within 5 to 9mm. Knowledge of the close relationship between the direction of the IMJ and the superior canal can be used in all transtemporal approaches, thus orienting the surgeon in a rather narrow field with limited retraction of the dura and brain.

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.

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.

Dose Reduction for Sinus and Temporal Bone Imaging Using Photon-Counting Detector CT With an Additional Tin Filter.

The aim of this study was to quantitatively demonstrate radiation dose reduction for sinus and temporal bone examinations using high-resolution photon-counting detector (PCD) computed tomography (CT) with an additional tin (Sn) filter. A multienergy CT phantom, an anthropomorphic head phantom, and a cadaver head were scanned on a research PCD-CT scanner using ultra-high-resolution mode at 100-kV tube potential with an additional tin filter (Sn-100 kV) and volume CT dose index of 10 mGy. They were also scanned on a commercial CT scanner with an energy-integrating detector (EID) following standard clinical protocols. Thirty patients referred to clinically indicated sinus examinations, and two patients referred to temporal bone examinations were scanned on the PCD-CT system after their clinical scans on an EID-CT. For the sinus cohort, PCD-CT scans were performed using Sn-100 kV at 4 dose levels at 10 mGy (n = 9), 8 mGy (n = 7), 7 mGy (n = 7), and 6 mGy (n = 7), and the clinical EID-CT was performed at 120 kV and 13.7 mGy (mean CT volume dose index). For the temporal bone scans, PCD-CT was performed using Sn-100 kV (10.1 mGy), and EID-CT was performed at 120 kV and routine clinical dose (52.6 and 66 mGy). For both PCD-CT and EID-CT, sinus images were reconstructed using H70 kernel at 0.75-mm slice thickness, and temporal bone images were reconstructed using a U70 kernel at 0.6-mm slice thickness. In addition, iterative reconstruction with a dedicated sharp kernel (V80) was used to obtain high-resolution PCD-CT images from a sinus patient scan to demonstrate improved anatomic delineation. Improvements in spatial resolution from the dedicated sharp kernel was quantified using modulation transfer function measured with a wire phantom. A neuroradiologist assessed the H70 sinus images for visualization of critical anatomical structures in low-dose PCD-CT images and routine-dose EID-CT images using a 5-point Likert scale (structural detection obscured and poor diagnostic confidence, score = 1; improved anatomic delineation and diagnostic confidence, score = 5). Image contrast and noise were measured in representative regions of interest and compared between PCD-CT and EID-CT, and the noise difference between the 2 acquisitions was used to estimate the dose reduction in the sinus and temporal bone patient cohorts. The multienergy phantom experiment showed a noise reduction of 26% in the Sn-100 kV PCD-CT image, corresponding to a total dose reduction of 56% compared with EID-CT (clinical dose) without compromising image contrast. The PCD-CT images from the head phantom and the cadaver scans demonstrated a dose reduction of 67% and 83%, for sinus and temporal bone examinations, respectively, compared with EID-CT. In the sinus cohort, PCD-CT demonstrated a mean dose reduction of 67%. The 10- and 8-mGy sinus patient images from PCD-CT were significantly superior to clinical EID-CT for visualization of critical sinus structures (median score = 5 ± 0.82 and P = 0.01 for lesser palatine foramina, median score = 4 ± 0.68 and P = 0.039 for nasomaxillary sutures, and median score = 4 ± 0.96 and P = 0.01 for anterior ethmoid artery canal). The 6- and 7-mGy sinus patient images did not show any significant difference between PCD-CT and EID-CT. In addition, V80 (sharp kernel, 10% modulation transfer function = 18.6 cm) PCD-CT images from a sinus patient scan increased the conspicuity of nasomaxillary sutures compared with the clinical EID-CT images. The temporal bone patient images demonstrated a dose reduction of up to 85% compared with clinical EID-CT images, whereas visualization of inner ear structures such as the incudomalleolar joint were similar between EID-CT and PCD-CT. Phantom and cadaver studies demonstrated dose reduction using Sn-100 kV PCD-CT compared with current clinical EID-CT while maintaining the desired image contrast. Dose reduction was further validated in sinus and temporal bone patient studies. The ultra-high resolution capability from PCD-CT allowed improved anatomical delineation for sinus imaging compared with current clinical standard.

Transcanal endoscopic ear surgery for traumatic ossicular injury

Background: Transcanal endoscopic ear surgery (TEES) for traumatic ossicular injuries (TOI) is not well studied.Objectives: To analyze the treatment outcomes of TEES for TOI.Material and methods: Retrospective case review of fifteen patients (15 ears) with TOI was performed. The patients underwent an either ossiculoplasty or stapes surgery according to status of the ossicular chain using ear endoscopes. Postoperative audiometric results and complications were analyzed.Results: All subjects demonstrated improvement in their air conduction threshold and air-bone gap (ABG). The mean preoperative air conduction threshold and ABG were 55.3 dB (SD: 12.8) and 33.0 dB (SD: 9.5), respectively. Postoperatively, the air conduction threshold and ABG significantly improved to 28.1 dB (SD: 16.0) and 8.1 dB (SD: 4.5), respectively. Separation of the incudomalleolar joint accompanied by defect of the tegmen, which was not discernible on preoperative imaging, could be identified without additional incision or mastoidectomy. No patients experienced complications or a sensorineural hearing loss. Conversion to open approach was not necessary for any of the 15 procedures performed.Conclusion and significance: TEES for TOI yielded favorable audiometric results without any complication. TEES can provide an alternative method to manage TOI with the advantage of avoidance of skin incisions and mastoidectomy.

Ciliated cell observation by SEM on the surface of human incudo-malleolar-joint articular cartilage: are they a new chondrocyte phenotype?

Background: Scanning electron microscopy (SEM) study of the human incus bone is scanty whilst, to our knowledge, no information regarding human incudo-malleolar joint articular-cartilage morphology has previously been provided.Aims/objectives: Our aim was to shed some light on this morphological issue and to propose some theoretical perspectives on its functional role.Material and methods: The human incudo-malleolar joint was documented with field emission SEM on samples recovered during ear surgery procedures after patients’ informed consent.Results: Normal articular cartilage chondrocytes, flattened cells with prominent nucleus and short microvilli were observed. Interestingly, cells provided with long cilia were identified. Type A cilia are arranged in a pyramidal formation with extra-long cilia stemming from the cluster, projecting upwards in an antenna-like formation ending with a dilated structure that as a whole, resembles the stereocilia with kinocilium. Types B, C and D cilia resemble those of the genital and respiratory tracts.Conclusions and significance: It is therefore possible to hypothesize that the observed ciliated cells may be a new chondrocyte phenotype with sensory function. Motile cilia confer the ability to distinguish variations in synovial fluid chemical composition and, in addition, they perhaps may also play some role in the mechanism of sound transmission.

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.

Anatomical measurement of the ossicles in patients with congenital aural atresia and stenosis

ObjectivesOur aims were to measure and compare anatomical parameters of the ossicles in normal, congenital aural stenosis (CAS), and congenital aural atresia (CAA) ears. MethodsThis retrospective study was performed using three-dimensional reconstructed images derived from computed tomography scans of 20 normal subjects, 20 CAS patients, and 20 CAA patients. ResultsThe lengths of the malleus handle and long process of the incus were greater in normal ears than in CAS and CAA ears (all P < 0.05). The angles of the incudostapedial joint and between the short and long processes of the incus were smaller in normal ears than in CAS and CAA ears (all P < 0.05). There were no significant differences in the positions of the malleus head and incudomalleolar joint, the size of the malleus head, the length of the short process of the incus, or the angle of the incudomalleolar joint (P > 0.05). ConclusionsAnatomical parameters of the lower part, but not of the upper part, of the ossicular chain in CAS and CAA ears differed from those in normal ears. Different branchial arch origins of the upper and lower parts of the ossicular chain may explain these findings. Dysplasia of the second arch, which develops into the lower part of the ossicular chain, may contribute to ossicular malformation in CAA and CAS. Accurate radiographic measurement of malformed ossicles may be useful for reconstructive surgery of CAA and CAS using the patient's native ossicular chain and for choosing an appropriate place for active middle ear implants.

Modeling of the incudo-malleolar joint within a biomechanical model of the human ear

Under large quasi-static loads, the incudo-malleolar joint (IM joint), connecting the malleus and the incus, is highly mobile. It can be classified as a mechanical filter decoupling large quasi-static motions while transferring small dynamic excitations. To investigate the influence of the behavior of the IM joint, a detailed simulation model of the IM-complex is created. Mathematical modeling of the IM joint behavior under quasi-static excitation requires adequate modeling of the mechanics of the diarthrodial joint. Therefore, the geometry of the articular surfaces, the ligaments, as well as their viscoelastic properties have to be included in the model. The contact of the articular surfaces is implemented using a penalty based contact formulation utilizing the geometric information obtained from micro computer tomography (micro-CT) scans. The ligaments of the joint capsule are modeled by distributing force elements along the joint capsule, with the position and orientation derived from the micro-CT scans. It is shown that the effects which were observed in measurements on human temporal bones are described adequately by the model, if the contact of the articular surfaces and the preload of the viscoelastic fibers are taken into account in the simulation model. In the following, the detailed model is implemented in an elastic multibody system of the entire ear. The model allows the study of different quasi-static load cases of the ossicles, such as it occurs in the reconstruction of the middle ear and form the basis for future simulative studies of sound transmission in natural or reconstructed ears.

Biomechanics of the incudo-malleolar-joint – Experimental investigations for quasi-static loads

Under large quasi-static loads, the incudo-malleolar joint (IMJ), connecting the malleus and the incus, is highly mobile. It can be classified as a mechanical filter decoupling large quasi-static motions while transferring small dynamic excitations. This is presumed to be due to the complex geometry of the joint inducing a spatial decoupling between the malleus and incus under large quasi-static loads.Spatial Laser Doppler Vibrometer (LDV) displacement measurements on isolated malleus-incus-complexes (MICs) were performed. With the malleus firmly attached to a probe holder, the incus was excited by applying quasi-static forces at different points. For each force application point the resulting displacement was measured subsequently at different points on the incus. The location of the force application point and the LDV measurement points were calculated in a post-processing step combining the position of the LDV points with geometric data of the MIC. The rigid body motion of the incus was then calculated from the multiple displacement measurements for each force application point. The contact regions of the articular surfaces for different load configurations were calculated by applying the reconstructed motion to the geometry model of the MIC and calculate the minimal distance of the articular surfaces.The reconstructed motion has a complex spatial characteristic and varies for different force application points. The motion changed with increasing load caused by the kinematic guidance of the articular surfaces of the joint. The IMJ permits a relative large rotation around the anterior-posterior axis through the joint when a force is applied at the lenticularis in lateral direction before impeding the motion. This is part of the decoupling of the malleus motion from the incus motion in case of large quasi-static loads.

Contribution of the incudo-malleolar joint to middle-ear sound transmission

The malleus and incus in the human middle ear are linked by the incudo-malleolar joint (IMJ). The mobility of the human IMJ under physiologically relevant acoustic stimulation and its functional role in middle-ear sound transmission are still debated. In this study, spatial stapes motions were measured during acoustic stimulation (0.25–8 kHz) in six fresh human temporal bones for two conditions of the IMJ: (1) normal IMJ and (2) IMJ with experimentally-reduced mobility. Stapes velocity was measured at multiple points on the footplate using a scanning laser Doppler vibrometry (SLDV) system, and the 3D motion components were calculated under both conditions of the IMJ. The artificial reduction of the IMJ mobility was confirmed by measuring the relative motion between the malleus and the incus. The magnitudes of the piston-like motion of the stapes increased with the reduced IMJ mobility above 2 kHz. The increase was frequency dependent and was prominent from 2 to 4 kHz and at 5.5 kHz. The magnitude ratios of the rocking-like motions to the piston-like motion were similar for both IMJ conditions. The frequency-dependent change of the piston-like motion after the reduction of the IMJ mobility suggests that the IMJ is mobile under physiologically relevant levels of acoustic stimulation, especially at frequencies above 2 kHz.

The incudomalleolar articulation in Down syndrome (trisomy 21): a temporal bone study.

One reason for conductive hearing loss (HL) in patients with Down syndrome (DS) is structural anomalies in the incudomalleolar joint (IMJ) that impair sound transmission. The majority of hearing losses in patients with DS are conductive. One reason is the high incidence of inflammatory processes such as otitis media. However, in some patients, the middle ear seems to be normal. The assumption of structural disorders causing a HL is supported by a previous study revealing structural abnormalities of the incudostapedial joint (ISJ) in these patients. In a retrospective analysis, histologic sections of the IMJ of 16 patients with DS were compared with 24 age- and sex-matched subjects with normal middle ear ossicles. The length of 8 parameters of the IMJ were measured at 3 positions and compared between the 2 groups. Age (p = 0.318) and sex distribution (p = 1) for the DS group and the matched controls were comparable. The IMJs (p < 0.001) and the cartilage of patients with DS are significantly wider in most measurements compared with controls. However, the joint space is not significantly different in the 2 groups. Conductive HL might be caused by a significantly wider IMJ in patients with DS supporting the findings of a previous study reporting similar findings for the ISJ. The etiology of these findings is unclear. Patients with DS have a high prevalence of deficient collagen synthesis. Immunohistochemical analysis may be needed to investigate the collagen structure of the ISJ and IMJ in patients with DS.

Ossicular Chain Trauma during Middle Ear Endoscopy

Objectives: (1) Evaluate the risk of ossicular chain trauma and injuries due to different middle ear endoscopic techniques and maneuvers. (2) Describe types, incidence, and causes of these injuries. (3) Suggest methods to avoid them. Methods: Thirty temporal bones were approached using 0°, 30°, and 70° otoendoscopes with 2.7 mm and 4 mm diameters. Three areas were systematically approached in each bone: retrotympanum, protympanum and epitympanum. They were also manipulated using 3 sets of otologic surgical instruments: regular straight, regular curved and especially designed for endoscopic ear surgery. Results: The most common injury was the fracture of the posterior stapedial curs (27%). Other types were incudostapedial joint dislocation (23%), fracture of foot plate (23%), stapes dislocation (17%), fracture both stapedial crura (13%), fracture of the incus long process (6%), and incudomalleolar joint dislocation (3%). Single injuries were 44% and combined or multiple injuries were 56%. Highest incidence of injuries was with the 70° otoendoscope (89%) and with both the straight and curved regular instruments (67%). The diameter of otoendoscopes did not affect the number of injuries. Positioning of the scopes and familiarity with the technique reduced the incidence of trauma. Conclusions: Middle ear endoscopy can lead to a significant risk of ossicular chain injuries with their sequelae on hearing. Minimizing this risk necessitates adequate familiarity with the anatomy, techniques and otoendoscopes and usage of especially designed surgical instruments. In addition, combining both microscopic and otoendoscopic approaches or surgically assisted otoendoscopic approaches can reduce this risk considerably.

Minor ossicular anomalies in the middle ear: role of submillimeter multislice computed tomography.

The objective was to elucidate clinical effectiveness of submillimeter multislice 2- and 3-dimensional computed tomography (CT) for diagnosis of congenital middle ear anomaly. Preoperative CT and operative findings were retrospectively analyzed in 36 ears of 33 patients. The distance between the malleal handle (MH) and the incus long process (ILP) was measured in 28 normal ears. Mean ± SD MH-ILP distance in normal ears was 1.8 ± 0.3 mm. In patients with middle ear anomaly, overall specificity, accuracy, and positive and negative predictive values were 99.7%, 98.7%, 91.7%, and 99.1%, respectively. Overall sensitivity was 82.1%, with relatively low sensitivities for detecting fused incudomalleolar joint, lenticular process defect, stapedial footplate defect, and oval window atresia and high sensitivities (80%-100%) for stapedial crural anomaly and certain fibrous connections. Submillimeter CT improved detectability of anomalies of the stapedial superstructure; however, it is still difficult to identify abnormalities of the footplate.