Anatomical and morphometric study of goat middle ear ossicles (Capra aegagrus hircus) / [Estudo anatômico e morfométrico dos ossículos da orelha média de caprinos (Capra aegagrus hircus)]

The social and economic roles of goat farming in Northeastern Brazil, allied to the fact that the use of goat middle ear ossicles for research and human ear surgery training has not yet been proposed, justify the study of their applicability as an experimental model. The middle ears of 19 goats (Capra aegagrus hircus) from the bone collection of the Laboratory and Didactic Anatomy Museum of Domestic and Wild Animals of the Federal University of Vale do São Francisco (UNIVASF) were dissected. The malleus, incus, and stapes were evaluated regarding their macroscopic morphology and biometry (length, width, and height). Ossicle morphology was similar to sheep, human, and bovine morphology. The malleus was 1.3 times heavier and 2.2 times longer than the incus, and 9.0 times heavier and 3.7 times longer than the stapes. The size relationship was positive between the stapes and the malleus and negative between the stapes and the incus. It is concluded that the middle ear size and the anatomical similarities with human ossicles make goats a useful model for experimental scientific studies, reconstructive surgery practice of the ossicular chain, and human ear surgery training.(AU)

Tanto o papel social quanto o econômico da caprinocultura na região Nordeste do Brasil, somados ao fato de que o uso de ossículos da orelha média de caprinos para estudos e treinamento cirúrgico otológico humano ainda não foi proposto, justificam o estudo de sua aplicabilidade como modelo experimental. Foram dissecadas as orelhas médias de 19 caprinos (Capra aegagrus hircus), provenientes do ossuário do Laboratório e Museu Didático de Anatomia dos Animais Domésticos e Silvestres - Universidade Federal do Vale do São Francisco. Martelos, bigornas e estribos tiveram a morfologia macroscópica e a biometria (comprimento, largura e altura) avaliadas. A morfologia dos ossículos assemelhou-se a de ovinos, humanos e bovinos. O martelo foi 1,3 vez mais pesado e 2,2 vezes mais comprido que a bigorna e 9,0 vezes mais pesado e 3,7 vezes mais comprido que o estribo. A relação de tamanho entre o estribo e o martelo foi positiva, e entre o estribo e a bigorna negativa. Conclui-se que o tamanho da orelha média e as semelhanças anatômicas com os ossículos humanos tornam os caprinos um modelo útil para estudos científicos experimentais, prática cirúrgica reconstrutiva da cadeia ossicular e treinamento cirúrgico otológico humano.(AU)

Relationship between short-term and mid-term hearing outcomes after stapedotomy in patients with otosclerosis: an investigation.

BACKGROUND: Although stapedotomy is effective for patients with clinical otosclerosis, the time of hearing stabilization has not yet been consistent. OBJECTIVE: To investigate the relationships between post-operative follow-up times, hearing outcomes, and threshold shift after stapedotomy. MATERIALS AND METHODS: Fifty-five patients with clinical otosclerosis that underwent stapedotomy were retrospectively studied. Pure tone audiometry tests were conducted within the first month (short-term) and within 1 year (mid-term) postoperatively. Data were analyzed for two rounds of audiometry tests at different postoperative follow-up times. RESULTS: Air conduction (AC) and bone conduction (BC) were significantly correlated with preoperative hearing levels (p<.01). AC, BC, and air bone gap (ABG) significantly improved at the short-term (p<.001) and continued to improve at the mid-term (p<.01). The success rate of surgery increased from 87% at short-term to 98% at mid-term. Less than 1/3 of cases encountered BC deterioration at short-term, whereas most improved at mid-term. CONCLUSIONS: Hearing results showed a trend of improvement between short-term and mid-term follow-ups after stapedotomy. AC, ABG, and success rate displayed significant improvement several months postoperatively. BC deterioration occurred in less than 30% of patients at short-term. The recovery of BC at 4 kHz was later than that of low frequencies.

A monotreme-like auditory apparatus in a Middle Jurassic haramiyidan.

Among extant vertebrates, mammals are distinguished by having a chain of three auditory ossicles (the malleus, incus and stapes) that transduce sound waves and promote an increased range of audible-especially high-frequencies1. By contrast, the homologous bones in early fossil mammals and relatives also functioned in chewing through their bony attachments to the lower jaw2. Recent discoveries of well-preserved Mesozoic mammals have provided glimpses into the transition from the dual (masticatory and auditory) to the single auditory function for the ossicles, which is now widely accepted to have occurred at least three times in mammal evolution3-6. Here we report a skull and postcranium that we refer to the haramiyidan Vilevolodon diplomylos (dating to the Middle Jurassic epoch (160 million years ago)) and that shows excellent preservation of the malleus, incus and ectotympanic (which supports the tympanic membrane). After comparing this fossil with other Mesozoic and extant mammals, we propose that the overlapping incudomallear articulation found in this and other Mesozoic fossils, in extant monotremes and in early ontogeny in extant marsupials and placentals is a morphology that evolved in several groups of mammals in the transition from the dual to the single function for the ossicles.

Morphological and morphometrical aspects of the auditory ossicles in goat (Capra hircus).

The present paper deals with a detailed description of the auditory ossicles in Capra hircus. The paper focuses on the morphological and morphometrical description of the ossicular assembly, formed by malleus, incus and stapes. The malleus (overall length, as average- 8.16 mm) comprises the head of malleus (Caput mallei), a slightly strictured part-neck (Collum mallei) with 3 distinctive processes (lateral, rostral and muscular) (Processus lateralis, Processus rostralis and Processus muscularis) and a handle (Manubrium mallei). The head of malleus has an oval aspect with an obtuse articular surface on its medial surface (Facies articularis). The neck is evident with three bony processes described-the anterior, almost triangular, the muscular one quite reduced and the lateral one which is the most developed one. The manubrium is the longest sector-4.4 mm and appears as a slightly curved piece. The incus presents a body of 1.3 mm and two processes-the short and long crus (Crus breve and Crus longum). The overall shape of the ossicle resembles a biradicular molar. The lenticular process is a continuation of the distal part of the long crus. The stapes-the smallest in size of the three ossicles (2.7 mm), has a head (Caput stapedis), an anterior (Crus rostrale) and a caudal (Crus caudale) arm and a footplate (Basis stapedis). The two processes are slightly different in size and morphology, delimiting the intercrural space that shows the presence of a bony spicule. The footplate (1.6 mm2 area) is ellipsoidal, with an anterior narrower extremity.

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.

The ossicular chain of Cainotheriidae (Mammalia, Artiodactyla).

This work describes an unparalleled sample of isolated fossil auditory ossicles of cainotheriid artiodactyls from the Paleogene karstic infillings of Dams (Tarn-et-Garonne, Quercy, France). This collection comprises a total of 18 mallei, 28 incudes and three stapedes. It allows the documentation of both intra- and interspecific variability of ossicular morphology within Cainotheriidae. We show that despite considerable intraspecific variability, the malleus, the incus and the stapes appear to be taxonomically informative at the Cainotheriidae scale. This work further provides the first description of a reconstructed ossicular chain of a terrestrial Paleogene artiodactyl species, found in a basicranium of the late Oligocene cainotheriine Caenomeryx filholi (Pech Desse locality).

Histological development and integration of the Zebrafish Weberian apparatus.

BACKGROUND: The Weberian apparatus enhances hearing in otophysan fishes, including Zebrafish (Danio rerio). Several studies have examined aspects of morphological development of the Weberian apparatus and hearing ability in Zebrafish. A comprehensive developmental description including both hard and soft tissues is lacking. This information is critical for both interpretation of genetic developmental analyses and to better understand the role of morphogenesis and integration on changes in hearing ability. RESULTS: Histological development of hard and soft tissues of the Weberian apparatus, including ossicles, ear, swim bladder, and ligaments are described from early larval stages (3.8 mm notochord length) through adult. Results show a strong relationship in developmental timing and maturation across all regions. All required auditory elements are present and morphologically integrated early, by 6.5 mm SL. Dynamic ossification patterns and changes in shape continue throughout the examined developmental period. CONCLUSIONS: This study provides the first comprehensive histological description of Weberian apparatus development in Zebrafish. Morphological integration was found early, before increases in hearing ability were detected in functional studies (>10 mm total length), suggesting morphological integration precedes functional integration. Further research is needed to examine the nature of the functional delay, and how maturation of the Weberian apparatus influences functionality.

Human auditory ossicles as an alternative optimal source of ancient DNA.

DNA recovery from ancient human remains has revolutionized our ability to reconstruct the genetic landscape of the past. Ancient DNA research has benefited from the identification of skeletal elements, such as the cochlear part of the osseous inner ear, that provides optimal contexts for DNA preservation; however, the rich genetic information obtained from the cochlea must be counterbalanced against the loss of morphological information caused by its sampling. Motivated by similarities in developmental processes and histological properties between the cochlea and auditory ossicles, we evaluate the ossicles as an alternative source of ancient DNA. We show that ossicles perform comparably to the cochlea in terms of DNA recovery, finding no substantial reduction in data quantity and minimal differences in data quality across preservation conditions. Ossicles can be sampled from intact skulls or disarticulated petrous bones without damage to surrounding bone, and we argue that they should be used when available to reduce damage to human remains. Our results identify another optimal skeletal element for ancient DNA analysis and add to a growing toolkit of sampling methods that help to better preserve skeletal remains for future research while maximizing the likelihood that ancient DNA analysis will produce useable results.

The middle ear of the pink fairy armadillo Chlamyphorus truncatus (Xenarthra, Cingulata, Chlamyphoridae): comparison with armadillo relatives using computed tomography.

The pink fairy armadillo Chlamyphorus truncatus is the smallest extant armadillo and one of the least-known fossorial mammals. The aim of this study was to establish if its middle ear is specially adapted to the subterranean environment, through comparison with more epigeic relatives of the groups Euphractinae (Chaetophractus villosus, Chaetophractus vellerosus, Zaedyus pichiy) and Dasypodinae (Dasypus hybridus). We examined the middle ears using micro-computed tomography and subsequent three-dimensional reconstructions. D. hybridus has a relatively small middle ear cavity, an incomplete bulla and 'ancestral' ossicular morphology. The other species, including Chlamyphorus, have fully ossified bullae and middle ear ossicles, with a morphology between 'transitional' and 'freely mobile', but in all armadillos the malleus retains a long anterior process. Unusual features of armadillo ears include the lack of a pedicellate lenticular apophysis and the presence, in some species, of an element of Paaw within the stapedius muscle. In common with many subterranean mammals, Chlamyphorus has a relatively flattened malleo-incudal articulation and appears to lack a functional tensor tympani muscle. Its middle ear cavity is not unusually enlarged, and its middle ear ossicles seem less robust than those of the other armadillos studied. In comparison with the euphractines, there is no reason to believe that the middle ear of this species is specially adapted to the subterranean environment; some aspects may even be indicative of degeneration. The screaming hairy armadillo, Chaetophractus vellerosus, has the most voluminous middle ear in both relative and absolute terms. Its hypertrophied middle ear cavity likely represents an adaptation to low-frequency hearing in arid rather than subterranean conditions.

How flexibility and eardrum cone shape affect sound conduction in single-ossicle ears: a dynamic model study of the chicken middle ear.

It is believed that non-mammals have poor hearing at high frequencies because the sound-conduction performance of their single-ossicle middle ears declines above a certain frequency. To better understand this behavior, a dynamic three-dimensional finite-element model of the chicken middle ear was constructed. The effect of changing the flexibility of the cartilaginous extracolumella on middle-ear sound conduction was simulated from 0.125 to 8 kHz, and the influence of the outward-bulging cone shape of the eardrum was studied by altering the depth and orientation of the eardrum cone in the model. It was found that extracolumella flexibility increases the middle-ear pressure gain at low frequencies due to an enhancement of eardrum motion, but it decreases the pressure gain at high frequencies as the bony columella becomes more resistant to extracolumella movement. Similar to the inward-pointing cone shape of the mammalian eardrum, it was shown that the outward-pointing cone shape of the chicken eardrum enhances the middle-ear pressure gain compared to a flat eardrum shape. When the outward-pointing eardrum was replaced by an inward-pointing eardrum, the pressure gain decreased slightly over the entire frequency range. This decrease was assigned to an increase in bending behavior of the extracolumella and a reduction in piston-like columella motion in the model with an inward-pointing eardrum. Possibly, the single-ossicle middle ear of birds favors an outward-pointing eardrum over an inward-pointing one as it preserves a straight angle between the columella and extrastapedius and a right angle between the columella and suprastapedius, which provides the optimal transmission.

How many bones? Every bone in my body.

Textbooks frequently report that there are 206 human bones, or 200 bones and 6 auditory ossicles. The human bone counts in history and within adulthood were reviewed. Tallies of 197 to 307 bones have been reported over the past several centuries. The relatively low modern reckoning of 206 was due to exclusion of teeth and sesamoid ossicles, and to reassessments of the hyoid, sacrum, coccyx, and sternum as unitary bones. An audit of bone counts during adulthood failed to confirm a rational justification for the total of 206. The number is higher in young adults and lower in the elderly. Difficulties in establishing a definitive bone count include individual differences and the inconsistency of viewing the adult cranium as a collection of 21 bones. Clin. Anat. 33:187-191, 2020. © 2019 Wiley Periodicals, Inc.

Micro-architecture study of the normal infant auditory ossicles with micro-computed tomography / Estudio de microarquitectura de los osículos auditivos infantiles normales con tomografía microcomputarizada

This study aimed to investigate the micro-anatomical morphology of ossicular chain in term fetus using micro-CT, in order to analyze the parameters of internal ossicular structure that may affect sound conduction.Four ossicular chains from two term fetuses were scanned by micro-CT. The related structural parameters of the trabeculae within the incus and malleus were calculated and compared. The fine anatomical structure of the auditory ossicles was analyzed.The microstructure of each auditory ossicles in term fetuses was clearly revealed by micro-CT. A marrow cavity was observed in the incus and malleus. In statistical analysis of the structural parameters of trabeculae in the incus and malleus, significant differences were found in BS/BV and Tb.Th (P < 0.05). Micro-CT enables the visualization of internal ossicular structure. The auditory ossicles in term fetus has good bone quality. The obtained bone structure data will help to clarify the physiological functions of normal fetal auditory ossicles.

Este estudio tuvo como objetivo investigar la morfología microanatómica de la cadena osicular en el feto a término con micro-CT, con el fin de analizar los parámetros de la estructura osicular interna que pueden afectar la conducción del sonido. Cuatro cadenas osiculares de dos fetos a término fueron examinadas por micro-CT. Se calcularon y compararon los parámetros estructurales relacionados de las trabéculas dentro de los incus y malleus. Se analizó la estructura anatómica fina de los osículos. Se observó claramente la microestructura de cada osículo en los fetos y la cavidad medular en el incus y el malleus. En el análisis estadístico de los parámetros estructurales de las trabéculas en el incus y el malleus, se encontraron diferencias significativas en BS / BV y Tb.Th (P <0,05). Micro-CT permite la visualización de la estructura osicular interna. Los osículos en el feto a término tienen buena calidad ósea. Los datos obtenidos de la estructura ósea ayudarán para aclarar las funciones fisiológicas de los osículos auditivos fetales normales.

Topography of vibration frequency responses on the bony tympano-periotic complex of the pilot whale Globicephala macrorhynchus.

In modern Cetacea, the ear bone complex comprises the tympanic and periotic bones forming the tympano-periotic complex (TPC), differing from temporal bone complexes of other mammals in form, construction, position, and possibly function. To elucidate its functioning in sound transmission, we studied the vibration response of 32 pairs of formaldehyde-glutaraldehyde-fixed TPCs of Globicephala macrorhynchus, the short-finned pilot whale (legally obtained in Taiji, Japan). A piezoelectric-crystal-based vibrator was surgically attached to a location on the cochlea near the exit of the acoustic nerve. The crystal delivered vibrational pulses through continuous sweeps from 5 to 50 kHz. The vibration response was measured as a function of frequency by Laser Doppler Vibrometry at five points on the TPC. The aim of the experiment was to clarify how the vibration amplitudes produced by different frequencies are distributed on the TPC. At the lowest frequencies (<12 kHz), no clear differential pattern emerged. At higher frequencies the anterolateral lip of the TP responded most sensitively with the highest displacement amplitudes, and response amplitudes decreased in orderly fashion towards the posterior part of the TPC. We propose that this works as a lever: high-frequency sounds are most sensitively received and cause the largest vibration amplitudes at the anterior part of the TP, driving movements with lower amplitude but greater force near the posteriorly located contact to the ossicular chain, which transmits the movements into the inner ear. Although force (pressure) amplification is not needed for impedance matching in water, it may be useful for driving the stiffly connected ossicles at the high frequencies used in echolocation.

Morphological and morphometrical study of the auditory ossicles in chinchilla.

This study is meant to illustrate and describe the features of the auditory ossicles of the chinchilla (Chinchilla lanigera), one of the species used more and more frequently in otology and ear surgery as animal model. Cephalic extremities of 12 C. lanigera individuals obtained from a private farm, where this species was bred for fur, were used in this study. The ossicles were obtained either by direct surgical harvesting by mastoid approach or after a dermestid beetle exposure followed by anatomical dissection. The three ossicles that form the assembly are the malleus, incus and stapes. After the removal of these ossicles, a series of anatomical descriptions were made, followed by seriate sets of measurements. The malleus and incus form a joined-single unit called the maleo-incal complex, with an elongated straight appearance, also due to the development of the anterior process. The handle of the malleus and the long process of incus are almost perpendicular to the main axis of the maleo-incal complex. The presence of the muscular process on the handle of the malleus is recorded. The overall shape of the incus is given by the uneven development of the two processes and the reduced neck part. The stapes is the smallest of the components that maintains the well-known architecture in accordance with the general model. The morphology of all three ossicles is backed by a series of measurements, some standard, some adapted to the morphology of the ossicles. From the very reduced comparative metrical data at our disposal, our study presents an average of 10% lower values for the ones presented earlier by other researchers in the same species.

Does cartilage tympanoplasty impair hearing in patients with normal preoperative hearing? A comparison of different techniques.

OBJECTIVES: To evaluate and compare functional outcomes of tympanoplasty procedures with temporalis fascia and four different types of cartilage grafts in chronic otitis media (COM) cases with normal preoperative hearing levels. METHODS: Records of patients who underwent type 1 tympanoplasty for non-complicated COM in a tertiary medical center between January 2010 and January 2017 were reviewed. Patients with central or marginal and dry perforations of the tympanic membrane, normal middle ear mucosa, intact ossicular chain and patients with a preoperative pure tone average (PTA) level of 25 dB or less and a word recognition score (WRS) of 88% or greater were included in the study. Graft success rates, preoperative and postoperative functional outcomes, and anatomical results were analyzed. RESULTS: One hundred and forty-four patients who met the inclusion criteria were evaluated in the study. PTA and Air-bone gap (ABG) levels decreased significantly both in TF and CG groups after the surgery (p = 0.001). Similarly, WRS scores increased significantly in both groups (p = 0.001). There was not a significant difference in terms of PTA increase, WRS increase, and ABG closure levels between cartilage and TF groups. Increase in PTA, closure in ABG, and increase in WRS levels were compared among TF, WsCCG, MCG, PCG, and CPIG groups. The increase in PTA levels was also found to be significantly superior in the TF group (p = 0,023). However, the multivariate analysis showed no significant difference for increase in WRS, closure in ABG and increase in PTA levels according to graft type (p = 0.285; p = 0.461; p = 0.106, respectively) and gender (p = 0.487; p = 0.811; p = 0.756, respectively). CONCLUSION: In COM cases with normal preoperative hearing, both TF and cartilage lead to superb functional and anatomical outcomes. There was not a significant difference in terms of PTA increase, WRS increase and ABG closure levels between cartilage and TF groups. The graft success rate of cartilage was found to be superior to TF, but there was not a statistically significant difference. Different types of cartilage grafts can be used in cases with normal preoperative hearing without the concern of hearing impairment.

Morphometric and macroanatomic examination of auditory ossicles in male wolves (Canis lupus).

BACKGROUND: The aim of the study was to determine morphometric and macroanatomic features of auditory ossicles and the tympanic bulla in wolf. MATERIALS AND METHODS: For this purpose, 7 skulls of adult male wolf were used in the study. Auditory ossicles was photographed on a dissection microscope after it was removed from the skull. A total of 14 morphometric measurements were taken among the different points of malleus, incus and stapes in Image J programme. Mean values of the measurements were obtained and statistically compared in terms of sides (right-left). RESULTS: In male wolves, the lengths of the right and left malleus were determined as mean 9.35 ± 0.14 and 9.57 ± 0.25 mm, the lengths of the incus as mean 3.01 ± 0.32 and 2.94 ± 0.16 mm, and the lengths of the stapes as mean 2.57 ± 0.12 and 2.59 ± 0.14 mm, respectively. The differences were not statistically significant when all the morphometric parameters were compared in terms of sides (p > 0.05). CONCLUSIONS: It is considered that this study will contribute to the anatomical studies to be conducted in the Canidae family regarding auditory ossicles.

The effect of single-ossicle ear flexibility and eardrum cone orientation on quasi-static behavior of the chicken middle ear.

In the single-ossicle ear of chickens, the quasi-static displacement of the umbo shows great asymmetry; umbo displacements are much larger for negative than for positive pressure in the middle ear, which is opposite to the typical asymmetry observed in mammal ears. To better understand this behavior, a finite-element model was created of the static response of the chicken middle ear. The role of flexibility of the extracolumella in the model was investigated, and the potential effect of the outward orientation of the tympanic-membrane cone was studied by building two adapted models with a flat membrane and an inverted conical membrane. It is found that the extracolumella must be made of flexible material to explain the large inward displacements of the umbo, and that displacements of the footplate are much smaller due to bending of the flexible extracolumella. However, increasing extracolumellar stiffness mostly reduces umbo displacement rather than increasing footplate displacement. The results suggest that the inverted orientation of the membrane cone is responsible for the change in asymmetry of the umbo displacement curve. The asymmetry of the footplate displacement curve in the normal model is smaller, but increases towards positive middle-ear pressure in the case of a flat or inverted membrane geometry.

Relative size variation of the otoliths, swim bladder, and Weberian apparatus structures in piranhas and pacus (Characiformes: Serrasalmidae) with different ecologies and its implications for the detection of sound stimuli.

The Weberian apparatus of otophysan fishes confers acute hearing that is hypothesized to allow these fishes to assess the environment and to find food resources. The otophysan family Serrasalmidae (piranhas and pacus) includes species known to feed on falling fruits and seeds (frugivore/granivores) that splash in rivers, herbivorous species associated with torrents and rapids (rheophiles), and carnivores that feed aggressively within shoals. Relevant sound stimuli may vary among these ecological groups and hearing may be tuned to different cues among species. In this context, we examined size variation of the Weberian ossicles, swim bladder chambers, and otoliths of 20 serrasalmid species from three broad feeding ecologies: frugivore/granivores, rheophiles, and carnivores. We performed 3D-reconstructions of high resolution tomographic data (µCT) from 54 museum specimens to estimate the size of these elements. We then tested for an ecology effect on covariation of auditory structure size and body size and accounted for phylogeny with phylogenetic generalized least squares analyses. Among ecological groups, we observed differences in relative sizes of otoliths associated with sound pressure and particle motion detection, and variation in Weberian ossicle size that may impact sound transmission. Rheophiles, which live in noisy environments, possess the strongest modifications of these structures.

Bone mineral density of human ear ossicles: An assessment of structure in relation to function.

Human ear ossicles are essential for normal sound conduction from the external environment to the inner ear. These bones are subjected to high biomechanical loads due to the sustained vibrations which occur with reception of sound. It is expected that the bones would undergo a significant amount of remodeling and change in bone mineral density during the lifespan of an individual. Therefore, the aim of the study was to evaluate the possible changes in bone mineral density of regions of the ossicular chain during postnatal life. Forty four left and 36 right sets of human ear ossicles, ranging from a sub-adult age group to a mature adult age group, were sourced from the School of Anatomical Sciences, University of Witwatersrand. The ear ossicles were scanned using a micro-focus CT X-ray. A three-dimensional reconstruction of each ossicle was created from the CT scan. Bone mineral density was then determined at specific sites on the ossicles. There was no statistically significant variation found in the bone mineral density in relation to the age of the specimens. However, the handle of the malleus, the incudo-stapedial joint and the insertion site for the tendon of stapedius had lower bone mineral densities when compared to adjacent articulation and nonattachment sites on the ossicular chain. This is possibly due to biomechanical stress in response to sound conduction rather than ageing. Lower bone mineral density may be indicative of regions that experience the highest biomechanical force, thus, resulting in increased remodeling. Clin. Anat. 31:1158-1166, 2018. © 2018 Wiley Periodicals, Inc.

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.