Annular Ligament Research Articles

Corrective Ulnar Osteotomy and Annular Ligament Reconstruction by Fascia Lata in Neglected Monteggia Fracture Dislocation in Children.

Corrective Ulnar Osteotomy and Annular Ligament Reconstruction by Fascia Lata in Neglected Monteggia Fracture Dislocation in Children.

Surgical treatment in children missed Monteggia lesions at Bhuj, Kutch, Gujarat: a retrospective study

<p class="abstract"><strong>Background:</strong> The treatment of an unrecognized Monteggia lesion continues to pose a therapeutic challenge, as evidenced by the variety of surgical techniques described. Moreover, there are high complication and redislocation rates following surgery. This report concerns a surgical technique to reduce a chronic dislocation of the radial head utilizing an ulnar osteotomy and internal fixation<span lang="EN-IN">.</span></p><p class="abstract"><strong>Methods:</strong> Present study was performed at department of orthopedics, Gujarat Adani institute of medical science, Bhuj, Kutch, Gujarat. Ethical clearance was taken from the institutional ethics board and informed consent was obtained from all the participants. Between July 2015 and September 2016 six children presented in a traumatic context with chronic dislocation of the radial head and malunion of the ulna. Patient mean age was 6.5 (range 4–8) years, and the mean interval between injury and surgical procedure was 17 (range 1–49) months. Surgery consisted of an ulnar osteotomy with angulation and lengthening, bone grafting at the osteotomy site, and internal fixation. Open reduction of the radial head, repair or reconstruction of the annular ligament or temporary fixation of the radial head with a transarticular wire was not undertaken. Cast immobilization with the forearm in neutral rotation was maintained for 4-6 weeks.<strong></strong></p><p class="abstract"><strong>Results:</strong> There was one case of nonunion. At an average follow-up of 3 (range 1.5–4.4) years, all patients had regained painless function of the forearm, good range of elbow and forearm motion, and maintenance of the radial head reduction<span lang="EN-IN">. </span></p><p class="abstract"><strong>Conclusions:</strong> Both angulation and elongation of the ulna are required to allow for reduction of the radial head. We do not see any indication for procedures directed at the radio-capitellar joint<span lang="EN-IN">.</span></p>

Dynamic property changes in stapedial annular ligament associated with acute otitis media in the chinchilla

Located at the end of the ossicular chain, the stapedial annular ligament (SAL) serves as a closed yet mobile boundary between the cochlear fluid and stapes footplate. It is unclear how SAL properties change with acute otitis media (AOM). This paper reports the measurements of SAL dynamic properties in chinchilla AOM model using dynamic mechanical analyzer (DMA) and frequency-temperature superposition (FTS) principle. AOM was analyzed in two infection groups: 4 days (4D) and 8 days (8D) post induction. SAL specimens were measured using DMA at three temperatures: 5, 25, and 37°C. To extend the testing frequencies to higher levels, FTS principle was employed. Then generalized Maxwell model was utilized to define the constitutive equations of the SAL. The complex shear moduli were obtained from seven samples of control, 4D, and 8D groups. Results show that the storage and loss shear moduli of SALs decreased due to AOM. The storage moduli for 4D and 8D ears were similar below 100Hz, and the loss modulus for 4D was significantly larger than 8D across the entire frequency range. This study reports data that contributes to ear biomechanics and improves understanding on the effects of AOM in middle ear tissues.

Oblique cord (chorda obliqua) of the forearm and muscle-associated fibrous tissues at and around the elbow joint: a study of human foetal specimens.

In adults, the oblique cord or chorda obliqua separates the origins of the flexor pollicis longus (FPL) and flexor digitorum profundus (FDP) muscles from the supinator muscle and elbow joint. This study examined the topographic anatomy of the oblique cord and related muscles in foetuses. Semiserial sections of five mid-term foetuses of gestational age (GA) 14-16 weeks and 12 late-stage foetuses of GA 28-30 weeks were histologically examined and three forearms at GA 30 weeks were macroscopically evaluated. Late-stage foetuses showed a fascial structure between the supinator and FDP muscles. The latter extended proximally to the elbow joint and the muscle origin thickened the distal, ulnar part of the capsule. The FPL origin also extended proximally but did not reach the joint capsule. These morphologies were consistent with macroscopic examinations. The brachialis muscle was widely inserted into the proximal, anterior part of the capsule. In addition, the medial collateral ligament was not covered by the pronator-flexor muscles but by the triceps brachii muscle. The oblique cord apparently did not form prenatally. After birth, the proximal parts of the FDP and FPL muscles were likely replaced by collagenous tissues, providing a specific type of intermuscular septum i.e., the oblique cord. This type of muscle-ligament transition was observed in the annular ligament of the radius. The foetal elbow joint was characterised by strong support by the FDP, brachialis and triceps brachii muscles. Therefore, the foetal elbow is not a miniature version of the adult elbow.

Concomitant injury of the annular ligament in fractures of the coronoid process and the supinator crest

Fractures of the coronoid process or the supinator crest, as well as arthroscopic resection of osteophytes around the coronoid process, can endanger the attachment of the annular ligament (AL) to the proximal ulna. The purpose of this study was to investigate the corresponding insertional areas of the AL within this context. In 30 embalmed human cadaveric elbow specimens, the insertional area of the AL at the anterior and posterior margin of the sigmoid notch was characterized. The distances and relations of the AL insertion anteriorly to the coronoid surface, the coronoid tip, and the depth of the coronoid process, as well as posteriorly to the supinator crest, were evaluated macroscopically. The mean distance of the anterior insertion area was 1.9 ± 0.6 mm (range, 1.0-3.1 mm) to the coronoid articular surface and 6.2 ± 1.7 mm (range, 2.9-10.2 mm) to the tip of the coronoid. The distance of the anterior insertion in relation to the depth of the coronoid process was 44% ± 11% (range, 30%-69%). The distance of the posterior insertion area to the level of the sigmoid notch measured from 3.5 ± 1.5 mm (range, 0.5-6.5 mm) to 17.7 ± 2.9 mm (range, 13.1-25.4 mm). Coronoid fractures involving 44% or more of the coronoid process and anterolaterally oriented fractures where one-third of the anterolateral facet is affected are accompanied by a complete anterior bony disruption of the AL. Arthroscopic resection of the coronoid tip should be limited to 1 mm distal to the coronoid articular surface to avoid injury to the AL. Fractures of the upper half of the supinator crest place the AL at risk at its posterior insertion.

Annular ligament reconstruction with the superficial head of the brachialis: surgical technique and biomechanical evaluation.

The purpose of this study was to perform biomechanical testing of annular ligament (AL) reconstruction using the superficial head of the brachialis tendon (SHBT) as a distally based tendon graft. We hypothesized that posterior translation of the radial head following AL reconstruction with an SHBT graft does not significantly differ from intact specimens. Six fresh-frozen elbow specimens were used. The stability of the radial head against posterior translation forces (30N) was evaluated in 0°, 45°, 90° and 120° of elbow flexion. Posterior translation was obtained for the intact AL, the sectioned AL and the reconstructed AL. Cyclic loading (100 cycles) in 90° of elbow flexion was performed for the intact and the reconstructed AL. Posterior translation of the radial head decreased during elbow flexion in native specimens. Sectioning of the AL significantly increased instability over the full range of motion. AL reconstruction with the SHBT restored the stability of the proximal radius but-other than the native AL-was not influenced by elbow flexion. In 120° of flexion the native AL provided significantly more stability when compared to the reconstructed AL. Cyclic loading did not provide significant differences between native and reconstructed specimens. We provide a feasible technique for AL reconstruction using the SHBT. The biomechanical results obtained in this study confirm the efficacy of the procedure. AL reconstruction restores the stability of the proximal radius, yet it cannot fully mimic the complex features of the intact AL.

Dynamics of the middle ear ossicles with an SMA prosthesis

During middle ear reconstruction, surgeons typically have to adjust the size and position of a medical prosthesis to fit the needs of each patient. In this paper, a prosthesis made of shape memory alloy is proposed to reduce operation time while accounting for the individual variability in middle ear lengths. This shape memory prosthesis (SMP) is activated by heat, so it is important to measure the regular and irregular behaviour prior to recommendation for medical practice. We present a two-degrees-of-freedom model of a reconstructed middle ear with an SMP that has two nonlinear springs, representing the properties of the annular ligament and the prosthesis. The properties of the SMP are described via polynomial dependence. Experiments on a temporal bone are used to determine the parameters of an intact ossicular chain and test a conventional titanium prosthesis. The dynamics of the reconstructed middle ear are investigated under different external excitation parameters. Bifurcation analysis was conducted and the stability of periodic solutions was examined to monitor the behaviour of the stapes. The results of this study provide interesting chaotic vibrations and regular oscillations with fluctuation. We determine that only the harmonic response of the stapes is advisable from a practical point of view, and this can only be achieved for small excitation amplitudes. Therefore, we show the importance of selecting appropriate prosthetic parameters to avoid irregular motions and deterministic chaos.

Impact of Prosthesis Length on Tympanic Membrane's and Annular Ligament's Stiffness and the Resulting Middle Ear Sound Transmission.

Prosthesis' length creates tension in ossicular reconstructions, which directly effects the middle ear sound transmission. Relatively long prostheses are often used to stabilize the middle ear reconstruction to prevent dislocation. Thereby, tension on the flexible components such as the tympanic membrane (TM) and the annular ligament (AL) is increased. Only little is known on the amount of displacement-related stiffening of the TM and AL, as well as the consecutive reduction in middle ear transfer function (METF). An expandable total ossicular replacement prosthesis was tensionfree inserted in nine cadaveric temporal bones between the malleus handle and the stapes footplate. Upon heat activation the prosthesis was lengthened, thus inducing tension on the reconstruction. The METF was assessed before and after elongation. TM's and AL's stiffness were determined by measuring their force-displacement characteristics. Upon activation the prostheses were elongated between 50 and 200 μm. A frequency-dependent METF reduction was measured with a decrease of 5 to 25 dB below 1.0 kHz. At frequencies >2.0 kHz the reduction was less prominent or the METF showed even an improvement of up to 10 dB. TM's stiffness remained constant during the elongation-induced displacement, whereas the AL's stiffness increased. The METF reduction below 1.0 kHz correlated with the increasing AL's stiffness. Tension has a significant impact on the METF after middle ear reconstruction. As little tension as possible should be used to enable best sound transmission. Stabilization of prosthesis should be achieved with dislocation devices to ensure secure coupling to the ossicular remnants without creating additional tension.

Morphology of the Lateral Ulnar Collateral Ligament of the Elbow

Objective: The lateral ulnar collateral ligament (LUCL) is considered to be the main factor against posterolateral rotatory instability (PLRI). The aim of this study was to clarify the morphological features of the LUCL and the related osseous landmarks on 3-dimensional (3D) images. We hypothesized that the characteristic features of the LUCL and related structures can be identified, which may assist surgeons in performing LUCL reconstruction with a more anatomic perspective. Materials and Methods: Thirty-five nonpaired, formalin-fixed human cadaveric elbows were evaluated in this study. After the identification of the LUCL, the outlines of the ligament were marked by using soft stainless wires. 3D images were created, and the insertions and running route of the LUCL and related osseous landmarks were analyzed. Results: The LUCL originated from the anterior edge of the prominence at the lateral epicondyle and inserted from the lesser sigmoid notch to the supinator crest with increasing width. In the 3D images, the LUCL formed an anterior curved shape and covered the radial head like a hammock. The insertion of the LUCL at the humerus was nearly at the center of the capitellum, with a width of 2.61 ± 1.02 mm. The insertion of the LUCL at the ulna was located from the lesser sigmoid notch to the supinator crest, with a width of 9.0 ± 2.8 mm. The proximal end of the LUCL insertion at the ulna was 7.0 ± 3.0 mm distal to the articular surface of the radial head. On the horizontal plane, the LUCL was located on the radial head at 99.5° ± 10.3° to 126.1° ± 12.4°. Conclusions: The LUCL insertion at the humerus was nearly at the center of the capitellum, and the LUCL insertion at the ulna was located from the lesser sigmoid notch to the supinator crest. This study showed that both the supinator crest and lesser sigmoid notch could be useful as osseous landmarks. The LUCL was attached to the annular ligament at 8 to 9 o’clock position in the radial head, which stabilizes the radial head. On the basis of these morphological features, the LUCL might act a posterior buttress for the radial head and the ulna to prevent its subluxation, and therefore it is considered to be the principal constraint of the elbow joint against PLRI. The results of this study may assist surgeons in performing LUCL reconstruction with a more anatomic perspective.

DYNAMIC SONOGRAPHY OF THE EQUINE METACARPO(TARSO)PHALANGEAL DIGITAL FLEXOR TENDON SHEATH.

Palmar/plantar annular desmitis is a common disease that may be associated with adhesions and structures affecting the flexor tendons, which requires tenoscopy to diagnose. The purpose of this descriptive study was to develop a dynamic sonographic technique for evaluating the motion of normal equine flexor tendons in relation to the palmar/plantar annular ligament and to compare findings with horses previously diagnosed with palmar/plantar annular desmitis. Ten healthy adult horses were examined prospectively and the images of four horses diagnosed with palmar/plantar annular desmitis were retrospectively evaluated. Dynamic sonography was performed at the level of the metacarpo/metatarsophalangeal joint by maximally extending and flexing the interphalangeal joints. Palmar/plantar annular ligament thickness (mm), size of any gap between the flexor tendons, and subjectively increased angulation of the long linear echoes of the superficial digital flexor tendon were measured. The presence of gliding motion between the palmar/plantar annular ligament and superficial digital flexor tendon was determined by consensus. Twenty-eight healthy control limbs (16 hind/12 fore) and four with palmar/plantar annular desmitis (3 hind/1 fore) were evaluated. Controls had unrestricted gliding motion between the palmar/plantar annular ligament and flexor tendons and zero to 13° of angulation of the long linear echoes. The four affected horses had restricted gliding motion and between 20-35° angulation of the long linear echoes. Dynamic ultrasound is a feasible technique for detecting restricted flexor tendon and palmar/plantar annular ligament gliding motion, as well as subjectively increased angulation of the long linear echoes of the flexor tendon in affected horses compared with controls and warrants further investigation.

Iodine potassium iodide improves the contrast-to-noise ratio of micro-computed tomography images of the human middle ear.

High-resolution imaging of middle-ear geometry is necessary for finite-element modeling. Although micro-computed tomography (microCT) is widely used because of its ability to image bony structures of the middle ear, it is difficult to visualize soft tissues - including the tympanic membrane and the suspensory ligaments/tendons - because of lack of contrast. The objective of this research is to quantitatively evaluate the efficacy of iodine potassium iodide (IKI) solution as a contrast agent. Six human temporal bones were used in this experiment, which were obtained in right-left pairs, from three cadaveric heads. All bones were fixed using formaldehyde. Three bones (one from each pair) were stained in IKI solution for 2 days, whereas the other three were not stained. Samples were scanned using a microCT system at a resolution of 20 μm. Eight soft tissues in the middle ear were segmented: anterior mallear ligament, incudomallear joint, lateral mallear ligament, posterior incudal ligament, stapedial annular ligament, stapedius muscle, tympanic membrane and tensor tympani muscle. Contrast-to-noise ratios (CNRs) of each soft tissue were calculated for each temporal bone. Combined CNRs of the soft tissues in unstained samples were 6.1 ± 3.0, whereas they were 8.1 ± 2.7 in stained samples. Results from Welch's t-test indicate significant difference between the two groups at a 95% confidence interval. Results for paired t-tests for each of the individual soft tissues also indicated significant improvement of contrast in all tissues after staining. Relatively large soft tissues in the middle ear such as the tympanic membrane and the tensor tympani muscle were impacted by staining more than smaller tissues such as the stapedial annular ligament. The increase in contrast with IKI solution confirms its potential application in automatic segmentation of the middle-ear soft tissues.

Biocompatible membrane of PDMS for the new chamber prosthesis stapes.

Stapes protheses are designed for patients with otosclerosis resulting immobilization or significant reduction of the stapes mobility. All currently used prostheses are called - piston prosthesis. However, its use to stimulate the cochlea is still imperfect. New chamber stapes prosthesis allows the perilymph excitation more effective than the piston prothesis. Moreover, the chamber prosthesis eliminates the common causes of piston-stapedotomy failures. The most important element of the new prosthesis is a flexible membrane. The membrane stiffness should be close to the stiffness of normal annular ligament. This work presents the process of selection of the membrane's thickness and its manufacturing technology. Method A 3D model of the chamber stapes prosthesis was build using Autodesk Inventor 2015. The model was imported to Abacus 6.13 computing environment. During numerical simulations, displacements corresponding to applied loads were calculated and the membrane thickness was adjusted so that its stiffness was the same as the ligament stiffness (~ 120 N/m). The compliance ratios calculated from the load-displacement curves for the membrane and the annular ligament were verified using linear regression analysis. After determining the thickness, the manufacturing technology of the membrane was developed. Results The best similarity between the membrane's and annular ligament's stiffness was achieved for PDMS membrane with the 0,15- mm thickness (similarity ratio R2=0,997752). In this work, the technological parameters of spin-coating process for membrane manufacture are also presented. Summary The proper functioning of the chamber stapes prosthesis requires the PDMS membrane with a thickness of 0,15 mm. The 0,15-mm membrane has the tiffness close to the stiffness of the normal annular ligament. Therefore, the chamber stapes prosthesis provides the perilymph stimulation at the level comparable to the healthy ear. New prosthesis is currently under pre-clinical investigation to optimize the shape of the inner chamber's surface.

Mineralization of the Equine Palmar/Plantar Annular Ligament Treated by Surgical Resection.

To document the clinical presentation, diagnosis, and surgical treatment of mineralization of the equine palmar/plantar annular ligament (PAL). Retrospective study. Ponies (n=7). Case records from 2 referral hospitals were examined to identify cases with lameness associated with PAL mineralization treated surgically. Follow-up information was obtained from the owners by telephone questionnaire. Duration of lameness before referral ranged from 5 weeks to 6 months, and degree of lameness from grade 1 to 5 out of 10. In 3 cases, records noted obvious pain when pressure was applied over the PAL. Pain resulting in lameness was localized to this area and all cases were treated surgically, although the extent of resected tissue varied among cases. Histological examination of resected tissue (4 cases) revealed fibrocartilaginous and/or osseous metaplasia. Following surgery, 6 of the 7 ponies became sound. Based on this limited case series, surgical treatment for mineralization of the PAL offers a favorable success rate without severe complications where conservative methods have failed.

Effects of successive tracheal resection and anastomosis on tracheal diameter and position of lobar bronchi in dogs.

OBJECTIVE To evaluate the effects of successive large-segment tracheal resection and anastomosis on tracheal diameter and position of lobar bronchi in dogs. ANIMALS 5 adult Beagles. PROCEDURES Right lateral radiographs were obtained for all dogs and used to measure tracheal length. Dogs were then euthanized, and successive segmental tracheal resections (intervals of 10% from 20% to 50% of the tracheal length), each of which was followed by anastomosis, were performed in each cadaver. Tracheobronchoscopy was performed before the first tracheal resection and after each of the anastomoses to evaluate tracheal diameter and changes in position of lobar bronchi. RESULTS Tracheal diameter was minimally affected by resections up to 50% of the tracheal length. Diameter of the trachea and position of bronchi were not affected by resection of 20% of the tracheal length. Changes in the position of various lobar bronchi were detected after resection of 30% of the tracheal length. CONCLUSIONS AND CLINCIAL RELEVANCE In this study, tracheal resections of 20% of the tracheal length were accommodated, possibly as a result of stretching of the annular ligament. Resections of ≥ 30% of the tracheal length altered the position of lobar bronchi. Clinical effects, if any, attributable to these changes in bronchial position remain to be elucidated.

Functional anatomy of the lateral collateral ligament of the elbow.

The aim of this study was to analyze the functional anatomy of the lateral collateral ligament complex (LCLC) and the surrounding forearm extensors. Using 81 human cadaveric upper extremities, the anatomy of the forearm extensors-especially the anconeus, supinator and extensor carpi ulnaris (ECU)-was analyzed. After removal of aforementioned extensors the functional anatomy of the LCLC was analyzed. The origin of the LCLC was evaluated for isometry. The insertion types of the lateral ulnar collateral ligament (LUCL) were analyzed and classified. The ECU runs parallel to the RCL to dynamically preserve varus stability. The supinator and anconeus muscle fibers coalesce with the LCLC and lengthen during pronation. The anconeus fibers run parallel to the LUCL in full flexion. The LCLC consists of the annular ligament (AL) and the isometric radial collateral ligament (RCL). During elbow flexion, its posterior branches (LUCL) tighten while the anterior branches loosen. When performing a pivot shift test, the loosened LUCL fibers do not fully tighten in full extension. The LUCL inserts along with the AL at the supinator crest. Three different insertion types could be observed. The LUCL represents the posterior branch of the RCL rather than a distinct ligament. It is non-isometric and lengthens during elbow flexion. The RCL was found to be of vital importance for neutralization of posterolateral rotatory forces. Pronation of the forearm actively stabilizes the elbow joint as the supinator, anconeus and biceps muscle work in unison to increase posterolateral rotatory stability.

The expression of tenascin-C and tenascin-W in human ossicles.

The ossicles of the middle ear (the malleus, incus and stapes) transmit forces resulting from vibrations of the tympanic membrane to the cochlea where they are coded as sound. Hearing loss can result from diseases such as rheumatoid arthritis (RA) that affect the joints between the ossicles or degenerative processes like otosclerosis that lead to ankylosis of the footplate of the stapes in the oval window of the cochlea. In this study, immunohistochemistry was used to determine if the extracellular matrix glycoproteins tenascin-C or tenascin-W are expressed in the incudomalleolar and incudostapedial joints of ossicles dissected from human cadavers. Tenascin-C, which is expressed during inflammatory conditions including RA, was seen in the articular cartilage of the incudomalleolar joints and the head of the stapes. Tenascin-W, in contrast, was enriched in the annular ligament that anchors the footplate of the stapes into the oval window of the cochlea.

Dynamics of a middle ear with fractional type of dissipation

In this paper, a model of spatial motion of the ossicular chain described as a system of two rigid bodies connected to the temporal bone through the system of particularly chosen massless viscoelastic rods was proposed. Several assumptions regarding the relative motion between incus and malleus, external loading force, distributed pressure of the perilymph on the stapes baseplate behind the oval window, and supporting ligaments were made. In order to avoid merging with fractional partial differential equations, the dissipation of energy due to the deformation of the eardrum is taken into account through deformation of its radial fibers while simple shear deformation pattern of the stapedial annular ligament was replaced by uniaxial deformation of viscoelastic rods. By use of the Gibbs–Appel approach and the complementary constitutive axioms corresponding to the fractional Kelvin–Zener model of viscoelastic body, the equations of motion were derived. The Cauchy problem given in terms of coupled fractional differential equations was transformed in the equivalent integer order form and solved numerically by standard numerical procedures. These results, obtained by means of the Atanackovic–Stankovic expansion formula, were compared with the ones received by use of Laplace’s transform and its numerical inversion. As a principal novelty, this model uses both fractional calculus and recently reported results on mechanical tests performed on human middle ear tissues. Thus, it can be used for either predicting of the middle ear behavior in normal and pathological conditions or simulations preceding implants design within restoration of the hearing function.

Fully implantable hearing aid in the incudostapedial joint gap

A fully implantable hearing aid is introduced which is a combined sensor-actuator-transducer designed for insertion into the incudostapedial joint gap (ISJ). The active elements each consist of a thin titanium membrane with an applied piezoelectric single crystal. The effectiveness of the operating principle is verified in a temporal bone study. We also take a closer look at the influence of an implantation-induced increase in middle ear stiffness on the transducer's output.An assembly of the transducer with 1 mm thickness is built and inserted into six temporal bones. At this thickness, the stiffness of the annular ligament is considerably increased, which leads to a loss in functional gain for the transducer. It is assumed that a thinner transducer would reduce this effect. In order to examine the performance for a prospective reduced pretension, we increased the gap size at the ISJ by 0.5 mm by removing the capitulum of the stapes in four temporal bones. The TM is stimulated with a broadband multisine sound signal in the audiological frequency range. The movement of the stapes footplate is measured with a laser Doppler vibrometer. The sensor signal is digitally processed and the amplified signal drives the actuator. The resulting feedback is minimized by an active noise control least mean square (LMS) algorithm which is implemented on a field programmable gate array. The dynamic range and the functional gain of the transducer in the temporal bones are determined.The results are compared to measurements from temporal bones without ISJ extension and to the results of Finite Elements Model (FE model) simulations.In the frequency range above 2 kHz a functional gain of 30 dB and more is achieved. This proposes the transducer as a potential treatment for high frequency hearing loss, e.g. for patients with noise-induced hearing loss. The transducer offers sufficient results for a comprehensive application. Adaptations in the transducer design or surgical approach are necessary to cope with ligament stiffening issues. These cause insufficient performance for low frequencies under 1 kHz.

Effects of Negative Middle Ear Pressure on Wideband Acoustic Immittance in Normal-Hearing Adults.

Wideband acoustic immittance (WAI) measurements are capable of quantifying middle ear performance over a wide range of frequencies relevant to human hearing. Static pressure in the middle ear cavity affects sound transmission to the cochlea, but few datasets exist to quantify the relationship between middle ear transmission and the static pressure. In this study, WAI measurements of normal ears are analyzed in both negative middle ear pressure (NMEP) and ambient middle ear pressure (AMEP) conditions, with a focus on the effects of NMEP in individual ears. Eight subjects with normal middle ear function were trained to induce consistent NMEPs, quantified by the tympanic peak pressure (TPP) and WAI. The effects of NMEP on the wideband power absorbance level are analyzed for individual ears. Complex (magnitude and phase) WAI quantities at the tympanic membrane (TM) are studied by removing the delay due to the residual ear canal (REC) volume between the probe tip and the TM. WAI results are then analyzed using a simplified classical model of the middle ear. For the 8 ears presented here, NMEP has the largest and most significant effect across ears from 0.8 to 1.9 kHz, resulting in reduced power absorbance by the middle ear and cochlea. On average, NMEP causes a decrease in the power absorbance level for low- to mid-frequencies, and a small increase above about 4 kHz. The effects of NMEP on WAI quantities, including the absorbance level and TM impedance, vary considerably across ears. The complex WAI at the TM and fitted model parameters show that NMEP causes a decrease in the aggregate compliance at the TM. Estimated REC delays show little to no dependence on NMEP. In agreement with previous results, these data show that the power absorbance level is most sensitive to NMEP around 1 kHz. The REC effect is removed from WAI measurements, allowing for direct estimation of complex WAI at the TM. These estimates show NMEP effects consistent with an increased stiffness in the middle ear, which could originate from the TM, tensor tympani, annular ligament, or other middle ear structures. Model results quantify this nonlinear, stiffness-related change in a systematic way, that is not dependent on averaging WAI results in frequency bands. Given the variability of pressure effects, likely related to intersubject variability at AMEP, TPP is not a strong predictor of change in WAI at the TM. More data and modeling will be needed to better quantify the relationship between NMEP, WAI, and middle ear transmission.

Impulse noise injury prediction based on the cochlear energy

The current impulse noise criteria for the protection against impulse noise injury do not incorporate an objective measure of hearing protection. A new biomechanically-based model has been developed based on improvement of the Auditory Hazard Assessment Algorithm for the Human (AHAAH) using the integrated cochlear energy (ICE) as the damage risk correlate (DRC). The model parameters have been corrected using the latest literature data. The anomalous dose–response inversion behavior of the AHAAH model was eliminated. The modeling results show that the annular ligament (AL) parameters are the dominant cause of the non-monotonic dose–response behavior of AHAAH. Based on parametric optimization analysis, a 40% reduction of the AL compliance from the AHAAH default value removed the dose–response inversion problem, and this value was found to be within the physiological range when compared with experimental data. The transfer functions from the new model are in good agreement with those of the human ear. A dose–response curve based on ICE was developed using the human walk-up temporary threshold shift (TTS) data. Furthermore, the ICE values calculated for the German rifle noise tests show excellent comparison with the injury outcomes, hence providing a significant independent validation of the improved model. The ICE was found to be the best DRC to both large weapons and small arms noise injury data, covering both protected and unprotected exposures, respectively. The new AHAAH model with ICE as the dose metric is adequate for use as a medical standard against impulse noise injury.