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At least 1,495 records · Page 83Linked to original sources
PubMed1984

Sound pickup utilizing an implantable piezoelectric ceramic bimorph element: application to the cochlear implant.

The degree of sound pickup possible with a piezoelectric ceramic bimorph element ( PCBE ) was tested as part of research on a total implantation system for a cochlear prosthesis. The PCBE functions as an electromechanical transducer and can be utilized as a device to sense vibration in the tympanic membrane by touching it to the malleus head. This method lends itself to the miniaturization and simplification required by an implantable device for sound pickup. The ability of the PCBE to function as a device to pick up sound was investigated using three normal human temporal bones. The sensitivity of the PCBE when coupled to the malleus was calculated as the ratio of the voltage generated by the PCBE to the sound pressure in front of the tympanic membrane, when these factors were processed with a spectrum analyzer. The best sensitivities registered with the three temporal bone specimens were -63, -61, -59 dB re 1 V/Pa, respectively, at 1 kHz. The frequency response curves had resonant frequencies at about 2 kHz and declined beyond 5 kHz. These results indicate that a PCBE coupled to the malleus head performs satisfactorily in regard to sound pickup and shows promise as a component of a totally implanted hearing system.

Bone Conduction↗
PubMed1993

[Hydroxyapatite in orthognathic surgery. Animal experimentation and clinical applications].

Bone cell conduction can occur within hydroxyapatite, a biocompatible, bioactive, synthetised ceramic material, when it is placed in contact with bone tissue. Results of experimental and clinical studies on maxillary osteotomy incisional lines have confirmed these properties, the quality and stability of the results and the good tolerance of this biomaterial making it a product of choice as a substitute of iliac bone grafts, when no longer indicated in this context.

Adult↗
PubMed1990

In search of pathologic correlates for hearing loss and vertigo in Paget's disease. A clinical and histopathologic study of 26 temporal bones.

Mixed sensorineural and conductive hearing loss is a common clinical manifestation of Paget's disease of the temporal bone, and while there are numerous clinical and pathologic reports on the condition, none have identified a consistent pathologic explanation for the hearing loss. We performed histologic studies on 26 temporal bones exhibiting Paget's disease from 16 persons, of whom 7 had audiometric testing performed. Contrary to common opinion, the conductive hearing loss is not caused by ossicular fixation; in fact, no cause could be found in the seven ears with documented conductive hearing losses. While the sensorineural hearing losses were greater than normal for age, we could not identify cochlear disorders that could be attributed to Paget's disease. It is concluded that the hearing losses in Paget's disease are caused by changes in bone density, mass, and form that serve to dampen the finely tuned motion mechanics of the middle and inner ears.

Adult↗
PubMed2000

Variation in bone mineral density of the sacrum in young adults and its significance for sacral fixation.

STUDY DESIGN: Bone mineral density variations throughout the sacrum were measured and correlated with sacral screw insertion torque. OBJECTIVE: To quantify bone mineral density variations within the S1 body and ala of young human specimens, especially along the pathways of sacral screws, and to examine the relation between sacral screw fixation and bone mineral density. SUMMARY OF BACKGROUND DATA: Vertebral bone quality is an essential factor in anterior or posterior screw fixation of the spine. Several studies have been conducted regarding bone mineral density variations in the cervical and thoracolumbar spine. However, such variations in bone mineral density in the sacrum have not been well documented. METHODS: The bone mineral density of 13 sacral specimens from young male cadavers (mean age, 31 years) was measured using highly accurate quantitative computed tomography. Variations in bone mineral density were measured in five transverse layers and seven vertical columns within the S1 body, and in four transverse layers and six vertical columns within the ala. The sacral screw insertion torque was measured (unicortical and bicortical), and the correlation with bone mineral density was calculated. RESULTS: The mean bone mineral density of the S1 body was 381.9 +/- 59 mg/cm3, which was 31.9% higher than that of the sacral ala (mean, 296.9 +/- 86 mg/cm3) (P < 0.05). Bone mineral density of the superior sacral endplate was higher than that of any other transverse layer. Columns near the lateral posterior and lateral anterior of the S1 body had the highest bone mineral density. In the ala, bone mineral density values of the internal columns (pedicle) were the highest. Screw insertion torque for bicortical purchase along the S1 pedicle correlated well with the bone mineral density of the S1 body (r = 0.67, P < 0.05). CONCLUSION: This study quantified the volumetric bone mineral density variations within the S1 body and ala, and a significant linear correlation between the screw insertion torque and bone mineral density was found. Optimal sacral screw insertion pathways were also outlined based on bone mineral density values.

Adult↗
PubMed1993

Brain stem auditory evoked potentials from bone stimulation in dogs.

Brain stem auditory evoked potential (BAEP) testing with air-conducted click stimuli can be used to diagnose sensorineural deafness in dogs if conductive deafness can be ruled out. Detection of conductive deafness can be performed by recording BAEP elicited by a vibratory stimulus transducer placed against the skull. Air- and bone-conducted BAEP were compared in dogs, varying bone stimulator placement, click polarity, and stimulus intensity. Optimal bone stimulator placement was determined to be over the mastoid process, followed by the mandible and the zygomatic arch. Condensation polarity clicks gave responses preferable to those elicited by rarefaction or alternating polarity. Bone-conducted BAEP peak latencies were significantly longer than air-conducted latencies after correction of the latencies for the air conduction time accompanying air-conducted stimuli. Significant differences between stimulus modalities were not seen for BAEP peak amplitudes or interpeak latencies. Latency-intensity and amplitude-intensity regressions had similar effects for both modalities: latencies decreased and amplitudes increased as stimulus intensity increased.

Acoustic Stimulation↗
PubMed1997

Assessment of an ectopic bone formation system with implantation of pelleted rat primary growth cartilage cells.

To assess the ectopic bone formation system, growth cartilage (GC) cells were implanted to ectopic sites, and the effect of the implanting sites and gender of animals on bone formation were examined. Each 5 x 10(5) batch of GC cells from young rat ribs was pelleted, cultured in calcification medium, and implanted to ectopic sites (in a peritoneal cavitiy or on subcutaneous muscle) in female or male rats. The implanted pellets formed bone after 3-4 weeks at the ectopic sites. Histological examination concluded that, first, a subcutaneous muscle site is more conductive to bone formation than a peritoneal cavity site and, second, the pelleted GC cells implanted in male rats formed bone more effectively than those in female rats. Therefore, at present, the ectopic bone formation system of pelleted primary GC cells onto subcutaneous muscle of male rats is an appropriate system for the evaluation of bone formation.

Animals↗
PubMed1999

[Emergency diseases of the larynx and pharynx (comparative statistics)].

473 patients with face skeleton traumas were treated. Bones of the nose, nose and paranasal sinuses, paranasal sinuses were injured in 83.7, 5.2 and 3.5% of the patients, respectively. Combined traumas of the nose, nasal sinuses, zygomatic bone and the orbit were observed in 7.6% of the examinees. Nasal fractures with displacement were encountered in 62%, without displacement in 38% of the patients. In most of the cases reposition of the nasal bones was conducted endonasally early after the trauma, late reposition was made 5-days after the trauma. In fractures of the zygomatic bone with displacement and of the orbit, reposition of the bone was carried out either through the maxillary bone or externally with Limberg's hook. In the fractures of the inferior orbital wall, revision of the bone wall was made via the external cut along the orbital margins. Multiple small fragments were removed, the plate of high molecular polyethylene 2 x 2.5 cm in size was inserted subperiosteally. After the revision, the maxillary sinus was tamponed with iodoform tampon for fixation. The tampon was removed in 9 days maximum. Participation of the dentist and ophthalmologist in surgical treatment of combined traumas of the face skeleton bones improves the operation outcome, reduces the number of complications, cosmetic defects and persistent functional disorders.

Adult↗
PubMed2001

Goldenhar's syndrome: congenital hearing deficit of conductive or sensorineural origin? Temporal bone histopathologic study.

BACKGROUND: Oculoauriculovertebral dysplasia (OAVD) (Goldenhar's syndrome) is a congenital syndrome with ipsilateral deformity of the ear and face, epibulbar lipodermoids, coloboma, and vertebral anomalies. Goldenhar's anomaly has often been associated with a degree of congenital hearing deficits, almost always of a conductive origin, but a sensorineural component is also suspected in some cases, evident through malformations of the inner ear. PATIENTS AND METHODS: Both temporal bones of a 10-day-old deceased patient with oculoauriculovertebral dysplasia were examined by light microscopy. RESULTS: The ear deformities included deformity of the auricle, atresia of the external auditory canal, and malformation of the tympanic cavity and ossicles. Abnormalities of the stria vascularis and the semicircular canals were also demonstrated. Further inner ear deformities were not identified in this case. CONCLUSION: These histopathologic findings appear to confirm the conductive component of the congenital hearing deficit, but a sensorineural component could not be omitted. The ear alterations favor early developmental field defects. The causes of this condition are controversial. Recent results in genetic research pertaining to the MSX class genes permit better understanding of the variety, variability, and different degrees of severity of the anomalies described here.

Goldenhar Syndrome↗
PubMed1977

Investigation of variable factors in drilling bone.

Experiments were conducted to investigate the pressures that are exerted on drills during the preparation of bone. Twenty operators used six different types of drills at high and low speeds to prepare standardized holes and slots in animal bone. The peak vertical forces exerted varied between 5.98 and 24.32 newtons (x = 12.45 newtons). The mean vertical forces varied between 4.22 and 18.93 newtons (x = 9.16 newtons). Spear point and twist drills were associated with significantly lower operating pressures and shorter operating times than round and fissure burs. These differences, however, were much less than the interoperator variations.

Animals↗
PubMed1997

Acoustic effect of malleus head removal and tensor tympani muscle section on middle ear reconstruction.

In the reconstruction of ears with a missing incus, an incus replacement prosthesis (IRP) is commonly used to connect malleus and stapes. In some cases, it is necessary to resect the malleus head and/or section the tensor tympani muscle (TTM) tendon. The acoustic effects of these maneuvers have not been well studied. We performed experiments in a temporal bone model to measure the effect of these maneuvers on middle ear sound transmission. Measurements of umbo and stapes displacement were made before and after malleus head removal and TTM section plus incus replacement with an IRP. After malleus head removal, there was a peak gain in stapes displacement of 6 dB below 0.5 kHz and 8 dB above 2.5 kHz. TTM section had a similar but lesser effect. A clinical example is described.

Acoustic Stimulation↗
PubMed2006

Middle ear cavity and ear canal pressure-driven stapes velocity responses in human cadaveric temporal bones.

Drive pressure to stapes velocity (V(st)) transfer function measurements are collected and compared for human cadaveric temporal bones with the drive pressure alternately on the ear canal (EC) and middle ear cavity (MEC) sides of the tympanic membrane (TM), in order to predict the performance of proposed middle-ear implantable acoustic hearing aids, as well as provide additional data for examining human middle ear mechanics. The chief finding is that, in terms of the V(st) response, MEC stimulation performs at least as well as EC stimulation below 8 kHz, provided that the EC is unplugged. Plugging the EC causes a reduced response for MEC drive below 2 kHz, due to a corresponding reduction of the pressure difference between the two sides of the TM. Between 8 and 11 kHz, the MEC drive transfer functions feature an approximately 17 dB drop in magnitude below the EC drive case, the cause of which remains unknown. The EC drive transfer functions reported here feature significantly less magnitude roll-off above 1 kHz than previous studies [with a slope of -2.3 vs -6.7 dB/octave for Aibara et al., Hear. Res. 152, 100-109 (2001)], and significantly more phase group delay (134 vs 62 micros for Aibara et al.).

Artifacts↗