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Results for “Bone Conduction”

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At least 1,369 records · Page 76Linked to original sources
PubMed1997

Electric current density imaging of bone by MRI.

Current density imaging (CDI) has been shown to be a feasible method to map spatial distribution of electric currents through bone structures and for studying osteoporosis and bone fracture models. For the osteoporosis model, bone sample was moistened in a solution of a sodium salt of ethylendiamintetraacetic acid (EDTA) which causes chemical reaction with hydroxyapatite Ca2+ ions and lowers the mineralisation degree of the solid bone. This enables clear visualisation of conventional magnetic resonance imaging and CDI. Sensitivity of conventional magnetic resonance and CD images of bone was improved by immersing the bone samples into physiological saline containing contrast agent Gd-DTPA prior to imaging. To stimulate effects of bone fracture on electric current conductivity through bone, a transverse cut was made through the bone, and the resulting gap was filled with an insulator. Electric current density images under these conditions have shown that regions of strong conductivity can be distinguished from regions of no conductivity at the site where the insulator restricts electric current. Real bone fracture was imaged as well. To demonstrate influence of electrolyte concentration on electric current spatial distribution, the bone samples were imaged after being immersed in various saline concentrations. The same contrast in current density images was produced with the combinations of higher electrolyte concentrations and lower voltages. Our observations demonstrate the feasibility of the method in mapping current density in bone structures, which could have implications in understanding and monitoring the effects of the electrical stimulation.

Animals↗
PubMed1998

Intraindividual comparison of the bone-anchored hearing aid and air-conduction hearing aids.

BACKGROUND: Some patients have to stop using their air-conduction hearing aid(s) because it causes or exacerbates chronic otitis. Then, a solution is the use of a bone-conduction hearing aid such as the percutaneous bone-anchored hearing aid (BAHA). OBJECTIVE: To compare patients' performance with their previous air-conduction hearing aid(s) and their BAHA using audiometric tests and a questionnaire. DESIGN: Prospective clinical evaluation in a single subject design. PATIENTS: The results of 34 consecutive patients from the Nijmegen, the Netherlands, BAHA series were included. The patients had bilateral conductive or mixed hearing loss and chronic ear problems. Before the BAHA was fitted, the patients used air-conduction hearing aids. RESULTS: The results of the speech recognition in noise test showed a small but significant improvement with the BAHA. This improvement was related to the size of the air-bone gap. The greater the air-bone gap, the poorer the results with the air-conduction hearing aid(s). The questionnaire demonstrated that the majority of patients preferred the BAHA; diminished occurrence of ear infections played a significant role. The patients did not express an evident preference concerning speech recognition. CONCLUSIONS: In patients with chronic ear problems a BAHA is an acceptable alternative if an air-conduction hearing aid is contraindicated. Preoperative assessment of the size of the air-bone gap is of some help to predict whether speech recognition may improve or deteriorate with the BAHA compared with the air-conduction hearing aid.

Adult↗
PubMed2005

[Results of stapedotomy in the cases of "floating footplate"].

One of the problems in the stapes surgery is the floating footplate. The frequency of incidence of this complication is 2% to 5.8% of all operations. The authors present the results of stapes operations in a group of 28 cases (2.5%) from all the 1120 operations, in which the surgeon experienced a floating footplate. The hearing results were evaluated on the base of the average gain of air-conduction thresholds and air-bone gap levels at 500, 1000, 2000 and 3000 Hz. The improvement of hearing we observed in 24 patients, 4 patients heard worse.

Adult↗
PubMed2006

QTL with pleiotropic effects on serum levels of bone-specific alkaline phosphatase and osteocalcin maps to the baboon ortholog of human chromosome 6p23-21.3.

UNLABELLED: Bone ALP and OC are under partial genetic control. This study of 591 pedigreed baboons shows a QTL corresponding to human 6p23-21.3 that accounts for 25% (bone ALP) and 20% (OC) of the genetic variance. A gene affecting osteoblast activity, number, or recruitment likely resides in this area. INTRODUCTION: Serum levels of bone alkaline phosphatase (ALP) and osteocalcin (OC) reflect osteoblast activity. Both of these measures are under partial genetic control. Genetic effects on bone ALP have not been previously localized to chromosomal regions in primates, nor has the degree to which genetic effects are shared (pleiotropic) between bone ALP and OC been studied. MATERIALS AND METHODS: We applied variance components methods to a sample of 591 adult pedigreed baboons to detect and quantify effects of genes that influence bone ALP and that have pleiotropic effects on bone ALP and OC. A univariate linkage analysis was conducted for bone ALP. Bivariate linkage analyses were conducted in areas for which the bone ALP results presented here and a previous univariate OC linkage analysis showed evidence for linkage on the same chromosome for both bone ALP and OC. RESULTS: A quantitative trait locus (QTL) for serum levels of bone ALP is evident on the baboon ortholog of human chromosomal region 6p (LOD 2.93). Thirty-seven percent (genetic correlation [rho(G)] = 0.61) of the genetic variance in bone ALP and OC is caused by pleiotropic effects of the same gene(s). Bivariate linkage analysis revealed a QTL in the region corresponding to human chromosome 6p23-21.3, with the strongest evidence for bivariate linkage near D6S422 (LOD = 2.97 at 22 cM from our pter-most marker). D6S422 maps to 20.4 Mb in the human genome. The QTL-specific heritability (h2) is 0.25 and 0.20 for bone ALP and OC, respectively. CONCLUSIONS: This first formal test for shared genetic effects on two serum markers of osteoblast activity indicates that a significant pleiotropic effect on bone ALP and OC levels, and thus on bone formation, is detectible. The fact that this region corresponds to one on mouse chromosome 13 that has repeatedly yielded QTLs for BMD should encourage more intensive study of the effect of genes in this region on bone maintenance and turnover.

Alkaline Phosphatase↗
PubMed1994

Audiological results of the bone-anchored hearing aid HC200: multicenter results.

Sixty-two patients with conductive or mixed hearing loss (average bone conduction threshold at 0.5, 1, and 2 kHz ranged from 1 to 44 dB hearing level) were fitted with a bone-anchored hearing aid (BAHA type HC200). Previously, 52 of them had used a conventional bone conduction hearing aid (CBHA) and 10 of them an air conduction hearing aid (ACHA). Audiological tests were conducted to compare the patients' performance with the BAHA to that with their previous conventional hearing aid. In the speech recognition in quiet test, only 5 patients in the CBHA group improved significantly: the majority had 100% scores with both hearing aids. In the speech recognition in noise test, 28 patients improved significantly. The mean improvement in the signal to noise ratio (S/N) in the CBHA group was -2.3 +/- 2.4 dB. That none of the patients in the CBHA group performed worse with the BAHA led us to the conclusion that the BAHA is superior to the CBHA. None of the patients in the ACHA group achieved a better speech recognition in quiet score using the BAHA. On average, there was no significant improvement in the S/N ratio in the ACHA group, although in 6 patients the S/N ratio improved significantly, and in 1 patient it worsened significantly. From the whole group, the performance of only 2 patients, both in the ACHA group, was significantly worse with the BAHA on one of the speech recognition tests.

Adolescent↗