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At least 1,477 records · Page 82Linked to original sources
PubMed1992

Bone mineral density in 15- to 21-year-old eumenorrheic and amenorrheic subjects.

The purposes of this study were to compare the lumbar spine bone mineral density of eumenorrheic and amenorrheic white subjects aged 15 to 21 years, and to describe the femoral neck bone mineral density in the eumenorrheic subjects. Twenty-eight eumenorrheic females had lumbar bone mineral density (mean +/- SD) of 1.213 +/- 0.117 g/cm2, and femoral neck bone mineral density of 1.032 +/- 0.092 g/cm2 measured with dual energy x-ray absorptiometry. Bone mineral density at neither site was related to age, energy intake, or calcium intake. Femoral neck bone mineral density was related to energy expenditure. Body composition was measured with total body electrical conductivity, and bone mineral density at both sites was related to body weight as much as fat-free mass. Eight amenorrheic subjects had a lumbar spine bone mineral density of 1.057 +/- 0.113 g/cm2, which was lower than in the eumenorrheic group. However, when controlling for weight, this difference was not significant. Peak lumbar and femoral neck bone mineral density may be reached at midadolescence.

Absorptiometry, Photon↗
PubMed1984

Acoustical characteristics of surgically altered human temporal bones.

The resonance qualities of the external auditory canal can increase the sound pressure level (SPL) at the tympanic membrane by as much as 20 dB between 2 and 4 kHz. Surgery on the canal, particularly in the form of a modified radical mastoidectomy, might be expected to affect this with resultant implications for speech discrimination. The creation of a modified radical mastoidectomy in 6 temporal bones altered the SPL at the tympanic membrane by +10 dB at 2 kHz, +14 dB at 2.5 kHz, -2 dB at 3 kHz, -12 dB at 3.5 kHz, -20 dB at 4 kHz, -16 dB at 5 kHz and -8 dB at 6 kHz. When this transfer function was applied to 2 subjects, speech discrimination in noise was reduced by 6%. Whether this is of any magnitude compared with the effect of the disease requires prospective studies in individuals undergoing a modified radical mastoidectomy.

Acoustics↗
PubMed1994

Intermittent cyclical etidronate in the prevention of corticosteroid-induced bone loss.

We conducted a prospective study of etidronate's effects on corticosteroid-induced bone loss in postmenopausal women with temporal arteritis for whom high-dose prednisone therapy was indicated. Group A (n = 10) received etidronate (400 mg/day for 2 weeks, then 11 weeks off etidronate; four cycles total) and prednisone: Group B (n = 10) received only prednisone. Vertebral bone mineral density (BMD) was measured blinded by dual X-ray absorptiometry. At 3, 6 and 12 months, vertebral BMD was significantly (P < 0.01) increased in Group A and decreased in Group B, based on mean actual and percent changes in BMD and mean changes in BMD Z-score from baseline. Between-group comparisons were also significant (P < 0.002) at each time point. No adverse events related to etidronate treatment were reported. Our results suggest that corticosteroid-induced bone loss may be prevented by instituting intermittent cyclical etidronate therapy when high-dose prednisone therapy is begun. Further research into bisphosphonate use in corticosteroid-induced bone loss (with larger patient populations, longer follow-up and fracture assessment) is warranted.

Adrenal Cortex Hormones↗
PubMed1982

Incudo-stapedial joint pathology: a tympanometric approach.

Two-component tympanometry with a high probe-tone frequency enables a better distinction to be made between mobile but normal middle-ear systems and middle-ear systems suffering from necrosis, luxation, or disruption. Susceptance and conductance tympanograms obtained from 14 patients with confirmed pathological middle-ear lesions and 8 postmortem temporal bones, experimentally manipulated either surgically or with a 1 N HCl solution, were compared to tympanograms obtained from 80 normal subjects of an earlier study. With a 660-Hz probe tone, normal middle ears generate bell-shaped or normal sharp W-shaped patterns, whereas the pathologies of the middle ear give rise to irregular multi-extrema tympanograms. The differences between the two types of multi-extrema curves are discussed in detail. The use of phase-angle tympanometry is recommended to enable a quick and accurate distinction between normal and abnormal types of multi-extrema tympanograms. This study also points out clearly that 220-Hz tympanograms do not allow clear differentiation between pathological and normal middle ears.

Acoustic Impedance Tests↗
PubMed2002

Conduction analysis of cement interface temperature in total knee arthroplasty.

We applied an axisymmetric model of the tibia to a finite element method and analyzed the heat conduction from bone cement in total knee arthroplasty using numerical simulation with the finite element analysis software, ABACUS. We hypothesized the thermal necrotic map of bone. Moreover, we suggested a method for preventing thermal necrosis of bone using this simulation. We adopted an initial temperature of 32?C and a cement layer of 3mm to our simulation and analyzed heat conduction. The maximum temperature into the cement layer was 65?C and 56?C at the bone-cement interface 200 sec after the start of heat generation. Bone necrosis was observed approximately 2mm from the bone-cement interface. To thin the cement layer, the maximum temperature and bone necrotic area reduced. At a cement layer of less than 1mm no bone necrotic area was observed. To lower the initial temperature of the bone surface, the maximum temperature and bone necrotic area was also reduced. At an initial temperature of less than 28?C we did not find any bone necrosis. Even if we hypothesized pouring cold water around the prosthesis, the maximum temperature did not reduce at any time, neither did the necrotic area reduce. We should make the cement layer as thin as possible and cool the bone before cementing to prevent thermal bone necrosis.

Arthroplasty, Replacement, Knee↗
PubMed1991

On the transmission of sound generated by an electromagnetic device from the mastoid process to the petrous bone.

An electromagnetic device (EMD) for sound transmission from the mastoid process to the petrous part of the temporal bone was designed, built, and analyzed. A theoretical model was developed in order to predict the EMD acoustical performance and the distortion caused by skull bones. This model enabled the investigation of various technical improvements and calibration options. The EMD was miniaturized by using rare earth magnets in the construction of both external transmitter and internal receiver. In vitro implantation of the internal receiver into the mastoid process was carried out by simple mastoidectomy techniques. The input and output powers of the system, including the EMD and skull bones components, were measured and the power transfer function was calculated. The sound, which was generated by the EMD and transmitted through the dry as well as simulated cadaver skull, had high fidelity in spite of some vibratory distortion at the lower sonic frequencies. Results suggest that further development of hearing aids based on electromechanical sound transmission should take into account the specific acoustic response pattern of the skull bones.

Bone Conduction↗