Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research
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J. Bone Miner. Res. · Jul 1995
Estimates of volumetric bone density from projectional measurements improve the discriminatory capability of dual X-ray absorptiometry.
To determine whether estimates of volumetric bone density from projectional scans of the lumbar spine have weaker associations with height and weight and stronger associations with prevalent vertebral fractures than standard projectional bone mineral density (BMD) and bone mineral content (BMC), we obtained posteroanterior (PA) dual X-ray absorptiometry (DXA), lateral supine DXA (Hologic QDR 2000), and quantitative computed tomography (QCT, GE 9800 scanner) in 260 postmenopausal women enrolled in two trials of treatment for osteoporosis. In 223 women, all vertebral levels, i.e., L2-L4 in the DXA scan and L1-L3 in the QCT scan, could be evaluated. Fifty-five women were diagnosed as having at least one mild fracture (age 67.9 +/- 6.5 years) and 168 women did not have any fractures (age 62.3 +/- 6.9 years). ⋯ The associations with vertebral fracture were stronger for QCT (odds ratio [QR] = 3.17; 95% confidence interval [CI] = 1.90-5.27), eVBMD (OR = 2.87; CI 1.80-4.57), WA BMDHol (OR = 2.86; CI 1.80-4.55) and WA-BMD (OR = 2.77; CI 1.75-4.39) than for BMAD*/BMD* (OR = 2.03; CI 1.32-3.12), BMAD (OR = 1.68; CI 1.14-2.48), lateral BMD (OR = 1.88; CI 1.28-2.77), standard PA BMD (OR = 1.47; CI 1.02-2.13) or PA BMC (OR = 1.22; CI 0.86-1.74). The areas under the receiver operating characteristic (ROC) curves for QCT and all estimates of volumetric BMD were significantly higher compared with standard PA BMD and PA BMC. We conclude that, like QCT, estimates of volumetric bone density from paired PA and lateral scans are unaffected by height and weight and are more strongly associated with vertebral fracture than standard PA BMD or BMC, or estimates of volumetric density that are solely based on PA DXA scans.
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J. Bone Miner. Res. · Oct 1994
Comparative StudyEffects of free mobilization and low- to high-intensity treadmill running on the immobilization-induced bone loss in rats.
After an immobilization period of 3 weeks, the effects of free remobilization (8 weeks) as well as low- and high-intensity treadmill running on the bone mineral content (BMC) and density (BMD) of the hindlimbs of Sprague-Dawley rats (n = 70) were studied using a dual-energy x-ray absorptiometric scanner. In the low-intensity running program, the rats were allowed to move freely in the cage for 1 week, after which they started to run on a treadmill twice a day for 7 weeks. The speed of the treadmill was 20 cm/s, with an uphill inclination of 10 degrees. ⋯ Immobilization for 3 weeks produced a significant BMC and BMD loss in the immobilized left femur and tibia (mean loss 9.6%, p < 0.001) but did not affect the right free limbs. Both low- and high-intensity running restored mineral content in the immobilized limb; however, an average 5% difference (p < 0.05) in mineral content of the right and left limb bones persisted. In the running groups, the values for the immobilized left limbs were at the same level or exceeded (range 3.8-11.6%, p < 0.05-0.01) and those of the free right limbs exclusively exceeded (range 5.3-15.9%, p < 0.05-0.01) the corresponding values of the age-matched control rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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J. Bone Miner. Res. · Aug 1994
Periosteal bone formation stimulated by externally induced bending strains.
The rat tibia four-point bending model is a new mechanical loading model in which force is applied through external pads to the rat lower limb. The advantages of the model are controlled force application to a well-defined bone, noninvasive external loading, and the addition of loads to normal daily activity. A disadvantage of the model is that the pads create local pressure on the leg at the contact sites. ⋯ Bending stimulates bone formation in regions with the highest bending strains. Similar forces applied only in the form of pressure loading do not stimulate tibial formation either at the contact site or between loading pads. These results suggest that externally applied forces of moderate magnitude stimulate bone formation primarily as a result of increased bending strains, not local pressure at the contact site.
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J. Bone Miner. Res. · Jan 1994
Randomized Controlled Trial Clinical TrialLong-term (3 years) prevention of trabecular postmenopausal bone loss with low-dose intermittent nasal salmon calcitonin.
The long-term effect of intermittent low-dose nasal salmon calcitonin on trabecular early postmenopausal bone loss was assessed as follow-up to a previously published study. Randomized controlled group comparison was made of 287 healthy women with 6-36 months of natural menopause and no treatment interfering with calcium metabolism at an outpatient clinic for research in bone and cartilage metabolism. The 287 women were randomly allocated to 3 years of treatment with either 500 mg/day, 5 days/week of calcium or the same amount of calcium plus 50 IU/day, 5 days per week of nasal salmon calcitonin. ⋯ The difference between the evolution of the two groups was significantly (p < 0.01) different after 6 months of treatment and remained so until the end of the study. No significant changes were recorded in biochemical parameters reflecting bone turnover. As previously shown during a 1 year follow-up, nasal salmon calcitonin given at low dose and intermittently, in association with calcium, can counteract trabecular postmenopausal bone loss.
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Bone formation was measured in rat tibiae after 12 days of applied loading. Bending forces were applied using a four-point loading apparatus. Sham loads were applied at the same magnitudes as bending forces but the loading pads were arranged so that bending was minimized. ⋯ Bending strains above a loading threshold of 40 N or about 1050 mu strain increased both bone-forming surface and the mineral apposition rate and subsequently increased the bone formation rate as much as sixfold. No evidence of increased bone formation was seen for applied strains below 1050 mu strain. Examination of bulk stained sections from animals exposed to the highest applied loads showed no evidence of microcracks.(ABSTRACT TRUNCATED AT 250 WORDS)