A controlled trial of the effect of calcium supplementation on bone density in postmenopausal women.

Background. The effectiveness of calcium in retarding bone loss in older postmenopausal women is unclear. Earlier work suggested that the women who were most likely to benefit from calcium supplementation were those with low calcium intakes. Methods. We undertook a double-blind, placebo-controlled, randomized trial to determine the effect of calcium on bone loss from the spine, femoral neck, and radius in 301 healthy postmenopausal women, half of whom had a calcium intake lower than 400 mg per day and half an intake of 400 to 650 mg per day. The women received placebo or either calcium carbonate or calcium citrate malate (500 mg of calcium per day) for two years. Results. In women who had undergone menopause five or fewer years earlier, bone loss from the spine was rapid and was not affected by supplementation with calcium. Among the women who had been postmenopausal for six years or more and who were given placebo, bone loss was less rapid in the group with the higher dietary calcium intake. In those with the lower calcium intake, calcium citrate malate prevented bone loss during the two years of the study; its effect was significantly different from that of placebo (P less than 0.05) at the femoral neck (mean change in bone density [+/- SE], 0.87 +/- 1.01 percent vs. -2.11 +/- 0.93 percent), radius (1.05 +/- 0.75 percent vs. -2.33 +/- 0.72 percent), and spine (-0.38 +/- 0.82 percent vs. -2.85 +/- 0.77 percent). Calcium carbonate maintained bone density at the femoral neck (mean change in bone density, 0.08 +/- 0.98 percent) and radius (0.24 +/- 0.70 percent) but not the spine (-2.54 +/- 0.85 percent). Among the women who had been postmenopausal for six years or more and who had the higher calcium intake, those in all three treatment groups maintained bone density at the hip and radius and lost bone from the spine. Conclusions. Healthy older postmenopausal women with a daily calcium intake of less than 400 mg can significantly reduce bone loss by increasing their calcium intake to 800 mg per day. At the dose we tested, supplementation with calcium citrate malate was more effective than supplementation with calcium carbonate.

[Normal values in children of bone mineral content measured by dual photon absorptiometry]. / Valeurs normales chez l'enfant du contenu minéral osseux mesuré par absorptiométrie biphotonique.

We analyzed the results of dual photon absorptiometry measurements in 43 normal children. Results were correlated with age, body weight, and stature. Reference stature-specific values for bone mineral content in children are proposed. Furthermore, our results show that mineralization continues beyond the end of statural growth.

Effects of age and sex on bone density at the hip and spine in a normal Caucasian New Zealand population.

We have studied a normal adult caucasian population (462 females, 264 males age range 20-84) using dual photon absorptiometry to establish patterns of bone reduction at the spine and hip. Subjects were either randomly selected from the electoral roll or volunteers. Bone mineral density reduction at the lumbar spine in females appeared to increase at 40 years and was sustained until 60 years. In males bone mineral density at the spine was preserved. The density at the hip in females decreased throughout adult life beginning before the menopause. In males bone density was preserved at the femoral neck and trochanteric region but not at Wards triangle where reduction occurred throughout life. When compared with other normal populations there was higher bone mineral density at the spine in postmenopausal New Zealand females but no significant difference at the hip.

Effect of physical activity on lumbar spine and femoral neck bone densities.

The lumbar spine and femoral neck densities of 123 and 141 normal adult women (50 +/- 10 years), respectively, measured by dual photon absorptiometry, were correlated with the number of hours of walking per day associated with their regular daily activities. This measure of exercise, obtained by detailed questionnaire and interview, was analyzed because it is regular, seasonally stable, and quantifiable. Both lumbar spine and femoral neck densities were significantly correlated with walking, with 0.8% and 1.9% increases in average bone density per hour of daily walking, respectively. This increase in density is substantial, considering that the age-related rate of bone loss in the same population is 0.7% and 0.5% per year of lumbar spine and femoral neck, respectively. This means that, on the average, a woman walking one additional hour per day has a femoral neck bone density comparable to that of a women 4 years younger who does not pursue this additional activity. This physical activity-associated enhancement of bone density may be critical at old age when osteoporosis is clinically manifested.

Screw fixation in the femoral head. Pull-out tests in cadavers.

The aim of our study was to determine whether a subchondral or a capital position of the thread of the gliding screw provided the best fixation. A pull-out test was performed on pairs of femoral neck cadaver specimens. The capital position of the thread provided the best fixation in all the pairs. A correlation was found between bone mineral content of the femoral heads and the holding power of the screws in both positions.

Contribution of the trabecular component to mechanical strength and bone mineral content of the femoral neck. An experimental study on cadaver bones.

Both proximal femora from 10 females were acquired at autopsy. The trabecular component of the femoral neck of one specimen from each pair was evacuated, while the contralateral specimen was left intact as a reference. Bone mineral content (BMC) of the femoral neck, demonstrated only a slight (mean 4.8%) individual side to side variation. After evacuation of the trabecular component, BMC was reduced with mean 23.5%. Mechanical strength of the specimens, determined by applying a force to the femoral head perpendicularly to the axis of the femoral shaft, was reduced by mean 39.5%. Correlation between BMC and fracture strength was poor. There was no correlation between reduction in BMC and reduction in mechanical strength after evacuation, indicating that bone fracture strength is influenced by factors other than the mineral content.

Effects of anticonvulsant drug therapy on bone mineral density in a pediatric population.

Twenty epileptic outpatients, aged 5-20 years and taking either phenobarbital or phenytoin for anticonvulsant therapy, were evaluated for femoral neck area bone mineral content and bone mineral density using dual photon absorptiometry. Duration of treatment averaged 51.4 months (range, 9-124 months). A group of 20 normal children who were matched for age, sex, and race served as controls. There were no statistically significant differences between the femoral neck area bone mineral densities of the epileptic patients as compared to the controls. There were also no correlations between duration of anticonvulsant therapy and bone mineral density, nor any differences in bone mineral density values when comparing epileptic patients taking phenobarbital with those patients taking phenytoin.

In vitro determination of bone mineral content of the femur neck. Use of computed tomography.

An accurate method for the in vitro measurement of mineral content of femoral bone by means of computed tomography (CT) is presented. The bone mineral content (BMC) of the femoral head in patients with a subcapital fracture was determined and compared with that in patients with osteo-arthritis. There was a satisfactory standard curve and a highly significant relationship between the CT number (Hounsfield number) and a standard bone equivalent reference (K2HPO4) was obtained at two different energies (96 and 125 kV). The calculated error in the calibration procedure was less than 1,5% and the overall error of the method was 8,8%. The femoral BMC of patients in the fracture group was found to be substantially lower (P less than 0.001) than that in osteoarthritis.

Different trends of age-related diminution of bone mineral content in the lumbar spine, femoral neck, and femoral shaft in women.

The bone mineral content (BMC) was measured by dual photon absorptiometry of 153Gd simultaneously in the lumbar spine, femoral neck, and femoral shaft in a cross-sectional study of 113 healthy women aged 20-89 years. The measurements suggest differences in the patterns of bone mineral decrease at the three sites of the skeleton in relation to age. The lumbar spine BMC decreases mainly during the usual time of menopause, whereas BMC decreases linearly in the femoral neck from young adulthood to old age. The femoral shaft BMC is nearly unaltered until the seventh decade, and thereafter BMC declines significantly. In each of the three age groups selected according to the usual time for menopause there was significant correlations between BMC of the scanning sites and nearly identical variance of BMC with age, suggesting homogeneity in the female population with regard to rate of bone diminution.

Legg-Calvé-Perthes disease. Histochemical and ultrastructural observations of the epiphyseal cartilage and physis.

UNLABELLED: Biopsy specimens of the lateral aspect of the femoral head and neck were obtained from five children with Legg-Calvé-Perthes disease and were studied using histochemistry and electron microscopy. Beneath the normal articular cartilage there was a thick zone of hyaline (epiphyseal) cartilage containing sharply demarcated areas of hypercellular and fibrillated cartilage with prominent blood vessels. The fibrillated cartilage was strongly positive to alcian blue, weakly positive to periodic acid-Schiff, and positive to aniline blue. The interterritorial matrix in the hypercellular areas was weakly positive to both alcian blue and periodic acid-Schiff. Ultrastructural examination of these areas revealed many irregularly oriented large collagen fibrils and variable amounts of proteoglycan granules. These results suggest that in the fibrillar areas there are: (1) a high proteoglycan content, (2) a decrease in structural glycoproteins, and (3) a different size of collagen fibrils from that of normal epiphyseal cartilage. The hypercellular areas had a decrease in proteoglycans, glycoproteins, and collagen. The lateral physeal margin was often irregular, with a marked reduction of collagen and proteoglycan granules, and contained numerous large lipid inclusions. CLINICAL RELEVANCE: The abnormal areas in the epiphyseal cartilage of patients with Legg-Calvé-Perthes disease have different histochemical and structural properties from normal cartilage and from fibrocartilage. This suggests that the disease could be a localized expression of a generalized, transient disorder of epiphyseal cartilage that is responsible for delayed skeletal maturation. The cartilage lesions are similar to those seen in the vertebral plates in patients with juvenile kyphosis. Whether the epiphyseal cartilage abnormalities are primary or are secondary to ischemia remains uncertain; however, it appears that the collapse and necrosis of the femoral head could result from the breakdown and disorganization of the matrix of the epiphyseal cartilage, followed by abnormal ossification.

Changes in crystal size and orientation of acidic glycosaminoglycans at the fracture site in fractured necks of femur.

The aim of this study was to try to elucidate the increased susceptibility of the neck of femur to fracture. Quantitative polarised light microscopy has been applied to fresh, undecalcified sections of samples of bone taken from the site of fracture, in specimens taken at operation from patients with fractures of the femoral neck or osteoarthritic femoral heads or from the equivalent site from otherwise normal subjects at necropsy. In all 21 specimens of fractured necks of femur, but in none of the other specimens, relatively large crystals (up to 2.5 X 0.5 micrometres) were found close to the site of fracture; the properties of these crystals were compatible with their being apatite. Measurement of the natural birefringence of the collagen showed no difference in the orientation of the collagen in all three types of specimen. However, the orientation of acidic glycosaminoglycans, measured by the birefringence of alcian blue bound to these moieties, was 45 per cent lower in the specimens from fractured necks of femur than in the other specimens, even though the total content of acidic glycosaminoglycans was unchanged. Although the decreased orientation was most marked close to the site of fracture, it was still apparent 15 millimetres from that site. These changes were unlikely to be simply the sequelae of fracture since they were not found in traumatic fractures of other bones. Thus it is conceivable that changes in the orientation of the ground substance allow formation of relatively large crystals of apatite and that such crystals, in the microcrystalline mass of apatite, are the cause of the increased fragility of such bones.

Measurement of bone mineral content in human vertebrae and hip by dual photon absorptiometry.

An instrument for clinical measurement of bone mineral content in the axial skeleton was constructed. Components include a modified dual probe scanner, a PDP-11 computer, a 153Gd source, and a NaTI) detector. The results were accurate and highly reproducible, and distinction of osteoporotic women from normal age-matched women was superior to that accomplished with single photon absorptiometry in the radius.

Bone-mineral content of the femoral neck and spine versus the radius or ulna.

The interrelationship between the bone-mineral content of sites on the radius or ulna and that of the femoral neck and lower thoracic vertebrae of twenty-four human skeletons was determined. The average correlation coefficients, -/r, were 0.82 and 0.57. Regression analysis showed that the bone-mineral content of the radius provides a good estimate of the bone-mineral content of the femoral neck (standard error of estimate approximately 16 per cent). Multiple regression analysis using the age of the subject and the bone-mineral content of the radius provides an equation with a similar standard error of estimate for the vertebrae.