[Bone mineral content and quantitative computerized tomography]. / Contenuto minerale osseo e tomografia computerizzata quantitativa.

Many methods are used to determine bone mineral content (BMC). Quantitative computed tomography (QCT) appears to be the most reliable method also because it allows the trabecular and the cortical bone to be measured separately. QCT is usually performed on the first four lumbar vertebral bodies. BMC is expressed in mg/ml and a mean value is calculated. Three hundred and fifteen subjects were studied (281 women and 34 men). The patients affected with Paget's disease or malignancies, with or without bone metastases, were not included in this study. The measurements were performed by means of a General Electric 9800 tomograph with software and calibration phantom (QCT-Bone program by Image Analysis). Fractured vertebrae were not included when calculating the mean value since an increased density is caused by fracture. The BMC of any studied vertebral body is considered in comparison with the BMC of the other lumbar vertebrae of the same subject. When the BMC of a given vertebral body exceeds the others by 25 mg/ml or more, nodules and/or stripes are observed during multiple-slice scanning of the bone. Lytic areas or angiomas are observed when the BMC of a given vertebral body is -25 mg/ml or higher. In calculating the mean vertebral BMC, vertebrae with both +25 and -25 must be excluded. In this way the method reliability increases.

[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.

Dietary calcium, sex hormones, and bone mineral density in men.

OBJECTIVE: To evaluate the factors that determine bone mineral density at axial and appendicular sites in normal men. DESIGN: Measurement of bone mineral density of the radius by single photon absorptiometry and of the lumbar spine and hip by dual photon absorptiometry to assess their relation with various determinants of bone mineral density. Dietary calcium was assessed from a questionnaire validated against a four day dietary record. SETTING: Local community, Sydney, Australia. PATIENTS: 48 Men (aged 21-79, median 44) recruited from the local community including 35 male cotwins of twin pairs of differing sex recruited from the Australian National Health and Medical Research Council twin registry for epidemiological studies on determinants of bone mineral density. MAIN OUTCOME MEASURES: Bone mineral density of the axial and appendicular skeleton and its relation to age, anthropometric features, dietary calcium intake, and serum sex hormone concentrations. RESULTS: Dietary calcium intake (g/day) was a significant predictor of bone mineral density of axial bones, explaining 24% and 42% of the variance at the lumbar spine and femoral neck respectively. This effect was independent of weight. In contrast with the axial skeleton, bone mineral density at each forearm site was predicted by weight and an index of free testosterone but not by dietary calcium intake. CONCLUSIONS: Dietary calcium intake has a role in the determination or maintenance, or both, of the axial but not the appendicular skeleton in adult men.

Accuracy and reproducibility of lumbar bone mineral status determined by dual photon absorptiometry in live male cynomolgus macaques (Macaca fascicularis).

Dual photon absorptiometry (DPA) was used to determine the in vivo bone mineral content (BMC) and bone mineral density of lumbar vertebrae (L2-4) in feral adult male cynomolgus macaques (Macaca fascicularis, n = 20). Following in vivo DPA scans, all animals were euthanized and the lumbar spine segment excised. The excised lumbar vertebrae, plus spinal cord, were formalin-fixed and measured three times by ex vivo DPA. The first ex vivo scan matched the monkey's own in vivo soft tissue beam attenuation ratio (Rs, ranging from 1.38 to 1.45). The second ex vivo scan was made creating a constant obese-like condition (Rs = 1.38), and the third creating a constant lean-like condition (Rs = 1.45). All scans were taken at a 1.0 mm point resolution, 1.0 mm line spacing, a 6 cm width, and a scan speed of 5 mm/sec. The second lumbar vertebra (L2) was ashed and the ash weight was compared to the measured L2BMC of the in vivo and ex vivo DPA analyses. Noninvasive in vivo DPA proved to be adequate in measuring the lumbar bone mineral content in male cynomolgus macaques. Ex vivo DPA at a high and constant Rs value of 1.45 provided for the best accuracy of formalin-fixed wet bone tissue when compared to the bone ash weight.

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.

Long-term physical exercise retards trabecular bone loss in lumbar vertebrae of aging female mice.

The present study examined the effect of long-term, moderate physical exercise on trabecular bone volume (TBV), calcium content, 3H-proline uptake, and the activities of alkaline and acid phosphatases in lumbar vertebrae of aging and senescent mice. It became apparent that if physical activity starts at an early stage of life, i.e., prior to middle age and is extended until old age, it exerts beneficial effects on trabecular bone mass and mineralization. Such a positive effect is not obtained if the training program is initiated after middle age. The training-induced reduction in bone loss was accompanied by a significant decrease in acid phosphatase activity whereas no changes took place with regard to the activity of alkaline phosphatase. Long-term physical exercise also enhanced the uptake of 3H-proline by lining cells along the bone trabecules. In spite of its moderate nature, the endured training program served as a stress factor for the involved animals, a fact that was manifested by an increase in the serum levels of corticosterone. Thus, it seems that whereas young animals respond favorably to such a stimulatory stress, older animals lose this ability of adaptation.

Maturation of bone and dentin matrices in rats flown on the Soviet biosatellite Cosmos 1887.

We have studied the chemistry, hydroxyapatite crystal size, and maturational changes in bone and dentin from rats exposed to microgravity for 12 days in a Soviet biosatellite (Cosmos 1887). Bone ash was reduced in vertebrae (L5) but not in the non-weight-bearing calvaria or mandibles. All tissues had a relatively normal percentage composition of Ca, P, and Mg. Nevertheless, flight rat calvaria and vertebral tissues tended to exhibit lower Ca/P and higher Ca/Mg ratios that any of their weight-matched controls groups, and gradient density analysis (calvaria) indicated a strong shift to the fractions lower specific gravity that was commensurate with impaired rates of matrix-mineral maturation. X-ray diffraction data were confirmatory. Bone hydroxyapatite crystal growth in the mandibles of flight rats was preferentially altered in such a way as to reduce their size (C-axis dimension). But in the mandibular diastemal region devoid of muscle attachments, flight rat bone and dentin were normal with respect to the Ca, P, Mg, and Zn concentrations and Ca/P and Ca/Mg ratios of age-matched controls. These observations affirm the concept that while microgravity most adversely affects the maturation of newly formed matrix and mineral moieties in weight-bearing bone, such effects occur throughout the skeleton.

Prevention of postmenopausal bone loss by tiludronate.

76 healthy women, who had been menopausal for less than 96 months and who had never received any form of treatment to prevent bone loss, were entered into a randomised double-blind study. For the first 6 months, half the patients received tiludronate 100 mg daily, while the others received placebo. During the second 6 months, all patients received placebo. Bone mineral density of the lumbar spine decreased significantly by 2.1% (SE 0.8%) in the placebo group and did not significantly change in the tiludronate group (+1.33 [0.8]%). The difference in response between the groups was significant, as were the differences between values for corrected urinary hydroxyproline and calcium. Treatment with tiludronate was not followed by increased secretion of parathyroid hormone. A 6 month course of oral tiludronate may counteract postmenopausal bone loss for at least a year by decreasing bone resorption.

A comparison of quantitative dual-energy radiographic absorptiometry and dual photon absorptiometry of the lumbar spine in postmenopausal women.

Noninvasive bone densitometry is an important aspect in the detection and management of osteoporosis and other forms of metabolic disease of calcified tissue. A system using quantitative dual-energy digital projection radiography (QDR) of the lumbar spine was systematically tested against dual-photon absorptiometry (DPA) of the lumbar spine in 131 women over 55 years of age and free from major risk factors for osteoporosis. All subjects were scanned by both QDR and DPA under the same conditions. Measurements for a given subject were made within 15 minutes of each other. Bone mineral densities (BMD) were determined for four individual levels in the lumbar spine (L1-L4). Regression equations for BMD vs. age, height, and weight were calculated. The results of this investigation indicate that DPA- and QDR-derived BMD values are comparable. BMD values derived by QDR were consistently lower than those obtained by DPA (DPA = 1.115 QDR + 0.137, r = 0.942). The L2 lumbar region was the most strongly correlated determination.

A comparison of single and multi-site BMC measurements for assessment of spine fracture probability.

In a prospective study of 699 women, 39 new spine fracture cases were observed during a mean follow-up of 3.6 yr. Spine fracture incidence was compared to initial bone mineral content (BMC) of the calcaneus, distal radius, proximal radius, and the lumbar spine. BMC at all four sites was significantly related to spine fracture incidence. Women at -1 s.d. for calcaneal BMC had a sevenfold greater probability of spine fracture than women at +1 s.d.; women at -2 s.d. had a 50-fold greater probability than women at +2 s.d., even after adjustment for the effects of age. Combinations of BMC at two sites further strengthened the relationship to spine fracture; the best two-site combination is calcaneus and distal radius BMC. Thus women can be categorized and stratified according to future fracture risk, and the selection of postmenopausal women for preventive treatments can be guided by measurements of BMC.

Efficacy of nonloading exercises in prevention of vertebral bone loss in postmenopausal women: a controlled trial.

A considerable increase in muscle strength and bone mass can be achieved in young adults through athletic exercise programs. We studied a less demanding nonloading exercise program for the back extensor muscles in postmenopausal women who were not on estrogen therapy. We randomly assigned 65 healthy Caucasian women without evidence of or risk factors for osteoporosis into an exercise group and a control group. The strength of the back extensor muscles and bone mineral density of the lumbar spine were measured at baseline and every 6 months for 2 years. In addition, a physical activity score was determined. Compliance was assessed by regular interviews and review of diaries. During the 2-year study, the mean rates of bone loss in the two groups were not statistically different. The strength of the back extensor muscles increased in both groups but significantly more (P = 0.002) in the exercise group. We conclude that postmenopausal bone loss is unaffected by a modest exercise program despite an increase in muscle strength. Nonloading muscle exercise may be ineffective in retarding vertebral bone loss in ambulatory, healthy postmenopausal women.

[Lumbar vertebrae mineral content in women. Normal values obtained using quantitative digital radiography]. / Contenu minéral osseux lombaire chez la femme. Valeurs normales obtenues par radiographie digitale quantitative.

The bone mineral content of the lumbar spine was measured in 120 normal women, using quantitative digital radiography (Hologic QDR 1000). From the results obtained, expressed in g/cm2, the curve of the lumbar spine mineral density according to age was established, in order to demonstrate a maximum at 32.8 years, a minimum around 80.5 years with total mineral loss of 32.5% and a maximum speed of bone loss at 56.5 years (6 years after the average menopausal age). Moreover, from measurements in 30 osteoporotic women, the value of the fracture threshold was estimated at 0.730 g/cm2.

Normal and abnormal features of the lumbar spine observed in dual photon absorptiometry scans.

Dual photon absorptiometry (DPA) is an extensively used technique for measuring the density of the lumbar spine. The presence of vertebral and extra-vertebral pathologies can lead to increased scatter of data and artifactual bias when constructing diagnostic reference value curves. The bone density of patients with such abnormalities cannot be compared with those of normals because it will appear artificially high. Furthermore, little effort has been made to identify and evaluate spinal abnormalities using the pictograms produced in this method. We have analyzed 60 DPA scans for morphologic changes, using x-rays for comparison, and have found practically complete concurrence between these two radiologic methods on features, though only the former is capable of accurately quantifying bone density. Examples of DPA presentation of anatomical morphology are shown to aid the user in interpreting DPA findings.

BGP (osteocalcin, bone-Gla-protein) in involutional osteoporosis.

The role of BGP (osteocalcin) as bone marker in the study and management control of involutional osteoporosis is emphasized and the different radioimmunoassays and their limitations are commented. Our results showed significantly lower sBGP levels in osteoporotic patients compared with control group and a positive linear correlation was found between sBGP and serum alkaline phosphatase but no correlation was obtained with urinary hydroxyproline/creatinine ratio, serum tartrate-resistant acid phosphatase or bone mineral content measured by dual photon absorptiometry.

[Measurement of bone mineral content by quantitative digital radiography. First results in the lumbar vertebrae]. / Mesure du contenu minéral osseux par radiographie digitale quantitative. Premiers résultats au niveau vertébral lombaire.

The precision of quantitative digital radiography (QDR) bone densitometer has been evaluated from measurements which were made on an anthropomorphic spine phantom of known mineral content and on volunteers. In vitro and in vivo, the coefficient of variation of the measured values was less than 0.4 p. 100 and the accuracy was very close to 100 p. 100. Measurements were also made on 30 patients and gave results that were well correlated with those obtained with two different dual photon absorptiometry (DPA) apparatus (Novo Lab 22a and Oris).

Fatty replacement of spinal bone marrow due to radiation: demonstration by dual energy quantitative CT and MR imaging.

Dual energy CT and quantitative magnetic resonance (MR) imaging were used to evaluate marrow changes due to radiation. The bright signal intensity seen on MR was shown by the two quantitative techniques to be due to a threefold increase in the marrow fat content compared with nonradiated levels and to a normal control. Fat estimates by MR and dual energy CT were in excellent agreement. Single energy CT overestimates the amount of bone loss in the radiation field. Dual energy CT and quantitative MR can be used to correct this error.

A comparison of rat femoral, sternebral and lumbar vertebral bone marrow fat content by subjective assessment and image analysis of histological sections.

A subjective assessment of the amount of fat within the available marrow space was made from histological sections of the femur, sternebrae and lumbar vertebrae in rats. The sternebrae and vertebrae showed considerably less variability than the femur. Comparison between subjective assessment and image analysis of femoral bone marrow fat showed that there is no great advantage to be gained from using the latter technique. It was concluded that evaluation of sternebral and vertebral bone marrow results in a more accurate assessment of fat content.

Prediction of vertebral strength by dual photon absorptiometry and quantitative computed tomography.

We measured the lumbar bone mineral of 19 cadavers (10 women, 9 men) by dual photon absorptiometry (DPA) and quantitative computed tomography (QCT). In addition, we determined the ultimate load and stress of each vertebra, and finally ash content and volumetric ash density of the vertebral body. We found that single energy QCT was inferior to DPA and dual energy QCT in the prediction of the ultimate load or stress of vertebrae (P less than 0.001). The ultimate stress was best predicted by using the dual energy QCT results (r = 0.71; SEE = 36.3 N/cm2) whereas the ultimate vertebral load was best predicted by using the DPA (BMC) results (r = 0.80; SEE = 740 N). If the QCT finding was multiplied with the surface area of the vertebral body it could be used to predict the ultimate load with good accuracy (r = 0.74; SEE = 841 N). All the above correlations were higher in women than in men. The frequency of vertebral compression fractures in the material was well correlated with the bone mineral findings. A nonlinear (third degree) relationship between mineral content and mechanical characteristics is proposed but within the area of measurement used in clinical practice a linear (first degree) equation is preferred.

Some factors which influence the evaluation of a dual photon measurement of lumbar spine bone mineral mass.

The accuracy of a commercial dual photon densitometer was found to be within 3.0% of true values when measured using a cadaver spine. The precision, the ratio of standard deviation to mean derived from repeated measurements of a tissue-equivalent phantom spine, was 1.6%. Patient size and the age of the radioisotope source had no discernable effect upon bone mineral mass measurements. The intervention of the technologist during data analysis can influence the determination of bone mineral mass in approximately 40% of measurements. When a lumbar spine phantom was measured on six different densitometers manufactured by three different companies, within-manufacturer variations of between 4% and 7% were found. Bone mineral densities differed by up to 30% between manufacturers. Values of lumbar spine mineral mass were measured for 206 apparently normal women. The resultant normal range was similar to others documented by the manufacturer. The differences between these studies and a published study of 892 normal women can best be explained on the basis of intermanufacturer differences.

Quantitative computed tomography of lumbar vertebrae in Japanese patients with osteoporosis.

Vertebral trabecular bone mineral density of both healthy Japanese subjects and Japanese patients with osteoporosis was measured by quantitative computed tomography (QCT) technique. The age-related reduction rate in vertebral trabecular bone mineral density of control females averaged 1.1% per year, from age 20 to 80, with an accelerated loss demonstrated after age 40. In the male controls, trabecular bone mineral density declined by an average of 0.9% per year. These values were found to be similar to the University of California at San Francisco (UCSF) QCT data (US Caucasians: 1.2% for female, 0.72% for male). Therefore, it appears that age-related rates of trabecular bone loss in the lumbar vertebrae may be similar for both Japanese and Caucasians. However, when compared to average values in UCSF QCT data of comparable age and sex, the mean values in Japanese appear to be approximately 10-20 mg/cm3 lower than Caucasian counterparts. All female patients with osteoporosis as evidenced by atraumatic vertebral fracture had QCT values below 50 mg/cm3. It is suggested that the Japanese may have lower trabecular bone mineral density than Caucasians but may also have a lower threshold for fracture of the vertebrae. Further studies are needed to establish the possible racial differences in vertebral trabecular bone mineral density, and to determine whether these possible disparities are related to genetic differences, or to differences in body size, dietary intake, physical activity or other lifestyle/environmental factors.