The relation between forearm and vertebral mineral density and fractures in postmenopausal women

Forearm bone mineral density measurement with different scanning positions: a study in right-handed Chinese using dual-energy X-ray absorptiometry

The purpose of our study was to determine whether different scanning positions influence forearm bone mineral density (BMD) measurements and to evaluate the association between forearm BMDs in different scanning positions and those of other skeleton sites. The study population consisted of 30 right-handed healthy Chinese volunteers. BMD was measured with GE Lunar Prodigy at the left forearm in both sitting and supine positions, and at lumbar spine and the right femur. All subjects received repeated measurements in the same day (repositioning), and the average of repeated BMD results was used for analysis. The BMD precision errors of the nondominant forearm in the sitting and supine positions varied from 1.13% to 2.46%. There were no statistically significant differences between BMD precision errors for each region of interest (ROI) between sitting and supine positions (all the p values were greater than 0.05). When comparing BMDs on the same side in the sitting position with those in the supine position, there were significant differences at both the 1/3 radius level and in the total radius (p<0.05). The BMD values at these ROIs obtained in the supine position were lower than those in the routine sitting position. The BMDs of the ultradistal radius in the both 2 different scanning positions were significantly associated with lumbar spine and femoral neck BMD, respectively. The total radius BMD in the different positions was associated with the BMD of the femoral neck. A change in body scanning position from sitting to supine will significantly influence forearm BMD results.

Assessment of cancellous bone quality in severe osteoarthrosis: bone mineral density, mechanics, and microdamage

The role of bone microdamage (microscopic cracks or microcracks and ultrastructural collagen matrix and bone mineral damage) in diseases such as osteoarthrosis and osteoporosis is poorly understood. Microdamage accumulation in vivo is influenced by age and cyclic loading, therefore, it would be useful if the burden of microdamage in bone could be assessed by noninvasive measures such as the radiological measurement of bone mineral density (BMD). The aim of this study was to investigate the relationship between BMD, compressive strength and stiffness, and microdamage in the cancellous bone of the proximal femur in patients with severe osteoarthrosis. Trabecular bone core samples, from the intertrochanteric region of the femur, were obtained from 34 patients, with a mean age of 70.3 +/- 11.1 years, undergoing total hip arthroplasty for osteoarthrosis. Cores selected from contact X-ray images were used for BMD measurement, compressive mechanical testing or left untested (uncrushed), en bloc staining for microdamage, and bone histomorphometry. The study shows a strong dependence of both the elastic modulus and ultimate failure stress of the bone samples on BMD and a significant relationship between the elastic modulus and trabecular anisotropy (Tr. An). In multiple linear regression, BMD and Tr. An together account for about 70% of the variance in the elastic modulus. Then including microcrack crack density (Cr.Dn) and damage volume fraction (DxV/BV) variables, Tr. An alone accounts for a relatively small amount of the variation (8.5%) in ultimate failure stress and elastic modulus. The Cr.Dn accounts for more of the variation in the ultimate failure stress than in the elastic modulus (50% vs. 7%). In this experiment, data for Cr.Dn provide a measure of damage associated with the ultimate failure of cancellous bone. In specimens that were not mechanically tested, in vivo microcrack accumulation increases exponentially with age. In conclusion, data from this study suggest that BMD and Cr.Dn are the major determinants of cancellous bone strength, whereas BMD and Tr. An are major determinants of cancellous bone stiffness. In bone specimens subjected to compressive testing there was no relationship between microdamage and BMD, suggesting that BMD cannot be used to monitor changes in the mechanical properties of bone due to microdamage accumulation.

Decrease of bone formation in adult women with fragility fractures

OBJECTIVES

To compare bone mineral density (BMD) and some markers of bone metabolism in women with fragility fractures and in normal age-matched subjects.

METHODS

A 100 women with at least one vertebral deformity > 25%, and 219 age-, BMI- and parity-matched healthy women, were recruited for the study. In all the patients fractures were symptomatic and occurred at least 1 year before densitometric measurement. Forearm bone mineral density (BMD) as well as biochemical assessment of some markers of bone turnover were measured in all the subjects.

RESULTS

BMD was significantly lower in the fracture than in the control group (0.326 +/- 0.073 vs. 0.379 +/- 0.079; P < 0.001). Fractured women showed alkaline phosphatase (ALP) and osteocalcin (OC) serum levels significantly lower than controls, while no differences were found in fasting urinary calcium and hydroxyproline excretion. Women without fractures showed a significant correlation between ALP and both age and years since menopause (YSM). Such a correlation is lacking in the fracture group.

CONCLUSIONS

Women with vertebral deformities likely due to a fracture had a forearm BMD and markers of bone formation lower than normal. Whether low bone density is due to a low peak of bone mass or to an increased postmenopausal bone loss sustained by an uncoupling between the two bone remodelling processes is still unclear.

Assessment of fracture risk by bone density measurements

Bone densitometry in its various applications has become an established tool for the diagnosis of osteoporosis. Bone density has been shown to be significantly associated with the risk of future fracture in many prospective studies. From long-term prospective studies, it can be concluded that peak bone density and bone loss are important predictors of subsequent fracture, and that fracture can be predicted over a longer period. Bone density predicts fracture even in elderly persons aged 80 years and older. However, in this population some fractures, such as the cervical hip fracture, may be more strongly influenced by other risk factors. The differences between the various densitometric techniques in predicting future osteoporotic fracture of any type is marginal. However, it seems that bone density measurements at the site of fracture do perform better than measurements at other sites. There is no evidence that measuring a second site improves the diagnostic capability of bone densitometry. The association between bone density and future fracture is partly independent of age and other significant predictors of fracture such as falls, cognizance, and mobility. Quantitative ultrasonic measures of bone quality have been shown to have a predictive capability that is comparable to that of bone density. From the perspective that bone densitometry and quantitative ultrasound independently predict fractures, these measures actually seem complementary rather than competitive. Simple geometric measures of the bones such as hip axis length and vertebral depth may be derived from images of bone densitometry scans and are also predictive of hip fracture or vertebral fracture independently of bone density. Using the current knowledge of the association between bone density, quantitative ultrasound, geometric properties, and fractures as well as clinical risk factors, new models for fracture prediction can be developed for future application in clinical practice for the benefit of the individual patient.

Effect of osteoarthritis in the lumbar spine and hip on bone mineral density and diagnosis of osteoporosis in elderly men and women

To determine in the elderly the effect of osteoarthritis on bone mineral density (BMD) and on diagnosis of osteoporosis, lumbar spine and hip were radiographed and BMD measured by dual-energy X-ray absorptiometry (DXA) in 120 men and 314 women, aged 60-99 years. Prevalence and severity of osteoarthritis were scored on osteophytes, joint space narrowing and bone sclerosis. Ultrasound measurements were also made at the heel to examine whether osteoarthritis at hip or lumbar spine influence bone at this remote site. Osteophytes were the commonest feature, with men having a higher prevalence than women, and lumbar spine having more disease than hip. Lumbar spine osteophytes affected 75% of men and 61.1% of women, and hip osteophytes affected 31.7% of men and 27.4% of women. Stepwise multiple regression analysis using age, weight, height, osteophytes, sclerosis and joint space narrowing indicated that lumbar osteophytes explained 16.6% of variation in lumbar spine BMD in women, and 22.4% in men. Hip osteophytes had a minimal effect on hip BMD, accounting for only 2.2% of variation in women, and none in men. Sclerosis and joint narrowing had little effect on BMD at lumbar spine or hip. Indirect effects of osteoarthritis on BMD were small and inconsistent across genders. Lumbar spine osteophytes in men explained 3.1% of hip BMD variation and 6% of variation in speed of sound at the heel, whereas hip osteophytes in women explained 2.2% of lumbar spine BMD variation. Osteoporosis at the hip, defined as BMD < 2.5 SD of the young normal mean, was present in 33.1% of women and 25.8% of men, whereas, at the lumbar spine it was present in only 24.2% of women and 4.2% of men. However, in women and men free of spinal osteoarthritis, 37.7% of women and 10% of men had osteoporosis. We conclude that lumbar spine osteophytes affect most subjects over the age of 60 years, and contribute substantially to lumbar spine BMD measured in the anteroposterior position by DXA. The effect is largely direct by virtue of osteophytes being included in the BMD measurement. However, a small indirect effect on remote skeletal sites is also present. Diagnosis of osteoporosis and assessment of osteoporotic fracture risk in the elderly should be based on hip BMD and not on anteroposterior lumbar spine, unless spinal osteoarthritis has been excluded.

Prediction of fracture load at different skeletal sites by geometric properties of the cortical shell

Quantitative bone assessment today is primarily based on the analysis of bone mineral density (BMD). The geometric properties of bone, which are an important parameter for skeletal strength, are generally not considered in the routine clinical assessment of osteoporosis. This study combined the geometric properties and the BMD values determined by peripheral quantitative computed tomography (pQCT) at the distal radius and at the femoral neck to predict fracture loads of the radius, femur, and lumbar vertebrae of 20 cadavers. Generalized osteopenia reduced the fracture loads at all three sites (p < 0.001). The strength of the radius and the femoral neck could best be predicted by considering either the second moment of inertia and trabecular BMD (R = 0.93) or the moment of inertia and the cortical BMD (R = 0.91). The geometric properties at the distal radius were highly correlated with the fracture load at the same skeletal site (R = 0.89) and were also used to estimate the fracture risk at the lumbar vertebrae (R = 0.75) and at the femoral neck (R = 0.87). We conclude that both geometry and density contribute substantially to the strength of the skeleton. The screening for osteoporosis and the prediction of fracture risk can be improved, therefore, by an additional consideration of the geometric properties of the cortex.

Mechanical validation of a tomographic (pQCT) index for noninvasive estimation of rat femur bending strength

Cross-sectional moment of inertia (CSMI) and volumetric cortical bone mineral density (vCtBMD) were assessed by peripheral quantitative computed tomography (pQCT) at femur midshafts from 103 Wistar female rats receiving 0 (n = 12) or 15-1000 mu g/kg/day sc of dexamethasone (n = 46) from 5 to 9 weeks of age, or 0 or 80 mg/kg 3/wk of AI(OH)(3) IP (n = 23,22) from 4 to 10 months of age. A bone strength index (BSI), calculated as the product CSMI x vCtBMD, was found to closely correlate (r = 0.94, R(2) = 0.89, p < 0.001) with the actual, mechanically tested bending breaking force of all bones. Correlation and determination coefficients obtained were higher than those usually reported employing different long-bone strength predictive formulae. The curve approached the origin and was linear throughout the wide range of CSMI, vCtBMD and BSI achieved because of age- and treatment-induced differences, showing a very low standard error of the estimate. Instead, different curve slopes and/or intercepts were found in separate analysis between data from each of the experiments when breaking force was correlated with CSMI or vCtBMD alone, or with the DEXA-assessed BMD of the mechanically assayed bone portion. Results suggest that noninvasive assessment of the BSI by means of pQCT technology provides an original tool for a precise and accurate estimation of long-bone bending strength that can be advantageously applied in crosssectional as well as longitudinal, in vivo studies employing animal models.

Dual energy X-ray absorptiometry of the spine--decubitus lateral versus anteroposterior projection in osteoporotic women: comparison to single energy X-ray absorptiometry of the forearm

We investigated the discriminatory ability of dual energy X-ray absorptiometry (DXA) of the lumbar spine in the anteroposterior vs. decubitus lateral projection in 53 elderly women with at least one vertebral fracture and 63 age-matched women without fracture. Twenty-three premenopausal healthy women served as a reference group. Spine measurements were compared to forearm measurements by single energy X-ray absorptiometry (SXA). Bone mineral density (BMD) of the women with fractures was 16% lower in the AP projection and 17% lower in the decubitus lateral projection compared to age-matched women without fractures. t-Scores (deviation from normal premenopausal values in SDs) were -2.1 to -2.3 in the women without fractures, and -3.9 (AP projection), -3.1 (lateral projection) and -3.8 (forearm) in the women with vertebral fractures. t-Scores as well as z-scores for bone mineral content of the vertebral body and the vertebral posterior elements (both measured with the lateral projection) were similar. ROC analysis showed no significant difference between the AP and the lateral projection of the spine. When subjects with vertebral endplate sclerosis (about 25% in each group, with considerably elevated spinal BMD) were excluded, it did not significantly change the diagnostic abilities for fractures. We found no diagnostic advantage of the lateral projection as compared to the AP projection or forearm measurement. Future studies will reveal whether absorptiometry in the lateral projection can be improved by supine lateral scanning.

Distal radius fracture is an early sign of general osteoporosis: bone mass measurements in a population-based study

To evaluate the bone mass by bone density measurements in patients with distal radius fracture, a prospective open case-control study was carried out in the county of Uppsala, Sweden, with population-based cases and controls. There were 111 patients with a distal radius fracture who were otherwise healthy and aged 53-76 years, together with 60 healthy controls of similar age, sex and menopausal status. The main outcome measures were bone mineral density (BMD) in the lumbar spine and hip measured with dual-energy X-ray absorptiometry, and in the (non-fractured) distal forearm determined by single-photon absorptiometry. It was found that at all measuring sites BMD was significantly lower in cases than in controls. The difference in the distal forearm was around 20% (p < 0.001) and in the spine and hip 5%-8% (p < 0.05-0.001). In the healthy subjects there were positive correlations (r = 0.39-0.65; p < 0.002) between the forearm BMD and that of both the spine and hip, whereas in the patients with distal radius fracture there was only a weak correlation between the forearm and spine BMD (r = 0.28; p < 0.05) and no association between the BMD of the forearm and hip (r < 0.01). It is concluded that patients with distal radius fracture who are otherwise healthy have a preferential bone loss at the distal forearm but also a generally low bone mass. Patients with fracture of the distal radius fracture should be considered for prophylactic measures against osteoporosis.

Long-term fracture prediction by bone mineral assessed at different skeletal sites

Bone mineral density (BMD) was measured at the lumbar spine and cervical and intertrochanteric regions of the proximal femur by dual-photon absorptiometry and bone mineral content was assessed at the distal and midradius by single-photon absorptiometry in an age-stratified random sample of 304 Rochester, Minnesota women aged 30-94 years. Over follow-up extending to 10 years (median 8.3 years), 93 women experienced 163 new fractures. After adjusting for age, these bone mineral measurements predicted the likelihood of any incident fracture due to moderate trauma, with relative hazards varying from 1.4 to 1.6 per SD decrease in baseline bone mineral. A 1 SD decrease in lumbar spine BMD increased the risk of a new vertebral fracture comparably to a 17 year increase in age; a 1 SD decrease in femoral BMD was comparable to a 13-14 year increase in age on the risk of a hip fracture. We conclude that bone mineral measurements made at a variety of skeletal sites can predict the occurrence for at least 8-10 years of moderate trauma fractures of the sort that might be related to osteoporosis.

Relationships between metacarpal morphometry, forearm and vertebral bone density and fractures in post-menopausal women

The relationships between metacarpal morphometric, vertebral and forearm density measurements and the prevalence of vertebral and peripheral fractures were examined in 239 postmenopausal women (median age 63, range 32-84 years). Metacarpal cortical area/total area ratio (CA/TA) was measured with needle calipers, forearm mineral density (FMD) by single photon absorptiometry and vertebral mineral density (VMD) by single energy quantitative computed tomography. Of the 239 subjects 97 had not suffered any fractures, 44 had at least one previous vertebral fracture but no peripheral fractures, 41 had a history of peripheral fracture but no vertebral fracture and 57 had suffered both peripheral and vertebral fractures. There were significant correlations between a single measurement of CA/TA and both FMD (r = 0.65, p < 0.001) and VMD (r = 0.41, p < 0.001). Similar correlations existed between the mean of multiple measurements of CA/TA and both FMD and VMD. CA/TA (p < 0.001), FMD (p < 0.001) and VMD (p < 0.001) were reduced in subjects who had suffered fractures, when compared with the no fracture group. The percentage of cases in each of the four fracture groups (vertebral fracture only, peripheral fracture only, peripheral and vertebral fracture, peripheral or vertebral fracture) misclassified with reference to the no fracture group were similar with CA/TA, FMD or VMD measurements. We suggest that metacarpal morphometry, which is widely available at relatively low cost, yields cross-sectional information about bone density and fracture risk, comparable with that obtained by forearm and vertebral densitometry.

Fracture of the distal forearm as a forecaster of subsequent hip fracture: a population-based cohort study with 24 years of follow-up

OBJECTIVE

To determine the long-term risk of hip fracture following fracture of the distal forearm.

DESIGN

Registry-based cohort study comparing patients with a fracture of the distal forearm with a population-based cohort. FRACTURE COHORT: All women and men above 40 years of age with a radiologically verified fracture of the distal forearm during a 5-year period, 1968-1972, in all 1,126 women and 212 men. CONTROL COHORT: An equal number of population-based, age- and sex-matched control persons selected from a population register.

MEASUREMENTS

All cohort members were followed up individually through record linkage until the first hip fracture, emigration, death, or the end of 1991. The cohort members contributed a total of 40,832 person-years of observation, and altogether 365 cases of hip fractures were observed.

RESULTS

Both women and men with a fracture of the distal forearm ran an increased risk of sustaining a subsequent hip fracture. The overall relative hazard for the women was 1.54 and for men 2.27. The increased risk in the women was independent of age at inclusion, but that in the men was more pronounced in the younger age groups.

CONCLUSIONS

Patients with a fracture of the distal forearm run an increased risk of sustaining a subsequent hip fracture. They therefore appear to constitute a group in which appropriate prophylactic measures against osteoporosis and fractures should be considered.

When bone mass fails to predict bone failure

New technology for noninvasive measurement of bone mass has enabled many studies of bone mass and its relationship to fracture, which challenge the view that bone mass is the only relevant factor in the etiology of fractures. Several studies have reported ROC curves that generally show values of about 80%. No convincing evidence suggests that one technique is superior to another. The reported relative risks or odds ratios for a fracture usually range between 1.2 and 2.5 per SD. There is no doubt that the risk of a fracture increases as the bone density decreases. However, even with a low bone mass, the risk of not fracturing a bone over the next year is over 90%. Most of the data suggest that patients with severe vertebral fractures have lower bone mass than those with mild fractures, but some women with similarly low bone mass have mild or no fractures. The weight of the evidence suggests that age has an effect on fracture incidence which is independent of bone mass. Trauma is such a major factor that it is surprising to find almost no studies that have controlled for it. The relationship between bone mass and bone failure is strong, but other factors must also be contributing to the bone failure which, like heart failure or renal failure, is a complex, multifactorial disease.

The spine deformity index in osteoporosis is not related to bone mineral and ultrasound measurements

In 34 female patients suffering from osteoporotic vertebral compression fractures, the spine deformity index (SDIM) was determined, according to the method of Minne et al (1988), to reflect the radiological severity of established osteoporosis. Peripheral (single-photon absorptiometry (SPA) of the non-dominant distal forearm) and axial (quantitative computed tomography (QCT) of the lumbar spine) bone mineral measurements, as well as the broadband ultrasound attenuation of the os calcis, were performed in the osteoporotic patients and in a control group of 20 age-matched women. No correlation could be found between bone mineral measurements and radiological severity of osteoporosis, expressed as SDIM. All three densitometry methods showed clearly reduced values in patients with vertebral crush fractures. Correlations established in the control group between peripheral and axial bone mass (SPA versus QCT) could no longer be found in the osteoporotic group, thus indicating changes in bone mineral density of the spine after the occurrence of osteoporotic fractures. Our data show that SDIM is an additional parameter of osteoporotic change in the spine, independent from bone mass measurements. In the management of osteoporotic patients, quantitative radiological methods (i.e. SDIM) in addition to densitometry might be of value for grading and monitoring the progress of disease.

Measurement of forearm bone mineral density in normal women by dual-energy X-ray absorptiometry

We report the results of forearm measurements, without the use of a water bath, using dual-energy X-ray absorptiometry (DEXA) in 100 normal women aged 29-69 years (average age, 52 years). Studies were performed using the Hologic QDR-1000, with bone mineral density (BMD) measured at three sites in the non-dominant forearm: ultradistal, distal one-third and a region between these two. The precision of the technique was 0.74%, 0.55% and 0.58%, respectively. The normal range for forearm BMD and variation with age was established. BMD was also measured in the lumbar spine (L1-L4) and femoral neck. Linear regression analysis gave a range of correlation coefficients between forearm and axial sites of r = 0.49-0.67. Standard errors of the estimate (SEE) in predicting axial from peripheral measurements gave average values from the three forearm sites of 0.085 g/cm2 for the femoral neck and 0.118 g/cm2 for the spine. Forearm measurements using DEXA can now be reliably performed in air. DEXA produces a high-resolution image, is fast and simple to perform, and enables both cortical and trabecular sites to be examined in one measurement. Forearm and axial measurements can be performed using the same equipment, where centres possess a suitable DEXA system.

Osteoporosis and Klinefelter's syndrome

OBJECTIVE

We wanted to measure forearm mineral density and bone-related biochemical variables in patients with Klinefelter's syndrome.

DESIGN

Measurements made in patients with Klinefelter's syndrome were compared to those obtained in age-matched normal male volunteers.

PATIENTS

We studied 22 patients with Klinefelter's syndrome (12 of whom had received sex hormone therapy) and 22 control subjects.

MEASUREMENTS

We measured forearm mineral density, forearm fat content, fat-corrected forearm mineral density, plasma calcium and ionized calcium, serum osteocalcin, testosterone and dehydroepiandrosterone sulphate, and urinary hydroxyproline/creatinine ratio.

RESULTS

Forearm mineral density was lower in the Klinefelter's group than in the control subjects (P less than 0.05) and below the control range in 5 patients. The fat content of the forearm was greater in the Klinefelter's group (P less than 0.002). Serum osteocalcin and testosterone were lower, while ionized calcium and the urinary hydroxyproline/creatinine ratio were higher in the Klinefelter's group (P less than 0.002). Serum dehydroepiandrosterone sulphate and testosterone were significantly related in the Klinefelter's group (r = 0.64, P less than 0.001), but not in the controls (r = 0.22, NS). Forearm mineral density and fat-corrected forearm mineral density were significantly related to serum testosterone in the Klinefelter's group (r less than 0.63; P less than 0.01), but not in the control subjects (r less than 0.03, NS).

CONCLUSIONS

Decreased bone density occurs in about 25% of patients with Klinefelter's syndrome and probably reflects both decreased bone formation and increased bone resorption.

Discriminatory ability of bone mass measurements (SPA and DEXA) for fractures in elderly postmenopausal women

We investigated the discriminatory ability of forearm bone mineral content (BMCarm) measured by single photon absorptiometry (SPA) and spinal bone mineral density (BMDspine) measured by dual-energy X-ray absorptiometry (DEXA) in 387 elderly postmenopausal women. Of these, 22 had never sustained a fracture (normal), 91 had had less than three vertebral wedge fractures (mild), 51 had experienced a peripheral fracture (moderate), and 24 had had more than three vertebral wedge or compression fractures (severe). BMCarm exceeded BMDspine slightly in the ability to discriminate the mild and moderate groups (P less than 0.01-0.001), whether calculations were performed on raw values or the Z-scores compared with premenopausal women. Receiver operating (ROC) analysis showed that at every cutoff level BMCarm had a similar ability as BMDspine to discriminate between the vertebral fracture (mild and severe) groups and healthy premenopausal and nonfractured postmenopausal women (normal), whereas BMCarm had a significantly higher discriminatory ability of peripheral fractures (P less than 0.05) (moderate) group compared with premenopausal women. We conclude that SPA and DEXA are equally capable as diagnostic procedures in women with established osteoporosis.

The index of radiographic area (IRA): a new approach to estimating the severity of vertebral deformity

To assess the overall severity of vertebral deformity for an individual, we developed the index of radiographic area (IRA), a computerized method for analyzing vertebral dimensions from lateral radiographs of the spine. Six coordinates for each vertebral body are recorded in a computer by means of a digitizer. A computer program identifies all abnormal vertebrae, computes the radiographic area of the remaining normal vertebrae, and then estimates the expected normal radiographic area for the abnormal vertebrae in that individual. Differences between the expected and observed radiographic area of all abnormal vertebrae are summed to produce the IRA score. The score correlated well with the quantitative score of vertebral deformity of an experienced radiologist (r = 0.85), and with the vertebral bone density by quantitative computed tomography (QCT) (r = 0.66). The IRA is a practical, standardized method for quantitating the overall severity of vertebral deformity in individuals who have vertebral fractures. Its reproducibility for longitudinal studies and clinical trials needs further study.

The impact of measurement errors on the diagnostic value of bone mass measurements: theoretical considerations

It has become clear over the last decade that correlations between measurements of forearm bone mineral content (BMCarm) by single-photon absorptiometry (SPA) and measurements of spinal bone mineral density (BMDspine) by dual-photon absorptiometry (DPA) in healthy subjects and patients with spinal fractures are invariably significant, but not very powerful (i.e. r = 0.5-0.7). Nonetheless, several recent studies have shown that appendicular bone mass measurements discriminate between spinal fracture and non-fracture at least as well as do spinal DPA measurements. Correlations of a given parameter with measured BMDspine are less important than those with true BMDspine. To establish the latter we made the following assumptions: (1) accuracy errors or SPA BMCarm and DPA BMDspine measurements of 2%-4% and 8%-10%, respectively; and (2) a measured biological variation of SD = 14% for both BMCarm and BMDspine, corresponding to that of healthy women at the menopause. On these assumptions, we found that a correlation between true BMCarm and true BMDspine at about r = 0.8-0.9 yields a correlation between measured BMCarm and measured BMDspine at about r = 0.6--corresponding to experimental data in healthy women at the menopause. Furthermore, we found that the correlation between DPA measured BMDspine and true BMDspine is about the same as that between the SPA measured BMCarm and the true BMDspine. Thus, with the assumptions given above, spinal (DPA) and fore-arm (SPA) measurements appears to predict equally the true BMDspine in healthy perimenopausal women.

The predictive value of bone loss for fragility fractures in women: a longitudinal study over 15 years

Fifteen years after their forearm bone mineral content was measured, 366 women were measured again with the same single photon technique. 96 of the women had sustained one or more fragility fractures during that period. The initial bone mineral content was less in those women who were to have fractures. The rate of loss over the years did not differ between fracture and non-fracture women--the initial bone mass was the better predictor. Peak bone mass in the women in this study occurred before the age of 40.

Effect of chronic carbonic anhydrase inhibitor therapy on bone mineral density in white women

A limited, dual-photon absorptiometry, single-center study of bone mineral density (BMD) was conducted on white female glaucoma subjects who were chronic users of the carbonic anhydrase (CA) inhibitors acetazolamide (Az) or methazolamide (Mz). In postmenopausal subjects long-term (greater than 4 years) CA inhibitor use was associated with a bone-sparing effect as judged by spinal BMD in comparison to controls matched for age, sex, weight, and ethnic group or in comparison to a national normative data base. Short-term (0-2 years) postmenopausal CA inhibitor users and premenopausal subjects using CA inhibitors showed no sparing of spinal BMD. Femoral neck BMD was not affected by CA inhibitor therapy in any of the groups. This study supports a proposed role for carbonic anhydrase in human bone resorption and suggests a possible future utility for carbonic anhydrase inhibitors in prophylaxis or management of primary involutional osteoporosis. Future studies are necessary to verify and expand these findings, assess the effects of CA inhibitors on bone mechanical competence, and further develop CA inhibitors with some specificity for bone.

A comparison of morphometric definitions of vertebral fracture

To compare the accuracy of several approaches for defining prevalent vertebral fractures from measurements of vertebral dimensions (morphometry), we measured the lateral dimensions of vertebral bodies of 115 normal premenopausal and 100 postmenopausal women. Of the postmenopausal women two observers agreed that 49 had definite vertebral fractures and 38 were definitely normal. Using these classifications as an independent reference, women were then classified as fractured or normal by several definitions based on vertebral morphometry. No morphometric definition of vertebral fracture agreed perfectly with the consensus classifications. In general, definitions that involved combinations of measurements of anterior (Ha), middle (Hm), and posterior (Hp) vertebral height classified women more accurately than did definitions based on a single measurement or ratio. The Ha/Hp ratio produced many false positives unless it was adjusted for normal variations in the shapes of different vertebral bodies. Definitions of fracture based on a greater than 15% reduction in heights or ratios had higher sensitivity but more false positives than definitions that used a more stringent (greater than 20%) criterion. All morphometric definitions of vertebral fracture separated the post-menopausal women into two groups (fractured and normal) that had significantly (P less than 0.001) different mean spine bone density by quantitative computed tomography. Definitions that had the lowest rates of false positives also produced the largest differences in bone density between those defined as fractured and those defined as normal.

A comparison of iliac bone histomorphometric data in post-menopausal osteoporotic and normal subjects

Transilial bone biopsies following in vivo fluorochrome labeling were obtained from 90 women with postmenopausal osteoporosis and 34 healthy post-menopausal women. Standard histomorphometric data were collected from undecalcified sections. The distribution of values for both structural and remodelling indices was the same for each group. Bone volume was 35% lower (P less than 0.001), wall thickness was 12% lower (P less than 0.001), and trabecular thickness was 11% lower (P less than 0.02) in osteoporotics. Trabecular separation was 34% greater (P less than 0.001) and trabecular number was 36% lower (P less than 0.001) in osteoporotics. Biopsy core width was 11% less (P less than 0.02) and cortical width was 35-50% less (P less than 0.001) in osteoporotics. Static indices of remodelling, mineralizing surfaces, and mineral apposition rate were similar in the two groups. The absolute values for bone histomorphometric variables for both groups are similar to most published data. Osteoporotics had poorer bone structure, marked by decreased trabecular connectivity and thin cortices. There were no major differences in dynamic indices of remodelling. Since the histomorphometric data were distributed the same in both groups, special subsets of osteoporotic subjects not in the normal population did not exist.

Bone mass measured by photon absorptiometry: comparison of forearm, heel, and spine

We assessed bone mass quantification at different skeletal sites by single and dual photon absorptiometric (SPA and DPA) methods. Improved DPA measurement of spinal bone mineral density in young healthy subjects showed a short- and long-term precision of 1.2% and 1.6%. Compared to the conventional DPA method the imprecision was reduced by more than 50%. The appendicular measurements were more precise (0.5-1.2%). We present the intercorrelations and predictive errors between peripheral measurements and improved spinal and total body bone measurements in early postmenopausal women (n = 144) recruited in 1988. To compare the improved system with the conventional methods, we retrieved data on age-matched early postmenopausal women (n = 151) recruited in 1983. In the 1988 population all peripheral methods had similar predictive errors in estimation of spinal bone mineral density (SEE = 11-13%) and total body bone mineral density (SEE = 4-5%). Measurement of trabecular bone in the heel and distal forearm did not improve the validity of predicting spinal bone mass. In a cadaver study (n = 11) the predictive error in estimation of the spinal ash weight from forearm measurements was of the same magnitude (15%) as that in estimation of the spinal BMC from the forearm (16%). We conclude that the predictive error in estimation of spinal bone mass from peripheral bone measurements is more likely to be caused by intra-skeletal variation in bone mass than by precision errors. However, this does not reflect the inability of peripheral bone mass measurements to predict fracture risk.

Does a single local absorptiometric bone measurement indicate the overall skeletal status? Implications for osteoporosis and osteoarthritis of the hip

Regional bone mineral content (BMC) and density (BMD) (head, arms, chest, spine, pelvis, legs) of a total body dual photon 153Gd absorptiometry (DPA) scan were measured in 20 healthy postmenopausal women, 27 postmenopausal women with hip fracture, and 17 postmenopausal women with osteoarthritis of the hip. In addition, local BMC and BMD were measured in the proximal and distal regions of the distal forearm (BMCprox, BMDprox, BMCdist, BMDdist) by single photon absorptiometry (SPA); and in the lumbar spine (BMCL2-L4 and BMDL2-L4) by 153Gd DPA. The overall impression was a reduction of bone mass in hip fracture patients compared with healthy controls and an increase in the bone mass of osteoarthritic patients. These results were valid using both regional values of the total body scan, and local forearm and lumbar spine measurements, and statistically significant using one-way analysis of variance. There were, however, also significant within-group between-region differences (one-way analysis of variance), showing that the bone mass of the pelvis and legs in hip fracture patients was more reduced than in the remaining skeleton; in osteoarthritic patients it was not increased but rather unchanged or slightly reduced. The differences between the level of the three local measurements (BMDprox BMDdist BMDL2-L4), on the one hand, and the level of the six regional BMD values, on the other hand, were investigated by the two-way analysis of variance: local measurements = rows; regional values = columns. This analysis showed that none of the three local measurements was statistically better than the other two in predicting the overall level of skeletal bone mass as judged by the six regional values. We conclude that serious osteoporotic bone loss has a generalized nature, however, with a tendency towards lower values in the regions affected by fracture (viz: low bone mass in the legs of femoral neck fracture patients). Osteoarthritis may be associated with a high bone mass in most areas, but low values in the affected regions. Local lumbar spine measurement of bone mass by DPA is not superior to local forearm measurement of bone mass by SPA in predicting the nature of overall osteoporotic or osteoarthritic bone change.

Dual photon absorptiometry of lumbar spine in west European (Belgian) postmenopausal females: normal range and fracture threshold

Bone mineral content (BMC) and bone mineral density (BMD) of lumbar spine have been measured in 695 healthy postmenopausal and 64 type I osteoporotic Belgian, Caucasian females. Bone loss is strongly correlated to time elapse from menopause (Tm) with a maximum rate of bone loss during the first five years of menopause. BMC (gHA) = 461 + 0.662 ln Tm -0.481 (ln Tm)2 and BMD (gHA/cm2) = 0.91 + 0.00711 ln Tm - 0.00846 (ln Tm)2 (in both cases p less than 0.001 and Tm expressed in months of menopause). After 20 years of menopause, 50 to 60% of normal women have vertebral BMC and BMD values below the 90th percentile of women with vertebral fractures and, thus, might be considered to have asymptomatic osteoporosis. We conclude that prevention of postmenopausal osteoporosis should be initiated as soon as possible after the onset of menopause and that bone density screening should be extended in elderly in order to detect and allow treatment of asymptomatic "densitometric" osteoporosis.

Malabsorption of calcium in corticosteroid-induced osteoporosis

We have examined the relation between radiocalcium absorption and serum 1,25-dihydroxyvitamin D [1,25(OH)2D3] levels in a set of 60 postmenopausal women on corticosteroid therapy (29 with and 31 without vertebral compression fractures) and compared these results with those from 31 normal postmenopausal women age-matched with the "normal" corticosteroid-treated women. Radiocalcium absorption was a function of serum 1,25(OH)2D3 in both corticosteroid-treated groups and in the set as a whole, but the impaired calcium absorption in the corticosteroid-treated patients with osteoporosis was not accounted for by their slightly reduced serum 1,25(OH)2D3 levels. This apparent resistance to the intestinal action of 1,25(OH)2D3 was quantified by a Z score which expresses, in standard deviation units, the difference between the measured calcium absorption and that predicted from the 1,25(OH)2D3 level. The Z score was significantly reduced in the osteoporotic group. Vertebral mineral density (VMD) was measured by quantitative computed tomography in 43 of the corticosteroid-treated cases and in all the normal postmenopausal women; analysis by VMD yielded similar conclusions.