How well do the FRAX (Australia) and Garvan calculators predict incident fractures? Data from the Geelong Osteoporosis Study.

This study reports that both FRAX and Garvan calculators underestimated fractures in Australian men and women, particularly in those with osteopenia or osteoporosis. Major osteoporotic fractures were poorly predicted, while both calculators performed acceptably well for hip fractures. INTRODUCTION: This study assessed the ability of the FRAX (Australia) and Garvan calculators to predict fractures in Australian women and men. METHODS: Women (n = 809) and men (n = 821) aged 50-90 years, enrolled in the Geelong Osteoporosis Study, were included. Fracture risk was estimated using FRAX and Garvan calculators with and without femoral neck bone mineral density (BMD) (FRAXBMD, FRAXnoBMD, GarvanBMD, GarvannoBMD). Incident major osteoporotic (MOF), fragility, and hip fractures over the following 10 years were verified radiologically. Differences between observed and predicted numbers of fractures were assessed using a chi-squared test. Diagnostics indexes were calculated. RESULTS: In women, 115 MOF, 184 fragility, and 42 hip fractures occurred. For men, there were 73, 109, and 17 fractures, respectively. FRAX underestimated MOFs, regardless of sex or inclusion of BMD. FRAX accurately predicted hip fractures, except in women with BMD (20 predicted, p = 0.004). Garvan underestimated fragility fractures except in men using BMD (88 predicted, p = 0.109). Garvan accurately predicted hip fractures except for women without BMD (12 predicted, p < 0.001). Fractures were underestimated primarily in the osteopenia and osteoporosis groups; MOFs in the normal BMD group were only underestimated by FRAXBMD and fragility fractures by GarvannoBMD, both in men. AUROCs were not different between scores with and without BMD, except for fragility fractures predicted by Garvan in women (0.696, 95% CI 0.652-0.739 and 0.668, 0.623-0.712, respectively, p = 0.008) and men, which almost reached significance (0.683, 0.631-0.734, and 0.667, 0.615-0.719, respectively, p = 0.051). Analyses of sensitivity and specificity showed overall that MOFs and fragility fractures were poorly predicted by both FRAX and Garvan, while hip fractures were acceptably predicted. CONCLUSIONS: Overall, the FRAX and Garvan calculators underestimated MOF and fragility fractures, particularly in individuals with osteopenia or osteoporosis. Hip fractures were predicted better by both calculators. AUROC analyses suggest that GarvanBMD performed better than GarvannoBMD for prediction of fragility fractures.

Increased bone mineral density in Aboriginal and Torres Strait Islander Australians: impact of body composition differences.

Bone mineral density (BMD) has been reported to be both higher and lower in Indigenous women from different populations. Body composition data have been reported for Indigenous Australians, but there are few published BMD data in this population. We assessed BMD in 161 Indigenous Australians, identified as Aboriginal (n=70), Torres Strait Islander (n=68) or both (n=23). BMD measurements were made on Norland-XR46 (n=107) and Hologic (n=90) dual-energy X-ray absorptiometry (DXA) machines. Norland BMD and body composition measurements in these individuals, and also in 36 Caucasian Australians, were converted to equivalent Hologic BMD (BMD(H)) and body composition measurements for comparison. Femoral neck (FN) and lumbar spine Z-scores were high in Indigenous participants (mean FN Z-score: Indigenous men +0.98, p<0.0001 vs. mean zero; Indigenous women +0.82, p<0.0001 vs. mean zero). FN BMD(H) was higher in Aboriginal and/or Torres Strait Islander than Caucasian participants, after adjusting for age, gender, diabetes and height and remained higher in men after addition of lean mass to the model. We conclude that FN BMD is higher in Aboriginal and/or Torres Strait Islander Australians than Caucasian Australian reference ranges and these differences still remained significant in men after adjustment for lean mass. It remains to be seen whether these BMD differences translate to differences in fracture rates.

Prognosis of fracture: evaluation of predictive accuracy of the FRAX algorithm and Garvan nomogram.

UNLABELLED: We evaluated the prognostic accuracy of fracture risk assessment tool (FRAX) and Garvan algorithms in an independent Australian cohort. The results suggest comparable performance in women but relatively poor fracture risk discrimination in men by FRAX. These data emphasize the importance of external validation before widespread clinical implementation of prognostic tools in different cohorts. INTRODUCTION: Absolute risk assessment is now recognized as a preferred approach to guide treatment decision. The present study sought to evaluate accuracy of the FRAX and Garvan algorithms for predicting absolute risk of osteoporotic fracture (hip, spine, humerus, or wrist), defined as major in FRAX, in a clinical setting in Australia. METHODS: A retrospective validation study was conducted in 144 women (69 fractures and 75 controls) and 56 men (31 fractures and 25 controls) aged between 60 and 90 years. Relevant clinical data prior to fracture event were ascertained. Based on these variables, predicted 10-year probabilities of major fracture were calculated from the Garvan and FRAX algorithms, using US (FRAX-US) and UK databases (FRAX-UK). Area under the receiver operating characteristic curves (AUC) was computed for each model. RESULTS: In women, the average 10-year probability of major fracture was consistently higher in the fracture than in the nonfracture group: Garvan (0.33 vs. 0.15), FRAX-US (0.30 vs. 0.19), and FRAX-UK (0.17 vs. 0.10). In men, although the Garvan model yielded higher average probability of major fracture in the fracture group (0.32 vs. 0.14), the FRAX algorithm did not: FRAX-US (0.17 vs. 0.19) and FRAX-UK (0.09 vs. 0.12). In women, AUC for the Garvan, FRAX-US, and FRAX-UK algorithms were 0.84, 0.77, and 0.78, respectively, vs. 0.76, 0.54, and 0.57, respectively, in men. CONCLUSION: In this analysis, although both approaches were reasonably accurate in women, FRAX discriminated fracture risk poorly in men. These data support the concept that all algorithms need external validation before clinical implementation.

Reference ranges for bone densitometers adopted Australia-wide: Geelong osteoporosis study.

Bone densitometry reports a measure of fracture risk in comparison with young adults (T-scores) and age-matched peers (Z-scores). To date, each manufacturer has provided its own reference range resulting in lack of uniformity. The Australia and New Zealand Bone and Mineral Society and Osteoporosis Australia have recognized the need to standardize the reference range and have recommended that data generated by the Geelong Osteoporosis Study (GOS) be used Australia-wide. The GOS recruited a random, population-based sample of adult women and measured bone mineral density (BMD) at the proximal femur and spine using a Lunar DPX-L. These data were used to establish reference ranges for Lunar machines and, using conversion equations, for Norland and Hologic machines. The new standardized Australian reference ranges for BMD will enable consistent diagnosis of osteoporosis and categorization of fracture risk across different types of densitometers.

The effect of room temperature on dual-energy X-ray absorptiometry.

There has been little published data on the effects of temperature on the performance of dual-energy X-ray absorptiometry (DXA) machines. We examined the effect of changes in ambient room temperature on the performance of three DXA scanners (DPXL, Expert-XL and Prodigy). The study involved repeat measurements of bone mineral density (BMD) using three different spine phantoms scanned at different ambient room temperatures, both before and after calibration procedures. The calibration or quality assurance (QA) scan calibrates the scanner, adjusting for the ambient room temperature at the time of calibration. There was a moderate correlation between change in temperature and change in BMD measured prior to recalibration for the Expert-XL ( r=0.58) during normal clinical scanning conditions. There was no observed change in phantom BMD with change in temperature measured using the DXPL or Prodigy. After temperature change, without repeat calibration measurements, there was a strong correlation between temperature change and change in BMD measured using the Expert-XL ( r=0.96, p<0.001). From the regression equation, a change of 2.5 degrees C could alter the calculated BMD result measured by the Expert-XL by 1.5%, which would significantly affect the precision of the DXA system. There was no significant correlation between temperature and BMD in the DXPL or Prodigy. The observed differences between the densitometers and the effect of temperature change are most likely due to the differing types of detector systems used. Operators must be made aware that solid state detectors of the sort used in the Expert-XL (charge-coupled devices, CCDs) are significantly affected by changes in ambient room temperature.

Coincidence detection FDG PET in the management of oncological patients: attenuation correction versus non-attenuation correction.

The aim of this study was to determine if attenuation correction (AC) in a dual-head, coincidence, positron emission tomography imaging system (Co-PET) improved image quality, lesion detection, patient staging and management of various malignant neoplasms, compared to non-attenuation corrected (NAC) images. Thirty patients with known or suspected malignant neoplasms underwent fluorodeoxyglucose (FDG) Co-PET, which was correlated with histopathology, computed tomography (CT) and other conventional imaging modalities and clinical follow-up. The number and location of FDG avid lesions detected on the AC images and NAC Co-PET images were blindly assessed by two independent observers. Semi-quantitative grading of image clarity and lesion-to-background quality was performed. This revealed markedly improved image clarity and lesion-to-background quality in the AC versus NAC Co-PET images. AC Co-PET was statistically superior to NAC Co-PET in relation to lesion detection (P<0.01) and tumour staging (P<0.01). NAC Co-PET demonstrated 51 of the 65 lesions (78%) detected by AC Co-PET. AC Co-PET altered tumour staging in five additional patients (16%) compared to NAC Co-PET. Management was altered in two of these five patients.

Potential roles for quantitative ultrasound in the management of osteoporosis.

OBJECTIVE: To assess the validity of four models for the role of quantitative ultrasound (QUS) in the management of osteoporosis. DESIGN: Cross-sectional survey and review of literature. SETTINGS: Nuclear medicine departments of three teaching hospitals in Sydney. SUBJECTS: 1000 women aged 22 to 88 years (mean, 59 years) referred for assessment of osteoporotic fracture risk. MAIN OUTCOME MEASURES: BMD categories as defined by dual-energy x-ray absorptiometry (DEXA) of the lumbar spine and proximal femur, and QUS category as defined by calcaneal ultrasound stiffness; prevalence of DEXA-defined osteoporosis in the different QUS categories. RESULTS: In women with QUS Achilles stiffness < or = 70 the prevalence of axial osteoporosis was 51%, whereas in the group with stiffness > 70 the prevalence of axial osteoporosis was 8%. In women 65 years and over the corresponding values were 59% and 17%. CONCLUSIONS: Of the four possible models for QUS, the use of QUS for the estimation of BMD, or in a "standalone" model, can not be recommended at the current time. The model of QUS as a "prescreening" modality may be acceptable assuming adequate education of clinicians and patients of its limitations, particularly the risk of false negatives. The model of QUS as one factor in a composite risk factor assessment of patients is promising but more data are required.

Temperature dependency of quantitative ultrasound.

Quantitative ultrasound (QUS) parameters are temperature dependent. We examined the effect of temperature on QUS using Lunar Achilles+ and Hologic Sahara units. In vivo studies were performed in a cadaveric foot and in 5 volunteers. QUS scans were performed in the cadaveric foot, using both machines, at temperatures ranging from 15 to 40 degrees C. To assess the effect of change in water bath temperature in the Achilles+, independently of foot temperature, 5 volunteers were studied at water temperatures ranging from 10 to 42 degrees C. In the cadaveric foot there were strong negative correlations between temperature and speed of sound (SOS) but a moderately positive correlation between temperature and broadband ultrasound attenuation (BUA). Stiffness and the Quantitative Ultrasound Index (QUI) in the cadaveric foot showed strong negative correlations with temperature, reflecting their high dependence on SOS. In the 5 volunteers, in whom foot temperature was assumed to be constant, there was a small change in Stiffness in the Achilles+, with variation in water temperature. In conclusion, while there are opposite effects of temperature on SOS and BUA in vivo, there is still a significant effect of temperature variation on Stiffness and the QUI. This may have clinical significance in particular subjects. The precision of QUS may be affected by temperature variation of the environment or of the patient's limb. Instruments utilizing a water bath may be able partly to compensate for changes in environmental temperature, but standardization of water bath temperature is crucial to maximize precision.

Quantitative heel ultrasound as a predictor for osteoporosis.

OBJECTIVE: To determine the diagnostic value of quantitative ultrasound (QUS) to predict bone mineral density (BMD) categories as defined by dual-energy x-ray absorptiometry. DESIGN: Cross-sectional survey. SETTING: Rheumatology department of a tertiary care hospital (Royal North Shore Hospital, Sydney, NSW), 1997-1998. SUBJECTS: 326 healthy women aged 45-80 years who had volunteered for a twin study. Our study included both members of non-identical twin pairs but only one randomly selected member of identical twin pairs. MAIN OUTCOME MEASURES: BMD categories as defined by dual-energy x-ray absorptiometry of lumbar spine and left hip, and QUS of calcaneus; sensitivity, specificity and likelihood ratios (LRs) of QUS parameters to diagnose osteoporosis as defined by BMD. RESULTS: The sensitivity of QUS to diagnose BMD osteoporosis varied between 9% and 47%, depending on the QUS parameter. The specificity of QUS was high (88%-100%). If all QUS parameters were normal, osteoporosis was unlikely (LR, 0-0.2). One QUS parameter, broadband ultrasound attenuation (BUA), was highly predictive of osteoporosis by BMD when in the osteoporotic range (LR, infinity), but had low sensitivity (9%). QUS results in the osteoporotic range for other parameters and all QUS results in the osteopenic range were less predictive (LR, 1.0-5.2) of osteoporotic BMD. CONCLUSION: These results suggest that, for most of those tested for osteoporosis by QUS in the community, uncertainty remains about expected BMD.

The potential effect on hip fracture incidence of mass screening for osteoporosis.

With ageing of the Australian population, treatment of osteoporosis-related hip fractures will impose an increasing burden on the healthcare system. Based on current age-adjusted hip fracture incidence and population projections for New South Wales, we estimated a 90% increase in hip fractures by the year 2021. Contributing significantly to this increase will be the number of men reaching the high risk age group for osteoporotic hip fractures. A suggested solution--screening and appropriate therapy for individuals at high risk of osteoporosis--may have only a modest impact. Our calculations show that, even with optimistic screening and therapy compliance rates, hip fractures could still increase by over 50%. Other approaches need to be further explored.

Quantitative diagnostic methods in osteoporosis: a review.

During the last two decades there have been major advances in the understanding of pathophysiology and in the diagnosis of osteoporosis. There are now, in addition to standard radiographs, a number of different diagnostic modalities available to doctors for the quantitative assessment of bone mass. These methodologies are having an increasingly important role, not only in the clinical diagnosis, but also in the monitoring of patients with osteoporosis. As the population ages there will be an increasing demand for these services, and radiologists need to be aware of the strength and limitations of the different modalities available.

Femoral neck axis length, height loss and risk of hip fracture in males and females.

Hip axis length (HAL) has been proposed as an independent predictor of hip fracture risk in Caucasian females. Femoral neck axis length (FNAL) is a similar measure of femoral geometry but does not include acetabular structures. The aim of this study was to examine the association between hip geometry, using FNAL, and hip fractures in elderly males and females in relation to other anthropometric data. The study group comprised 123 females (23 hip fracture patients and 100 age-matched controls) and 137 males (13 hip fracture patients, 65 age-matched controls and 59 current-height-matched controls). All subjects had femoral neck bone mineral density measured by dual-energy X-ray absorptiometry. From these scans, FNAL was measured as the linear distance from the base of the greater trochanter to the apex of the femoral head. FNAL was correlated significantly with current height (r = 0.47 and r = 0.56 for females and males respectively; p < 0.0001) and peak height (r = 0.45 and r = 0.57 for females and males respectively; p < 0.0001) in both sexes. In females, FNAL in the fracture patients (91.5 +/- 5.4 mm, mean +/- SD) was not significantly different from FNAL in controls (89.7 +/- 5.4 mm; p = 0.2). Fracture patients had the same current height as controls and a trend towards a greater peak height (163 +/- 6 cm vs 160 +/- cm; p = 0.09). After adjusting FNAL for current or peak height there was no difference in FNAL between fracture patients and controls. In males, FNAL in the fracture patients (103.9 +/- 3.9 mm) was not significantly different from that of age-matched controls (103.4 +/- 6.3 mm; p = 0.79). Fracture patients had a significantly lower current height (168 +/- 6 cm) than the age-matched controls (174 +/- 6 cm; p = 0.0008) but had the same peak height. When adjusted for peak height there were no significant differences between height of hip fracture patients (102.0 +/- 4.9 cm), age-matched controls (102.1 +/- 5.1 cm) and current-height-matched controls (102.6 +/- 5.3 cm). Fracture patients had a significantly greater height loss (peak height minus current height) than either control group. In logistic regression analyses peak height in females and height loss in males but not FNAL were independent predictors of hip fracture. The greater height, FNAL and presumably HAL in males versus females is not associated with increased hip fracture risk. However, in this study of elderly males and females, peak height (females) and height loss (males) were independent risk factors for hip fracture. Moreover, FNAL appears to have limited utility in the prediction of hip fracture risk and any role of HAL in the prediction of hip fracture does not relate to its major component of femoral neck length.

Correcting the magnification error of fan beam densitometers.

Dual-energy X-ray absorptiometry (DXA), using a narrow pencil-shaped X-ray beam coupled to a single detector, has been used extensively. More recently, DXA using a fan- shaped X-ray beam coupled to an array of detectors has been introduced. This new generation of scanners causes an inherent magnification of scanned structures as the distance from the X-ray source decreases. This magnification, which occurs in the medial-lateral direction but not in the craniocaudal direction, does not affect bone mineral density (BMD). There are, however, significant changes of bone mineral content (BMC), bone area, and parameters of hip geometry, with varying distance of the bone scanned from the X-ray source. Variability of soft tissue thickness in vivo, by altering the distance of the skeleton from the scanning table and X-ray source, may cause clinically significant errors of BMC, bone area, and proximal femur geometry when measured using fan-beam densitometers. We analyzed the geometry of Lunar and Hologic fan beam scanners to derive equations expressing the true width of scanned structures in terms of the apparent width and machine dimensions. We also showed mathematic ally that performing an additional scan, at a different distance from the X-ray source than the first scan, provides simultaneous equations that can be solved to derive the real width of a scanned bone. This hypothesis was tested on the Lunar Expert using aluminium phantoms scanned at different table heights. There was an excellent correlation, r = 0.99 (p < 0.001), between the predicted phantom width and the measured phantom width. In conclusion, this study shows that the magnification error of fan beam DXA can be corrected using a dual scanning technique. This has important implications in the clinical usefulness of BMC and geometrical measurements obtained from these scanners.

Influence of handedness on calcaneal ultrasound: implications for assessment of osteoporosis and study design.

Calcaneal ultrasound has been increasingly studied for its potential in the assessment of osteoporotic fracture risk. The accuracy of such an assessment is, in part, dependent on the reproducibility of the measurement. This study examines the impact of handedness on ultrasound measurements [broadband ultrasound attenuation (BUA) and velocity of sound (VOS)] in the calcaneus. Two hundred and sixty-four subjects (57 men and 297 women) aged 51.1 +/- 13.6 years (mean +/- SD) were studied. For each subject, calcaneal ultrasound measurements were performed on both heels with a McCue CUBA ultrasound densitometer. Right-handed dominance (94.7%) was determined by structured interview. In men, BUA measurements were significantly higher on the dominant side: mean difference 4.1 +/- 1.5 dB/MHz (mean +/- SD; p = 0.009), equivalent to 4.2 +/- 1.5% and more than 4 times the average rate of annual change in BUA. The difference between sides was greater in young (< 50 years) than old men (> 50 years). Among the women, the difference was not statistically significant (0.7 +/- 0.9 dB/MHz; p = 0.4); however, it was significant in younger women (20-30 years) (99 +/- 4 vs 90 +/- 4 dB/MHz, p = 0.01). By contrast VOS did not differ between sides in either men or women irrespective of age. Within-subject standard deviation of BUA was 9.8 dB/MHz for men and 8.6 dB/ MHz for women and the component due to right and left difference was 8.4 dB/MHz for men and 6.9 dB/MHz for women. This variability of BUA between right and left heels could increase the false-positive rate by up to 28% for a cut-off of 2 SD below the mean. These data indicate that variation between left and right heel measurements of BUA is higher than that of random error measurements, particularly in men and younger, presumably more physically active subjects. Although VOS measurements were not side dependent, in the smaller number of studies examining VOS and fracture risk, VOS appears to have a weaker predictive power than BUA. Clinical and epidemiological studies involving calcaneal BUA measurements should standardize the side measured to either the dominant or non-dominant heel, to reduce within-subject variation and increase their power.

Magnification error of femoral geometry using fan beam densitometers.

Hip axis length (HAL) has been reported as an independent risk factor for hip fracture. DEXA machines using fan beam techniques have become increasingly available. Errors in calculated hip axis length may be expected because of different degrees of magnification by the fan beam. The magnitude of this error on measurement of hip geometry was studied, using an anthropomorphic femur phantom with both fan beam (Lunar Expert and Hologic QDR-2000) and pencil beam (Lunar DPXL) densitometers. The clinical relevance of these findings was also examined using patient measurements of buttock soft tissue thickness. Femoral neck axis length (FNAL), which correlates well with HAL, was used as a measurement of hip geometry. There was a linear increase or decrease of FNAL with increasing distance of the phantom above the scanning table, when measured with the Lunar Expert or Hologic QDR-2000, respectively. There was no significant difference in FNAL at different heights using the pencil beam densitometer. The maximal difference in buttock soft tissue thickness in 30 women studied was 8.7 cm. From the equations, derived from the phantom studies, this difference would result in an 8.2% (1.4 SD) increase, or an 11.4% (1.9 SD) decrease in FNAL in the largest woman as compared with the smallest woman when measured using the Lunar Expert or Hologic QDR-2000, respectively. We conclude that there may be unpredictable degrees of magnification of FNAL in vivo, caused by differences in buttock thickness, when measured using a fan beam densitometers. Until these problems are resolved. FNAL, or related parameters of femoral geometry, should be measured using pencil beam instruments.

A comparison of longitudinal measurements in the spine and proximal femur using lunar and hologic instruments.

Absolute values of bone mineral density (BMD), using dual-energy X-ray absorptiometry (DXA), differ between instruments from different manufacturers. Despite these differences, the rates of change calculated from serial measurements on different densitometers have been assumed to be comparable. We compared the change in BMD in 34 subjects in the lumbar spine and at the standard sites in the proximal femur, from measurements performed using a Lunar DPX-L and a Hologic QDR-1000. Measurements were obtained on the same day, and repeated on the same day, on both machines after a mean interval of 4.8 years (range 4.1-6.3 years). There were strong positive correlations between the percentage change in BMD calculated using the two machines in the lumbar spine, trochanteric region, and total proximal femur: r = 0.82, 0.84, and 0.73, respectively (p < 0.0001 at all sites). In the femoral neck and in Ward's triangle, the correlations were not as high: r = 0.55 (p = 0.003) and 0.43 (p = 0.028), respectively. At all sites, despite the significant correlations, the agreement between the two densitometers was not high and there may be significant errors in individual subjects if one uses measurements from one densitometer to predict the change in BMD using the scanner of the other manufacturer. There is less of a problem comparing group data in the lumbar spine and trochanteric region, although errors are still likely to occur in comparing group data of bone loss, calculated using different densitometers, in the other proximal femur sites. In conclusion, the study suggests that caution is necessary in combining bone loss data derived using densitometers from different manufacturers, particularly in the proximal femur. This has important implications for multicenter studies.

Screening for osteoporosis: what is the role of heel ultrasound?

Could focused population screening detect osteoporosis earlier and improve the management of this major health care problem? Quantitative ultrasound of the calcaneus is currently being proposed as a suitable screening technique. Correlations between quantitative ultrasound of the calcaneus and dual energy x-ray absorptiometry of bone mineral density of the spine and proximal femur are not high enough to reliably predict bone mineral density at the lumbar spine or proximal femur from the ultrasound results. Some ongoing longitudinal studies suggest that quantitative ultrasound may none the less detect individuals at increased risk of fracture, but its use for mass screening for osteoporosis would be premature.

Lifestyle factors and bone density in the elderly: implications for osteoporosis prevention.

Epidemiologic evidence suggests that lifestyle factors, such as exercise, calcium intake, and tobacco consumption, have effects on bone density. However, the influence of these factors in the elderly has not been well documented. To examine the effects of lifestyle factors in the elderly, we measured bone density (BMD) at the lumbar spine and proximal femur in 709 elderly men and 1080 women participating in the Dubbo Osteoporosis Epidemiology study (DOES), a community-based, longitudinal, epidemiologic study of osteoporosis in men and women over the age of 60. BMD was significantly higher in men than in women (20% at all sites). There was an age-related decline in BMD at the femoral neck in both sexes and at the lumbar spine in women. Between the ages of 60 and 80, the decrease in BMD at the femoral neck among women was 18.9%, which is almost twice the decrease in BMD among men (10.1%). Tobacco consumption was associated with a reduction in BMD at both sites in both sexes (5-8%), and this effect was independent of calcium intake or body weight. Exsmokers had BMD intermediate between that of current smokers and never smokers, suggesting the influence of tobacco was partially reversible. Quadriceps strength predicted bone density at the proximal femur in elderly men but not in women. Analyzing BMD (adjusted for age and weight) in tertiles of muscle strength and calcium intake revealed an interaction between calcium intake and muscle strength on bone density; BMD at the femoral neck among those with higher quadriceps strength and calcium intake was approximately 5% higher (P < 0.05) than in those with low quadriceps strength and calcium intake in both men and women.(ABSTRACT TRUNCATED AT 250 WORDS)

Peak bone mass and osteoporosis prevention.

The incidence of osteoporotic fractures increases with advancing age. Despite advances in therapy, reversal of bone loss in established osteoporosis remains problematic and deformities and disability due to fractures often persist. Therefore the logical approach to osteoporosis treatment is preventive. Risk of fracture is determined largely by bone density, which is the end result of peak value achieved at skeletal maturity and subsequent age- and menopause-related bone loss. Thus the determinants of peak bone density and bone loss require full characterization. Environmental and lifestyle factors are important determinants of bone density, particularly physical activity and diet. For example, muscle strength and physical fitness predict bone density, so that regular moderate exercise may help maintain bone mass but probably does not reverse loss. Long-term calcium intake appears to be important for achievement and maintenance of peak bone density, especially in males. Smoking and excessive alcohol intake are deleterious to bone mass. Cultural norms in diet, lifestyle and physical activity obviously have an impact on bone density. Genetic factors have a strong role in determining the wide range in 'normal' peak bone mass. Moreover we have found strong genetic determinants of rates of change of bone mass in the lumbar spine and similar trends for sites in the femoral neck. We have shown previously that genetic factors influence bone turnover indices, particularly osteocalcin. Investigating these relationships with restriction fragment length polymorphisms, we have identified variants of the vitamin D receptor gene which predict osteocalcin levels and presumably bone turnover.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of spinal and femoral bone density by dual X-ray absorptiometry: comparison of lunar and hologic instruments.

Clinical application of techniques for assessing bone mineral density (BMD) requires accurate and precise measurements that can be related to clearly defined normal ranges. In this study we investigated the clinical interpretation of BMD values in a group of individuals measured on the same day with two different dual-energy x-ray densitometers (Lunar DPX and Hologic QDR 1000). The BMD results were analyzed as absolute values in g/cm2 and with respect to young and age-specific normals as defined by each manufacturer. Absolute BMD values measured by the two instruments were highly correlated (lumbar spine r = 0.98, femoral neck r = 0.95; p less than 0.0001). In the lumbar spine, the two instruments assigned almost identical values when expressed as a percentage of age-matched values and as a percentage of young normals, despite a small but systematic difference between the values assigned for the latter index. In the femoral neck, however, there were significant differences in assignments between instruments, expressed both as a percentage of young normal (mean difference 6.2%) and with respect to age-matched values (mean difference 3.3%). In particular, in premenopausal subjects femoral neck values with the Hologic instrument were assigned significantly lower values. This study shows effective comparability between these two instruments for absolute and relative values for the lumbar spine, as well as for absolute values at the femoral neck, but important differences for normality assignments at the femoral neck. These latter differences may produce bias in the "diagnosis" of femoral neck osteoporosis and may have important implications for clinical decision making.(ABSTRACT TRUNCATED AT 250 WORDS)