Utility of ultrasound to assess risk of fracture

Prediction of trabecular bone qualitative properties using scanning quantitative ultrasound

Microgravity induced bone loss represents a critical health problem in astronauts, particularly occurred in weight-supporting skeleton, which leads to osteopenia and increase of fracture risk. Lack of suitable evaluation modality makes it difficult for monitoring skeletal status in long term space mission and increases potential risk of complication. Such disuse osteopenia and osteoporosis compromise trabecular bone density, and architectural and mechanical properties. While X-ray based imaging would not be practical in space, quantitative ultrasound may provide advantages to characterize bone density and strength through wave propagation in complex trabecular structure. This study used a scanning confocal acoustic diagnostic and navigation system (SCAN) to evaluate trabecular bone quality in 60 cubic trabecular samples harvested from adult sheep. Ultrasound image based SCAN measurements in structural and strength properties were validated by μCT and compressive mechanical testing. This result indicated a moderately strong negative correlations observed between broadband ultrasonic attenuation (BUA) and μCT-determined bone volume fraction (BV/TV, R²=0.53). Strong correlations were observed between ultrasound velocity (UV) and bone's mechanical strength and structural parameters, i.e., bulk Young's modulus (R²=0.67) and BV/TV (R²=0.85). The predictions for bone density and mechanical strength were significantly improved by using a linear combination of both BUA and UV, yielding R²=0.92 for BV/TV and R²=0.71 for bulk Young's modulus. These results imply that quantitative ultrasound can characterize trabecular structural and mechanical properties through measurements of particular ultrasound parameters, and potentially provide an excellent estimation for bone's structural integrity.

Association between low bone mass and calcium and caffeine intake among perimenopausal women in Southern Brazil: cross-sectional study

CONTEXT AND OBJECTIVE

Osteoporosis is a skeletal abnormality characterized by reduction and alteration of bone microarchitecture that results in increased fragility and greater predisposition to fractures. Age and low bone mass are the main non-modifiable risk factors for osteoporotic fractures. The modifiable factors include sedentary lifestyle, inadequate calcium intake, excessive alcohol and/or caffeine consumption, smoking and low body weight. The aim here was to evaluate the association between low bone mass and calcium and caffeine intake among perimenopausal women in Southern Brazil.

DESIGN AND SETTING

Cross-sectional study conducted in Porto Alegre and Canoas, Rio Grande do Sul, Brazil.

METHODS

Women (n = 155) of mean age 53.6 ± 9.5 years were evaluated through a cross-sectional study in Southern Brazil. Food frequency questionnaires, bone mass evaluation using calcaneal ultrasound and anthropometric assessment were used.

RESULTS

The prevalence of overweight was 67.7%. In the bone mass screening, 30.3% had low bone mass and 4.5% had osteoporosis. The median calcium intake was 574.94 mg/day and the caffeine intake was 108.11 mg/day. No association was found between bone mass and anthropometric parameters, calcium intake or caffeine intake. It was found that 38.4% of the women had low bone mass.

CONCLUSIONS

No association was found between calcium and caffeine intake and bone mass. High prevalence of low bone mass was observed.

Characterization of controlled bone defects using 2D and 3D ultrasound imaging techniques

Ultrasound is emerging as an attractive alternative modality to standard x-ray and CT methods for bone assessment applications. As of today, however, there is a lack of systematic studies that investigate the performance of diagnostic ultrasound techniques in bone imaging applications. This study aims at understanding the performance limitations of new ultrasound techniques for imaging bones in controlled experiments in vitro. Experiments are performed on samples of mammalian and non-mammalian bones with controlled defects with size ranging from 400 microm to 5 mm. Ultrasound findings are statistically compared with those obtained from the same samples using standard x-ray imaging modalities and optical microscopy. The results of this study demonstrate that it is feasible to use diagnostic ultrasound imaging techniques to assess sub-millimeter bone defects in real time and with high accuracy and precision. These results also demonstrate that ultrasound imaging techniques perform comparably better than x-ray imaging and optical imaging methods, in the assessment of a wide range of controlled defects both in mammalian and non-mammalian bones. In the future, ultrasound imaging techniques might provide a cost-effective, real-time, safe and portable diagnostic tool for bone imaging applications.

A new technique for precisely and accurately measuring lumbar spine bone mineral density in mice using clinical dual energy X-ray absorptiometry (DXA)

Dual Energy X-ray Absorptiometry (DXA) is effective in measuring bone mineral density (BMD) in mice for early detection of osteoporosis. However, scanners designed for use with small animals (i.e. PIXImus) are very expensive. Used human DXA machines are cheaper to obtain, but analysis of scans from these instruments is operator-dependent. Obtaining reliable data depends on having a single operator analyze the scans in a blinded fashion. Scan quality is improved by excising the bone prior to scanning, which does not allow serial measurements. This study describes a novel method of analyzing lumbar spine BMD in mice using whole body DXA. This non-invasive technique has a high degree of precision and reproducibility, with good correlation between multiple observers. Inter-observer variability (0.063 ± 0.00317 g/cm² [mean ± SD], 5.05 [% coefficient of variation (CV)], repeat scan variability (0.063 ± 0.00364 g/cm² [mean ± SD], 5.94 [%CV]) were very low compared to variability between different animals (0.063 ± 0.00588 g/cm² [mean ± SD], 9.64 [%CV]) and variability seen in same animal over time (0.011 ± 0.00885 g/cm² [mean ± SD], 80.68 [%CV]). The measurement error is thus smaller than the biological variation. Accuracy was determined by comparing average peak BMD from two scans per mouse in-vivo (0.066 g/cm²) versus excised spine (0.065 g/cm²). Furthermore, correlation between bone ash weights and whole body lumbar spine BMD measurements (p < 0.0001) was highly significant. This technique thus shows a high degree of precision and accuracy, even with multiple observers, for measuring BMD in mice using a DXA machine designed for clinical use.

Quantitative ultrasound of the calcaneus in greek women: normative data are different from the manufacturer's normal range

Quantitative ultrasound (QUS) is considered a useful method in evaluating bone status. The aim of the present study was to establish the reference data for the QUS measurements of the calcaneus in a Greek population. We measured a QUS parameter, stiffness index (SI), at the right calcaneus in 1500 women using the Achilles express Ultrasonometer (GE Lunar, Madison, WI). Participants were divided into 7 groups according to their age with a 10-yr span in each group. A progressive decline was found in the SI values after the age of 39 yr in the current study. When the SI values were compared between the age groups, high statistically significant differences were obvious, especially between 20-29 and 50- to 59-yr age groups and 60-69 and 70- to 79-yr age groups (p < 0.0005). Additionally, in the Greek normal range (GNR), the SI values of those aged 60-69 and 70-79 yr were significantly higher (81.84+/-16.14 and 77.45+/-17.65, respectively) than those in the manufacturer's normal range (MNR; 75.84+/-16.14 and 69.10+/-17.65, p < 0.005, respectively). Using the manufacturer's values, significantly fewer women were classified as normal (48% vs 67.3%), although those with T-score < or =-2.5 were more (15.7%) compared with our Greek value (1.5%), and classification of subjects into risk-of-fracture categories was significantly different (kappa: 0.459, 66.2%, p < 0.0005). Multiple regression analysis showed that weight was the most significant predictor for SI in the age groups 30-39 (beta = 0.280, p < 0.05), 40-49, 60-69, and 70-79 yr (beta = 0.185, p < 0.005; beta = 0.329, p < 0.0005; beta = 0.494, p<0.0005, respectively). Using conventional categories of risk, we report a different classification of our subjects from those proposed by the manufacturer, supporting the concept that data specific to the Greek population are necessary.

Ultrasonic guided waves in bone

Recent progress in quantitative ultrasound (QUS) has shown increasing interest toward measuring long bones by ultrasonic guided waves. This technology is widely used in the field of nondestructive testing and evaluation of different waveguide structures. Cortical bone provides such an elastic waveguide and its ability to sustain loading and resist fractures is known to be related to its mechanical properties at different length scales. Because guided waves could yield diverse characterizations of the bone's mechanical properties at the macroscopic level, the method of guided waves has a strong potential over the standardized bone densitometry as a tool for bone assessment. Despite this, development of guided wave methods is challenging, e.g., due to interferences and multiparametric inversion problems. This paper discusses the promises and challenges related to bone characterization by ultrasonic guided waves.

New imaging technologies in the diagnosis of osteoporosis

In the context of osteoporosis, bone quality--which encompasses trabecular and cortical micro-architecture, mass, and tissue mechanical & compositional properties--plays an important and as yet undiscovered role. Non-invasive assessment of bone quality has recently received considerable attention, as bone density alone has not been able to predict existing or future osteoporotic fractures, or to explain therapeutic effects of emerging treatments. The goal of this review, therefore, is to present imaging modalities and related analysis methods capable of assessing bone quality for improved diagnosis and care of osteoporotic individuals. The techniques described include quantitative ultrasound, quantitative computed tomography, peripheral quantitative tomography, micro computed tomography, magnetic resonance, radiographic texture analysis, as well as finite element analysis based on the above-mentioned imaging modalities. The performance of these techniques in predicting osteoporotic fracture and assessing strength indices are discussed.

Lifestyle factors affecting heel ultrasound in Greek females across different life stages

The use of quantitative ultrasound (QUS) of the bone is rapidly gaining in popularity, and QUS is widely used worldwide for the assessment of skeletal status. Although much has been learned about the influence of various factors on ultrasonic parameters in various populations, similar information at the local level is not available. This study was carried out to examine the effects of anthropometric, dietary, physical activity, reproductive, and other lifestyle factors on QUS parameters in healthy Greek women, including children (n=217), adults (n=235), and elderly (n=369) subjects. Calcaneal QUS measurements were performed with the SAHARA device, which measures broadband ultrasound attenuation (BUA) and speed of sound (SOS) through the os calcis; a composite parameter, the quantitative ultrasound index (QUI), and an estimate of heel bone mineral density (eBMD) were also derived. All QUS indices were higher in adult women than in girls or elderly women (P<0.05). The latter had a similar BUA to girls, but lower SOS, QUI, and eBMD (P<0.05). Most QUS parameters correlated positively with height, weight, body mass index (BMI), hip circumference, organized physical activity, and activity promoting bone mass, but negatively with the time devoted to sedentary activities and absolute carbohydrate intake (P<0.05). Age of menarche and years since menopause were negatively associated with QUS in the adult and elderly women, respectively (P<0.05). The latter relationship, however, was due to the confounding effect of advancing age. Overweight and obese females had significantly higher BUA and eBMD than normal-weight subjects (P<0.05), but similar SOS and QUI; this held true for all age groups. Likewise, in all ages, individuals spending more than 2 h/week on organized activities had significantly higher QUS indices than those spending less time on exercise (P<0.05). Further, postmenarchial girls had significantly higher age-adjusted BUA, SOS, QUI, and eBMD than premenarchial ones (P<0.05). Similarly, all QUS parameters were significantly higher in adult women with an early onset of menarche (<14 years old) than in those with a late onset (P<0.05), but no effects of menarche were detected among the elderly. No significant effects of calcium intake (which was generally adequate), smoking or alcohol drinking (which were generally low) on QUS indices were observed, in either age group. Available independent variables could explain approximately 16%-24% of the total variance in BUA, SOS, QUI and eBMD. The most important positive predictors of QUS were adulthood, time devoted to organized activities, and weight or BMI, while age and carbohydrate intake per se contributed negatively. In conclusion, age, body size, physical activity, and some aspects of reproductive history and diet appear to variably affect calcaneal QUS indices among otherwise healthy Greek women at different life stages.

Bone fractal analysis

Fractal analysis is a quantitative method used to evaluate complex anatomic findings in their elementary component. Its application to biologic images, particularly to cancellous bones, has been well practiced within the past few years. The aims of these applications are to assess changes in bone and the loss of spongious architecture, indicate bone fragility, and to show the increased risk for fracture in primary or secondary osteoporosis. The applications are very promising to help complete the studies that can define bone density (bone mineral density by dual energy x-ray absorptiometry or quantitative computed tomography), and also have the capacity to distinguish the patients with a high or low risk for fracture. Their extension to the clinical fields, to define a test for fracture risk, is still limited by difficult application to the medical quantitative imaging of bones, between correct application at superficial bones and unreliable application to deep bones. The future evolution and validity do not depend upon fractal methods but upon well-detailed imaging of the bones in clinical conditions.

Discriminatory ability of quantitative ultrasound measurements is similar to dual-energy X-ray absorptiometry in a Brazilian women population with osteoporotic fracture

The discriminating ability and relevance of clinical risk factors, quantitative ultrasound (QUS) variables, X-ray-based bone mineral density (BMD) and hip axis length (HAL) measurements to evaluate the risk of osteoporotic fracture in elderly Brazilian women were examined in this study. QUS at the calcaneus (Achilles +, Lunar), HAL and BMD measurements (DPX-L, Lunar) at several anatomical sites were performed in 275 postmenopausal Caucasian women. Patients with suspected secondary osteoporosis were excluded. One hundred twenty-two (44.4%) women had had previous osteoporotic fracture. All of the subjects were over 50 years old (range 53-93) and answered a questionnaire that included details concerning aspects of lifestyle, diet, hormonal factors and drug use. Lateral thoracic and lumbar radiographs were taken and an independent radiologist reviewed the X-rays for the presence of vertebral fractures. After adjustments for age, the most relevant risk factors to discriminate patients with osteoporotic fracture from normal non-fracture controls were Stiffness index (OR 2.8 per standard deviation; 95% confidence interval 2.3, 8.7), familial history of hip fracture (OR 2.6 per standard deviation; 95% confidence interval 2.2, 5.4), femoral neck BMD (OR 2.3 per standard deviation; 95% confidence interval 1.9, 4.2), age (OR 2.1 per standard deviation; 95% confidence interval 1.6, 2.8) and weight (OR 1.9 per standard deviation; 95% confidence interval 1.5, 2.6). HAL measurements did not associate significantly with the risk of hip fracture in this population. The ability of QUS measurements discriminate between patients with fractures from those without was similar to, if not better, than X-ray-based BMD measurements. However, a combination of QUS and BMD measurements did not significantly improve fracture discrimination compared with either technique alone. Association of clinical risk factors with QUS or BMD measurements seems, on the other hand, to increase the sensibility to identify patients at risk of osteoporotic fractures.

The effect of age, weight, and lifestyle factors on calcaneal quantitative ultrasound: the ESOPO study

Quantitative ultrasound (QUS) techniques have been shown to be as good as bone mineral density (BMD) assessed by dual-energy X-ray absorptiometry (DXA), in predicting fracture risk: QUS technique could increase substantially the accessibility to a reliable bone osteoporosis risk evaluation, but little is know regarding the relationship of QUS to risk factors that have been found to predict DXA-BMD values and this is even more true in men. We studied 6,811 postmenopausal women 40 to 80 years of age and 4,981 men 60-80 years of age representative of the general population of all regions of Italy. All participants were questioned on lifestyle habits and on their medical history. After a physical examination "bone stiffness" (called here for simplicity, stiffness), which is derived from the values of broadband ultrasound attenuation (BUA) and speed of sounds (SoS) was measured by a heel QUS device (Achilles apparatus, Lunar, Madison, USA). The most common recognized determinants of bone mass (either categorical or continuous variables) were modeled with stiffness by multiple regression analysis or ANOVA. Stiffness was strongly related to age and weight. After adjusting for these variables, the women who had taken hormone replacement therapy for more than a year had significantly higher stiffness values. The difference versus nonusers remained significant for up to 20 years-since-menopause (YSM). This effect was so strong that for further analysis these women were excluded. By multivariate analysis, stiffness was then found to be significantly related to recalled body weight at 25 years of age, actual and past cigarettes smoked per day, and dairy calcium intake. Stiffness was also associated with a number of categorial factors adjusted for age, weight, and YSM: prior ovariectomy, history of more than 2 months confined to bed, outdoor physical activity, smoking, chronic use of any drug, and past corticosteroid use. All these categorial and continuous variables predicted stiffness equally in men and women. In conclusion, QUS bone measurements discriminate postmenopausal women according to past use of hormone replacement therapy. Risk factors usually associated to BMD as measured by DXA are also associated to calcaneal bone stiffness as measured by QUS, and most risk factors for osteoporosis usually observed in women are equally applicable to men.

Influence of region of interest and bone size on calcaneal BMD: implications for the accuracy of quantitative ultrasound assessments at the calcaneus

There is considerable technological diversity among quantitative ultrasound (QUS) devices used to assess osteoporosis. Because the distance between the transducer and the footplate remains constant, the location of the calcaneus measured will vary with foot size. This study was designed to quantify the variation in bone mineral density (BMD) between a manufacturer's region of interest (ROI_M), which is fixed relative to the footplate, and an anatomical region of interest (ROI_A), which is defined as 20% of calcaneal length. The effect of foot length and width on QUS variables measured using two Food and Drug Administration cleared QUS devices, the Sahara (Hologic) and the Achilles+ (Lunar) was assessed. 26 healthy subjects (12 male and 14 female), aged 22-54 years (35.6+/-10 years) and with foot lengths of 21.5 cm to 29.7 cm (25.1+/-2.3 cm) were recruited. QUS assessments were performed at the right calcaneus. In addition, a Hologic 4500 densitometer was used to measure the BMD of the calcaneus in the ROI_M and ROI_A. The sizes of the ROIs were approximated to the sizes of the transducers of the Sahara and Achilles+ devices. The results showed a significant difference in BMD between the two ROI locations for the Sahara device (BMD 0.642+/-0.135 g cm(-2) vs 0.616+/-0.114 g cm(-2), p=0.014), but no significant difference was found in BMD between the two locations for the Achilles device (BMD 0.661+/-0.120 g cm(-2) vs 0.662+/-0.123 g cm(-2), p=0.818). At the ROI_A, there was a significant difference in BMD between the two QUS devices (p<0.001). The correlation between QUS variables and BMD was slightly higher for the ROI_M (r=0.68-0.79, since this is site-matched) than the ROI_A (r=0.59-0.70) for the Achilles device, while for the Sahara device the correlations were r=0.35-0.40 and r=0.51-0.54, respectively. The smaller ROI of the Sahara device resulted in more than 50% of the subjects having BMD differences of greater than 5% between the ROI_A and the ROI_M, compared with only 20% of the subjects on the Achilles device. ROIs containing cortical bone edge and other soft tissues were found in 58% of cases for the Achilles device and 46% of cases for the Sahara device. The greatest differences occurred in very small and very large feet. Calcaneal length correlated significantly with Sahara speed of sound (SOS), and heel width correlated significantly with Achilles SOS. Heel width also correlated significantly with Sahara broadband ultrasound attenuation (BUA) but not Achilles+ BUA. These results suggest that variation in ROI and bone size might affect the accuracy of QUS measurements, since the calcaneus is heterogeneous both in terms of its external geometry and its internal structure and density.

Age-associated changes in bone ultrasonometry of the os calcis

This cross-sectional study updated age changes for ultrasonometry (QUS) of the os calcis in a large sample of healthy German women. The speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI) of the os calcaneus were measured in 5148 women (mean age 55.2 +/- 10.6 yr) using the Achilles ultrasonometer (GE/Lunar). There was an overall decline of 16% for BUA, 4% for SOS, and 32% for SI between late adolescence and old age. In premenopausal women, BUA decreased only slightly (-2%), whereas postmenopausal women showed a significantly increased decline (-12%). In contrast, SOS continuously decreased from the age of 15; there was a decline of 2% from adolescence to menopause. The SI of premenopausal women decreased only by 9%, but the postmenopausal decline of almost 21% was significantly greater. In accordance to our previous report, the age regression for SI in the larger sample differed from the earlier sample, indicating an increased bone loss with aging after the menopause. The SI values in premenopausal German women were comparable to those for British and American women 20-50 yr of age. After age 50, the SI of German women was significantly 3-7% higher in comparison to the British and American reference population.

Quantitative ultrasound and dual X-ray absorptiometry measurements of the calcaneus in patients on maintenance hemodialysis

It has been suggested that quantitative ultrasound measurements (QUS), which reflect mainly bone density, could be influenced by bone micro-architecture. The aim of the study was to assess whether the relationship of QUS to dual X-ray absorptiometry (DXA) would reflect abnormalities of bone structure observed in renal osteodystrophy. QUS and bone mineral density of the calcaneus (BMDc) were measured by DXA in 30 patients on maintenance hemodialysis and 34 age- and gender-matched controls. QUS parameters and BMDc were significantly lower in hemodialysis patients than in controls (speed of sound [SOS] and broadband ultrasound attenuation [BUA], p = 0. 030; stiffness, p = 0.003; BMDc, p = 0.006). Bone measurements were not correlated with serum parathyroid hormone (PTH). The regression lines of SOS, BUA, and stiffness to BMDc were not significantly different from that of the controls. When dividing the patients into two subgroups according to their median PTH (203 pg/mL), the slopes of the regression lines of BUA to BMDc were significantly different between these two subgroups (p = 0.052). The slope of the subgroup with PTH </= 203 pg/mL was significantly different from that of the controls (p = 0.030). In conclusion, QUS of the calcaneus can be used for bone assessment in patients on maintenance hemodialysis. The differences in the slopes of patients with a less pronounced degree of hyperparathyroidism compared with patients with a higher degree of hyperparathyroidism and to controls suggest that BUA of the calcaneus contains information on bone complementary to DXA measured at the same site. The clinical relevance of this finding is presently unclear.

The association between heel ultrasound and hormone replacement therapy is modulated by a two-locus vitamin D and estrogen receptor genotype

Evidence supports the role of estrogen deprivation in the process of bone remodeling and increased risk of fracture in postmenopausal women but little is known about the genetic basis of individual differences in response to therapy. In a cross-sectional study, 425 ambulatory postmenopausal French-Canadian women from Quebec (age range, 42-85 years old) were genotyped for a common Bsm I polymorphism at the vitamin D receptor (VDR) gene as well as a Pvu II polymorphism in the estrogen receptor (ESR1) gene. Heel ultrasound was determined by right calcaneal quantitative ultrasound (QUS) and results were expressed as an age-and-weight-adjusted stiffness index (heel SI z score). Our aim was to investigate the interaction between hormone-replacement therapy (HRT) and receptor genotypes in an effect on heel SI. Notably, a two-locus genotype (VDR-bb/ESR-PP) present in 9.5% of women was responsible for over 30% of the total HRT-related heel SI difference in the whole sample. Women bearing this combined VDR/ESR1 genotype who received HRT for more than 5 years had a 21% (1.25 SD) greater heel SI (p = 0.002) than those bearing the same genotype but who received HRT for <5 years. This may translate into a 2- to 3-fold difference in the risk of fracture. Although follow-up studies are needed, our findings suggest that QUS of the heel in postmenopausal women taking HRT is affected by variation in VDR and ESR1 loci, jointly.

Assessment by quantitative ultrasonometry of the effects of hormone replacement therapy on bone mass

OBJECTIVE

This study was undertaken to evaluate the impact of hormone replacement therapy on results of quantitative ultrasonometry of the heel.

STUDY DESIGN

A total of 2006 healthy perimenopausal women (mean age, 52.2 (10.3 years) were recruited in 5 German centers: 611 women (30%) had received hormone replacement therapy and 1395 (70%) had not. About 90% of the hormone replacement therapy users were current users, and the rest had stopped <6 months before the study. Speed of sound, broadband ultrasonographic attenuation, and the stiffness index were compared among the following groups: all users and nonusers of hormone replacement therapy, hormone replacement therapy users and nonuser control subjects matched for age and body mass index, and hormone replacement therapy users grouped in relation to the duration of hormone replacement therapy use and age and control subjects matched for body mass index.

RESULTS

Women who were using hormone replacement therapy had significantly higher values (P <.001) than did nonusers for all ultrasonographic variables, even after we controlled for age and body mass index. Women who had used hormone replacement therapy for >3 years had significantly higher values (P <.001) than did matched control subjects for all variables. Differences increased with the duration of hormone replacement therapy use.

CONCLUSION

Quantitative ultrasonometric measurement at the heel differentiates hormone replacement therapy users from nonusers, reflects duration of hormone replacement therapy use, and could be useful in both clinical trials and patient management.

The genetics of osteoporosis: 'complexities and difficulties'

Osteoporosis is characterized by a decrease in bone mass as well as a deterioration of the bone architecture resulting in an increased risk of fracture. Although the disease is multifactorial, twin studies have shown that genetic factors account for up to 80% of the variance in bone mineral density, the best known predictor of the risk of osteoporosis. Some loci, such as the vitamin D and estrogen receptor genes, as well as the collagen type Ialpha1 locus, are promising genetic determinants of bone mass, and possibly other bone phenotypes, but this is controversial and the molecular basis of osteoporosis remains largely undefined. Considering that the effect of each candidate gene is expected to be modest, discrepancies between allelic association studies may have arisen because different populations carry different genetic backgrounds and exposure to environmental factors. Also, we realize the importance of gene-gene as well as gene-environment interactions as significant determinants of bone density and risk of osteoporosis. The use of new tools such as small nucleotide polymorphism maps now allows the possibility to perform allelic association studies in the context of whole-genome search. However, specific study design strategies in large epidemiological studies as well as the best statistical approach will need to be established. We may expect the development of population-specific at-risk profiles for osteoporosis that would include genetic and environmental factors, as well as their interactions. This should eventually lead to better prevention strategies and more adapted therapies against osteoporosis.

Bone loss. Quantitative imaging techniques for assessing bone mass in rheumatoid arthritis

Osteoporosis is associated with low bone mass and microarchitectural deterioration of bone tissue with clinical manifestation of low trauma fractures. Rheumatoid arthritis (RA) is a risk factor due to generalized and articular bone loss. This minireview presents past and current bone mass measurement techniques in RA. These techniques include: plain radiographs, absorptiometry, quantitative computed tomography (QCT) and ultrasound. The most widely used technique is dual x-ray absorptiometry (DXA). RA patients have lower bone mass as compared with normals and substantial bone loss may occur early after the onset of disease. Measurement of bone mineral density (BMD) at the hand using either DXA or ultrasound maybe a useful tool in the management of RA patients.

Quantitative ultrasound of the os calcis in postmenopausal women with spine and hip fracture

Quantitative ultrasonometry (QUS) of the os calcis has been shown to predict hip fracture in late postmenopausal women, and vertebral and forearm fracture in early postmenopausal women. Speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI) of the os calcis were measured using the Achilles ultrasonometer (Lunar, Madison, WI). Osteoporosis risk factors were assessed by a detailed questionnaire. We examined 1314 normal women from age 48 to 79 yr, with a mean age 60 +/- 7.5 yr. In addition, we examined women of similar age, of whom 80 had suffered a hip fracture and 40 a spine fracture. The short-term precision in vivo expressed as the coefficient of variation was 1.2% for BUA, 0.2% for SOS, and 1.3% for SI. A total of 813 women were measured at both the right and left heel. There was high correlation between the two sides (r = 0.80-0.93) (p < 0.001), with no systematic offset. The ultrasound variables decreased significantly (p < 0.001) with age in healthy women; the annual decrease was -0.4% for BUA, -0.07% for SOS, and -0.7% for SI. BUA, SOS and SI discriminated (p < 0.001) between fracture and non-fracture subjects, but the fracture groups were 2 to 4 yr older. The T-score in the controls averaged -2.1 while that in the fracture patients averaged about -3.0. After control for age, years since menopause, and body size, BUA, SOS as well as the SI remained significantly lower (11 to 12% for SI) in women with fracture. The Z-score was -0.8 (p < 0.01) in spine fracture cases, and -0.9 (p < 0.001) in hip fracture patients. QUS provides a gradient of fracture risk comparable to X-ray densitometry of the axial skeleton, and gives comparable Z- and T-scores in younger postmenopausal women. It provides a precise, radiation-free, low-cost, and rapid method for fracture risk assessment in clinical practice.

An evaluation of a new gel-coupled ultrasound device for the quantitative assessment of bone

Quantitative ultrasound (QUS) is now being accepted as a tool in the assessment of bone status. Most QUS devices measure broadband ultrasound attenuation (BUA) and speed of sound (SOS). A newly introduced device, the Acoustic Osteo-Screener (AOS-100), measures both SOS and an attenuation related parameter called the transmission index (TI) and provides a derived parameter called osteo sono-assessment index (OSI). The purpose of this study was to examine the reproducibility of this new device, compare the results with the UBA 575+ and evaluate the effect of using two platforms to compensate for different foot sizes on the measured values. 83 subjects aged 21-89 years, who gave informed consent, were recruited. Subjects were assigned to three different groups determined by age and health status. The short-term measurement precision (expressed as root mean square coefficient of variation) of SOS (0.13-0.16%) and TI (1.18-1.96%) was similar to and better than that obtained for the UBA 575+. Significant negative correlations were found between the differences in SOS measured with the two platforms (adaptors to adjust the position of the foot relative to the foot plate) and foot length (p < 0.0001). This implies that small feet are more influenced by the differences of measured location. All QUS parameters measured with the small platform were found to be significantly smaller than those with the large platform (p < 0.0001). The mean percentage differences were 0.6% in SOS, 2.8% in TI and 4.3% in OSI with the large foot platform giving larger value results. Proper use of the platforms resulted in more reproducible SOS and TI. This study demonstrated that the newly developed AOS-100 parameters TI and OSI were highly reproducible. This study also demonstrated that the use of an inappropriate platform can cause discrepancies in QUS readings and poor reproducibility.

Comparison of ultrasound and bone mineral density assessment of the calcaneus with different regions of interest in healthy early menopausal women

This study investigated the effect of different sized regions of interest (ROIs) on quantitative ultrasound (QUS) variables of the calcaneus. The effect on QUS of using a fixed ROI as opposed to an ROI adjusted for foot length was also assessed. Eighty Caucasian women, aged 50-57 yr (mean 53 +/- 2) who were healthy and within 0. 5-5 yr of the onset of menopause participated in this study. Using the QUS-1(trade mark) Ultrasonometer (Metra Biosystems, Mountain View, CA), we assessed broadband ultrasound attenuation ([BUA] and UBI-4, dB/MHz), the average transit time through the heel ([TTH], mus) and a multiple-factor index (UBI-4T = UBI-4/TTH, dB/[MHz. mus]). The QUS measurement results were calculated from three different sizes of ROI as well as one in a fixed location and one adjusted for foot size. Bone thickness, bone width, bone mineral content ([BMC], g/cm), bone mineral density area ([BMD(a)], g/cm(2)), and bone mineral density volume ([BMD(v)], g/cm(3)) were measured by single-energy photon absorptiometry. Lateral radiography of the foot was used to ensure the QUS scanning location in a subgroup. The results showed that there was a 1.4-5.9% difference in QUS parameters among different ROIs (p = 0.076-0.001). No significant differences between fixed and adjusted location were found regarding the mean values of QUS. The correlation between the fixed and adjusted locations was very strong, although there was a 12-42% unexplained variation. On the other hand, QUS in the size-adjusted ROI increased the correlation with BMC/BMD compared to the fixed QUS assessments. After controlling for body weight and height, a significant correlation between QUS and bone mass variables remained, and in some cases correlations became stronger. Lateral radiography showed that when using a fixed location to scan a large foot, the scanning area might be close to the bone edge, an area of higher BMD and potential acoustic artifacts. When scanning a small foot, the scanning area was confined to the middle of the calcaneus. Our results indicate that bone size has a modest effect on BUA. There is a better correlation with BMD when the measurement region is appropriately located in the calcaneus. This suggests that measurement location based on foot size may improve the accuracy of the measurements, resulting in good diagnostic sensitivity.