Quantitative ultrasound of bone in institutionalized elderly women: a cross-sectional and longitudinal study

Relationship between environmental exposure to cadmium and bone metabolism in a non-polluted area of Japan

OBJECTIVES

The purpose of this study was to investigate the effects of environmental low-grade cadmium exposure on bone in the population of a non-polluted area. We investigated the relationship between environmental cadmium exposure (via rice intake) and bone metabolism in middle-aged and elderly women living in a non-polluted area in Japan.

METHODS

Four hundred and twenty-nine women over the age of 39 years (54.6 ± 9.1 years; arithmetic mean ± SD) participated in this study in 2003. We investigated blood and urine, and rice intake, and performed ultrasonic bone evaluation, and obtained individual information about the subjects' health. Multiple regression analysis was performed in the statistical analysis.

RESULTS

The arithmetic mean of cadmium content in rice was 70.8 ± 44.7 μg/kg (AM ± SD). The geometric mean of daily cadmium intake (Cd intake) from rice calculated based on food consumption data was 9.12 μg/day (GSD 2.33). The geometric means of serum and urine cadmium concentrations were 1.57 μg/l (GSD 2.11) and 1.93 μg/g creatinine (cr.) (GSD 2.05), respectively. Multiple regression analysis showed positive correlations between (1) urinary free deoxypyridinoline (FDPD-U) and Cd intake (p < 0.05), (2) urinary cross-linked N-telopeptides of type I collagen (NTx-U) and Cd intake (p < 0.05), and (3) FDPD-U or NTx-U and cadmium concentration in urine (p < 0.01). No significant correlation between the parameters of ultrasonic bone evaluation and cadmium associated biomarkers was observed.

CONCLUSIONS

The results of the present study suggest the possibility of bone metabolic disorder induced by environmental low-grade cadmium exposure. With respect to osteoporosis, a long-term follow-up survey is required to assess the tolerable intake of cadmium in environmental exposure.

Effect of community-based nutrition education intervention on calcium intake and bone mass in postmenopausal Vietnamese women

Objective

To examine the effect of community-based nutrition education intervention on calcium intake and bone mass in Vietnamese postmenopausal women.

Design

A controlled trial was conducted in two groups as intervention and control. The intervention group was given nutrition education during 18 months to improve calcium intake, while the control subjects had the usual diet. Calcium intake and bone mass were evaluated every 6 months. Bone mass was assessed by speed of sound (SOS) at calcaneus, referred to as quantitative ultrasound measurement. Anthropometric indices and serum parathyroid hormone (PTH) were determined at baseline and at the end of intervention.

Setting

Two rural communes of Hai Duong province located in the Red River Delta in Vietnam.

Subjects

A total of 140 women aged 55–65 years, who were more than 5 years postmenopausal and with low calcium intake (<400 mg/d), were recruited. After 18 months of intervention, 108 women completed the study.

Results

Calcium intake in the intervention group had increased significantly (P < 0·01) while it had no significant changes in controls. SOS values were not changed significantly in the intervention subjects while it decreased significantly by 0·5 % in the controls (P < 0·01). The intervention led to a decrease in serum PTH by 12 % (P < 0·01). In the controls, there was an increase in serum PTH by 32 % (P < 0·001).

Conclusion

Nutrition education intervention was effective in improving calcium intake and retarding bone loss in the studied subjects.

Hip and nonvertebral fracture prediction in nursing home patients: role of bone ultrasound and bone marker measurements

CONTEXT

Absolute fracture risk in nursing home patients is the highest among the communities studied. Screening for high-risk patients in such an environment is usually difficult.

OBJECTIVE

The objective was to investigate whether quantitative bone ultrasound measurements and/or markers of bone turnover/metabolism help in predicting which patients will incur hip or nonvertebral fractures.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective study, mobile teams enrolled 1664 female patients from 95 nursing homes in Austria.

MAIN OUTCOME MEASURES

Calcaneal stiffness (n = 1117), radial speed of sound (SOS) (n = 1332), and phalangeal SOS (n = 1498) measurements were performed at baseline. Serum samples (n = 960) were analyzed for serum calcium and phosphate, 25 hydroxyvitamin D, PTH, osteocalcin, C-terminal telopeptide crosslinks, and osteoprotegerin (OPG). Patients were prospectively followed for hip and other nonvertebral fractures for 2 yr.

RESULTS

A total of 117 hip fractures and 269 nonvertebral fractures developed during a mean observation period of 2 yr. Prevalence of vitamin D deficiency and secondary hyperparathyroidism was high. A history of a past fracture was significantly associated with a hazard ratio (HR) of 1.47 (95% confidence interval, 1.01-2.15) and 1.65 (1.26-2.16) for the development of hip and nonvertebral fractures, respectively. Cox regression analysis revealed a multivariate adjusted elevation in both hip [HR 1.30 (1.12-1.43)] and nonvertebral [HR 1.14 (1.02-1.25)] fracture risk for each sd decrease in calcaneal stiffness. Patients in the lowest quartile for calcaneal stiffness Z-score had 2.5 and 1.2 times higher rates of hip and nonvertebral fractures when compared with patients in the highest quartile. Fracture rates were not statistically associated with baseline radial or phalangeal SOS measurements or with serum osteocalcin, C-terminal telopeptide crosslinks, and OPG concentrations. When adjusted for bone mass, higher serum OPG levels were associated with fewer hip as well as nonvertebral fractures [HR 0.85 (0.73-0.99) and 0.89 (0.80-0.99) per increment of 1]. Higher serum phosphate levels indicated an increased hip [HR 1.54 (1.07-2.21)] and nonvertebral fracture risk [HR 1.40 (1.10-1.78) per increase of 1 mg/dl]. Body mass index was protective of hip fractures [HR 0.94 (0.90-0.98) per increase of 1] as well as medication with acetylsalicylic acid [HR 0.59 (0.36-0.95) for hip and 0.72 (0.52-0.99) for nonvertebral fractures]. In contrast, current use of glucocorticoids [HR 5.65 (1.77-18.0)] and opiates [HR 1.85 (1.18-2.92)] exerted a negative effect on prospective hip fracture risk.

CONCLUSION

Calcaneal stiffness measurements proved to be useful in predicting hip fractures and to a lesser extent nonvertebral fractures in nursing home residents. Radial and phalangeal bone ultrasound measurements and baseline markers of bone turnover, however, were not indicative of future fracture risk in this population.

Quantitative ultrasound measurements of bone: measurement error, discordance, and their effects on longitudinal studies

The performance of quantitative ultrasound (QUS) for the assessment of osteoporotic fracture must be fully defined if it is to be used in the clinical setting. We have examined the precision and reproducibility of two ultrasound instruments in 1,267 institutionalized elderly men and women (mean age 82.1 and 85.9 years, respectively). Measurement of BUA and VOS was reliable, least significant change for BUA being 2.4% and for VOS 0.3% using the CUBA McCue instrument and 2.7% for BUA using the Metra QUS-2. Importantly, age was not found to influence the precision of either parameter. Comparison of the instruments showed the QUS-2 measures BUA higher than the CUBA by 1.9 dB/MHz (+/-9.55 dB/MHz). Moreover classification of individuals as osteoporotic by machine-derived T-score was different between instruments (kappa = 0.44 in men and kappa = 0.62 in women). Fifty-six residents were remeasured by CUBA after 2.2 years; BUA was observed to decrease by 5.2% (+/-16.5%, p = 0.02) without significant change in VOS, suggesting BUA is more useful in longitudinal studies. In conclusion, ultrasound measurements were highly reliable and sensitive to longitudinal change even in the very elderly. However, diagnosis by T-score criteria was instrument specific, and such criteria should be interpreted with caution in the assessment of fracture risk.

Effect of daily walking steps on ultrasound parameters of the calcaneus in elderly Japanese women

In this cross-sectional study, we investigated the effect of daily walking steps on ultrasound parameters of the calcaneus in elderly Japanese women. The subjects were 143 community-dwelling elderly women aged 61-87 years (mean age 71.4+/-5.5 years). The speed of sound (SOS), broadband ultrasound attenuation (BUA) and the stiffness index (Stiffness) of the calcaneus were measured. Walking steps were recorded using a pedometer for 7 consecutive days as an outcome measure of physical activity. In univariate analyses, steps/day significantly decreased with aging. SOS, BUA and Stiffness showed negative correlations with age and positive correlations with weight. Linear relationships were not seen between any of the ultrasound parameters and daily walking steps. Then, the ultrasound parameters were adjusted for age and/or weight using multiple regression models, and the relationships between the adjusted ultrasound measurements and walking steps were examined using quadratic regression models. Walking activity up to approximately 12,000 steps/day was positively associated with the adjusted ultrasound measurements, above which additional walking steps had no positive effect. We conclude that daily walking steps may be suitable for evaluating the relationship between ultrasound parameters and physical activity in elderly women, but further research is needed to confirm the effect of daily walking steps on the rate of bone loss.

A longitudinal study of the relationship between osteo sono-assessment index and lifestyle in elderly female in nursing homes

The aim of this study was to investigate the longitudinal effect of mobility and daily activity, in the form of exercise and everyday activities, on the bones of 102 elderly female nursing home residents who had physical disabilities as well as marked postmenopausal bone loss, using calcaneal ultrasound apparatus for bone evaluation.Of the 102 subjects initially measured, 74 (mean age, 83.5±6.55 years; range, 64-99 years) could be measured again approximately one year later. The osteo sono-assessment index (OSI) in this study was determined using an ultrasound bone evaluation device. This device measures the speed of sound (SOS) and transmission index (TI) as ultrasound passes through the calcaneus. The OSI is calculated by computer analysis (OSI=TI×SOS(2)). For mobility, the OSI decreased significantly by an average of 1.8% after 11.8 months in all of the residents who were using a wheelchair (n=41, p<0.01). In contrast, the OSI rose significantly by a mean of 1.9% in the ambulatory group (n=33, p<0.01).The OSI increased significantly in residents who exercised every day, were out of bed for at least seven hours per day, and walked on a regular basis, suggesting that exercise, mainly in the form of walking, may increase the calcaneal OSI.

Discriminatory ability of quantitative ultrasound parameters and bone mineral density in a population-based sample of postmenopausal women with vertebral fractures: results of the Basel Osteoporosis Study

The discriminatory potential to classify subjects with or without vertebral fractures was tested cross-sectionally with different methods for the measurement of bone status in a population-based sample of postmenopausal women. Quantitative ultrasound (QUS) measurement at the calcaneus (Lunar Achilles, Hologic Sahara), the proximal phalanges (Igea Bone Profiler), and measurement of bone mineral density (BMD) with dual-energy X-ray absorptiometry (DXA; Lunar Expert) at several anatomic sites was performed in 500 postmenopausal women (aged 65-75 years) randomly selected from the population. In addition, 50 young female subjects (20-40 years old) had QUS measurements and served as controls to express QUS results as T-score values. Radiographs of the lumbar and thoracic spine were performed in the elderly women. Two independent radiologists reviewed the X-rays for the presence of vertebral fractures. Of 486 eligible study participants, no fracture was seen in 396 participants. Single vertebral fractures were observed in 71 subjects; 19 individuals presented multiple fractures. The overall prevalence of vertebral fractures was 18.5%. Participants without vertebral fractures were compared with subjects with vertebral fractures. Normal statistical distributions were found for all bone measurement results. Risk of vertebral fracture in subjects with no and multiple vertebral fracture was estimated using age adjusted odds ratios (ORs) for QUS and dual-energy X-ray absorptiometry (DXA) values. Each SD decrease in bone measurement increased the risk of multiple vertebral fracture by 3.0 (95% CI, 1.6-5.6) for the Achilles stiffness, by 3.8 (95% CI, 1.8-8.2) for the Sahara QUI, 2.1 (95% CI, 1.3-3.4) for the Bone Profiler amplitude-dependent speed of sound (AD-SOS), and 2.1 (95% CI, 1.2-3.9) and 2.4 (95% CI, 1.3-4.3) for DXA lumbar spine and for DXA total hip, respectively. Results of a discriminant analysis showed sensitivities between 84% and 58% and specificities between 72% and 58% for the respective DXA and QUS parameters. Optimum fracture thresholds for QUS measurements derived from this analysis were calculated also. Optimum T-score threshold values for QUS measurements tended to be higher than those for DXA measurements. However, the performance of QUS measurements is at least comparable with DXA measurements in identifying subjects with multiple vertebral fractures randomly selected from the population.

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.

Almost all institutionalized women are osteoporotic, when measured by heel and finger ultrasound

OBJECTIVES

Since there is a need for simple methods to identify individuals with osteoporosis, we investigated bone status (heel and finger) with ultrasound in an institutionalized elderly population and studied the association between these measures, risk factors for osteoporosis and prevalent osteoporotic fractures.

DESIGN

Cross-sectional study. Subjects. Nursing home residents, 237 women and 84 men, mean age 84 years.

RESULTS

Altogether 82% of those eligible could undergo heel ultrasound, 65% finger ultrasound and 41% measurements at both sites. Using a transcription of the WHO criterion of osteoporosis, 95% of the women who underwent heel ultrasound were classified as osteoporotic (mean T-score = -4.8) and 92% had Z-scores below zero (mean Z-score=-1.6), whereas 51% of the men were osteoporotic (mean T-score=-2.6) and 77% had Z-scores below zero (mean Z-score=-1.3). Based on finger ultrasound measurements, 99% of the women were classified as osteoporotic (mean T-score=-5.0) and 93% had Z-scores below zero (mean -1.6). The variations in ultrasound values were only moderately explained by age, current weight and walking ability. Amongst women, the association with a prevalent osteoporotic fracture decreased by 43% (95% CI=10-63%) for every SD increase in speed of sound (SOS) of the heel, but no such relationship was found for finger SOS.

CONCLUSIONS

Our results from ultrasound measurements at two different anatomical sites indicate that virtually all institutionalized elderly women could be classified as osteoporotic, when measured by these techniques.

Quantitative ultrasound in postmenopausal osteoporosis

Ultrasound has been proposed as a low-cost, radiation-free method for osteoporosis assessment in postmenopausal women. Large prospective studies have shown that ultrasound parameters can be used for fracture risk estimate in this population, providing that adequate quality control is performed. The places of both ultrasound and the current gold standard method for bone assessment, dual energy x-ray absorptiometry, are still to be determined. Further studies are needed on the diagnosis of osteoporosis using ultrasound, because current diagnostic thresholds, designed by the World Health Organization, do not apply to this-new technology. Monitoring of skeletal changes and treatment effects by ultrasound cannot be recommended.

Evaluation of error bounds on calcaneal speed of sound caused by surrounding soft tissue

For absorptiometry measurements, soft tissue may have an impact on quantitative ultrasound (QUS) measurements. In the present study, we focused primarily on the quantification of measurement error on speed of sound (SOS) caused by surrounding soft tissue. The relevant soft tissue parameters affecting the inherent SOS inaccuracies are thickness and sound velocity. To meet our goal, SOS measurements were taken at the right heel using a QUS imaging device in 21 healthy subjects. Site-matched measurements of soft tissue thickness (STT) and bone width were performed using magnetic resonance imaging of the heel. Several bone velocities were calculated either by accounting for bone width (SOSBW) only or by taking into account the exact path lengths of all major components traversed by ultrasound &lapr;V(b)). Given that soft tissue composition is difficult to determine in vivo, we chose to estimate lower and upper error bounds on bone velocity (V(b lower) and V(b upper)) by spanning the full range of available values in the literature. The mean BW was 30.7 +/- 2.7 mm and the mean medial and external STTs were 8.8 +/- 1.7 and 8.5 +/- 1.5 mm, respectively. Accounting for true BW only resulted in no significant difference between SOS (1533 +/- 37) and SOSBW (1531 +/- 33). By contrast, accounting for both true BW and surrounding soft tissue resulted in an increase in the calculated bone velocity and statistically significant differences between SOS and V(b upper) (1568 +/- 36) and V(b lower) (1542 +/- 34). Root mean square errors between SOS and the calculated velocities were 0.34, 2. 32, and 0.70% for SOSBW, V(b upper), and V(b lower), respectively. We report here measurement errors caused by soft tissue to be 3 to 20 times higher than the SOS short-term precision (SOS coefficient of variation of 0.1%). Our results suggest that inaccuracies in SOS measurement caused by overlying soft tissue cannot be neglected. Overlying soft tissues may influence outcomes of longitudinal studies, especially if variations in tissue thickness and composition occur during the longitudinal follow-up. A practical way of minimizing the measurement error could be to perform an adequate correction for the overlying soft tissue. However, ideally, this should require knowing both the thickness and sound velocity in soft tissue. One might preferably conduct experimental investigations that directly control soft tissue thickness and composition to resolve this problem.

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.

Hip fracture discrimination by imaging ultrasound measurements of the calcaneus

Quantitative ultrasound measurements of the os calcis have recently been upgraded with imaging facilities. This has made measurements of a specific region of interest possible and improved the reproducibility of the method, but the diagnostic ability of imaging ultrasound has not yet been investigated thoroughly. We measured broadband ultrasound attenuation (BUA) and speed of sound (SOS) using imaging ultrasound as well as forearm bone mineral density (BMDarm) using dual-energy X-ray absorptiometry in three age-matched groups of women: (1) 25 women who were admitted to hospital due to a hip fracture; (2) 23 women who were admitted to hospital due to a fall without any fracture; and (3) 26 normal women. Furthermore, BMD of the hip (BMDhip) was measured in a subgroup of the hip fracture patients and those who had fallen. All measurements were performed during the index hospitalization in order to avoid any influence from bone loss due to immobilization after the fracture. We found a -0.48 SD deviation from expected age-matched values in BUA among the hip fracture patients, whereas the patients who had fallen showed a +0.16 SD deviance. For SOS, the figures were -0.70 SD for the hip fracture group and -0.06 SD for the patients who had fallen. For BMD of the arm we found values of -0.65 SD and +0.08 SD, respectively, whereas the figures for BMD of the hip were -0.66 SD and +0.13 SD, respectively. All parameters were significantly lower in the hip fracture group compared with the patients who had fallen. None of the parameters in the patients who had fallen deviated significantly from expected normal age-matched values. Neither BMD of the arm or BMD of the hip separated hip fracture patients and patients who had fallen significantly better than ultrasound (BUA or SOS) did. We conclude that imaging ultrasound (BUA or SOS) separates age-matched groups of hip fracture and non-fracture patients as well as BMD measurements do.

Evaluation of quantitative ultrasound and dual X-Ray absorptiometry measurements in women with and without fractures

Dual X-ray absorptiometry (DXA) is considered a gold standard for bone measurements in the assessment of osteoporosis. Other techniques such as quantitative ultrasound (QUS) are promising to detect patients with osteoporosis-related fractures and to predict fracture risk. In this cross-sectional retrospective study, we analyzed the behavior of QUS and DXA measurements alone and in combination with regard to the presence of fractures in 320 women, 147 with nontraumatic fractures. Speed of sound (SOS), broadband ultrasound attenuation (BUA), and a third parameter derived from SOS and BUA called stiffness were measured at the calcaneus using an Achilles device (Lunar, Madison, WI). Lumbar (BMDL) and hip (BMDH( bone mineral density were measured by DXA (Hologic QDR 1000, Waltham, MA). Mean SOS, BUA, stiffness, and BMDL and BMDH were significantly lower in women with fractures compared with women without fractures. Logistic regression adjusted for age identified stiffness as the parameter most strongly associated with the presence of fracture: its sensitivity was 54% and specificity 70%. Hip BMD was second, with a sensitivity of 54% and a specificity of 69%. Combining QUS and DXA measurements did not improve the specificity nor the sensitivity. There was no difference in the odds ratios with regard to the technique that was chosen for bone assessment. In conclusion, these results suggest that low QUS measurements are associated with the presence of fractures in a way similar to DXA. In our study, the combination of QUS and DXA did not improve the discrimination of women with fractures.

Influence of anthropometric parameters and biochemical markers of bone metabolism on quantitative ultrasound of bone in the institutionalized elderly

The assessment of bone quality by quantitative ultrasound (QUS), a transportable and relatively cheap method, shows some correlations with bone mineral density (BMD) as measured by dual-energy X-ray absorptiometry (DXA) and with fracture risk. To examine its correlation with bone metabolism in a population of institutionalized elderly people known to be at high risk for vitamin D deficiency and secondary hyperparathyroidism, QUS of the calcaneus and biochemical parameters were measured in 264 women aged 85 +/- 7 (SD) years and in 103 men aged 81 +/- 8 years living in 19 nursing homes. Vitamin D deficiency was frequent in this population: 41.9% of the women and 31.4% of the men had a serum 25-hydroxyvitamin (25OHD) level below the 2.5th percentile level of 3276 normal Swiss adults (6.2 micrograms/l or 15.5 mmol/l). Hyperparathyroidism was less frequent: serum parathyroid hormone (PTH) levels were above the 97.5th percentile level of normal adults (70 pg/l) in 18.9% of women and 9.8% of men. In women, QUS data correlated significantly with age (r = -0.297), body mass index (BMI) (r = 0.403), calcium (r = 0.220), PTH (r = -0.296), 25OHD (r = 0.298) and alkaline phosphatase (AP) (r = -0.170) for broadband ultrasound attenuation (BUA), and with age (r = -0.195), BMI (r = 0.208), PTH (r = -0.174), 25OHD (r = 0.140) and AP (r = -0.130) for speed of sound (SOS). In men, ultrasound data correlated with BMI (r = 0.326), calcium (r = 0.199), 25OHD (r = 0.258) and AP (r = -0.311) for BUA, and with AP (r = -0.196) for SOS. In women, but not in men because of their smaller number, a multivariate analysis was performed to examine relationships between age, BMI, biochemical markers and QUS. Age, BMI, PTH and phosphate explained 30% of the variance of BUA and 10% for SOS. In conclusion, QUS of bone evaluates characteristics of bone that are influenced, at least partially, by age, BMI and the secondary hyperparathyroidism due to vitamin D deficiency.

The role of quantitative ultrasound in the assessment of bone: a review

Quantitative ultrasound (QUS) bone measurement is a promising, relatively new technique for the diagnosis of osteoporosis. Unlike to the more established method of bone densitometry [measurement of bone mineral density (BMD) e.g. using dual X-ray absorptiometry (DEXA)], QUS does not use ionizing radiation. It is cheaper, takes up less space and is easier to use than densitometry techniques. The two QUS parameters currently measured are broadband ultrasound attenuation (BUA) and speed of sound (SOS). The reported age-related changes for healthy women range from -0.27% to -1.62% per year for BUA and from -0.06% to -0.19% per year for SOS. Precision ranges from 1.0 to 3.8% (CV) for BUA and from 0.19 to 0.30% (CV) for SOS. The new method of imaging ultrasound has improved the precision of QUS measurements. QUS is significantly correlated with BMD. Studies with the latest equipment have shown r-values between 0.6 and 0.9 in site-specific measurements, and QUS is thus believed to reflect mainly BMD. However, other studies indicate that QUS measures something other than the actual mineral content of bone, namely bone quality, e.g. in vitro studies have shown that QUS reflects trabecular orientation independently of BMD. In both cross-sectional and prospective studies, QUS seems to be as good a predictor of osteoporotic fractures as BMD. In two large prospective studies, QUS also predicted fracture risk independently of BMD. QUS has just begun to be used systematically for monitoring the response to anti-osteoporotic treatments in prospective trials. In the studies performed, QUS has been found to be useful in the follow-up of patients. QUS is thus a promising new technique for bone assessment.

Quantitative ultrasound techniques for the assessment of osteoporosis: expert agreement on current status. The International Quantitative Ultrasound Consensus Group

Quantitative ultrasound (QUS) methods have been introduced in recent years for the assessment of skeletal status in osteoporosis. The performance of QUS techniques has been evaluated in a large number of studies. Reviewing existing knowledge, an international expert panel formulated the following consensus regarding the current status of this technology. To date, evidence supports the use of QUS techniques for the assessment of fracture risk in elderly women. This has been best established for water-based calcaneal QUS systems. Future studies should include the predictive validity of other QUS systems. Additional clinical applications of QUS, specifically the assessment of rates of change for monitoring disease progression or response to treatment, require further investigation. Its low cost and portability make QUS an attractive technology for assessing risk of fractures in larger populations than may be suitable or feasible for bone densitometry. Additional investigations that assess innovative QUS techniques in well defined research settings are important to determine and utilize the full potential of this technology for the benefit of early detection and monitoring of osteoporosis.

How can we measure bone quality?

Osteoporosis is a systematic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue. This leads to diminished biomechanical competence of the skeleton and is associated with low-trauma or atraumatic fractures. In the past decade, considerable progress has been made in the development of methods for assessing the skeleton non-invasively, so that osteoporosis can be better managed. While dual X-ray absorptiometry (DXA) is still the preferred methodology, several limitations will be addressed. Another densitometric technique which is widely accepted for diagnosis of spinal osteoporosis is single energy QCT. Measurements of vertebral trabecular bone mineral density (BMD) demonstrate larger percentage decrements between vertebrally-fractured subjects and normal controls, and confer higher relative risks for vertebral fracture than either anteroposterior or lateral DXA measurements. As an emerging alternative to photon absorptiometry techniques, there is a growing interest in the use of quantitative ultrasound (QUS) measurements for the non-invasive assessment of osteoporotic fracture risk in the management of osteoporosis. The attractiveness of QUS lies in the fact that indirect and in vitro experience has suggested that ultrasound may give information not only about BMD but also about architecture and elasticity. Whether or not combining QUS and DXA improve fracture prediction is still unclear and needs further analysis. Due to the growing evidence supporting the use of QUS in osteoporosis and the large number of QUS devices already on the market, a general clinical consensus on the application of QUS is urgently needed. Other techniques that are less widely used for the management of osteoporosis. For example, peripheral quantitative computed tomography, quantitative magnetic resonance (QMR) and magnetic resonance microscopy are promising tools for the evaluation of the skeleton. For example, the ability of QMR and high resolution magnetic resonance imaging has been explored and shows promise as a technique for assessing trabecular bone structure in osteoporosis.

Peripheral measurement techniques for the assessment of osteoporosis

Peripheral measurement techniques have been the first to be developed for the assessment of osteoporosis, and they remain useful. Besides traditional approaches such as radiographic absorptiometry (RA), radiogrammetry, and single-photon absorptiometry (SPA), new peripheral approaches have been developed that offer powerful ways to assess skeletal status in osteoporosis. These include single x-ray absorptiometry (SXA), peripheral dual x-ray absorptiometry (pDXA), peripheral quantitative computed tomography (pQCT), quantitative ultrasound (QUS) techniques, and magnetic resonance imaging (MRI) approaches. This review describes the current role of peripheral imaging techniques vis-à-vis their central imaging counterparts. Peripheral measurement techniques are attractive because equipment cost is substantially lower, radiation exposure is small, and the devices require less space and sometimes are even portable. Additionally, QUS and MRI offer the potential to measure aspects of bone status beyond the limits of bone densitometry. Peripheral techniques represent important diagnostic methods for the assessment of osteoporosis.

The epidemiology and pathogenesis of osteoporosis

Osteoporosis is an increasing health care concern as populations age throughout the developed and developing world. The social and economic costs of osteoporosis are due to its clinical outcome of fracture which increases exponentially with age. This review will highlight some of the key epidemiological aspects of osteoporosis incorporating areas of more recent interest. These include the definition; the magnitude of the problem encompassing differing incidence and prevalence patterns of both low bone mass and fracture in different cultural groups; the social consequences of fracture, including economic costs, morbidity and mortality; the evaluation of fracture risk, including the role of bone density, bone quality and the risk of falling; as well as an overview of some of the factors involved in determining low bone mass. Bone mineral density (BMD) is the most easily measured and accurate predictor of fracture risk. For any individual, BMD is the combination of their peak bone density and subsequent bone loss, both of which are influenced by genetic, hormonal and environmental factors. An understanding of key issues relating to this important disease may lead to earlier detection of the individual at high risk for fracture and rational approach to prevention and management.

Quantitative ultrasound imaging at the calcaneus using an automatic region of interest

A new approach to measuring bone properties at the calcaneus using ultrasound parametric imaging has recently emerged. However, an additional source of observer-related error is the substantial regional variations in the pattern of ultrasound parameters. The contribution of intra-observer and inter-observer variability to the coefficient of variation can be eliminated using an algorithm which selects the region of interest (ROI) completely automatically. The objective of the present study was the clinical assessment of an automatic ROI for both broadband ultrasonic attenuation (BUA) and speed of sound (SOS) measurement using ultrasound parametric imaging. The automatic ROI was defined as the circular region of lowest attenuation in the posterior tuberosity of the calcaneus. We have tested this algorithm using clinical images of the calcaneus from 265 women. Mean coefficients of variation were 1.6% (95% confidence interval 1.4%-1.9%) and 0.26% (95% confidence interval 0.23%-0.32%) for BUA and SOS respectively (standardized CV was 2.1% for BUA and 2.6% for SOS). Z-scores in an osteoporotic group were -0.61 and -0.52 for BUA and SOS respectively. In healthy women, the age-related decline was -0.50 dB/ MHz per year (0.7%/year) for BUA and -1.2 m/s per year (0.08%/year) for SOS. In the subgroup of healthy postmenopausal women, using stepwise multiple regression, we found that BUA was predicted best by years since menopause (YSM) and weight, with overall model r2 = 0.28; SOS was predicted best by YSM only (r2 = 0.21). Neither the range of biological variation of ultrasound parameters nor the clinical value were affected by the choice of the region of lowest attenuation for measurement. The automatic procedure was totally independent of operator interaction, therefore excluding loss of precision due to intra- or inter-observer variability. The results showed the high precision and robustness of the procedure. These factors make this approach viable for routine clinical use.

Longitudinal changes in ultrasound parameters of the calcaneus

We examined with a median follow-up of 1.4 years (range 1.0-2.0 years) the rates of change per year in ultrasound parameters of the calcaneus. Speed of sound (SOS), Broadband ultrasound attenuation (BUA) and Stiffness were measured twice in 543 subjects (224 men) participating in the Rotterdam Study. SOS fell by -2.5 m/s per year in both sexes (95% CI -4.0 to -1.1 m/s per year in men and -3.6 to -1.4 m/s per year in women). Stiffness decreased by -0.62 (-1.33 to 0.09) per year in men and -0.66 (-1.24 to -0.08) per year in women. In men the rate of change in SOS and Stiffness tended to increase with age. BUA did not change significantly during follow-up in either sex. The prospectively assessed rates of loss differed considerably from those observed cross-sectionally, especially for SOS in men (cross-sectional -0.7 m/s per year, longitudinal -2.5 m/s per year). There was substantial variation between individuals both in changes per year in SOS and in changes per year in BUA. With a median follow-up time of 1.4 years, approximately 27% of the variation in the rate of change for SOS could be explained by measurement error while for BUA this was approximately 9% and for Stiffness 11%. Only a small percentage of subjects had changes larger than could be accounted for by measurement error (SOS: men 26.8%, women 21.6%; BUA: men 28.5%, women: 38.8%; Stiffness: men 32.6%, women 35.1%). The latter may limit the use of ultrasound measurements as a follow-up tool in individuals rather than in populations.