Does combining the results from multiple bone sites measured by a new quantitative ultrasound device improve discrimination of hip fracture?

Quantitative Ultrasound Examination (QUS) of the Calcaneus in Long-Term Martial Arts Training on the Example of Long-Time Practitioners of Okinawa Kobudo/Karate Shorin-Ryu

Quantitative research of bone tissue related to physical activity (PA) and sport has a preventive dimension. Increasing the parameters of bone tissue strength, especially reaching the maximum value of peak bone strength in childhood, adolescence, and early adulthood due to practicing sports can contribute to maintaining bone health throughout life. Practicing martial arts (tai chi, traditional karate, judo, and boxing) can effectively improve the quality of bone and reduce the risk of falls and fractures. The study aimed to evaluate the calcaneus bones among Okinawa Kobudo/Karate Shorin-Ryu practitioners using the quantitative ultrasound method as an indicator for assessing bone fracture risk. Forty-four adult martial arts practitioners with a mean age of 36.4 participated in this study. Quantitative ultrasound (QUS) with a portable Bone Ultrasonometer was used in this study. Speed of sound (SOS), broadband ultrasound attenuation (BUA), and the stiffness index (SI) were measured. Subjects were assigned to two groups of black and color belts, according to the advancement in Kobudo/karate practice. The measurements of the SI, BUA, SOS, T-score, and Z-score were significantly higher in subjects from the advanced, long-term practice (black belts) (p < 0.05). The long-term martial arts training in traditional karate and Kobudo significantly impacts the parameters of the calcaneus quantitative ultrasound measurements. Significantly higher bone density was observed among the black belt holders. Long-term practice subjects achieved results far beyond the norm for their age groups. Further studies using non-invasive methods of bone quantification are needed to determine the specific conditions for preventing osteoporosis through physical activity, sports, and martial arts, particularly the duration of the activity, the magnitude of loads, and other related factors.

Comparison of quantitative ultrasonography and dual X-ray absorptiometry for bone status assessment in South African children living with HIV

Children living with HIV (CLHIV) have decreased bone mineral content (BMC) and density (BMD), increasing risk for fracture and future osteoporosis. While DXA is the gold-standard for bone assessments, it lacks availability in resource-constrained settings (RCS). Quantitative ultrasound (QUS) offers an alternative owing to its portability, low cost, ease of handling, and lack of ionizing radiation. While QUS has detected reduced bone quality in CLHIV, the relationship between QUS and DXA in this population remains unexplored. At baseline and 12 months, BMC and BMD of the whole body, lumbar spine, and radius were measured by DXA in a longitudinal cohort of CLHIV in Johannesburg, South Africa. Calcaneal speed of sound (SOS) and broadband ultrasound attenuation (BUA) and radius SOS were obtained by QUS, and calcaneal stiffness index (SI) was calculated. Spearman correlations, with and without HIV stratification, were performed between QUS and DXA measurements at each visit and for absolute difference in measurements between visits. At baseline and 12-months, calcaneal BUA and SI displayed strong positive correlations with DXA, with only modest correlations between radial QUS and DXA at baseline. Longitudinal measures of QUS did not correlate with DXA. At both baseline and 12-months, individuals with DXA whole-body BMD z-score < -1 displayed significantly lower calcaneal BUA and SI. Cross-sectionally, calcaneal QUS correlates strongly with whole body DXA and may represent a viable diagnostic alternative in RCS. Longitudinally, the two methods do not correlate well, possibly reflecting that each method assesses distinct aspects of bone architecture.

Quantitative Ultrasound (QUS) in the Management of Osteoporosis and Assessment of Fracture Risk: An Update

Quantitative ultrasound (QUS) presents a low cost and readily available alternative to DXA measurements of bone mineral density (BMD) for osteoporotic fracture risk assessment. It is performed in a variety of skeletal sites, among which the most widely investigated and clinically used are first the calcaneus and then the radius. Nevertheless, there is still uncertainty in the incorporation of QUS in the clinical management of osteoporosis as the level of clinical validation differs substantially upon the QUS models available. In fact, results from a given QUS device can unlikely be extrapolated to another one, given the technological differences between QUS devices. The use of QUS in clinical routine to identify individuals at low or high risk of fracture could be considered primarily when central DXA is not easily available. In this later case, it is recommended that QUS bone parameters are used in combination with established clinical risk factors for fracture. Currently, stand-alone QUS is not recommended for treatment initiation decision making or follow-up. As WHO classification of osteoporosis thresholds cannot apply to QUS, thresholds specific for given QUS devices and parameters need to be determined and cross-validated widely to have a well-defined and certain use of QUS in osteoporosis clinical workflow. Despite the acknowledged current clinical limitations for QUS to be used more widely in daily routine, substantial progresses have been made and new results are promising.

The Association Between Long-term Exposure to Ambient Air Pollution and Bone Strength in China

CONTEXT

Evidence regarding the association of long-term exposure to air pollution on bone strength or osteoporosis is rare, especially in highly polluted low- and middle-income countries. Little is known about whether the association between air pollution and bone strength changes at different bone strength distributions.

OBJECTIVE

Using the baseline data from the China Multi-Ethnic Cohort, we investigated the association between long-term air pollution exposure and bone strength.

METHODS

We used multiple linear models to estimate the association between air pollution and bone strength, and we conducted quantile regression models to investigate the variation of this association in the distribution of bone strength. The 3-year concentrations of PM1, PM2.5, PM10, and NO2 for each participant were assessed using spatial statistical models. Bone strength was expressed by the calcaneus quantitative ultrasound index (QUI) measured by quantitative ultrasound, with higher QUI values indicating greater bone strength.

RESULTS

A total of 66 598 participants were included. Our analysis shows that every 10 μg/m3 increase in 3-year average PM1, PM2.5, PM10, and NO2 was associated with -5.38 units (95% CI: -6.17, -4.60), -1.89 units (95% CI: -2.33, -1.44), -0.77 units (95% CI: -1.08, -0.47), and -2.02 units (95% CI: -2.32, -1.71) changes in the QUI, respectively. In addition, populations with higher bone strength may be more susceptible to air pollution.

CONCLUSION

Long-term exposure to PM1, PM2.5, PM10, and NO2 was significantly associated with decreased bone strength in southwestern China adults. Air pollution exposure has a more substantial adverse effect on bones among populations with higher bone strength.

Ultrasonic Backscatter Measurements of Human Cortical and Trabecular Bone Densities in a Head-Down Bed-Rest Study

This study aims to investigate the feasibility of quantitative ultrasonic backscatter in evaluating human cortical and trabecular bone densities in vivo based on a head-down-tilt bed rest study, with 36 participants tested through 90 d of bed rest and 180 d of recovery. Backscatter measurements were performed using an ultrasonic backscatter bone diagnostic instrument. Backscatter parameters were calculated with a dynamic signal-of-interest method, which was proposed to ensure the same ultrasonic interrogated volume in cortical and trabecular bones. The backscatter parameters exhibited significant correlations with site-matched bone densities provided by high-resolution peripheral quantitative computed tomography (0.33 < |R| < 0.72, p < 0.05). Some bone densities and backscatter parameters exhibited significant changes after the 90-d bed rest. The proposed method can be used to characterize bone densities, and the portable ultrasonic backscatter bone diagnostic device might be used to non-invasively reveal mean bone loss (across a group of people) after long-term bed rest and microgravity conditions of spaceflight missions.

Fragility fracture discriminative ability of radius quantitative ultrasound: a systematic review and meta-analysis

The fragility fracture discriminative ability of radius quantitative ultrasound (QUS) was evaluated in a systematic review of 13 studies, including 16,681 individuals and 1296 fractures. The radial speed of sound (SOS) per standard deviation (SD) decrease contributed to an increased risk of total and hip fracture by 32% and 66% in women. Osteoporotic fracture, as a devastating consequence of osteoporosis, brings severe socio-economic burden. The availability of dual-energy X-ray absorptiometry (DXA), as the gold standard of diagnosis, was quite limited in remote areas. Radius QUS measured by SOS shows potential in fracture discriminative ability where DXA equipment is not available. This study aimed to provide a comprehensive evaluation of the association between radius QUS and fracture risk. A detailed article search was carried out on PubMed, EMBASE, Cochrane Libraries, CNKI, Wan-Fang database, VIP, and SinoMed for studies published between January 1980 and February 2020. We determined the estimated relative risk (RR) for fracture per each radial SOS SD decrease. A meta-analysis of studies was performed under the random-effects model. A total of 16,681 individuals were included in this review. Among the participants, 5892 were male and 10,789 were female. A total of 1296 cases of fragility fracture were included. With each SD decrease in radial SOS, the risk of overall fragility fracture and hip fracture was increased by 21% and 55%, respectively. Particularly, the risk was increased by 32% and 66% for women. The association was even stronger for postmenopausal women. Radius QUS showed great potential as an effective tool for fracture risk evaluation, especially for women.

Quantitative ultrasound (QUS) axial transmission method reflects anisotropy in micro-arrangement of apatite crystallites in human long bones: A study with 3-MHz-frequency ultrasound

Anisotropic arrangement of apatite crystallites, i.e., preferential orientation of the apatite c-axis, is known to be an important bone quality parameter that governs the mechanical properties. However, noninvasive evaluation of apatite orientation has not been achieved to date. The present paper reports the potential of quantitative ultrasound (QUS) for noninvasive evaluation of the degree of apatite orientation in human bone for the first time. A novel QUS instrument for implementation of the axial transmission (AT) method is developed, so as to achieve precise measurement of the speed of sound (SOS) in the cortex (cSOS) of human long bone. The advantages of our QUS instrument are the following: (i) it is equipped with a cortical bone surface-morphology detection system to correct the ultrasound transmission distance, which should be necessary for AT measurement of long bone covered by soft tissue of non-uniform thickness; and (ii) ultrasound with a relatively high frequency of 3 MHz is employed, enabling thickness-independent cSOS measurement even for the thin cortex by preventing guide wave generation. The reliability of the proposed AT measurement system is confirmed through comparison with the well-established direct transmission (DT) method. The cSOS in human long bone is found to exhibit considerable direction-dependent anisotropy; the axial cSOS (3870 ± 66 m/s) is the highest, followed by the tangential (3411 ± 94 m/s) and radial (3320 ± 85 m/s) cSOSs. The degree of apatite orientation exhibits the same order, despite the unchanged bone mineral density. Multiple regression analysis reveals that the cSOS of human long bone strongly reflects the apatite orientation. The cSOS determined by the AT method is positively correlated with that determined by the DT method and sensitively reflects the apatite orientation variation, indicating the validity of the AT instrument developed in this study. Our instrument will be beneficial for noninvasive evaluation of the material integrity of the human long-bone cortex, as determined by apatite c-axis orientation along the axial direction.

Can low-frequency guided waves at the tibia paired with machine learning differentiate between healthy and osteopenic/osteoporotic subjects? A pilot study

PURPOSE

Axial transmission quantitative acoustics (ax-QA) has shown to be a promising tool for assessing bone health and properties in a safe, inexpensive, and portable manner. This study investigated the efficacy of low-frequency ax-QA measured at the tibia, paired with a support vector machine (SVM) approach for combining multiple acoustic indicators, to diagnose osteoporosis as defined by bone mineral density.

METHODS

This pilot study measured 41 female subjects using ax-QA (flexural mode, 3 kHz) at the tibia and using dual X-ray absorptiometry (DXA) at the lumbar spine, femoral neck, and distal radius. For each location, a threshold classifier and SVM were trained to differentiate between healthy and non-healthy subjects based on the phase velocity at different frequencies. Receiver Operating Characteristics and area under curve values (AUC) were used to assess the classifiers' performances for various thresholds and class-weights.

RESULTS

The SVM outperformed the threshold classifier for all three bone locations at low false positive rates. While differentiation between healthy and non-healthy bone states was poor for the spine (AUC: 0.56 ± 0.04), good to moderate performances were observed for the radius (AUC: 0.83 ± 0.03) and hip (AUC: 0.71 ± 0.04).

CONCLUSIONS

Low-frequency ax-QA has demonstrated potential for complementing DXA in screening for osteoporosis at the radius and hip. Through further addition of acoustic indicators ax-QA could provide a diagnostic alternative in third-world countries, and bring bone health screening and monitoring into the hands of clinicians and general health practitioners everywhere.

Recent advancements in the analysis of bone microstructure: New dimensions in forensic anthropology

Bone is a mechanically active, three-dimensionally (3D) complex, and dynamic tissue that changes in structure over the human lifespan. Bone tissue exists and remodels in 3D and changes over time, introducing a fourth dimension. The products of the remodelling process, secondary and fragmentary osteons, have been studied substantially using traditional two-dimensional (2D) techniques. As a result, much has been learned regarding the biological information encrypted in the histomorphology of bone, yielding a wealth of information relating to skeletal structure and function. Three-dimensional imaging modalities, however, hold the potential to provide a much more comprehensive understanding of bone microarchitecture. The visualization and analysis of bone using high-resolution 3D imaging will improve current understandings of bone biology and have numerous applications in both biological anthropology and biomedicine. Through recent technological advancements, we can hone current anthropological applications of the analysis of bone microstructure and accelerate research into the third and fourth dimensional realms. This review will explore the methodological approaches used historically by anthropologists to assess cortical bone microstructure, spanning from histology to current ex vivo imaging modalities, discuss the growing capabilities of in vivo imaging, and conclude with an introduction of novel non-histological modalities for investigating bone quality.

Dispersion characteristics of the flexural wave assessed using low frequency (50-150kHz) point-contact transducers: A feasibility study on bone-mimicking phantoms

Guided waves-based techniques are currently under development for quantitative cortical bone assessment. However, the signal interpretation is challenging due to multiple mode overlapping. To overcome this limitation, dry point-contact transducers have been used at low frequencies for a selective excitation of the zeroth order anti-symmetric Lamb A0 mode, a mode whose dispersion characteristics can be used to infer the thickness of the waveguide. In this paper, our purpose was to extend the technique by combining a dry point-contact transducers approach to the SVD-enhanced 2-D Fourier transform in order to measure the dispersion characteristics of the flexural mode. The robustness of our approach is assessed on bone-mimicking phantoms covered or not with soft tissue-mimicking layer. Experiments were also performed on a bovine bone. Dispersion characteristics of measured modes were extracted using a SVD-based signal processing technique. The thickness was obtained by fitting a free plate model to experimental data. The results show that, in all studied cases, the estimated thickness values are in good agreement with the actual thickness values. From the results, we speculate that in vivo cortical thickness assessment by measuring the flexural wave using point-contact transducers is feasible. However, this assumption has to be confirmed by further in vivo studies.

Quantitative Ultrasound (QUS) in the Management of Osteoporosis and Assessment of Fracture Risk

The use of quantitative ultrasound (QUS) for a variety of skeletal sites, associated with the absence of technology-specific guidelines, has created uncertainty with respect to the application of QUS results to the management of individual patients in clinical practice. However, when prospectively validated (this is not the case for all QUS devices and skeletal sites), QUS is a proven, low-cost, and readily accessible alternative to dual-energy X-ray absorptiometry (DXA) measurements of bone mineral density (BMD) for the assessment of fracture risk. Indeed, the clinical use of QUS to identify subjects at low or high risk of osteoporotic fracture should be considered when central DXA is unavailable. Furthermore, the use of QUS in conjunction with clinical risk factors (CRF),allows for the identification of subjects who have a low and high probability of osteoporotic fracture. Device- and parameter-specific thresholds should be developed and cross-validated to confirm the concurrent use of QUS and CRF for the institution of pharmacological therapy and monitoring therapy.

Simulation of acoustic guided wave propagation in cortical bone using a semi-analytical finite element method

Axial transmission techniques have been extensively studied for cortical bone quality assessment. However, the modeling of ultrasonic guided waves propagation in such a complex medium remains challenging. The aim of this paper is to develop a semi-analytical finite element method to simulate the propagation of guided waves in an irregular, multi-layer, and heterogeneous bone cross-section modeled with anisotropic and viscoelastic material properties. The accuracy of the simulations was verified against conventional time-domain three-dimensional finite element. The method was applied in the context of axial transmission in bone to investigate the feasibility of first arrival signal (FAS) to monitor degradation of intracortical properties at low frequency. Different physiopathological conditions for the intracortical region, varying from healthy to osteoporotic, were monitored through FAS velocity using a 10-cycle tone burst excitation centered at 32.5 kHz. The results show that the variation in FAS velocity is mainly associated with four of the eight modes supported by the waveguide, varying with velocity values between 550 and 700 m/s along the different scenarios. Furthermore, the FAS velocity is shown to be associated with the group velocity of the mode with the highest relative amplitude contribution at each studied scenario. However, because of the evolution of the mode with the highest contribution, the FAS velocity is shown to be limited to discriminate intracortical bone properties at low frequency.

Simulation study of axial ultrasonic wave propagation in heterogeneous bovine cortical bone

The effect of the heterogeneity of the long cortical bone is an important factor when applying the axial transmission technique. In this study, the axial longitudinal wave velocity distributions in specimens from the mid-shaft of a bovine femur were measured, in the MHz range. Bilinear interpolation and the piecewise cubic Hermite interpolating polynomial method were used to construct three-dimensional (3D) axial velocity models with a resolution of 40 μm. By assuming the uniaxial anisotropy of the bone and using the results of previous experimental studies [Yamato, Matsukawa, Yanagitani, Yamazaki, Mizukawa, and Nagano (2008b). Calcified Tissue Int. 82, 162-169; Nakatsuji, Yamamoto, Suga, Yanagitani, Matsukawa, Yamazaki, and Matsuyama (2011). Jpn. J. Appl. Phys. 50, 07HF18], the distributions of all elastic moduli were estimated to obtain a 3D heterogeneous bone model and a uniform model. In the heterogeneous model, moduli at the surface were smaller than those inside the model. The elastic finite-difference time-domain method was used to simulate axial ultrasonic wave propagation in these models. In the heterogeneous model, the wavefront of the first arriving signal (FAS) was dependent on the heterogeneity, and the FAS velocity depended on the measured position. These phenomena were not observed in the uniform model.

In Vivo Characterization of Cortical Bone Using Guided Waves Measured by Axial Transmission

Cortical bone loss is not fully assessed by the current X-ray methods, and there is an unmet need in identifying women at risk of osteoporotic fracture, who should receive a treatment. The last decade has seen the emergence of the ultrasound (US) axial transmission (AT) techniques to assess a cortical bone. Recent AT techniques exploit the multimode waveguide response of the long bones such as the radius. A recent ex vivo study by our group evidenced that a multimode AT approach can yield simultaneous estimates of cortical thickness (Ct.Th) and stiffness. The aim of this paper is to move one step forward to evaluate the feasibility of measuring multimode guided waves (GW) in vivo and to infer from it cortical thickness. Measurements were taken on the forearm of 14 healthy subjects with the goal to test the accuracy of the estimated thickness using the bidirectional AT method implemented on a dedicated 1-MHz linear US array. This setup allows determining in vivo the dispersion curves of GW transmitted in the cortical layer of the radius. An inverse procedure based on the comparison between the measured and modeled dispersion curves predicted by a 2-D transverse isotropic free plate waveguide model allowed an estimation of cortical thickness, despite the presence of soft tissue. The Ct.Th values were validated by comparison with the site-matched estimates derived from X-ray high-resolution peripheral quantitative computed tomography. Results showed a significant correlation between both measurements ( r² = 0.7 , , and [Formula: see text] mm). This pilot study demonstrates the potential of bidirectional AT for the in vivo assessment of cortical thickness, a bone strength-related factor.

US White and Black Women Do Not Represent the Bone Mineral Density of Sub-Saharan Black Women

Reference populations from the United States (US) are often used around the world for representative measures of bone mineral density (BMD) by sex, age, and race. We examined BMD in adult black Zimbabwean women and compared it to that of US women (white and black). In a cross-sectional study, we recruited healthy black Zimbabwean women working at Parirenyatwa Hospital regardless of designation, who were not pregnant and had no diseases or medications known to affect BMD. Dual-energy X-ray absorptiometry scans of the left hip and lumbar spine (L1-L4) were performed for each participant by 1 operator, on 1 dual-energy X-ray absorptiometry machine. Results are presented for 289 participants aged 20-69 years, with a mean weight, height, and body mass index (BMI) of 71.7 ± 15.1 cm, 164.9 ± 6.3 kg, and 26.3 ± 5.3 kg/m(2), respectively. At 5% level of significance, age and BMD were weakly associated for the total lumbar spine (p ≤ 0.001) but not for the total hip (p = 0.890) and femur neck (p = 0.062). BMI and weight were positively correlated with BMD for all 3 sites (p ≤ 0.001). Compared to US white women, mean BMD for black Zimbabwean women in this study was 4.5%-7.4% lower for the lumbar spine but 2.0%-4.8% higher for the total hip and 0.2%-10.2% higher for the femur neck for 20-59 years. Compared to US black women, mean BMD for black Zimbabwean women was 9.1%-11.5% lower for the lumbar spine and 1.4%-8.1% lower for the total hip for 20-59 years. Black Zimbabwean women also had lower mean weight and BMI per decade age group as compared to US women. Differences in weight and BMI offer a possible explanation for the differences in BMD between black Zimbabwean women and US white and black women. Including adjustments for body frame when calculating Z-scores may accurately reflect BMD.

Modeling of transient wave propagation in a heterogeneous solid layer coupled with fluid: application to long bones

The aim of this work is to evaluate the effects of the heterogeneity and anisotropy of material properties of cortical bone on its ultrasonic response obtained by using axial transmission method. The heterogeneity and anisotropy of material properties are introduced by using a parametric probabilistic model. The geometrical configuration of the tested sample is described by a tri-layer medium composed of a heterogeneous and anisotropic solid layer sandwiched between two acoustic fluid layers of which one of these layers is excited by an acoustic linear source. The numerical results focus on studying of an interest quantity, called velocity of the first arriving signal, showing that it strongly depends on the dispersion induced by statistical fluctuations of stochastic elasticity field.

Impact of Walking and Running on the Heel bone: the Adventist Health Study-2

Aims

Physical activity is well recognized for its bone health benefit. We examined the benefit of walk/run/jog on bone health using broadband ultrasound attenuation (BUA) of the calcaneus.

Methodology

Caucasian and African American males (n=593) and females (n=1,106) had their calcaneal BUA measured two years later after enrollment into the AHS-2. The association between calcaneal BUA (dB/Mhz) and the distance of walk/run/ jog level per week (miles) was assessed using multiple linear regression.

Results

In a multivariable model adjusted for important covariates, BUA was positively associated with BMI (P < .001), total calcium intake (P =0.31), total protein intake (P =0.38) and inversely associated with age (P < .001) and smoking (P < .05). Compared to women who did not walk/ run/ jog, women walking 10 or more miles per week had an increase in BUA by 4.08 (dB/Mhz) (P _trend=0.03). Similarly, compared to men who did not walk/ run/ jog, men walking 10 or more miles per week had an increase in BUA by 5.97 (dB/Mhz) (P _trend=0.01).

Conclusions

We concluded that BUA is positively associated with walk/ run/jog after accounting for age, BMI, smoking status, calcium intake, protein intake and estrogen usage.

Association between low-frequency ultrasound and hip fractures -- comparison with DXA-based BMD

BACKGROUND

New methods for diagnosing osteoporosis and evaluating fracture risk are being developed. We aim to study the association between low-frequency (LF) axial transmission ultrasound and hip fracture risk in a population-based sample of older women.

METHODS

The study population consisted of 490 community-dwelling women (78-82 years). Ultrasound velocity (V(LF)) at mid-tibia was measured in 2006 using a low-frequency scanning axial transmission device. Bone mineral density (BMD) at proximal femur measured using dual-energy x-ray absorptiometry (DXA) was used as the reference method. The fracture history of the participants was collected from December 1997 until the end of 2010. Lifestyle-related risk factors and mobility were assessed at 1997.

RESULTS

During the total follow-up period (1997-2010), 130 women had one or more fractures, and 20 of them had a hip fracture. Low V(LF) (the lowest quartile) was associated with increased hip fracture risk when compared with V(LF) in the normal range (Odds ratio, OR = 3.3, 95% confidence interval (CI) 1.3-8.4). However, V(LF) was not related to fracture risk when all bone sites were considered. Osteoporotic femoral neck BMD was associated with higher risk of a hip fracture (OR = 4.1, 95% CI 1.6-10.5) and higher risk of any fracture (OR = 2.4, 95% CI 1.6-3.8) compared to the non-osteoporotic femoral neck BMD. Decreased VLF remained a significant risk factor for hip fracture when combined with lifestyle-related risk factors (OR = 3.3, 95% CI 1.2-9.0).

CONCLUSION

Low V(LF) was associated with hip fracture risk in older women even when combined with lifestyle-related risk factors. Further development of the method is needed to improve the measurement precision and to confirm the results.

Multisite quantitative ultrasound for the prediction of fractures over 5 years of follow-up: the Canadian Multicentre Osteoporosis Study

This study assessed the ability of multisite quantitative ultrasound (mQUS) to predict fracture over a 5-year follow-up. Participants were a subset of the Canadian Multicentre Osteoporosis Study. mQUS-assessed speed of sound (SOS in m/s) at three sites (distal radius, tibia, and phalanx) and extensive questionnaires were completed, after which participants were followed for 5 years and incident fractures recorded. Two survival analyses were completed for each site--a univariate analysis and an adjusted multivariate analysis controlling for age, antiresorptive use, femoral neck bone mineral density, number of diseases, previous fractures, body mass index (BMI), parental history of hip fracture, current smoking, current alcoholic drinks >3 per day, current use of glucocorticoids, and rheumatoid arthritis diagnosis (variables from the FRAX 10-year fracture risk assessment tool). The unit of change for regression analyses was one standard deviation for all measurement sites, specific to site and sex. Separate analyses were completed for all clinical fractures, nonvertebral fractures, and hip fractures by sex. There were 2633 women and 1108 men included, and they experienced 204 incident fractures over 5 years (5.5% fractured). Univariate models revealed statistically significant (p < 0.05) predictive ability of mQUS for all three measurement sites for women alone for all three fracture types (one standard deviation decrease in SOS was associated with a 52% to 130% increase in the risk of fracture), but not for the men's group. The adjusted model found that measures at the distal radius and tibia in the women's group could significantly (p < 0.05) predict all clinical fractures and nonvertebral fractures within the next 5 years (one standard deviation decrease in SOS was associated with a 25% to 31% increase in the risk of fracture). mQUS provided significant 5-year clinical fracture prediction in women, independent of bone mineral density and other significant risk factors for fracture, when measured at the distal radius and tibia sites.

Discrimination of fractures by low-frequency axial transmission ultrasound in postmenopausal females

SUMMARY

In this cross-sectional study, 95 postmenopausal women, with and without fracture history, were measured by low-frequency axial transmission ultrasound. The measured ultrasound velocity discriminated the fractured subjects from the nonfractured ones equally or better than peripheral quantitative computed tomography (pQCT) and dual energy x-ray absorptiometry (DXA). These results suggest that low-frequency ultrasound is suitable for bone fragility assessment.

INTRODUCTION

Quantitative low-frequency axial transmission ultrasound is a promising modality for assessing mineral density and geometrical properties of long bones such as radius and tibia. The aim of the current study was to evaluate the ability of low-frequency axial transmission ultrasound to discriminate fractures retrospectively in postmenopausal women.

METHODS

A cross-sectional study involved 95 female subjects aged 45-88 years, whose fracture information was gathered retrospectively. The fracture group was defined as subjects with one or more low-/moderate-energy fractures. The radius and tibial shaft were measured with a custom-made ultrasonometer to assess the velocity of the low-frequency first-arriving signal (V (LF)). Site-matched pQCT was used to measure volumetric cortical and subcortical bone mineral density (sBMD), and cortical thickness (CTh). Areal BMD (aBMD) was measured using DXA for the whole body (WB), lumbar spine, and hip.

RESULTS

The majority (19/32; 59 %) of the fractures were in the upper limb. V (LF) in the radius, but not in the tibia, discriminated fractures with an age- and BMI-adjusted odds ratio (OR) of 2.06 (95 % CI 1.21-3.50, p < 0.01). In the radius, CTh and cortical BMD (CBMD) significantly discriminated fractures, as did the total, cortical, and sBMD in the tibia (adjusted OR 1.35-2.15, p < 0.05). Sensitivity and specificity were similar among all the measurements (area under the receiver operating characteristic curve 0.74-0.81, p < 0.001).

CONCLUSIONS

Low-frequency axial transmission ultrasound in the radius was able to discriminate fractured subjects from the nonfractured ones. This suggests that low-frequency axial transmission ultrasound has the potential to assess bone fragility in postmenopausal women.

Soy milk and dairy consumption is independently associated with ultrasound attenuation of the heel bone among postmenopausal women: the Adventist Health Study-2

Soy milk has become a popular substitute for dairy milk with important health claims. We hypothesized that soy milk, based on its nutrient composition, is comparable to dairy products and, therefore, beneficial for bone health. To test this hypothesis, we examined the benefit of soy milk and dairy products intake on bone health using broadband ultrasound attenuation of the calcaneus. Postmenopausal white women (n = 337) who had completed a lifestyle and dietary questionnaire at enrollment into the Adventist Health Study-2 had their calcaneal broadband ultrasound attenuation measured 2 years later. The association between osteoporosis (defined as a T-score <-1.8) and some dietary factors (soy milk, dairy) and selected lifestyle factors was assessed using logistic regression. In a multivariable model adjusted for demographics, hormone use, and other dietary factors, osteoporosis was positively associated with age (odds ratio [OR] = 1.08; 95% confidence interval [CI], 1.06-1.12) and inversely associated with body mass index (OR = 0.91; 95% CI, 0.86-0.97) and current estrogen use (OR = 0.27; 95% CI, 0.13-0.56). Compared with women who did not drink soy milk, women drinking soy milk once a day or more had 56% lower odds of osteoporosis (OR = 0.44; 95% CI, 0.20-0.98; P(trend) = .04). Women whose dairy intake was once a day or more had a 62% reduction in the likelihood of having osteoporosis (OR = 0.38; 95% CI, 0.17-0.86; P(trend) = .02) compared with women whose dairy intake was less than twice a week. Among individual dairy products, only cheese showed an independent and significant protection (OR = 0.28; 95% CI, 0.12-0.66; P(trend) = .004) for women eating cheese more than once per week vs those who ate cheese less than once a week. We concluded that osteoporosis is inversely associated with soy milk intake to a similar degree as dairy intake after accounting for age, body mass index, and estrogen use.

Impact of attenuation on guided mode wavenumber measurement in axial transmission on bone mimicking plates

Robust signal processing methods adapted to clinical measurements of guided modes are required to assess bone properties such as cortical thickness and porosity. Recently, an approach based on the singular value decomposition (SVD) of multidimensional signals recorded with an axial transmission array of emitters and receivers has been proposed for materials with negligible absorption, see Minonzio et al. [J. Acoust. Soc. Am. 127, 2913-2919 (2010)]. In presence of absorption, the ability to extract guided mode degrades. The objective of the present study is to extend the method to the case of absorbing media, considering attenuated plane waves (complex wavenumber). The guided mode wavenumber extraction is enhanced and the order of magnitude of the attenuation of the guided mode is estimated. Experiments have been carried out on 2 mm thick plates in the 0.2-2 MHz bandwidth. Two materials are inspected: polymethylacrylate (PMMA) (isotropic with absorption) and artificial composite bones (Sawbones, Pacific Research Laboratory Inc, Vashon, WA) which is a transverse isotropic absorbing medium. Bulk wave velocities and bulk attenuation have been evaluated from transmission measurements. These values were used to compute theoretical Lamb mode wavenumbers which are consistent with the experimental ones obtained with the SVD-based approach.

Trabecular and cortical bone separately assessed at radius with a new ultrasound device, in a young adult population with various physical activities

The aim was to evaluate a new ultrasound device in a young adult population and to assess its reproducibility via comparison to DXA measurements and geometrical measurements from high-resolution radiographs. Ninety-three subjects aged between 20 and 51 years were recruited and divided into four groups according to their gender and physical activity status: 22 male athletes, 19 male controls, 21 female athletes, and 31 female controls. Ultrasonic measurements were assessed by the prototype LD-100 (Oyo Electric Co., Kyoto, Japan) on the dominant distal radius. Attenuation in the radius (dB), cortical bone thickness (mm), radius thickness (mm), mass density of cancellous bone (mg/cm(3)), and elasticity (GPa) of cancellous bone were obtained. BMD was measured by DXA at the dominant distal radius. Radius images were obtained with a direct high-resolution digital X-ray device (BMA, D(3)A Medical Systems), and radius and cortical thicknesses were estimated using a specific software (ImageJ, Bethesda, USA), in an area site-matched with LD-100. There was a significant positive correlation between site-matched BMD measurement and LD-100 parameters (p<0.004), X-ray radius thickness, and LD-100 parameters except elasticity (p<0.05, r>0.32), X-ray cortical thickness and LD-100 attenuation and cortical thickness (p<0.01). A significantly higher attenuation, cortical and radius thicknesses were found in athletes compared to controls (p<0.05). The radius thickness measured on radiographs was significantly higher in athletes versus controls in both sexes, and cortical thickness was significantly higher in male athletes versus controls. These data suggest a positive influence of physical activity on bone cortical measurements. This study also confirmed the particular interest of bone assessment by ultrasound.

Influence of viscoelastic and viscous absorption on ultrasonic wave propagation in cortical bone: Application to axial transmission

Cortical bone and the surrounding soft tissues are attenuating and heterogeneous media, which might affect the signals measured with axial transmission devices. This work aims at evaluating the effect of the heterogeneous acoustic absorption in bone and in soft tissues on the bone ultrasonic response. Therefore, a two-dimensional finite element time-domain method is derived to model transient wave propagation in a three-layer medium composed of an inhomogeneous transverse isotropic viscoelastic solid layer, sandwiched between two viscous fluid layers. The model couples viscous acoustic propagation in both fluid media with the anisotropic viscoelastic response of the solid. A constant spatial gradient of material properties is considered for two values of bone thicknesses (0.6 and 4 mm). In the studied configuration, absorption in the surrounding fluid tissues does not affect the results, whereas bone viscoelastic properties have a significant effect on the first arriving signal (FAS) velocity. For a thin bone, the FAS velocity is governed by the spatially averaged bone properties. For a thick bone, the FAS velocity may be predicted using a one-dimensional model.

Clinical risk factors for osteoporotic fracture: a population-based prospective cohort study in Korea

Clinical risk factors (CRFs), either alone or in combination with bone mineral density, are used to determine the fracture risk for clinical assessment and to determine intervention thresholds. Because fracture risk is strongly affected by ethnicity and population-specific differences, we sought to identify Korean-specific CRFs for fracture, in combination with quantitative ultrasound (qUS) measurements of the radius and tibia. A total of 9351 subjects (4732 men and 4619 women) aged 40 to 69 years were followed for a mean of 46.3 +/- 2.2 months. We obtained CRF information using a standardized questionnaire and measured anthropometric variables. Speed of sound at the radius (SoSR) and tibia (SoST) were measured by qUS. Fracture events were recorded using a questionnaire, and a height-loss threshold was used as an indicator of vertebral fracture. Relative risks were calculated by Cox regression analysis. A total of 195 subjects (61 men and 134 women) suffered low-trauma fractures. Older age, lower body mass index (BMI), and previous fracture history were positively associated with fracture risk in both sexes. Decreased hip circumference, lack of regular exercise, higher alcohol intake, menopause, and osteoarthritis history were further independent CRFs for fracture in women. However, neither SoSR nor SoST was independently associated with fracture risk. In this study, we identified the major Korean-specific CRFs for fracture and found that smaller hip circumference was a novel risk factor. This information will allow optimal risk-assessment targeting Koreans for whom treatment would provide the greatest benefit.

Analysis of the most energetic late arrival in axially transmitted signals in cortical bone

Axial transmission techniques are particularly suitable for the ultrasonic assessment of cortical bone. The generic term "axial transmission technique" indicates a measurement configuration in which emitters and receivers are placed on the same side of the skeletal site, along the bone axis. Whereas axially transmitted signals are composed of several contributions, only the first arriving signal was shown to be a robust indicator of bone status, because its velocity discriminates osteoporotic from healthy patients in clinical studies. Later arrivals may provide additional bone indicators enhancing diagnostic value, but the precise determination of their velocities is challenging. In this paper, we focus on the most energetic contribution and we applied a singular-value decomposition-based extraction method not yet employed in the domain of bone assessment with the aim of determining the velocity of this contribution. Signals acquired in vitro on human radii, together with academic models, were used to reveal the relationship between the velocity of the most energetic component and bone properties. The velocity of the most energetic component is highly correlated to cortical layer thickness in the in vitro database (R(2)= 0.6, P < 10(-5) compared with R(2)= 0.20, P < 10-(2) for the first arriving signal), consistent with a flexural type of wave on regular tubes or plates. Conclusions are in agreement with published papers based on other axial transmission and signal processing approaches.

The Optimal Linear Combination of Multiple Predictors Under the Generalized Linear Models

Multiple alternative diagnostic tests for one disease are commonly available to clinicians. It's important to use all the good diagnostic predictors simultaneously to establish a new predictor with higher statistical utility. Under the generalized linear model for binary outcomes, the linear combination of multiple predictors in the link function is proved optimal in the sense that the area under the receiver operating characteristic (ROC) curve of this combination is the largest among all possible linear combination. The result was applied to analysis of the data from the Study of Osteoporotic Fractures (SOF) with comparison to Su and Liu's approach.

The Evaluation of Renal Osteodystrophy with Cortical Quantitative Ultrasound at Various Bone Sites

BACKGROUND

In this study we evaluated bone abnormalities of patients with chronic renal failure (CRF) by cortical quantitative bone ultrasound (QUS) measurements at different bone sites because these abnormalities may be of variable etiology and may start before symptoms or radiological changes are manifested.

METHODS

Of fifteen patients with chronic renal failure, seven had moderate-severe disease and eight had been on chronic hemodialysis from 5 to 17 years, with renal osteodystrophy (ROD) confirmed by bone biopsies. Twelve normal subjects of similar age and gender volunteered for the control group.

RESULTS

Patients and controls differed in creatinine clearance, in serum phosphate levels and in serum total alkaline phosphatase. Mean intact-PTH levels differed significantly amongst the three groups of subjects. All patients with ROD had intact-PTH higher than 200 pg/mL. The cortical ultrasound parameter, speed of sound (SOS), was slower in patients with more severe renal failure at all bone sites measured. The group with ROD had significantly lower cortical ultrasound values than the other patients and the control group at all sites. SOS values at the proximal phalanx, distal radius and midtibial sites were positively and significantly correlated. Cortical ultrasound measurements at the radial site correlated with midtibial and phalangeal sites but the correlation between midtibial and phalangeal sites did not reach significance. IPTH levels correlated negatively and significantly with cortical QUS values at all sites being the correlations higher at phalangeal and radial sites than at the midtibial region.

CONCLUSIONS

The differences in cortical ultrasound observed indicate the potential clinical application of this methodology to evaluate bone abnormalities in chronic renal failure, especially in patients on chronic hemodialysis.

Influence of a gradient of material properties on ultrasonic wave propagation in cortical bone: application to axial transmission

The aim of this work is to evaluate the effect of a spatial gradient of material properties (mass density and stiffness coefficients) of cortical bone on its ultrasonic response obtained with an axial transmission device. Therefore, a two-dimensional finite element time-domain method is derived to model transient wave propagation in a three-layer medium composed of an inhomogeneous transverse isotropic solid layer sandwiched between two acoustic fluid layers and excited by an acoustic linear source located in one fluid layer, delivering broadband ultrasonic pulses. The model couples the acoustic propagation in both fluid media with the elastodynamic response of the solid layer. A constant spatial gradient of material properties is considered for two values of bone thicknesses corresponding to relatively thick and thin bone widths. For a thin bone (0.6 mm) compared to wavelength (around 4 mm at 1 MHz), the results are in good agreement with a S(0) Lamb wave assuming a homogeneous material with spatially averaged material properties. For a thick bone (4 mm), the results are in agreement with the propagation of a lateral wave and allow the derivation of an equivalent contributing depth in the case of a transverse isotropic inhomogeneous solid layer.

In vivo performance evaluation of bi-directional ultrasonic axial transmission for cortical bone assessment

Our objective was to assess a new quantitative ultrasound device suitable for the measurement of speed of sound in radius. The so-called "bidirectional" technique allows an accurate estimation of velocity based on a compensation for soft tissue effects implemented directly inside the probe. Velocity measurements at 1 MHz of the first arriving signal were performed at the one third distal radius in 358 enrolled women. The average velocity by age decade increases to a peak velocity of 4043 m/s in the class 30-39 y (n = 19) and decreases thereafter. Fracture discrimination was investigated on the subset of the population for which dual-energy x-ray absorptiometry measurement was available, in addition to first arriving signal velocity measurements. The study group consisted of 122 postmenopausal women without history of fracture (group NF) and 44 postmenopausal patients (group F) with osteoporotic fractures (hip, spine, Colles fracture). When adjusted for age and bone mass index, the odds ratio (OR) for fracture prediction by ultrasound velocity, was 1.81 (1.21; 2.70) and OR associated to neck femur BMD was 2.07 (1.31-3.29). For the full model including age and body mass index as cofactors, the area under the receiver operating characteristic curve was 0.77, either for ultrasound velocity or neck femur bone mineral density. Despite the small population and the variety of fractures in the fracture group, our data indicate that the velocity of the first arriving signal measured by bidirectional technique discriminates patients with osteoporotic fracture from controls.

Imaging of metabolic bone diseases

Bone scintigraphy and X-ray are complementary in the assessment of Paget's disease. Whereas bone scintigraphy allows visualization of the whole skeleton and 'hot spots', X-ray enables visualization of more detailed images of the pagetic bone lesion. X-ray may be invaluable in the diagnosis of osteomalacia, especially in children. As osteomalacia is characterized by impaired bone mineralization, the use of bone density measures may lead to misinterpretation of the condition as osteoporosis. Dual-energy X-ray absorptiometry at the femoral neck is the 'gold standard' for the assessment of osteoporosis. However, all devices are useful to predict the risk of fracture. In the future, high-resolution computer tomography and magnetic resonance imaging may become valuable clinical tools, capturing the architectural aspect of bone strength and improving fracture prediction models.

Good maintenance of physical benefits in a 12-month exercise and nutritional intervention by voluntary, home-based exercise: a 6-month follow-up of a randomized controlled trial

We assessed the maintenance of physical benefits in a 12-month exercise and nutritional intervention in postmenopausal women (55-75 years of age) after 6-month postintervention follow-up by voluntary, home-based exercise, and examined whether physical factors responded differently to high or low exercise frequency during the 6-month postintervention period. Forty-five women completed the 12-month intervention program, followed by 6-month cessation of intervention, and were compared with 19 matched controls. Twenty-one of the former exercisers reported that they continued exercise training at least 30 min at least 3 days/week (high-frequency exerciser, HFE), while the remaining 24 former exercisers reported that they had done exercise training at least 30 min twice per week or less during the postintervention follow-up (low-frequency exerciser, LFE). The following items were measured at baseline, 12, and 18 months: bone strength, CS-30 test, 10-m obstacle walk, whole-body reaction time, one-leg stance, and grip strength. After 6-month postintervention follow-up, the beneficial effect on bone was not fully maintained. These benefits in physical performance obtained in the 12-month intervention program, except one-leg stance, were fully maintained for 6 months by voluntary, home-based exercise. The gained benefit in one-leg stance was not fully maintained; LFE showed a significant decrease over the 6-month postintervention follow-up period, suggesting that continued exercise training of at least 30 min at least 3 days/week is required to maintain the balance benefit. These findings suggest that a continued exercise program of voluntary, home-based exercise may be effective to maintain the physical benefits of exercise intervention that may lower fracture risk in later life.

Quantitative ultrasound in the management of osteoporosis: the 2007 ISCD Official Positions

Dual-energy X-ray absorptiometry (DXA) is commonly used in the care of patients for diagnostic classification of osteoporosis, low bone mass (osteopenia), or normal bone density; assessment of fracture risk; and monitoring changes in bone density over time. The development of other technologies for the evaluation of skeletal health has been associated with uncertainties regarding their applications in clinical practice. Quantitative ultrasound (QUS), a technology for measuring properties of bone at peripheral skeletal sites, is more portable and less expensive than DXA, without the use of ionizing radiation. The proliferation of QUS devices that are technologically diverse, measuring and reporting variable bone parameters in different ways, examining different skeletal sites, and having differing levels of validating data for association with DXA-measured bone density and fracture risk, has created many challenges in applying QUS for use in clinical practice. The International Society for Clinical Densitometry (ISCD) 2007 Position Development Conference (PDC) addressed clinical applications of QUS for fracture risk assessment, diagnosis of osteoporosis, treatment initiation, monitoring of treatment, and quality assurance/quality control. The ISCD Official Positions on QUS resulting from this PDC, the rationale for their establishment, and recommendations for further study are presented here.

A novel growth hormone receptor gene deletion mutation in a patient with primary growth hormone insensitivity syndrome (Laron syndrome)

OBJECTIVE

Growth hormone (GH) insensitivity syndrome (Laron syndrome) is known to be caused by genetic disorders of the GH-IGF-1 axis. Although many mutations in the GH receptor have been identified, there have been only a few reports of deletions of the GH receptor gene.

DESIGN

A Japanese adult female patient with Laron syndrome was subjected to chromosome analysis with basic G-banding and also with a high accuracy technique. Each exon of the GH receptor gene was amplified by means of PCR. Since this patient was diagnosed with osteoporosis, the effects of alendronate on bone mineral density (BMD) were also examined.

RESULTS

The chromosome analysis with the high accuracy technique demonstrated a large deletion of the short arm in one allele of chromosome 5 from p11 to p13.1 [46, XX, del (5) (p11-p13.1)]. PCR amplification of exons of the GH receptor gene showed that only exons 2 and 3 were amplified. Low-dose IGF-1 administration (30microg/kg body weight) failed to increase her BMD, whereas alendronate administration resulted in an increase associated with a decrease in urinary deoxypyridinoline (DPD) and serum osteocalcin concentrations.

CONCLUSIONS

The GH receptor gene of the patient was shown to lack exons 4-10. To the best of our knowledge, this is the third case report of Laron syndrome with large GH receptor deletion. Alendronate was effective for the enhancement of BMD.

An assessment of the use of quantitative ultrasound and the Osteoporosis Self-Assessment Tool for Asians in determining the risk of nonvertebral fracture in postmenopausal Chinese women

This cross-sectional study aims to assess the effectiveness of a simple, noninvasive scoring system, the Osteoporosis Self-Assessment Tool for Asians (OSTA), and quantitative bone ultrasound (QUS) in assessing nonvertebral fracture risk in Chinese postmenopausal women. A group of 513 community-dwelling women including 271 postmenopausal individuals participated in this study. Speed of sound (SOS m/s) at the radius, phalanx, and tibia were assessed by using the Omnisense prototype (Sunlight Ltd., Israel). Body height and weight were measured, and body mass index (BMI) and OSTA indices were calculated. Self-reported fractures were identified using a structured questionnaire. Phalanx SOS was significantly lower among postmenopausal women with a history of nonvertebral fracture occurred after menopause than those without (3755 m/s vs. 3841 m/s, P = 0.017, adjusted for age and weight), with an AUC of 0.66. The AUC of the OSTA for predicting nonvertebral fracture occurred after menopause was 0.64. SOS at the radius, phalanx, and tibia showed a positive correlation with OSTA index (r = 0.376-0.401, P < 0.001). The prevalence of nonvertebral fractures also increased significantly with the decreasing order of OSTA index (chi2 = 5.432, P = 0.02). The OSTA values of <or=-1 and phalanx QUS T-score of <or=-1.95 can differentiate postmenopausal nonvertebral fracture with sensitivity of 75% and 81%, respectively, and specificity of 48% and 40%, respectively. Combining OSTA and phalanx QUS yielded a sensitivity of 83% and a specificity of 84% to detect postmenopausal nonvertebral fracture, with an AUC of 0.64. We conclude that OSTA and phalanx QUS are simple and effective clinical tools for identifying postmenopausal women at increased risk of nonvertebral fractures and can thereby facilitate the appropriate and more cost-effective use of bone densitometry to prevent osteoporotic fractures in developing countries.

Instrumentation for in vivo ultrasonic characterization of bone strength

Although it has been more than 20 years since the first recorded use of a quantitative ultrasound (QUS) technology to predict bone fragility, the field has not yet reached its maturity. QUS has the potential to predict fracture risk in several clinical circumstances and has the advantages of being nonionizing, inexpensive, portable, highly acceptable to patients, and repeatable. However, the wide dissemination of QUS in clinical practice is still limited and suffering from the absence of clinical consensus on how to integrate QUS technologies in bone densitometry armamentarium. Several critical issues need to be addressed to develop the role of QUS within rheumatology. These include issues of technologies adapted to measure the central skeleton, data acquisition, and signal processing procedures to reveal bone properties beyond bone mineral quantity and elucidation of the complex interaction between ultrasound and bone structure. This article reviews the state-of-the art in technological developments applied to assess bone strength in vivo. We describe generic measurement and signal processing methods implemented in clinical ultrasound devices, the devices and their practical use, and performance measures. The article also points out the present limitations, especially those related to the absence of standardization, and the lack of comprehensive theoretical models. We conclude with suggestions of future lines and trends in technology challenges and research areas such as new acquisition modes, advanced signal processing techniques, and modelization.

Prediction of bone mechanical properties using QUS and pQCT: study of the human distal radius

The objective was to compare the prediction of bone mechanical properties provided by axial transmission to that provided by peripheral quantitative computed tomography (pQCT) at the distal radius. The distal radius is the location for Colles' fractures, a common osteoporosis related trauma situation. Measurements of the radial speed of sound were performed using three axial transmission devices: a commercial device (Sunlight Omnisense, 1.25 MHz), a bi-directional axial transmission prototype (1 MHz), both measuring the velocity of the first arriving signal (FAS), and a low frequency (200 kHz) device, measuring the velocity of a slower wave. Co-localized pQCT measurements of bone mineral density and cortical thickness were performed. Ultrasound and pQCT parameters were compared to mechanical parameters such as failure load and Young's modulus, obtained using quasistatic compressive mechanical testing and finite elements modelling (FEM). Correlations of the ultrasound and pQCT parameters to mechanical parameters were comparable. The best predictor of failure load was the pQCT measured cortical thickness. The best predictor of Young's modulus was the bi-directional SOS. The low frequency device significantly correlated to cortical thickness and failure load. The results suggest that different axial transmission approaches give access to different bone mechanical parameters. The association of different axial transmission techniques should be able to provide a good prediction of bone mechanical parameters, and should therefore be helpful for fracture risk prediction.

Effect of porosity on effective diagonal stiffness coefficients (cii) and elastic anisotropy of cortical bone at 1 MHz: a finite-difference time domain study

Finite-difference time domain (FDTD) numerical simulations coupled to real experimental data were used to investigate the propagation of 1 MHz pure bulk wave propagation through models of cortical bone microstructures. Bone microstructures were reconstructed from three-dimensional high resolution synchrotron radiation microcomputed tomography (SR-muCT) data sets. Because the bone matrix elastic properties were incompletely documented, several assumptions were made. Four built-in bone matrix models characterized by four different anisotropy ratios but the same Poisson's ratios were tested. Combining them with the reconstructed microstructures in the FDTD computations, effective stiffness coefficients were derived from simulated bulk-wave velocity measurements. For all the models, all the effective compression and shear bulk wave velocities were found to decrease when porosity increases. However, the trend was weaker in the axial direction compared to the transverse directions, contributing to the increase of the effective anisotropy. On the other hand, it was shown that the initial Poisson's ratio value may substantially affect the variations of the effective stiffness coefficients. The present study can be used to elaborate sophisticated macroscopic computational bone models incorporating realistic CT-based macroscopic bone structures and effective elastic properties derived from muCT-based FDTD simulations including the cortical porosity effect.

Bone Mineral Density in Children with Non-Cystic Fibrosis Bronchiectasis

BACKGROUND

Bronchiectasis presents as a common sequela of several chronic pulmonary diseases. Bone mineral density (BMD) is generally decreased in children with cystic fibrosis (CF). Although children with non-CF bronchiectasis have similar risk factors for osteopenia/osteoporosis, data on BMD in this group of patients are lacking.

OBJECTIVE

To evaluate BMD in children with non-CF bronchiectasis.

METHODS

In this study, we evaluated BMD of the radius and tibia in 32 children (17 girls) with non-CF bronchiectasis and in 23 healthy controls matched for age, sex and pubertal stage by quantitative ultrasound (speed of sound). Daily calcium intake and pulmonary function tests and data about steroid use were noted.

RESULTS

Mean age was 12.5 +/- 4.6 years. Six children (18%) had moderate-to-severe lung disease (FEV(1) <60% predicted). All except 2 children (94%) were receiving inhaled steroids. There was no significant difference in BMD (expressed as z-score) of the radius and tibia between the patient and control groups (tibia z-scores: -0.1 +/- 0.9 vs. -0.8 +/- 0.8 and radius z-scores -1.3 +/- 1.4 vs. -1.0 +/- 0.9 in bronchiectasis patients and controls, respectively, p > 0.05). However, more children with non-CF bronchiectasis had osteopenia (z-scores between -1 and -2 SD) and osteoporosis (z-score <or=2 SD) compared to the control group (62 vs. 30%, p = 0.019). There was a significant correlation between age and radius z-scores (r = -0.365, p = 0.04). There was no correlation between BMD and severity of lung illness, calcium intake or cumulative steroid doses.

CONCLUSION

Osteopenia is more common in children with non-CF bronchiectasis compared to controls and the risk of osteoporosis and osteopenia increases with age.

Wavelet-based signal processing of in vitro ultrasonic measurements at the proximal femur

To estimate osteoporotic fracture risk, several techniques for quantitative ultrasound (QUS) measurements at peripheral sites have been developed. As these techniques are limited in the prediction of fracture risk of the central skeleton, such as the hip, we are developing a QUS device for direct measurements at the femur. In doing so, we noticed the necessity to improve the conventional signal processing because it failed in a considerable number of measurements due to multipath transmission. Two sets of excised human femurs (n = 6 + 34) were scanned in transmission mode. Instead of using the conventional methods, the radio-frequency signals were processed with the continuous wavelet transform to detect their time-of-flights for the calculation of speed-of-sound (SOS) in bone. The SOS-values were averaged over a region similar to the total hip region of dual X-ray absorptiometry (DXA) measurements and compared with bone mineral density (BMD) measured with DXA. Testing six standard wavelets, this algorithm failed for only 0% to 6% of scan in test set 1 compared with 29% when using conventional algorithms. For test set 2, it failed for 2% to 12% compared with approximately 40%. SOS and BMD correlated significantly in both test sets (test set 1: r2 = 0.87 to 0.92, p < 0.007; test set 2: r2 = 0.68 to 0.79, p < 0.0001). The correlations are comparable with correlations recently reported. However, the number of evaluable signals could be substantially increased, which improves the perspectives of the in vivo measurements.

[Quantitative ultrasound]

Methods of quantitative ultrasound (QUS) can be used to obtain knowledge about bone fragility. Comprehensive study results exist showing the power of QUS for the estimation of osteoporotic fracture risk. Nevertheless, the variety of technologies, devices, and variables as well as different degrees of validation of the single devices have to be taken into account. Using methods to simulate ultrasound propagation, the complex interaction between ultrasound and bone could be understood and the propagation could be visualized. Preceding widespread clinical use, it has to be clarified if patients with low QUS values will profit from therapy, as it has been shown for DXA. Moreover, the introduction of quality assurance measures is essential. The user should know the limitations of the methods and be able to interpret the results correctly. Applied in an adequate manner QUS methods could then, due to lower costs and absence of ionizing radiation, become important players in osteoporosis management.

Fracture Risk (FRISK) Score: Geelong Osteoporosis Study

PURPOSE

To develop and evaluate a fracture risk (FRISK) score based on multiple-site bone mineral density (BMD) measurements and other risk factors, to enable prediction of future fracture occurrence.

MATERIALS AND METHODS

All participants gave written informed consent, and the study was approved by the Barwon Health Research and Ethics Advisory Committee. BMD was measured at the femoral neck and spine in two concurrently recruited groups: women 60 years of age or older who had sustained a low-trauma fracture of the hip, spine, humerus or distal forearm during a 2-year ascertainment period (n = 231; mean age, 74 years +/- 7 [standard deviation]) and a population-based random sample of women who had not sustained a fracture during the recruitment period (n = 448; mean age, 72 years +/- 8). Falls in the previous year and the number of self-reported fractures in adult life were recorded. Coefficients of a multiple logistic regression model were used as weightings for a combined model. A longitudinal population-based sample was used to assess the fracture risk equation (n = 600; median age, 74 years; interquartile range, 67-82 years).

RESULTS

The FRISK score was obtained from the following equation: 9.304 - 4.735BMD(SP) - 4.530BMD(FN) + 1.127FS + 0.344NPF + 0.037W, where BMD(SP) is spinal BMD (in grams per square centimeter), BMD(FN) is femoral neck BMD, FS is falls score, NPF is number of previous fractures, and W is weight (in kilograms). The FRISK score successfully predicted 75% of fractures 2 years after baseline measurements in subjects in the longitudinal study with 68% specificity.

CONCLUSION

This study resulted in the derivation of a fracture risk score that successfully predicted 75% of fractures 2 years after baseline.