Bone mineral density assessment: comparison of dual-energy X-ray absorptiometry measurements at the calcaneus, spine, and hip

The assessment of canal flare index and proximal femoral bone density can improve stem selection for peri-prosthetic bone maintenance after total hip arthroplasty

INTRODUCTION

Bone maintenance after total hip arthroplasty (THA) is important for implant success. This study aimed to investigate the relationship between patient characteristics and periprosthetic bone maintenance after THA for better implant selection.

MATERIALS AND METHODS

This retrospective cohort study enrolled 112 consecutive patients who underwent THA using full hydroxyapatite (HA) compaction with short (n = 55) or short-tapered wedge (n = 61) stems. Periprosthetic bone mineral density (BMD) was compared between the two groups after propensity score matching, and the relationship between periprosthetic BMD changes and patient background was analyzed.

RESULTS

Both groups showed similar periprosthetic BMD changes after adjusting for patient background using propensity score matching. Canal flare index > 3.7 in patients that underwent THA using tapered-wedge stem (odds ratio (OR), 3.2; 95% confidence interval (CI), 1.3-7.9, p = 0.013) and baseline zone 1 BMD > 0.65 in patients that received with short HA compaction stems (OR, 430.0; 95% CI 1.3-1420, p = 0.040) were associated with proximal periprosthetic bone maintenance after THA.

CONCLUSION

Considering their predictive value, canal flare index and zone 1 BMD assessment might be useful strategies for implant selection during THA.

Discordance between quantitative ultrasound and dual-energy X-ray absorptiometry in bone mineral density: The Vietnam Osteoporosis Study

Objectives

Calcaneal quantitative ultrasound measurement (QUS) has been considered an alternative to dual-energy X-ray absorptiometry (DXA) based bone mineral density (BMD) for assessing bone health. This study sought to examine the utility of QUS as an osteoporosis screening tool by evaluating the correlation between QUS and DXA.

Methods

The study was a part of the Vietnam Osteoporosis Study that involved 1270 women and 773 men aged 18 years and older. BMD at the femoral neck, total hip and lumbar spine was measured using DXA. Osteoporosis was diagnosed based on the femoral neck T-score using World Health Organization criteria. Broadband ultrasound attenuation (BUA) at the calcaneus was measured by QUS. The concordance between BUA and BMD was analyzed by the linear regression model.

Results

In all individuals, BUA modestly correlated with femoral neck BMD (r = 0.35; P < 0.0001) and lumbar spine BMD (r = 0.34; P < 0.0001) in both men and women. In individuals aged 50 years and older, approximately 16% (n = 92/575) of women and 3.2% (n = 10/314) of men were diagnosed to have osteoporosis. Only 0.9% (n = 5/575) women and 1.0% (n = 3/314) men were classified as "Low BUA". The kappa coefficient of concordance between BMD and BUA classification was 0.09 (95% CI, 0.04 to 0.15) for women and 0.12 (95% CI, 0.03 to 0.22) for men.

Conclusions

In this population-based study, QUS BUA modestly correlated with DXA BMD, suggesting that BUA is not a reliable method for screening of osteoporosis.

Vertebral fracture assessment (VFA) for osteoporosis screening in US postmenopausal women: is it cost-effective?

Vertebral fracture assessment (VFA) is cost-effective when it was incorporated in the routine screening for osteoporosis in community-dwelling women aged ≥ 65 years, which support guidelines, such as the National Osteoporosis Foundation (NOF) for the diagnostic use of VFA as an important addition to fracture risk assessment.

INTRODUCTION

To evaluate the cost-effectiveness of VFA as a screening tool to reduce future fracture risk in US community-dwelling women aged ≥ 65 years.

METHODS

An individual-level state-transition cost-effectiveness model from a healthcare perspective was constructed using derived data from published literature. The time horizon was lifetime. Five screening strategies were compared, including no screening at all, central dual-energy X-ray absorptiometry (DXA) only, VFA only, central DXA followed by VFA if the femoral neck T-score (FN-T) ≤ - 1.5, or if the FN-T ≤ - 1.0. Various initiation ages and rescreening intervals were evaluated. Oral bisphosphonate treatment for 5-year periods was assumed. Incremental cost-effectiveness ratios (2017 US dollars per quality-adjusted life-year (QALY) gained) were used as the outcome measure.

RESULTS

The incorporation of VFA slightly increased life expectancy by 0.1 years and reduced the number of subsequent osteoporotic fractures by 3.7% and 7.7% compared with using DXA alone and no screening, respectively, leading to approximately 30 billion dollars saved. Regardless of initiation ages and rescreening intervals, central DXA followed by VFA if the FN-T ≤ - 1.0 was most cost-effective ($40,792 per QALY when the screening is initiated at age 65 years and with rescreening every 5 years). Results were robust to change in VF incidence and medication costs.

CONCLUSION

In women aged ≥ 65 years, VFA is cost-effective when it was incorporated in routine screening for osteoporosis. Our findings support the National Osteoporosis Foundation (NOF) guidelines for the diagnostic use of VFA as an important addition to fracture risk assessment.

Markers of Bone Health, Bone-Specific Physical Activities, Nutritional Intake, and Quality of Life of Professional Jockeys in Hong Kong

Weight-making practices, regularly engaged in by horse racing jockeys, have been suggested to impair both physiological and mental health. This study aimed to assess bone health markers, nutritional intake, bone-specific physical activity (PA) habits, and quality of life of professional jockeys in Hong Kong (n = 14), with gender-, age-, and body mass index-matched controls (n = 14). Anthropometric measurements, serum hormonal biomarkers, bone mineral density, bone-specific PA habits, nutritional intake, and quality of life were assessed in all participants. The jockey group displayed significantly lower bone mineral density at both calcanei than the control group (left: 0.50 ± 0.06 vs. 0.63 ± 0.07 g/cm²; right: 0.51 ± 0.07 vs. 0.64 ± 0.10 g/cm², both ps < .01). Thirteen of the 14 jockeys (93%) showed either osteopenia or osteoporosis in at least one of their calcanei. No significant difference in bone mineral density was detected for either forearm between the groups. The current bone-specific PA questionnaire score was lower in the jockey group than the control group (5.61 ± 1.82 vs. 8.27 ± 2.91, p < .05). Daily energy intake was lower in the jockeys than the controls (1,360 ± 515 vs. 1,985 ± 1,046 kcal/day, p < .01). No significant group difference was found for micronutrient intake assessed by the bone-specific food frequency questionnaire, blood hormonal markers, and quality of life scores. Our results revealed suboptimal bone conditions at calcanei and insufficient energy intake and bone-loading PAs among professional jockeys in Hong Kong compared with healthy age-, gender-, and body mass index-matched controls. Further research is warranted to examine the effect of improved bone-loading PAs and nutritional habits on the musculoskeletal health of professional jockeys.

Superoxide Dismutase 2 Polymorphisms and Osteoporosis in Asian Indians: A Genetic Association Analysis

Oxidative stress plays an important role in the development of osteoporosis. The present cross-sectional study focuses on mapping single nucleotide polymorphisms (SNPs) in the mitochondrial manganese superoxide dismutase (SOD2) gene in Asian Indians. The bone mineral density (BMD) of study subjects was assessed by dual x-ray absorptiometry. Individuals were classified as normal (n = 82) or osteoporotic (n = 98). Biochemical parameters such as vitamin D, total oxidant status (TOS) and SOD2 enzyme activity were estimated from plasma samples. Semi-quantitative PCR was carried out using GAPDH as an endogenous control. Genomic DNA was isolated from whole blood and SNPs were evaluated by PCR sequencing. Thirteen SNPs are reported in the examined region of the SOD2 gene, out of which in our samples SNPs rs5746094 and rs4880 were found to be polymorphic. Allele G of rs5746094 (intronic) and allele C of rs4880 (exonic) are significantly higher in the osteoporotic individuals. Presence of allele C of rs4880 and increased level of TOS among osteoporotic individuals were found to be associated with disease risk.

Cancer survivorship, a unique and growing cohort in medical practice: radiology perspective

The unique medical and psychologic burdens of cancer survivorship have only recently been recognized. This rapidly expanding cohort of patients will be seen increasingly by non-oncology physicians who must consider medical issues related to their cancer or its therapy for any presenting symptoms. Appropriate use of clinical imaging is essential for diagnosing treatment-related complications, recurrent tumor, or emergence of second primaries. This article will review clinical imaging in common medical problems uniquely found in cancer survivors.

Development of a parametric finite element model of the proximal femur using statistical shape and density modelling

Skeletal fractures associated with bone mass loss are a major clinical problem and economic burden, and lead to significant morbidity and mortality in the ageing population. Clinical image-based measures of bone mass show only moderate correlative strength with bone strength. However, engineering models derived from clinical image data predict bone strength with significantly greater accuracy. Currently, image-based finite element (FE) models are time consuming to construct and are non-parametric. The goal of this study was to develop a parametric proximal femur FE model based on a statistical shape and density model (SSDM) derived from clinical image data. A small number of independent SSDM parameters described the shape and bone density distribution of a set of cadaver femurs and captured the variability affecting proximal femur FE strength predictions. Finally, a three-dimensional FE model of an 'unknown' femur was reconstructed from the SSDM with an average spatial error of 0.016 mm and an average bone density error of 0.037 g/cm(3).

Site specificity of bone architecture between the distal radius and distal tibia in children and adolescents: An HR-pQCT study

High-resolution quantitative computerized tomography permits evaluation of site specific differences in bone architecture. The purpose of this study was to compare bone architecture between distal radius and distal tibia. We present bone architecture at the distal radius and distal tibia in 151 male and 172 female participants, as follows: total bone area (mm(2)), total bone density (mg HA/cm(3)), trabecular bone density (mg HA/cm(3)), cortical bone density (mg HA/cm(3)), cortical thickness (μm), trabecular number (1/mm), trabecular thickness (μm), and trabecular separation (μm). We evaluated differences in and correlations between bone variables (absolute values) across sites. We calculated individual z scores and used regression to assess discordance between sites. In pubertal and postpubertal male and female participants, absolute values of total bone area, cortical bone density, cortical thickness, and trabecular thickness were significantly lower at the radius compared with the tibia (P < 0.01). Absolute values for trabecular bone density were significantly lower at the radius compared with the tibia in postpubertal male and female participants (P < 0.01). Absolute values for trabecular separation was significantly lower at the radius compared with the tibia in pubertal female participants (P < 0.01). Bone architecture was moderately to highly correlated between sites (r = 0.34-0.85). There was discordance between z scores at the radius and tibia within male participants (pubertal R (2) between 36 and 64%; postpubertal R (2) between 22 and 77%) and female participants (pubertal R (2) between 10 and 44%; postpubertal R (2) between 25 and 62%). In conclusion, it is vital to evaluate bone architecture at the specific skeletal site of interest.

Assessment of clinical risk factors to validate the probability of osteoporosis and subsequent fractures in Korean women

This cross-sectional, observational study was designed to identify clinical risk factors of osteoporosis and fractures in Korean women to validate the probability of osteoporosis and subsequent fractures. A total of 1541 Korean women were recruited nationally. Fracture history of any site, risk factors of osteoporosis, and fall-related risk factors were surveyed and physical performance tests were conducted. Peripheral dual-energy X-ray absorptiometry was used to measure calcaneus bone mineral density (BMD). The number of positive responses on the modified 1-min osteoporosis risk test was related to the risk of osteoporosis. The frequency of osteoporosis was higher in those with a height reduction of >4 cm and a reduced body mass index (BMI). Multivariate analysis showed that older age and lower BMI were related to higher relative risk of osteoporosis. Time required to stand up from a chair and questions related to fall injury were significantly related to clinical fracture history of any site. Multivariate analysis showed that the relative risk of fractures at any site was higher in older subjects with a lower T-score and parental hip fracture history. This study shows that age and BMI are the most significant clinical risk factors for osteoporosis and that age, BMD, and parental history of hip fracture are highly applicable risk factors for validating the probability of osteoporotic fractures in Korean women.

Oxidative stress as a risk factor for osteoporosis in elderly Mexicans as characterized by antioxidant enzymes

Background

Oxidative stress (OxS) has recently been linked with osteoporosis; however, we do not know the influence of OxS as an independent risk factor for this disease.

Methods

We conducted a case-control study in 94 subjects ≥60 years of age, 50 healthy and 44 with osteoporosis. We measured total antioxidant status, plasma lipid peroxides, antioxidant activity of superoxide dismutase and glutathione peroxidase (GPx), and calculated the SOD/GPx ratio. Bone mineral density was obtained at the peripheral DXA in calcaneus using a portable Norland Apollo Densitometer^®. Osteoporosis was considered when subjects had a BMD of 2.5 standard deviations or more below the mean value for young adults.

Results

GPx antioxidant activity was significantly lower in the group of subjects with osteoporosis in comparison with the group of healthy subjects (p < 0.01); in addition, the SOD/GPx ratio was significantly higher in the group of individuals with osteoporosis (p < 0.05). In logistic regression analysis, we found OxS to be an independent risk factor for osteoporosis (odds ratio [OR] = 2.79; 95% confidence interval [95% CI] = 1.08–7.23; p = 0.034).

Conclusion

Our findings suggest that OxS is an independent risk factor for osteoporosis linked to increase of SOD/GPx ratio.

SULT1E1 genetic polymorphisms modified the association between phytoestrogen consumption and bone mineral density in healthy Korean women

Sulfotransferase 1E1 (SULT1E1) catalyze estrogen into sulfate conjugation and is involved in the metabolism of phytoestrogen. A community-based cross-sectional study was conducted on 397 Korean women, to evaluate the association between genetic polymorphisms of SULT1E1 and bone mineral density (BMD) and the combined effect of the genetic polymorphism and phytoestrogen intake for BMD in Korean women. BMDs of the distal radius and the calcaneus were measured by dual-energy X-ray absorptiometry. Genotypes of SULT1E1 IVS1-447 C>A, IVS4-1653 T>C, and *959 G>A were determined by the 5'-nuclease assay (TaqMan). Phytoestrogen intake was estimated by a food-frequency questionnaire validated against multiple 24-hour recalls. Women with the SULT1E1 *959 GG genotype had a 4.5% lower BMD at the distal radius (P (trend )= 0.05) and a 7.9% lower BMD at the calcaneus compared to those with AA genotype (P (trend) < 0.01), whereas the SULT1E1 IVS1-447 CC genotype and IVS4-1653 TT genotype were not associated with BMD. There was no significant trend of BMD with the numbers of CTG-containing haplotypes, but calcaneal BMDs significantly differed between SULT1E1 CTA-CTA haplotype and CTG-CCA haplotype (P < 0.05). When stratified by SULT1E1 genotype, the correlation between phytoestrogen consumption and BMD at the calcaneus was noteworthy in women with SULT1E1 *959 GG genotype (r = 0.25, P = 0.01) or SULT1E1 IVS 4-1653 TT genotype (r = 0.15, P = 0.02). This trend remained significant only in postmenopausal women (r = 0.36, P = 0.01) after multiple testing was corrected by the false discovery rate method. In conclusion, the genetic polymorphism of SULT1E1 *959 G > A was associated with BMD at the distal radius and calcaneus, and the association between phytoestrogen consumption and calcaneal BMD might be modified by this genetic polymorphism.

The effect of age and bone mineral density on the absolute, excess, and relative risk of fracture in postmenopausal women aged 50-99: results from the National Osteoporosis Risk Assessment (NORA)

INTRODUCTION

This study evaluates the effect of age and bone mineral density (BMD) on the absolute, excess, and relative risk for osteoporotic fractures at the hip, wrist, forearm, spine, and rib within 3 years of peripheral BMD testing in postmenopausal women over a wide range of postmenopausal ages.

METHODS

Data were obtained from 170,083 women, aged 50-99 years, enrolled in the National Osteoporosis Risk Assessment (NORA) following recruitment from their primary care physicians' offices across the United States. Risk factors for fracture and peripheral BMD T-scores at the heel, forearm, or finger were obtained at baseline. Self-reported new fractures at the hip, spine, rib, wrist, and forearm were obtained from questionnaires at 1- and 3-year follow-ups. Absolute, excess (attributable to low BMD), and unadjusted and adjusted relative risks of fracture were calculated.

RESULTS

At follow-up, 5312 women reported 5676 fractures (868 hip, 2420 wrist/forearm, 1531 rib, and 857 spine). Absolute risk of fracture increased with age for all fracture sites. This age-effect was most evident for hip fracture--both the incidence and the excess risk of hip fracture for women with low BMD increased at least twofold for each decade increase in age. The relative risk for any fracture per 1 SD decrease in BMD was similar across age groups (p>0.07). Women with low BMD (T-score <-1.0) had a similar relative risk for fracture regardless of age.

CONCLUSIONS

At any given BMD, not only the absolute fracture risk but also the excess fracture risk increased with advancing age. Relative risk of fracture for low bone mass was consistent across all age groups from 50 to 99 years.

Genetic polymorphisms of OPG, RANK, and ESR1 and bone mineral density in Korean postmenopausal women

To evaluate the effects of genetic polymorphisms of OPG, RANK, and ESR1, which regulate osteoclastogenesis, on bone mineral density (BMD), a cross-sectional study was conducted in 650 Korean postmenopausal women. BMDs of the distal radius and the calcaneus were measured by dual energy X-ray absorptiometry (DXA). Genetic polymorphisms of OPG 163 A > G, 1181 G > C; RANK 421 C > T, 575 T > C; and ESR1 1335 C > T, 2142 G > A were determined by matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) mass spectrometry. The differences between the BMDs of the genotypes of OPG, RANK, and ESR1 were analyzed by multiple linear regression model adjusted for age and body mass index. Women with the OPG 1181 CC genotype had higher BMDs at the distal radius (7%) and calcaneus (10%) than those with the GG genotype; and these differences were statistically significant (P = 0.001 and P = 0.007, respectively). A significant association was also observed between RANK 575 T > C and calcaneus BMD (P for trend = 0.017). No significant association was observed between BMDs and the polymorphisms of ESR1. The association between OPG 1181 G > C and BMD was profound in subjects with the RANK 575 TT or ESR1 2142 GG genotypes; women with OPG 1181 CC had higher BMDs at the distal radius (11%) and calcaneus (11%) than those with OPG 1181 GG only in women with RANK 575 TT genotype (P = 0.002 and P = 0.021, respectively). These results suggest that OPG genetic polymorphisms, especially with the RANK 575 TT or ESR1 2142 GG genotypes, are related to low BMD in postmenopausal Korean women.

Bone mineral density measurement in the calcaneus with DXL: comparison with hip and spine measurements in a cross-sectional study of an elderly female population

We investigated the relationship between calcaneal and axial bone mineral density in an elderly female population. We also investigated the influence of changing the reference populations on T-score values. Bone mineral density (BMD) was determined in 388 women (mean age 73 years) participating in a cross-sectional study. BMD values were determined at the left hip and the lumbar spine, L1-L4, using Hologic QDR 4500 equipment for dual X-ray absorptiometry (DXA). The calcaneal measurements were made with DEXA-T, a device using a dual X-ray and laser (DXL) technique that combines DXA measurement with measurement of the heel thickness using a laser reflection technique. DEXA-T is an older version of the Calscan DXL device now commercially available. T-score values were calculated for hip measurements with both the original reference population of the Hologic device and the NHANES III reference population. T scores for heel measurements were calculated with the original reference population of the peripheral device and the Calscan database, a new calcaneal reference population. Changing the reference populations had a great influence on both the heel and the hip T scores, especially those of the femoral neck where the percentage of subjects identified as osteoporotic decreased from 53% to 23%. We conclude that, with the NHANES III and the larger Calscan database, using the cut-off point of -2.5 SD, the heel measurements had optimal accuracy for detecting osteoporosis at either the combination of the lumbar spine and the femoral neck or the combination of the lumbar spine, the femoral neck, the total hip and the trochanter. BMD measurements of the calcaneus with DXL correlated fairly well with measurements at axial sites at the group level, while in individual subjects large deviations were observed between all the measured sites. We also conclude that the influence of the reference populations on the T scores is substantial when different DXA methods are being compared; the total number of subjects classified as osteoporotic varied from 7% to 53% between the sites and with different reference populations.

Influence of image-capturing parameters on digital X-ray radiogrammetry

The purpose of this study was to evaluate the importance of different image-capturing conditions, which might influence the characteristics of radiographs and, consequently, impact calculations of bone mineral density (BMD) and Metacarpal Index (MCI) using digital X-ray radiogrammetry (DXR). Radiographs of the left hand of deceased males were acquired three times using systematically varied parameters: 4-8 miliamp seconds (mA); 40-52 kV; film-focus distance (FFD); 90-130 cm; film sensitivity, 200/400; and different image modalities (conventional vs original digital radiographs as well as digital printouts). Furthermore, the interradiograph reproducibility using both conventional equipment and printouts vs originals of digital images and the intraradiograph reproducibility (either conventional or digital printouts) were evaluated. All BMD and MCI measurements were obtained with the DXR technology. The interradiograph reproducibility of DXR-BMD using conventional images under standardized conditions (6 mAs; 42 kV; 1 m FFD; film sensitivity of 200) was calculated to be coefficient of variation (CV) = 0.49% for Agfa Curix film and CV = 0.33% for Kodak T-MAT-Plus film, whereas reproducibility error using digital images ranged from CV = 0.57% (digital printouts; Philips) to CV = 1.50% (original digital images; Siemens). The intraradiograph reproducibility error was observed to be CV = 0.13% (conventional; Kodak film) vs CV = 0.27% (digital printouts; Philips). The BMD calculation was not noticeably affected by changes of FFD, exposure level, or film sensitivity/film brand, but was influenced by tube voltage (CV = 0.99% for Kodak film to CV = 2.05% for Siemens digital printouts). No significant differences were observed between the BMD and MCI data. DXR provides measurements of MCI and BMD with high precision and reproducibility. The measurements are unaffected by all tested image-capturing conditions, with the exception of tube voltage. In addition, different digital image devices clearly have an effect on DXR reproducibility.

Predictive value of low BMD for 1-year fracture outcomes is similar for postmenopausal women ages 50-64 and 65 and Older: results from the National Osteoporosis Risk Assessment (NORA)

The relationship of low bone mass and fracture in younger postmenopausal women has not been extensively studied. In a large cohort of postmenopausal women > or =50 years of age, we found the relationship of BMD measured at peripheral sites and subsequent 1-year fracture risk to be similar between women <65 and those > or =65 years of age.

INTRODUCTION

Low bone mass and fractures are prevalent in older postmenopausal women. However, the frequency of low bone mass and fracture in younger postmenopausal women has not been studied extensively. There are very limited data regarding the association between BMD measurements and fractures in postmenopausal women who are between the ages of 50 and 64.

MATERIALS AND METHODS

In the National Osteoporosis Risk Assessment (NORA) we studied the frequency of low bone mass and its association with fracture in women 50-64 years of age in comparison with women > or =65 of age. NORA enrolled 200,160 postmenopausal women > or =50 years of age who had no prior diagnosis of osteoporosis. Baseline BMD was measured at the heel, forearm, or finger. A 1-year follow-up survey requesting incident fractures since baseline was completed by 163,935 women, 87,594 (53%) of whom were 50-64 years of age. The association between BMD and fracture was assessed using logistic regression, adjusted for important covariates.

RESULTS

Thirty-one percent of women 50-64 years of age had low bone mass (T scores < or = -1.0) compared to 62% of women > or =65 years of age. During the first year of follow-up, 2440 women reported fractures of wrist/forearm, rib, spine, or hip, including 440 hip fractures. Nine hundred four women 50-64 years of age reported fractures, including 86 hip fractures, accounting for 37% of fractures and 20% of hip fractures reported in the entire NORA cohort. Relative risk for osteoporotic fracture was 1.5 for each SD decrease in BMD for both the younger and older groups of women.

CONCLUSION

Low BMD in younger postmenopausal women 50-64 years of age showed a 1-year relative risk of fracture similar to that found in women > or =65 years of age.

Osteoporosis imaging

Because osteoporotic fractures may be prevented, diagnostic techniques are essential in the assessment of osteoporosis. Conventional radiographs of the spine are not suited for diagnosing early osteoporosis, but they show fractures that may have no clinical symptoms. The radiologist should be aware of the enormous significance of these fractures for future osteoporotic fractures. Bone mass measurements are standard techniques in the diagnosis of osteoporosis, which are the basis of the WHO definition of osteoporosis. In this article the authors presented these standard techniques and newer diagnostic techniques that provide insights in the structure of trabecular bone.

Bone mass measurements

The clinical application of bone densitometry is one of the advances in the field of osteoporosis that has led to the increased patient awareness of this increasingly prevalent disease. Bone densitometry has made it possible for clinicians to diagnose osteoporosis before the first fracture has occurred; predict risk for fracture in postmenopausal women, men, and in patients who are receiving glucocorticoids; and can be used as a surrogate marker to follow the efficacy of therapies and to examine those patients that might be osteoporosis-specific therapeutic nonresponders.