Application of high-resolution skeletal imaging to measurements of volumetric BMD and skeletal microarchitecture in Chinese-American and white women: explanation of a paradox

Low bone mineral density and its influencing factors in spinal muscular atrophy without disease-modifying treatment: a single-centre cross-sectional study

BACKGROUND

Children with spinal muscular atrophy (SMA) are at risk of low bone mineral density (BMD) and bone fragility. This study aims to assess lumbar spine BMD measured by quantitative computed tomography (QCT) and investigate influencing factors of low BMD in children with SMA without disease-modifying treatment.

METHODS

Demographic data, laboratory parameters, QCT data, and data on spinal radiographs were collected. A linear regression model was carried out to explore the correlations between BMD and its related factors.

RESULTS

Sixty-six patients with SMA who had complete records between July 2017 and July 2023 were analyzed, with SMA with a mean age of 5.4 years (range, 2.4-9.7 years), including type 1 in 14, type 2 in 37, and type 3 in 15. 28.8% of patients (19/66) were diagnosed with low BMD (Z-scores ≤ - 2), and the mean BMD Z-scores on QCT was - 1.5 ± 1.0. In our model, BMD Z-scores was associated with age (β=-0.153, p = 0.001). SMA phenotype and serum bone metabolism markers, such as serum phosphorus (P), alkaline phosphatase (ALP) and 25-Hydroxyvitamin D (25-OH-D) levels did not independently predict low BMD. ROC analysis showed that the age ≥ 6.3 years predicts a Z-scores ≤ -2.0 with a sensitivity of 68.4% and a specificity of 68.1%.

CONCLUSIONS

Low BMD were highly prevalent in children with SMA without disease-modifying treatment in our centre. Regular monitoring of BMD is necessary for all types of SMA children, especially those aged ≥ 6.3 years.

Racial/Ethnic Differences in Bone Mineral Density for Osteoporosis

PURPOSE OF REVIEW

We primarily aim to review differences in bone mineral density (BMD) for osteoporosis among different racial/ethnic groups and to highlight the magnitude of racial/ethnic differences in obesity and diabetes. We also explore the factors contributing to the BMD differences among various subgroups. In addition, we investigate the existing disparities in research, educational initiatives, screening practices, and treatment options for osteoporosis and discuss these findings' clinical and public health implications.

RECENT FINDINGS

Racial/ethnic differences in BMD for osteoporosis exist in the USA and other countries. There are disparities regarding osteoporosis screening and treatment. Understanding the factors contributing to these differences can help develop targeted interventions and policies to reduce their impact. Clinicians should consider the racial/ethnic differences in BMD when making treatment decisions and providing preventive care. Future research could contribute to developing effective strategies for preventing osteoporosis among different racial/ethnic groups. This review offered a comprehensive examination of differences in BMD across various racial and ethnic groups, elucidating the influence of genetic, lifestyle, and cultural factors on these differences. This review also highlighted the disparities in osteoporosis screening, treatment options, research on medical effectiveness, and educational outreach tailored to each subgroup. Recognizing the importance of addressing these inequalities, we present this review to advocate for targeted interventions to reduce disparities in osteoporosis and improve bone health for all populations.

Osteoporosis and Fracture Risk among Older US Asian Adults

PURPOSE OF REVIEW

This review summarizes the current knowledge regarding osteoporosis and fracture among older US Asian adults.

RECENT FINDINGS

Asian adults have lower (areal) bone density than non-Hispanic White adults and thus are more likely to be diagnosed and treated for osteoporosis, despite their lower risk of hip fracture. The latter may relate to favorable characteristics in hip geometry, volumetric bone density, and bone microarchitecture; lower risk of falls; and other clinical factors. The fracture risk calculator FRAX accounts for the lower risk of hip fracture among US Asian adults. However, data on major osteoporotic fracture risk remain limited. Fracture rates also vary by Asian subgroup, which may have implications for fracture risk assessment. Furthermore, among women receiving bisphosphonate drugs, Asian race is a risk factor for atypical femur fracture, an uncommon complication associated with treatment duration. Recent clinical trial efficacy data pertaining to lower bisphosphonate doses and longer dosing intervals may be relevant for Asian adults. More research is needed to inform osteoporosis care of US Asian adults, including risk-benefit considerations and the optimal duration of bisphosphonate treatment. Greater evidence-based guidance for primary fracture prevention among US Asian adults will ensure health equity in the prevention of osteoporotic fractures.

Ethnic determinants of skeletal health in female patients with fragility fracture in a culturally diverse population

Background

Low bone density leads to fragility fracture, with significant impact on morbidity and mortality. While ethnic differences in bone density have been observed in healthy subjects, this has not yet been explored in fragility fracture patients.

Aims

To assess if ethnicity is associated with bone mineral density and serum markers of bone health in female patients who experience fragility fractures.

Methods

219 female patients presenting with at least one fragility fracture at a major tertiary hospital in Western Sydney Australia were studied. Western Sydney is a region with great cultural diversity, comprising people from over 170 ethnicities. Within this cohort, the three largest broad ethnic groups were Caucasians (62.1 %), Asians (22.8 %), and Middle Eastern patients (15.1 %). Location and nature of the presenting fracture and other relevant past medical history were obtained. Bone mineral density, measured by dual-energy X-ray absorptiometry, and bone-related serum markers were compared between ethnicities. Covariates (age, height, weight, diabetes, smoking, and at-risk drinking) were adjusted in multiple linear regression model.

Results

Although Asian ethnicity was associated with lower bone mineral density at the lumbar spine in fragility fracture patients, this association was no longer significant after adjustment for weight. Ethnicity (Asian or Middle Eastern) was not a determinant of bone mineral density at any other skeletal site. Caucasians had lower estimated glomerular filtration rate compared to Asian and Middle Eastern subjects. Serum parathyroid hormone concentrations were significantly lower in Asians compared to other ethnicities.

Conclusion

Asian ethnicity and Middle Eastern ethnicity were not major determinants of bone mineral density at the lumbar spine, femoral neck, or total hip.

Skeletal Microstructure in Caribbean Hispanic Women

Hispanic individuals are underrepresented in skeletal research. Bone mineral density (BMD) and fracture data are conflicting. We investigated skeletal health in elderly Caribbean Hispanic (HW), non-Hispanic white (NHW), and non-Hispanic black (NHB) women in a population-based study in New York City. We utilized high-resolution peripheral quantitative CT (HRpQCT), dual-energy X-ray absorptiometry (DXA), and finite element analysis (FEA). Of 442, 48.4% were HW, 21.3% NHW, and 30.3% NHB. Adjusted analyses are shown. Compared to NHW, HW had 8.5% (p < 0.01) lower spine areal BMD (aBMD) and 5.1% lower trabecular bone score (TBS). The frequency of morphometric vertebral fractures did not differ between HW and NHW. By HRpQCT, HW had 2.9% higher cortical (Ct) volumetric BMD (vBMD), 7.9% greater Ct area (Ct.Ar) and 9.4% greater Ct thickness (Ct.Th) at the radius compared to NHW. Results were similar at the tibia but trabecular microstructure tended to be worse. Ultimately, failure load (FL) did not differ between HW and NHW at either site. aBMD was 3.8% to 11.1% lower at the spine, femoral neck, and radius in HW compared to NHB (all p < 0.001) and vertebral fractures were twice as common. Compared to NHB, HW had 7.7% to 10.3% lower Ct.Ar at both the radius and tibia as well as 8.4% lower total vBMD, 6.3% lower trabecular number, and 10.3% lower Ct.Th at the tibia associated with 18.2% and 12.5% lower FL at both sites, respectively. In conclusion, HW had lower spine aBMD and TBS versus NHW women, whereas microstructural differences at the radius and tibia were small and not associated with differences in FL. In contrast, HW had lower aBMD, as well as deteriorated radial and tibial microstructure associated with worse FL compared to NHB women. Our results provide insight into racial/ethnic differences in skeletal health, adding to data that may be used to improve osteoporosis screening and treatment in HW. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Bone microstructure in proton pump inhibitor users

OBJECTIVES

We assessed skeletal microstructure and stiffness in proton pump inhibitor (PPI) users compared to non-users with high resolution peripheral quantitative computed tomography (HRpQCT) and microfinite element analysis (μFEA) and other modalities. Relationships between PPI dose/frequency and bone parameters were evaluated.

METHODS

We cross-sectionally assessed skeletal health in 601 older (≥age 65 years) adults (130 PPI users and 471 non-users) participating in a multi-ethnic population-based study of aging.

RESULTS

PPI users tended to have more comorbidities and take more medications than non-users. Female PPI users (n = 100) were more likely to be non-Caucasian, shorter with higher BMI, and more likely to have diabetes, lower physical activity and be using anti-depressants and thiazide diuretics compared to non-users (n = 302). Male PPI users (n = 30) were more likely to have liver disease than non-users (n = 169). In women, historical fractures (53.0 % vs. 43.4 %, p = 0.05) and falls (38 % vs. 26.8 %, p = 0.04) tended to be more frequent in PPI users compared to non-users. Number of falls was higher in women reporting daily rather than intermittent PPI use (1.8/year vs. 1.0/year, p < 0.001). In women, there were no differences in any HRpQCT or μFEA parameter. By HRpQCT, covariate-adjusted cortical volumetric bone density (Ct.vBMD) was 4.2 % lower in male PPI users vs. non-users at the tibia (p = 0.04), but this did not result in reduced stiffness. There were no other differences by HRpQCT at the tibia or radius.

CONCLUSIONS

PPI use was not associated with altered skeletal microstructure or stiffness in elderly men and women. The results do not support a relationship between PPI use and microstructure.

Spine trabecular bone scores and bone mineral density of postmenopausal Taiwanese women

OBJECTIVES

The aims of the study were to determine the mean trabecular bone score (TBS) of postmenopausal Taiwanese women and to analyze the value of TBS in predicting osteoporosis.

METHODS

A total of 1,915 postmenopausal women with lumbar spine and hip bone mineral density (BMD) and spine TBS were enrolled from a single medical center into this study. The women's BMD and TBS were measured using dual x-ray absorptiometry (Discovery Wi; Hologic, Bedford, Mass) and iNsight software (Med-Imaps SASU, Merignac, France), respectively. The women's demographic characteristics; lumbar spine, total hip, and femoral neck BMD; and lumbar spine TBS were recorded, and correlations among the parameters were identified using a 2-tailed Pearson test, in which a P value less than 0.05 was considered statistically significant. We developed simple linear regression models to represent changes related to TBS and performed an analysis of variance on the selected variables.

RESULTS

The average age of the women was 62.5 ± 9.1 years (range, 25.7-93.7 years). The mean TBS was 1.300 ± 0.086 (range, 1.015-1.596). The TBS was weakly and negatively correlated with body mass index ( r = -0.078) and moderately and positively correlated with the lumbar spine BMD ( r = 0.619). The patients' lowest BMD values among those measured at multiple sites revealed a higher rate of osteoporosis (32.5%) than those measured at individual sites. Degraded TBS were noted in 21.2% of the participants, and a combination of BMD and TBS results predicted more individuals (7.8%) at a high risk of fracture than did the BMD result only. The rates of both osteoporosis and degraded TBS increased with age.

CONCLUSIONS

Bone mineral density and TBS can be used in combination to predict osteoporosis in a greater number of postmenopausal Taiwanese women. Because the incidence of osteoporosis is the highest among older women, clinicians should pay careful attention to TBS degradation among older patients without low BMD.

Thiazide use and skeletal microstructure: Results from a multi-ethnic study

Background

Thiazide diuretics, a commonly used class of anti-hypertensives, have been associated with increased areal bone mineral density (aBMD). Data regarding effects on fracture are conflicting and no information is available regarding effects on skeletal microstructure and mechanical competence.

Methods

We compared skeletal microstructure, volumetric BMD (vBMD), stiffness and prevalent fractures in current thiazide diuretic users and non-users from a population-based multiethnic cohort of elderly adults age ≥ 65 years (N = 599) with high resolution peripheral quantitative computed tomography (HR-pQCT) and micro-finite element analysis.

Results

Female current thiazide diuretic users had higher weight and BMI and were more likely to be non-Caucasian compared to non-users. There were no differences in age, historical fractures or falls between female users and non-users. Female thiazide users tended to have lower calcium and vitamin d intake compared to non-users. After adjusting for age, weight, race and other covariates, 1/3-radius mean aBMD by dual energy x-ray absorptiometry (DXA) was 3.2% (p = 0.03) higher in female users vs. non-users. By HRpQCT, adjusted mean cortical vBMD was 2.4% (p = 0.03) higher at the radius in female users vs. non-users, but there was no difference in stiffness. DXA results were similar in the subset of Black females. There was no difference in any adjusted aBMD or cortical skeletal parameters by DXA or HRpQCT respectively in males.

Conclusions

Thiazide use was associated with a modestly higher aBMD at the predominantly cortical 1/3-radius site and radial cortical vBMD by HRpQCT in females. The effect on cortical bone may offer skeletal benefits in women taking thiazides for other indications such as hypertension, hypercalciuria or recurrent nephrolithiasis.

Effect of Race/ethnicity, Insurance Status, and Area Deprivation on Hip Fracture Outcomes Among Older Adults in the United States

This retrospective cohort study used electronic health records to explore the effect of race/ethnicity, insurance status, and area deprivation on post-discharge outcomes in older patients undergoing hip fracture surgery between 2015 and 2018 (N = 1,150). Inverse probability of treatment weight-adjusted regression analysis was used to identify the effects of the predictors on outcomes. White patients had higher 90- and 365-day readmission risks than Black patients and higher all-period readmissions than the Other racial/ethnic (Hispanic, Asian, American Indian, and Multicultural) group (p < .000). Black patients had a higher risk of 30- and 90-day readmission than the Other racial/ethnic group (p < .000). Readmission risk across 1-year follow-up was generally higher among patients from less deprived areas than more deprived areas (p < .05). The 90- and 365-day mortality risk was lower for patients from less deprived areas (vs. more deprived areas) and patients with Medicare Advantage (vs. Medicare), respectively (p < .05). Our findings can guide efforts to identify patients for additional post-discharge support. Nevertheless, the findings regarding readmission risks contrast with previous knowledge and thus require more validation studies.

SURPRISINGLY FEW WOMEN WITH SEVERE OSTEOPOROSIS BY BONE DENSITOMETRY UNDERGO WORKUP FOR SECONDARY CAUSES - A RETROSPECTIVE EVALUATION

We describe clinical features of women with extremely low bone density, and investigate secondary causes of osteoporosis. Our hypothesis was that this population would be enriched in identifiable causes of osteoporosis. We performed a retrospective review of medical records of all women seen at our university over 4 years with T-score on bone densitometry at/below -4 at any site. Historical and fracture details were abstracted. We considered a thorough work up to include Vitamin D, PTH, CBC, chemistry panel, cortisol, transglutaminase, myeloma screen, tryptase and 24-hour urine calcium.

RESULTS

137 women were identified with T-score at/below -4. Percent identified as Asian was 26% (higher than local prevalence of 8%). Average BMI was 21.6 kg/m². Clearly identifiable causes of osteoporosis were noted in 57% (inflammatory disorder, glucocorticoid or antacid exposure, prolonged immobilization and alcoholism were most prevalent). Of the remainder, full work up was performed only in 8%. Endocrine consultation and white race predicted thoroughness of secondary work-up.

CONCLUSION

Fragility fractures, leanness and Asian race were common in women with very low T-score. However, few new causes were identified. Underlying etiology was either immediately evident or inadequately studied, especially in minorities.

Smoking Is Associated with Sex-Specific Effects on Bone Microstructure in Older Men and Women

BACKGROUND

Smoking is a risk factor for fracture, but the mechanism by which smoking increases fracture risk is unclear.

METHODS

Musculoskeletal health was compared with dual energy X-ray absorptiometry (DXA), high resolution peripheral quantitative computed tomography (HR-pQCT), trabecular bone score, and vertebral fracture assessment in current and past smokers and nonsmokers from a multiethnic study of adults ≥ age 65. Skeletal indices were adjusted for age and weight.

RESULTS

Participants (n = 311) were mean age (±SD) 76.1 ± 6.5 years, mostly female (66.0%) and non-white (32.7% black/39.4% mixed race/26.3% white). Mean pack-years was 34.6 ± 20.4. In men (n = 106), weight and BMI were lower (both p < 0.05) in current vs past smokers. Male smokers consumed half the calcium of never and past smokers. BMD by DXA did not differ by smoking status at any skeletal site in either sex. Current male smokers had 13.5%-15.3% lower trabecular bone score vs never and past smokers (both p < 0.05). By HR-pQCT, trabecular volumetric BMD was 26.6%-30.3% lower and trabeculae were fewer, thinner and more widely spaced in male current vs past and never smokers at the radius (all p < 0.05). Cortical indices did not differ. Tibial results were similar, but stiffness was also 17.5%-22.2% lower in male current vs past and never smokers (both p< 0.05). In women, HR-pQCT trabecular indices did not differ, but cortical porosity was almost twice as high in current vs never smokers at the radius and 50% higher at the tibia (both p < 0.05).

CONCLUSIONS

In summary, current smoking is associated with trabecular deterioration at the spine and peripheral skeleton in men, while women have cortical deficits. Smoking may have sex-specific skeletal effects. The consistent association with current, but not past smoking, suggests the effects of tobacco use may be reversible with smoking cessation.

Race/ethnic difference in trabecular bone score in midlife women: The Study of Women's Health Across the Nation (SWAN)

There was no difference in Trabecular Bone Score (TBS) comparing White and Black women after adjusting for body mass index (BMI) and diabetes status. Japanese women had lower TBS than White women. Our results diverge from established differences in fracture rates by race/ethnicity.

INTRODUCTION

The TBS was developed as an indirect measure of vertebral bone microarchitecture derived from texture analysis of lumbar spine DXA scans. There is little information on race/ethnic differences in TBS.

METHODS

We compared TBS in 656 White, 492 Black, and 268 Japanese pre- and early perimenopausal women. We used a beta version of TBS that accounts for tissue thickness using DXA measured soft tissue thickness rather than BMI. The relation between BMI and tissue thickness corrected TBS differed by BMI; we used a three-segment linear spline to adjust for BMI.

RESULTS

The women were, on average, 46.5 years of age; 50% were premenopausal. In BMI and diabetes adjusted models, there was no difference in TBS between White and Black women. TBS was modestly (2%) lower in the Japanese women compared to White women, p = 0.04. In a sensitivity analysis, restricting the analysis to those with BMI 24-31 kg/m², results were similar.

CONCLUSIONS

TBS was similar in Black and White women after accounting for tissue thickness and adjusting for BMI, diabetes, and other covariates. The Japanese women had modestly lower TBS. These results diverge from established race/ethnic differences in fracture rates and areal bone mineral density, underscoring the need for further studies.

Ethnic Differences in Bone Microarchitecture

PURPOSE OF THE REVIEW

The aim of this review is to briefly introduce updates in global fracture epidemiology and then to highlight recent contributions to understanding ethnic differences in bone density, geometry and microarchitecture and consider how these might contribute to differences in fracture risk. The review focuses on studies using peripheral quantitative computed tomography techniques.

RECENT FINDINGS

Recent studies have contributed to our understanding of the differences in fracture incidence both between countries, as well as between ethnic groups living within the same country. In terms of understanding the reasons for ethnic differences in fracture incidence, advanced imaging techniques continue to increase our understanding, though there remain relatively few studies. It is a priority to continue to understand the epidemiology, and changes in the patterns of, fracture, as well as the underlying phenotypic and biological reasons for the ethnic differences which are observed.

Current anti-depressant use is associated with cortical bone deficits and reduced physical function in elderly women

BACKGROUND

Anti-depressants, particularly selective serotonin reuptake inhibitors (SSRIs), are associated with an increased risk of fracture. The mechanism is unclear and may be due to effects on bone metabolism, muscle strength, falls or other factors. It is unknown if serotonin norepinephrine reuptake inhibitors (SNRIs) have similar effects.

METHODS

We compared musculoskeletal health in current female anti-depressant users and non-users from a population-based multiethnic (35.6% black, 22.3% white and 42.1% mixed) cohort study of adults ≥65 years old in New York (N = 195) using dual x-ray absorptiometry (DXA), trabecular bone score (TBS), vertebral fracture assessment (VFA), high resolution peripheral quantitative computed tomography (HR-pQCT), body composition, and grip strength.

RESULTS

Current anti-depressant users were more likely to be white than non-white (OR 1.9, 95% CI 1.2-2.9) and were shorter than non-users, but there were no differences in age, weight, BMI, physical activity, calcium/vitamin D intake, falls or self-rated health. There were more pelvic fractures in current vs. non-users (7.1% vs. 0%, p = 0.04). Age- and weight-adjusted T-score by DXA was lower in current users at the 1/3-radius (-1.6 ± 1.1 vs. -1.0 ± 1.4, p = 0.04) site only. There was no difference in TBS, vertebral fractures or fat/lean mass by DXA. Age- and weight-adjusted grip strength was 13.3% lower in current users vs. non-users (p = 0.04). By HR-pQCT, age- and weight-adjusted cortical volumetric BMD (Ct. vBMD) was 4.8% lower in users vs. non-users at the 4% radius site (p = 0.007). A similar cortical pattern was seen at the proximal (30%) tibia. When assessed by anti-depressant class, deteriorated cortical microstructure was present only in SSRI users at the radius and only in SNRI users at the proximal tibia.

CONCLUSIONS

Anti-depressant use is associated with cortical deterioration and reduced physical function, but effects may be class-specific. These findings provide insight into the mechanism by which anti-depressants may contribute to the increased fracture risk in older women.

Bone Mineral Density in Older U.S. Filipino, Chinese, Japanese, and White Women

BACKGROUND/OBJECTIVES

Bone mineral density (BMD) reference data exist for U.S. White, Black, and Hispanic (Mexican American) populations but not for U.S. Asians. Few studies have compared BMD findings among different U.S. Asian ethnicities.

DESIGN

Retrospective observational study.

SETTING

Large northern California healthcare system.

PARTICIPANTS

Asian and White women aged 50 to 79 years with BMD testing from 1998 to 2017 excluding those with estrogen or osteoporosis treatment, recent fracture, or select disorders affecting skeletal health.

MEASUREMENTS

Femoral neck (FN)-BMD and height data.

METHODS

Differences in FN-BMD were examined by ethnicity and age, comparing Filipino, Chinese, and Japanese women and non-Hispanic White women. Differences in BMD were also examined after adjustment for height.

RESULTS

There were 37,224 Asian women (including 11,147 Filipino, 10,648 Chinese, and 2,519 Japanese) and 115,318 non-Hispanic White women. Mean height was similar among the Asian subgroups and about 6 to 8 cm lower than Whites. Mean FN-BMDs differed by less than 3% for Filipino, Chinese, and Japanese and all were lower than Whites, with smaller Asian-White differences among younger women (<3%; ages 50-59) and larger differences among older women (6-8%; ages 65-79). Adjusting FN-BMD for height reduced White-Asian differences by about 30% to 40%.

CONCLUSION

Mean FN-BMD and height for Filipino, Chinese, and Japanese women were similar but consistently lower than White women, especially among older women. Although Asian-White BMD differences were substantially attenuated after height adjustment; some differences persisted for older women. Future studies should investigate potential age-cohort effects and the extent to which these BMD differences influence fracture risk and clinical care.

Trabecular bone score: a useful clinical tool for the evaluation of skeletal health in women of short stature

PURPOSE

Areal bone mineral density (aBMD) by DXA is underestimated in those with smaller bones and overestimated in those with larger bones. Trabecular bone score (TBS) predicts fracture risk, and is not influenced by bone size. The aim of this study was to evaluate TBS and BMD in women with short stature.

METHODS

We retrospectively analyzed DXA scans of all women aged 50-90 years with short stature (<144 cm) obtained in a single center, from 2006 to 2016. The comparison group comprised women >161 cm in height, matched for age and LS BMD, selected from the same database.

RESULTS

The study population included 342 women. The two groups were similar in age, and aBMD at the LS and total hip. Femoral neck aBMD was lower in cases than in taller women. In contrast, TBS was higher in women with short stature than in their taller counterparts (1.347 ± 0.102 vs. 1.250 ± 0.110; p < 0.001). Bone mineral apparent density (BMAD) and the LS TBS-adjusted BMD T-score were also significantly higher in shorter than in taller women. From the entire cohort, 121 women (67 cases) were osteoporotic by aBMD determinations. Among these subjects, TBS was also greater in cases (1.303 ± 0.103) than in women with standard height (1.190 ± 0.099; p < 0.001). Despite being considered osteoporotic, 36% of short women, but none of the taller ones, had a normal TBS.

CONCLUSIONS

TBS can be a useful adjunct to aBMD for assessing bone quality in short women, in whom aBMD measurement tends to read lower, and, thus could overestimate fracture risk.

Regional Variations of HR-pQCT Morphological and Biomechanical Measurements of the Distal Radius and Tibia and Their Associations with Whole Bone Mechanical Properties

High-resolution peripheral quantitative computed tomography (HRpQCT) is a promising imaging modality that provides in vivo three-dimensional assessment of bone microstructure by scanning fixed regions of the distal radius and tibia. However, how microstructural parameters and mechanical analysis based on these segment scans correlate to whole distal radius and tibia mechanics is not well-characterized. On 26 sets of cadaveric radius and tibia, HRpQCT scans were performed on the standard scan segment, a segment distal to the standard segment, and a segment proximal to the standard segment. Whole distal bone stiffness was determined through mechanical testing. Segment bone stiffness was estimated using linear finite element (FE) analysis based on segment scans. Standard morphological and Individual Trabecula Segmentation (ITS) analyses were used estimate microstructural properties. Significant variations in microstructural parameters were observed among segments at both sites. Correlation to whole distal bone stiffness was moderate for microstructural parameters at the standard segment, but correlation was significantly increased for FE-predicted segment bone stiffness based on standard segment scans. Similar correlation strengths were found between FE-predicted segment bone stiffness and whole distal bone stiffness. Additionally, microstructural parameters at the distal segment had higher correlation to whole distal bone stiffness than at standard or proximal segments. Our results suggest that FE-predicted segment stiffness is a better predictor of whole distal bone stiffness for clinical HRpQCT analysis, and that microstructural parameters at the distal segment is more highly correlated with whole distal bone stiffness than at the standard or proximal segments.

Hemiarthroplasty or Total Hip Arthroplasty: Is There a Racial Bias in Treatment Selection for Femoral Neck Fractures?

Introduction

Hip fractures in the elderly individuals are associated with significant morbidity and mortality, and outcomes are directly related to prompt surgical intervention with either total hip arthroplasty (THA) or hemiarthroplasty. Minority hip fracture patients have increased delays to surgical intervention and poorer functional outcomes. This study explored racial biases in the surgical treatment decision between THA and hemiarthroplasty for displaced femoral neck fractures as well as racial disparities in postoperative complications, readmission rates, and 30-day mortality.

Methods

We retrospectively reviewed the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) from 2006 to 2014. Patients were identified using diagnosis code for transcervical femoral neck fractures and Current Procedural Terminology codes for THA or hemiarthroplasty. A multivariable regression analysis was conducted including race, demographic information, and medical comorbidities.

Results

Of 11 408 patients, race was recorded in 8538 individuals. Most patients were white (88.3%), followed by Hispanic (4.7%), African American (4.1%), and Asian/Native Hawaiian/Pacific Islander/American Indian/Alaska Native (2.9%). No differences were observed in the likelihood of receiving a THA versus hemiarthroplasty among racial groups. Only younger age and steroid use were independent risk factors for receiving a THA. Race was significantly associated with postoperative mortality (P = .014) and major postoperative complications for the Asian cohort (P = .013).

Discussion

The NSQIP data do not support a racial bias in the selection of patients for THA versus hemiarthroplasty. However, this study found racial disparities in postoperative mortality and complications. The reasons underlying the differences in postoperative outcomes are uncertain but may be the result of specific challenges to accessing care.

Conclusion

There was no racial bias in the treatment of femoral neck fractures. However, there were racial disparities in postoperative mortality and complication rates. Further research is warranted to elucidate the true causes of these observed disparities.

Age-specific 1-year mortality rates after hip fracture based on the populations in mainland China between the years 2000 and 2018: a systematic analysis

We used statistical approaches to calculate 1-year mortality rates and reveal the relationship between age and the 1-year mortality rate after hip fracture based on data from mainland China between the years 2000 and 2018.

INTRODUCTION

Data on the 1-year mortality rates after hip fracture in mainland China remain limited and localized. We aimed to analyze the 1-year mortality rates and reveal the variations in 1-year mortality by age after hip fracture based on data from mainland China.

METHODS

We searched PubMed, EMBASE, Cochrane Library, CNKI, Wanfang, and CBM-SinoMed for all relevant articles in English or Chinese to estimate the 1-year mortality rates after hip fracture in mainland China. A random-effects meta-analysis model was fitted to pool the overall 1-year mortality rates. A multilevel mixed-effects meta-regression model was developed. Based on the final model, the age-specific 1-year mortality rates after hip fracture in mainland China were generated.

RESULTS

The pooled estimate of the 1-year mortality rate was 13.96% after hip fracture (95% CI 12.26 to 15.86%), 17.47% after femoral intertrochanteric fracture (95% CI 14.29 to 21.20%), and 9.83% after femoral neck fracture (95% CI 6.96 to 13.72%) between the years 2000 and 2018. We found that the 1-year mortality rates ranged from 2.65% (95% CI 1.76 to 3.99%) in those aged 50~54 years to 28.91% (95% CI 24.23 to 34.30%) in those aged 95~99 years after hip fracture; ranged from 1.73% (95% CI 0.58 to 4.99%) in those aged 50~54 years to 50.11% (95% CI 46.03% to 53.97%) in those aged 95~99 years after femoral intertrochanteric fracture; and ranged from 1.66% (95% CI 1.31 to 2.11%) in those aged 60~64 years to 37.71% (95% CI 27.92 to 48.63%) in those aged 95~99 years after femoral neck fracture.

CONCLUSION

In this systematic review and meta-analysis, we calculated the 1-year mortality rate after hip fracture in mainland China and found that this rate was lower than that in most countries. We also estimated the age-specific mortality rates for different age groups after hip fracture. These findings will be beneficial for the prevention and treatment of hip fracture in mainland China.

Chinese Women in Both the United States and Hong Kong Have Cortical Microstructural Advantages and More Trabecular Plates Compared With White Women

We cross-sectionally compared racial differences in bone quality between Chinese women in the United States (US) and Hong Kong (HK) with white women. A total of 514 women were included. We measured bone geometry, mass, microstructure, and stiffness by high-resolution peripheral quantitative computed tomography (HR-pQCT), individual trabecula segmentation (ITS), and microfinite element analysis (μFEA). After adjustment for age and body mass index (BMI), premenopausal Chinese women in the US and HK had smaller bone area but greater radial cortical (Ct.) thickness and Ct. and trabecular (Tb.) volumetric bone mineral density (vBMD) versus white women but did not differ from each other. At the radius, Tb. number was lower and spacing greater in Chinese women from HK and the US versus white women, whereas Chinese women did not differ from each other. Tb. thickness was highest in Chinese women from HK, intermediate in Chinese-Americans, and lowest in white women. Chinese women had more trabecular plates versus white women, leading to greater age- and BMI-adjusted stiffness for premenopausal Chinese women in HK and the US (both p < 0.05) versus white women. Tibial differences were similar in premenopausal women; analogous trends in microstructure were present in postmenopausal women at the tibia, although stiffness did not differ. In contrast, at the radius, cortical, plate-to-rod ratio, and stiffness were similar between postmenopausal HK and white women. Adjusting for age, weight, and height rather than age and BMI tended to reduce differences in bone size and Tb. parameters but accentuate cortical differences such that Chinese premenopausal women in both locations and postmenopausal women from HK had higher stiffness at both skeletal sites compared with white women. Compared with white women, Chinese women in the US and HK have vBMD and microstructural advantages leading to higher or similar mechanical competence in pre- and postmenopausal women, respectively, despite smaller bone size.

Normative Standards for HRpQCT Parameters in Chinese Men and Women

Assessing bone architecture using high-resolution peripheral quantitative computed tomography (HRpQCT) has the potential to improve fracture risk assessment. The Normal Reference Study aimed to establish sex-specific reference centile curves for HRpQCT parameters. This was an age-stratified cross-sectional study and 1072 ambulatory Chinese men (n = 544) and women (n = 528) aged 20 to 79 years, who were free from conditions and medications that could affect bone metabolism and had no history of fragility fracture. They were recruited from local communities of Hong Kong. Reference centile curves for each HRpQCT parameter were constructed using generalized additive models for location, scale, and shape with age as the only explanatory variable. Patterns of reference centile curves reflected age-related changes of bone density, microarchitecture, and estimated bone strength. In both sexes, loss of cortical bone was only evident in mid-adulthood, particularly in women with a more rapid fashion probably concurrent with the onset of menopause. In contrast, loss of trabecular bone was subtle or gradual or occurred at an earlier age. Expected values of HRpQCT parameters for a defined sex and age and a defined percentile or Z-score were obtained from these curves. T-scores were calculated using the population with the peak values as the reference and reflected age- or menopause-related bone loss in an older individual or the room to reach the peak potential in a younger individual. These reference centile curves produced a standard describing a norm or desirable target that enables value clinical judgements. Percentiles, Z-scores, and T-scores would be helpful in detecting abnormalities in bone density and microarchitecture arising from various conditions and establishing entry criteria for clinical trials. They also hold the potential to refine the diagnosis of osteoporosis and assessment of fracture risk. © 2018 American Society for Bone and Mineral Research.

Bone mass, microarchitecture and strength are influenced by race/ethnicity in young adult men and women

Lower rates of fracture in both Blacks compared to Whites, and men compared to women are not completely explained by differences in bone mineral density (BMD). Prior evidence suggests that more favorable cortical bone microarchitecture may contribute to reduced fracture rates in older Black compared to White women, however it is not known whether these differences are established in young adulthood or develop during aging. Moreover, prior studies using high-resolution pQCT (HR-pQCT) have reported outcomes from a fixed-scan location, which may confound sex- and race/ethnicity-related differences in bone structure.

PURPOSE

We determined differences in bone mass, microarchitecture and strength between young adult Black and White men and women.

METHODS

We enrolled 185 young adult (24.2±3.4yrs) women (n=51 Black, n=50 White) and men (n=34 Black, n=50 White) in this cross-sectional study. We used dual-energy X-ray absorptiometry (DXA) to determine areal BMD (aBMD) at the femoral neck (FN), total hip (TH) and lumbar spine (LS), as well as HR-pQCT to assess bone microarchitecture and failure load by micro-finite element analysis (μFEA) at the distal tibia (4% of tibial length). We used two-way ANOVA to compare bone outcomes, adjusted for age, height, weight and physical activity.

RESULTS

The effect of race/ethnicity on bone outcomes did not differ by sex, and the effect of sex on bone outcomes did not differ by race/ethnicty. After adjusting for covariates, Blacks had significantly greater FN, TH and LS aBMD compared to Whites (p<0.05 for all). Blacks also had greater cortical area, vBMD, and thickness, and lower cortical porosity, with greater trabecular thickness and total vBMD compared to Whites. μFEA-estimated FL was significantly higher among Blacks compared to Whites. Men had significantly greater total vBMD, trabecular thickness and cortical area and thickness, but greater cortical porosity than women, the net effects being a higher failure load in men than women.

CONCLUSION

These findings demonstrate that more favorable bone microarchitecture in Blacks compared to Whites and in men compared to women is established by young adulthood. Advantageous bone strength among Blacks and men likely contributes to their lower risk of fractures throughout life compared to their White and women counterparts.

Cortical microstructure compensates for smaller bone size in young Caribbean Hispanic versus non-Hispanic white men

Hispanic men have smaller bone size but thicker and denser cortices compared to white men, leading to similar mechanical competence.

INTRODUCTION

The purpose of this study was to assess differences in vBMD and microarchitecture in young Caribbean Hispanic (n = 30) and non-Hispanic Caucasian (n = 30) men.

METHODS

We measured areal bone mineral density (aBMD) at the spine, total hip (TH), femoral neck (FN), and forearm by dual-energy X-ray absorptiometry (DXA) and bone geometry, mass, microarchitecture, and mechanical competence by high-resolution peripheral quantitative computed tomography (HRpQCT), individual trabecula segmentation (ITS), and finite element analysis (FEA).

RESULTS

Hispanic men were slightly older, shorter, and heavier and had higher BMI compared with white men. aBMD, measured by DXA, did not differ at the spine, TH, or forearm before or after adjustment for age, height, weight, and the interaction of height and weight. At the FN, marginally significant higher BMD in Hispanics prior to adjustment was attenuated and no longer differed after adjustment for covariates. Adjusted HRpQCT indices indicated smaller total and trabecular area at the radius but greater total volumetric density and cortical thickness in Hispanic versus white men. The adjusted difference in cortical density at the radius was of borderline significance. Trabecular and ITS microstructure tended not to differ at the radius. At the tibia, results were similar. Bone size tended to be smaller and covariate-adjusted cortical density and cortical thickness were greater in Hispanic versus white men. Additionally, cortical porosity was lower at the tibia in Hispanic compared to white men. Stiffness and failure load did not differ at either skeletal site by ethnicity.

CONCLUSION

In conclusion, greater cortical thickness and density as well as lower cortical porosity tend to compensate for smaller bone size in Hispanic men, leading to similar mechanical competence compared with white men.

Dual-energy X-ray Absorptiometry

Bone mineral density (BMD) measurement by dual-energy X-ray absorptiometry (DXA) is the most commonly used method to assess fracture risk. DXA utilizes two different energy X-rays to calculate BMD and, by comparison to a young normative database, the T-score. In 1994, the World Health Organization defined osteoporosis based on T-score, changing the paradigm of the field and forever placing DXA measurements in the center of osteoporosis diagnosis. Since then, many large studies have demonstrated the predictive value of BMD by DXA-for every standard deviation decline in BMD, there is a relative risk of 1.5-2.5 for fracture. This predictive ability is similar to how blood pressure can predict myocardial infarction. Limitations of DXA are also important to consider. While BMD by DXA can identify those at risk, there is a significant overlap in the BMD of patients who will and will not fracture. Special considerations are also needed in men and ethnic minority groups. These groups may have different bone size, thus affecting the normative range of BMD, and/or distinct bone structure that affect the association between BMD and fractures. Finally, BMD can be affected by positioning errors or artifacts, including osteoarthritis, fracture, and jewelry. Of course, DXA has tremendous strengths as well-namely its wide availability, its low radiation exposure, and a large body of evidence that relate DXA measurements to fracture risk. For these reasons, DXA remains the cornerstone of fracture assessment now and for the foreseeable future.

Differences in bone quality and strength between Asian and Caucasian young men

This is a cross-sectional study to assess differences in bone quality in young Asian and Caucasian (n = 30/group) men between 25 and 35 years. We found that Asians had smaller bones, thicker and denser cortices, and more plate-like trabeculae, but stiffness did not differ between groups.

INTRODUCTION

We conducted a cross-sectional study to assess differences in bone quality in young Asian and Caucasian (n = 30/group) men between 25 and 35 years.

METHODS

We measured bone mineral density (BMD) at the spine, total hip (TH), femoral neck (FN), and forearm by dual energy X-ray absorptiometry (DXA), and bone geometry, density, microarchitecture, and mechanical competence at the radius and tibia by high-resolution peripheral quantitative computed tomography (HR-pQCT) with application of individual trabecula segmentation (ITS) and trabecular and whole bone finite element analysis (FEA). We measured load-to-strength ratio to account for differences in bone size and height, respectively. We used Wilcoxon rank sum and generalized linear models adjusted for height, weight, and their interaction for comparisons.

RESULTS

Asians were 3.9 % shorter and weighed 6.5 % less than Caucasians. In adjusted models: by DXA, there were no significant race-based differences in areal BMD; by HR-pQCT, at the radius, Asians had smaller total and trabecular area (p = 0.003 for both), and denser (p = 0.01) and thicker (p = 0.04) cortices at the radius; by ITS, at the radius Asians, had more plate-like than rod-like trabeculae (PR ratio p = 0.01), greater plate trabecular surface (p = 0.009) and longer rod length (p = 0.002). There were no significant race-based differences in FEA or the load-to-strength ratio.

CONCLUSIONS

Asians had smaller bones, thicker and denser cortices, and more plate-like trabeculae, but biomechanical estimates of bone strength did not differ between groups. Studies are needed to determine whether these differences persist later in life.

Racial Differences in Bone Microarchitecture and Estimated Strength at the Distal Radius and Distal Tibia in Older Adolescent Girls: a Cross-Sectional Study

BACKGROUND

Previous studies have demonstrated that an individual's race and ethnicity are important determinants of their areal bone mineral density (aBMD), assessed by dual-energy X-ray absorptiometry. However, there are few data assessing the impact of race on bone microarchitecture and strength estimates, particularly in older adolescent girls and young adults. We hypothesized that bone microarchitecture and strength estimates would be superior in Blacks compared to White and Asian American adolescent girls and young adults of similar age based on reports of higher aBMD in Blacks.

METHODS

We assessed BMD using dual-energy X-ray absoptiometry (DXA), bone microarchitecture at the distal radius and distal tibia using high-resolution peripheral quantitative computed tomography (HRpQCT) and estimated measures of bone strength using micro-finite element analysis (FEA) in 35 White, 15 Asian American, and 10 Black girls 14-21 years.

RESULTS

After controlling for height, most DXA measures of aBMD and aBMD Z scores were higher in Black girls compared with Whites and Asian Americans. HRpQCT and FEA showed that at the distal radius, Blacks had greater cortical perimeter, cortical area, trabecular thickness, trabecular BMD, estimated failure load, and stiffness than the other two groups. For the distal tibia, trabecular number and BMD were higher in Blacks than Asian Americans.

CONCLUSIONS

Particularly at the distal radius, adolescent and young adult White and Asian American girls have less favorable bone microarchitecture and lower bone strength than Blacks, possibly explaining the lower risk of fracture seen in Blacks.

LEVEL OF EVIDENCE

Level II.

BEYOND DXA: ADVANCES IN CLINICAL APPLICATIONS OF NEW BONE IMAGING TECHNOLOGY

Dual-energy X-ray absorptiometry (DXA) is generally a very useful tool for assessing bone mineral density (BMD) and fracture risk. However, observational studies have shown that in certain instances, BMD as measured by DXA systematically over- or underestimates fracture risk. We herein describe the clinical conundrums encountered when assessing fracture risk by DXA in patients with primary hyperparathyroidism or type 2 diabetes and those of Chinese ethnicity. Furthermore, we discuss how advanced imaging technology that examines skeletal microarchitecture is furthering our understanding of fracture risk in these clinical situations.

ABBREVIATIONS

BMD = bone mineral density BMI = body mass index BMS = bone material strength BMT = bone microindentation testing 3D = 3-dimensional DM2 = type 2 diabetes mellitus DXA = dual-energy X-ray absorptiometry μFEA = microstructural finite element analysis FRAX = fracture risk assessment tool HRpQCT = high-resolution peripheral quantitative computed tomography ID = indentation distance IDI = indentation distance increase ITS = individual trabecular segmentation PHPT = primary hyperparathyroidism PTH = parathyroid hormone TBS = trabecular bone score.

Racial and Socioeconomic Disparities in Hip Fracture Care

BACKGROUND

Despite declines in both the incidence of and mortality following hip fracture, there are racial and socioeconomic disparities in treatment access and outcomes. We evaluated the presence and implications of disparities in delivery of care, hypothesizing that race and community socioeconomic characteristics would influence quality of care for patients with a hip fracture.

METHODS

We collected data from the New York State Department of Health Statewide Planning and Research Cooperative System (SPARCS), which prospectively captures information on all discharges from nonfederal acute-care hospitals in New York State. Records for 197,290 New York State residents who underwent surgery for a hip fracture between 1998 and 2010 in New York State were identified from SPARCS using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes. Multivariable regression models were used to evaluate the association of patient characteristics, social deprivation, and hospital/surgeon volume with time from admission to surgery, in-hospital complications, readmission, and 1-year mortality.

RESULTS

After adjusting for patient and surgery characteristics, hospital/surgeon volume, social deprivation, and other variables, black patients were at greater risk for delayed surgery (odds ratio [OR] = 1.49; 95% confidence interval [CI] = 1.42, 1.57), a reoperation (hazard ratio [HR] = 1.21; CI = 1.11, 1.32), readmission (OR = 1.17; CI = 1.11, 1.22), and 1-year mortality (HR = 1.13; CI = 1.07, 1.21) than white patients. Subgroup analyses showed a greater risk for delayed surgery for black and Asian patients compared with white patients, regardless of social deprivation. Additionally, there was a greater risk for readmission for black patients compared with white patients, regardless of social deprivation. Compared with Medicare patients, Medicaid patients were at increased risk for delayed surgery (OR = 1.17; CI = 1.10, 1.24) whereas privately insured patients were at decreased risk for delayed surgery (OR = 0.77; CI = 0.74, 0.81), readmission (OR = 0.77; CI = 0.74, 0.81), complications (OR = 0.80; CI = 0.77, 0.84), and 1-year mortality (HR = 0.80; CI = 0.75, 0.85).

CONCLUSIONS

There are race and insurance-based disparities in delivery of care for patients with hip fracture, some of which persist after adjusting for social deprivation. In addition to investigation into reasons contributing to disparities, targeted interventions should be developed to mitigate effects of disparities on patients at greatest risk.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Altered trabecular bone morphology in adolescent and young adult athletes with menstrual dysfunction

CONTEXT

Young amenorrheic athletes (AA) have lower bone mineral density (BMD) and an increased prevalence of fracture compared with eumenorrheic athletes (EA) and non-athletes. Trabecular morphology is a determinant of skeletal strength and may contribute to fracture risk.

OBJECTIVES

To determine the variation in trabecular morphology among AA, EA, and non-athletes and to determine the association of trabecular morphology with fracture among AA.

DESIGN AND SETTING

A cross-sectional study performed at an academic clinical research center.

PARTICIPANTS

161 girls and young women aged 14-26 years (97 AA, 32 EA, and 32 non-athletes).

MAIN OUTCOME MEASURE

We measured volumetric BMD (vBMD) and skeletal microarchitecture using high-resolution peripheral quantitative computed tomography. We evaluated trabecular morphology (plate-like vs. rod-like), orientation, and connectivity by individual trabecula segmentation.

RESULTS

At the non-weight-bearing distal radius, the groups did not differ for trabecular vBMD. However, plate-like trabecular bone volume fraction (pBV/TV) was lower in AA vs. EA (p=0.03), as were plate number (p=0.03) and connectivity (p=0.03). At the weight-bearing distal tibia, trabecular vBMD was higher in athletes vs. non-athletes (p=0.05 for AA and p=0.009 for EA vs. non-athletes, respectively). pBV/TV was higher in athletes vs. non-athletes (p=0.04 AA and p=0.005 EA vs. non-athletes), as were axially-aligned trabeculae, plate number, and connectivity. Among AA, those with a history of recurrent stress fracture had lower pBV/TV, axially-aligned trabeculae, plate number, plate thickness, and connectivity at the distal radius.

CONCLUSIONS

Trabecular morphology and alignment differ among AA, EA, and non-athletes. These differences may be associated with increased fracture risk.

Significant bone microarchitecture impairment in premenopausal women with active celiac disease

Patients with active celiac disease (CD) are more likely to have osteoporosis and increased risk of fractures. High-resolution peripheral quantitative computed tomography (HR-pQCT) permits three-dimensional exploration of bone microarchitectural characteristics measuring separately cortical and trabecular compartments, and giving a more profound insight into bone disease pathophysiology and fracture. We aimed to determine the volumetric and microarchitectural characteristics of peripheral bones-distal radius and tibia-in an adult premenopausal cohort with active CD assessed at diagnosis. We prospectively enrolled 31 consecutive premenopausal women with newly diagnosed CD (median age 29 years, range: 18-49) and 22 healthy women of similar age (median age 30 years, range 21-41) and body mass index. Compared with controls, peripheral bones of CD patients were significantly lower in terms of total volumetric density mg/cm(3) (mean ± SD: 274.7 ± 51.7 vs. 324.7 ± 45.8, p 0.0006 at the radius; 264.4 ± 48.7 vs. 307 ± 40.7, p 0.002 at the tibia), trabecular density mg/cm(3) (118.6 ± 31.5 vs. 161.9 ± 33.6, p<0.0001 at the radius; 127.9 ± 28.7 vs. 157.6 ± 15.6, p < 0.0001 at the tibia); bone volume/trabecular volume ratio % (9.9 ± 2.6 vs. 13.5 ± 2.8, p<0.0001 at the radius; 10.6 ± 2.4 vs. 13.1 ± 1.3, p < 0.0001 at the tibia); number of trabeculae 1/mm (1.69 ± 0.27 vs. 1.89 ± 0.26, p 0.009 at the radius; 1.53 ± 0.32 vs. 1.80 ± 0.26, p 0.002 at the tibia); and trabecular thickness mm (0.058 ± 0.010 vs. 0.071 ± 0.008, p < 0.0001 at the radius with no significant difference at the tibia). Cortical density was significantly lower in both regions (D comp mg/cm(3) 860 ± 57.2 vs. 893.9 ± 43, p 0.02; 902.7 ± 48.7 vs. 932.6 ± 32.6, p 0.01 in radius and tibia respectively). Although cortical thickness was lower in CD patients, it failed to show any significant inter-group difference (a-8% decay with p 0.11 in both bones). Patients with symptomatic CD (n = 22) had a greater bone microarchitectural deficit than those with subclinical CD. HR-pQCT was used to successfully identify significant deterioration in the microarchitecture of trabecular and cortical compartments of peripheral bones. Impairment was characterized by lower trabecular number and thickness-which increased trabecular network heterogeneity-and lower cortical density and thickness. In the prospective follow-up of this group of patients we expect to be able to assess whether bone microarchitecture recovers and to what extend after gluten-free diet.

Age-related differences in volumetric bone mineral density, microarchitecture, and bone strength of distal radius and tibia in Chinese women: a high-resolution pQCT reference database study

In a cohort of 393 Chinese women, by using high-resolution peripheral quantitative computed tomography (HR-pQCT), we found that significant cortical bone loss occurred after midlife. Prominent increase in cortical porosity began at the fifth decade but reached a plateau before the sixth decade. Trabecular bone loss was already evident in young adulthood and continued throughout life.

INTRODUCTION

This study aimed to investigate age-related differences in volumetric bone mineral density (vBMD), microarchitecture, and estimated bone strength at peripheral skeleton in Chinese female population.

METHODS

In a cross-sectional cohort of 393 Chinese women aged 20-90 years, we obtained vBMD, microarchtecture, and micro-finite element-derived bone strength at distal radius and tibia using HR-pQCT.

RESULTS

The largest predictive age-related difference was found for cortical porosity (Ct.Po) which showed over four-fold and two-fold differences at distal radius and tibia, respectively, over the adulthood. At both sites, cortical bone area, vBMD, and thickness showed significant quadratic association with age with significant decrease beginning after midlife. Change of Ct.Po became more prominent between age of 50 and 57 (0.26 %/year at distal radius, 0.54 %/year at distal tibia, both p ≤ 0.001) but thereafter, reached a plateau (0.015 and 0.028 %/year, both p > 0.05). In contrast, trabecular vBMD and microarchitecture showed linear association with age with significant deterioration observed throughout adulthood. Estimated age of peak was around age of 20 for trabecular vBMD and microarchitecture and Ct.Po and age of 40 for cortical vBMD and microarchitecture. Estimated stiffness and failure load peaked at mid-30s at the distal radius and at age 20 at distal tibia.

CONCLUSIONS

Age-related differences in vBMD and microarchitecture in Chinese women differed by bone compartments. Significant cortical bone loss occurred after midlife. Prominent increase in Ct.Po began at the fifth decade but appeared to be arrested before the sixth decade. Loss of trabecular bone was already evident in young adulthood and continued throughout life.

Defects in cortical microarchitecture among African-American women with type 2 diabetes

SUMMARY

Patients with type 2 diabetes mellitus (DM2) have increased fracture risk. We found that African-American women with DM2 have increased cortical porosity and lower cortical bone density at the radius than non-diabetic controls. These cortical deficits are associated with hyperglycemia and may contribute to skeletal fragility associated with DM2.

INTRODUCTION

Fracture risk is increased in patients with type 2 diabetes mellitus (DM2) despite normal areal bone mineral density (aBMD). DM2 is more common in African-Americans than in Caucasians. It is not known whether African-American women with DM2 have deficits in bone microstructure.

METHODS

We measured aBMD at the spine and hip by DXA, and volumetric BMD (vBMD) and microarchitecture at the distal radius and tibia by HR-pQCT in 22 DM2 and 78 non-diabetic African-American women participating in the Study of Women Across the Nation (SWAN). We also measured fasting glucose and HOMA-IR.

RESULTS

Age, weight, and aBMD at all sites were similar in both groups. At the radius, cortical porosity was 26% greater, while cortical vBMD and tissue mineral density were lower in women with DM2 than in controls. There were no differences in radius total vBMD or trabecular vBMD between groups. Despite inferior cortical bone properties at the radius, FEA-estimated failure load was similar between groups. Tibia vBMD and microarchitecture were also similar between groups. There were no significant associations between cortical parameters and duration of DM2 or HOMA-IR. However, among women with DM2, higher fasting glucose levels were associated with lower cortical vBMD (r=-0.54, p=0.018).

CONCLUSIONS

DM2 and higher fasting glucose are associated with unfavorable cortical bone microarchitecture at the distal radius in African-American women. These structural deficits may contribute to the increased fracture risk among women with DM2. Further, our results suggest that hyperglycemia may be involved in mechanisms of skeletal fragility associated with DM2.

A trabecular plate-like phenotype is overrepresented in Chinese-American versus Caucasian women

This study used extreme phenotype selection to define two trabecular bone phenotypes in a cohort of Chinese-American and Caucasian women. A trabecular plate-predominant phenotype is more common in Chinese-Americans while the rod-predominant phenotype is more typical of Caucasians. The robustness of these phenotypic associations with respect to lifestyle factors suggests that this trait may have a genetic basis and that these phenotypes can be utilized in future genetic studies.

INTRODUCTION

Compared to Caucasians, Chinese-Americans have more plate-like trabecular bone when measured by individual trabecula segmentation (ITS). These findings suggest a phenotypic difference between the races, which may be amenable to genetic analysis. We sought to identify a single ITS plate trait to pursue in genetic studies by conducting an extreme phenotype selection strategy to numerically define two distinct phenotypes-plate-like and rod-like-and determine whether the selected phenotypic associations were independent of lifestyle factors in order to conduct future genetic studies.

METHODS

A previously described cohort of 146 Chinese-American and Caucasian women with high-resolution peripheral quantitative computed tomography imaging and ITS analyses were studied with logistic regression and receiver operator characteristic analyses.

RESULTS

The tibial plate-to-rod (TPR) ratio was the best ITS discriminator of race. Using extreme phenotypic selection, two TPR ratio phenotypes were defined numerically: plate-like as a TPR ratio value in the highest quartile (≥1.336) and rod-like as a TPR ratio value in the lowest quartile (≤0.621). Women with a plate-like phenotype were 25.7 times more likely (95 % CI 7.3-90.1) to be Chinese-American than women with rod-like morphology. After controlling for constitutional and lifestyle covariates, women in the highest vs. lowest TPR ratio quartile were 85.0 times more likely (95 % CI 12.7-568.0) to be Chinese-American.

CONCLUSION

Using extreme phenotype selection, we defined a plate- and rod-like trabecular bone phenotype for the TPR ratio trait. The former phenotype is more common in Chinese-American women, while the latter is more typical of Caucasian women. The robustness of these phenotypic associations after controlling for differences in constitution and lifestyle suggest that the TPR ratio may have a genetic basis and that the extreme phenotypes defined in this analysis can be utilized for future studies.

Bone structural and mechanical indices in Adolescent Idiopathic Scoliosis evaluated by high-resolution peripheral quantitative computed tomography (HR-pQCT)

Adolescent Idiopathic Scoliosis (AIS) is associated with systemic low bone mass. It could persist into adulthood and was shown to be an important prognostic factor for curve progression in AIS. Previous studies were confined to areal bone mineral density (aBMD) measured by Dual-energy X-ray Absorptiometry (DXA) which was a two-dimensional measurement for a three-dimensional structure. This conventional measurement was inadequate to evaluate volumetric bone density and bone quality which are important determinants for bone strength and bone health status as defined in the 2000 NIH consensus statement. High-resolution peripheral quantitative computed tomography (HR-pQCT) was therefore used in this study for three-dimensional evaluation of volumetric bone mineral density and bone micro-architecture as well as estimation of bone strength. In this study, 214 newly diagnosed AIS girls and 187 age and gender-matched normal control aged between 11 and 13years old were recruited for HR-pQCT evaluations on bone geometry, trabecular bone micro-architecture and volumetric BMD (vBMD) at the non-dominant distal radius. We demonstrated that AIS was associated with lower Cortical Bone Area, Cortical Bone vBMD, Trabecular Number and greater Trabecular Separation. With multivariate linear regression analysis and after adjustment for age, dietary calcium intake and physical activity level, the association of AIS with lower Cortical Bone vBMD, lower Trabecular Number and greater Trabecular Separation remained statistically significant. The findings of this study indicated that AIS was associated with an abnormal bone quality profile suggestive of alteration in endocortical modeling, derangement in trabecular bone structure and disturbance in bone mineralization. The cause for these changes and how they are related to the etiopathogenesis of AIS warrant further studies.

Assessment of bone microarchitecture in postmenopausal women on long-term bisphosphonate therapy with atypical fractures of the femur

Reports of atypical femoral fractures (AFFs) in patients receiving long- term bisphosphonate therapy have raised concerns regarding the genesis of this rare event. Using high-resolution peripheral quantitative computed tomography (HR-pQCT), we conducted a study to evaluate bone microarchitecture in patients who had suffered an AFF during long-term bisphosphonate treatment. The aim of our study was to evaluate if bone microarchitecture assessment could help explain the pathophysiology of these fractures. We compared bone volumetric density and microarchitectural parameters measured by HR-pQCT in the radius and tibia in 20 patients with AFFs with 35 postmenopausal women who had also received long-term bisphosphonate treatment but had not experienced AFFs, and with 54 treatment-naive postmenopausal women. Control groups were similar in age, body mass index (BMI), and bone mineral density (BMD). Mean age of the 20 patients with AFFs was 71 years, mean lumbar spine T-score was -2.2, and mean femoral neck T-score was -2. Mean time on bisphosphonate treatment was 10.9 years (range, 5-20 years). None of the patients had other conditions associated with AFFs such as rheumatoid arthritis, diabetes or glucocorticoid use. There were no statistically significant differences in any of the parameters measured by HR-pQCT between postmenopausal women with or without treatment history and with or without history of atypical fractures. We could not find any distinctive microarchitecture features in the peripheral skeleton of women who had suffered an atypical fracture of the femur while receiving bisphosphonate treatment. This suggests that risk of developing an atypical fracture is not related to bone microarchitecture deterioration. Our results indicate that there may be other individual factors predisposing to atypical fractures in patients treated with bisphosphonates, and that those are independent of bone microarchitecture. In the future, identification of those factors could help prevent and understand the complex physiopathology of these rare events.

Decreased quantity and quality of the periarticular and nonperiarticular bone in patients with rheumatoid arthritis: a cross-sectional HR-pQCT study

Rheumatoid arthritis (RA) is a highly bone destructive disease. Although it is well established that RA leads to bone loss and increased fracture risk, current knowledge on the microstructural changes of bone in RA is still limited. The purpose of this study was to assess the microstructure of periarticular and nonperiarticular bone in female and male RA patients and compare it with respective healthy controls. We performed two high-resolution peripheral quantitative computed tomography (HR-pQCT; Xtreme-CT) scans, one of the distal radius and one of the ultradistal radius in 90 patients with RA (60 females, 30 males) and 70 healthy controls (40 females, 30 males) matched for sex, age, and body mass index. Volumetric bone mineral density (vBMD), bone geometry, and bone microstructure including trabecular bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), cortical thickness (Ct.Th) and cortical porosity (Ct.Po) were assessed. At the distal and ultradistal radius, trabecular (p=0.005 and p<0.001) and cortical BMD (p<0.001 and p<0.001) were significantly decreased in male and female patients with RA, respectively. BV/TV was also decreased at both sites, based on lower Tb.N in female RA (p<0.001 for both sites) and lower Tb.Th (p=0.034 and p=0.005) in male RA patients compared with respective healthy controls. Cortical thinning (p=0.018 and p=0.002) but not Ct.Po (p=0.070 and p=0.275) was pronounced in male and female RA patients at the distal radius. Cortical perimeter was increased in male and female RA patients at both sites. Multiple regression models showed that bone geometry (cortical perimeter) is predominantly influenced by age of the RA patient, cortical thickness by both age and disease duration, and trabecular microstructure predominantly by the disease duration. In summary, these data show profound deterioration of bone microstructure in the appendicular skeleton of RA patients at both periarticular and nonperiarticular sites.

Lower cortical porosity and higher tissue mineral density in Chinese American versus white women

Asian women have lower rates of hip and forearm fractures compared to other racial groups despite lower areal bone mineral density (aBMD). We have demonstrated microarchitectural differences, including greater cortical thickness (Ct.Th) and cortical volumetric BMD (Ct.BMD), in Chinese American versus white women. Yet it is not known whether greater Ct.BMD in Chinese American women is a result of greater tissue mineral density (TMD) or reduced cortical porosity (Ct.Po). Using an advanced segmentation algorithm based on high-resolution peripheral quantitative computed tomography (HR-pQCT) images, we tested the hypothesis that Chinese American women have better cortical skeletal integrity owing to lower Ct.Po and higher Ct.TMD compared with white women. A total of 78 Chinese American women (49 premenopausal and 29 postmenopausal) and 114 white women (46 premenopausal and 68 postmenopausal) were studied. Premenopausal Chinese American versus white women had greater Ct.Th, Ct.BMD, and Ct.TMD at both the radius and tibia, and decreased Ct.Po (p < 0.05). A similar pattern was observed between postmenopausal Chinese American and white women. As expected, postmenopausal versus premenopausal women had lower Ct.BMD at the radius and tibia in both races (p < 0.001). Ct.Po largely increased between premenopausal and postmenopausal women, whereas Ct.TMD decreased by 3% to 8% (p < 0.001) in both races. Age-related differences in Ct.Po and Ct.TMD did not differ by race. In summary, both reduced Ct.Po and greater Ct.TMD explain higher Ct.BMD in Chinese American versus white women. Thicker and preserved cortical bone structure in Chinese American women may contribute to greater resistance to fracture compared to white women.

The Chinese skeleton: insights into microstructure that help to explain the epidemiology of fracture

Osteoporotic fractures are a major public health problem worldwide, but incidence varies greatly across racial groups and geographic regions. Recent work suggests that the incidence of osteoporotic fracture is rising among Asian populations. Studies comparing areal bone mineral density and fracture across races generally indicate lower bone mineral density in Asian individuals including the Chinese, but this does not reflect their relatively low risk of non-vertebral fractures. In contrast, the Chinese have relatively high vertebral fracture rates similar to that of Caucasians. The paradoxically low risk for some types of fractures among the Chinese despite their low areal bone mineral density has been elucidated in part by recent advances in skeletal imaging. New techniques for assessing bone quality non-invasively demonstrate that the Chinese compensate for smaller bone size by differences in hip geometry and microstructural skeletal organization. Studies evaluating factors influencing racial differences in bone remodeling, as well as bone acquisition and loss, may further elucidate racial variation in bone microstructure. Advances in understanding the microstructure of the Chinese skeleton have not only helped to explain the epidemiology of fracture in the Chinese, but may also provide insight into the epidemiology of fracture in other races as well.

Circulating sclerostin levels and markers of bone turnover in Chinese-American and white women

CONTEXT

Chinese-American women have bone microarchitectural features that confer greater bone stiffness compared to white women, but the physiology underlying these findings has not been investigated.

OBJECTIVE

The purpose of the study was to assess racial differences in serum sclerostin and bone turnover markers (BTMs), and to explore their associations with each other, volumetric bone mineral density (BMD), and bone microarchitecture in Chinese-American and white women.

DESIGN AND SETTING

We conducted a cross-sectional study at a university hospital.

PARTICIPANTS

We studied 138 women.

RESULTS

Serum osteocalcin was 19-28% lower in pre- and postmenopausal Chinese-American vs white women, respectively (both P < .01). C-Terminal telopeptide of type I collagen (CTX) level was 18-22% lower in pre- and postmenopausal Chinese-American vs white women (both P < .05). Pre- vs postmenopausal differences in osteocalcin and CTX were greater in white vs Chinese-American women. Sclerostin levels were similar in both races, but BTMs were differentially associated with sclerostin by race and menopausal status. BTMs were not correlated with sclerostin in Chinese-Americans. CTX and bone-specific alkaline phosphatase were positively associated with sclerostin (r = 0.353, r = 0.458; both P < .05) in white premenopausal women. In contrast, in postmenopausal white women, the associations of sclerostin with amino-terminal propeptide of type I procollagen, isoform 5b of tartrate-resistant acid phosphatase, and CTX were negative (all P < .05). Adjusting for covariates, sclerostin was positively associated with areal BMD in both races.

CONCLUSIONS

Lower BTMs in Chinese-American women and greater age-related differences in BTMs among white women provide a physiological framework to account for racial differences in BMD, microarchitecture, and fracture.

Abnormal bone quality versus low bone mineral density in adolescent idiopathic scoliosis: a case-control study with in vivo high-resolution peripheral quantitative computed tomography

BACKGROUND CONTEXT

Adolescent idiopathic scoliosis (AIS) is associated with low bone mass that could persist into early adulthood and is an important prognostic factor for curve progression. Previous studies were confined to areal bone mineral density measurement that was a two-dimensional investigation for a three-dimensional structure. Evaluation of volumetric BMD (vBMD) and other bone quality parameters are important for gaining in-depth understanding of the etiopathogenesis of AIS.

PURPOSE

The objective of this study was to carry out direct in vivo measurement of bone quality in AIS using high-resolution peripheral quantitative computed tomography (HR-pQCT) and compare the correlation of bone quality with osteopenia between AIS and control subjects.

STUDY DESIGN/SETTING

A case-control study.

PATIENT SAMPLE

Newly diagnosed AIS girls (n=112) and non-AIS girls (n=115) between 11 and 13 years.

OUTCOME MEASURES

Areal bone mineral density of bilateral femoral necks and HR-pQCT of the nondominant distal radius were performed.

METHODS

Areal bone mineral density of femoral necks was measured by dual-energy X-ray absorptiometry. Subjects were classified into the osteopenic (Z score less than or equal to -1) and nonosteopenic (Z score more than -1) groups. Bone quality parameters, including bone morphometry, trabecular bone microarchitecture, and vBMD, were measured by HR-pQCT (XtremeCT; Scanco Medical, Zurich, Switzerland).

RESULTS

In AIS, the osteopenic group had lower measurements in cortical area, cortical thickness, average vBMD, compact bone vBMD, trabecular vBMD, trabecular bone volume to tissue volume ratio, and trabecular thickness compared with nonosteopenic AIS subjects. In contrast, among the non-AIS controls, the osteopenic group had lower measurements only in bone morphometry, average vBMD, and compact bone vBMD but not in trabecular vBMD and all other trabecular bone microarchitecture parameters.

CONCLUSIONS

This is the first study using HR-pQCT to compare the correlation of bone quality with osteopenia in AIS and non-AIS subjects. It provides new insights and highlights the unique bone quality profile with predominant changes in the trabecular compartment in association with osteopenia being notably only detected in the AIS subjects. Further studies in this area are warranted for defining the metabolic nature and biomechanical sequelae of derangement in bone mass and bone quality and their roles in the etiopathogenesis of AIS.

Differences in skeletal microarchitecture and strength in African-American and white women

African-American women have a lower risk of fracture than white women, and this difference is only partially explained by differences in dual-energy X-ray absorptiometry (DXA) areal bone mineral density (aBMD). Little is known about racial differences in skeletal microarchitecture and the consequences for bone strength. To evaluate potential factors underlying this racial difference in fracture rates, we used high-resolution peripheral quantitative computed tomography (HR-pQCT) to assess cortical and trabecular bone microarchitecture and estimate bone strength using micro-finite element analysis (µFEA) in African-American (n = 100) and white (n = 173) women participating in the Study of Women's Health Across the Nation (SWAN). African-American women had larger and denser bones than whites, with greater total area, aBMD, and total volumetric BMD (vBMD) at the radius and tibia metaphysis (p < 0.05 for all). African-Americans had greater trabecular vBMD at the radius, but higher cortical vBMD at the tibia. Cortical microarchitecture tended to show the most pronounced racial differences, with higher cortical area, thickness, and volumes in African-Americans at both skeletal sites (p < 0.05 for all), and lower cortical porosity in African-Americans at the tibia (p < 0.05). African-American women also had greater estimated bone stiffness and failure load at both the radius and tibia. Differences in skeletal microarchitecture and estimated stiffness and failure load persisted even after adjustment for DXA aBMD. The densitometric and microarchitectural predictors of failure load at the radius and tibia were the same in African-American and white women. In conclusion, differences in bone microarchitecture and density contribute to greater estimated bone strength in African-Americans and probably explain, at least in part, the lower fracture risk of African-American women.

Similarities and differences between sexes in regional loss of cortical and trabecular bone in the mid-femoral neck: the AGES-Reykjavik longitudinal study

The risk of hip fracture rises rapidly with age, and is notably higher in women. After falls and prior fragility fractures, the main clinically recognized risk factor for hip fracture is reduced bone density. To better understand the extent to which femoral neck density and structure change with age in each sex, we carried out a longitudinal study in subjects not treated with agents known to influence bone mineral density (BMD), to investigate changes in regional cortical thickness, as well as cortical and trabecular BMD at the mid-femoral neck. Segmental quantitative computed tomography (QCT) analysis was used to assess bone measurements in two anatomic subregions, the superolateral (superior) and inferomedial (inferior). A total of 400 older individuals (100 men and 300 women, aged 66-90 years) who were participants in the Age Gene/Environment Susceptibility-Reykjavik Study (AGES-Reykjavik), were studied. Participants had two QCT scans of the hip over a median follow-up of 5.1 years (mean baseline age 74 years). Changes in bone values during follow-up were estimated from mixed effects regression models. At baseline women had lower bone values in the superior region than men. At follow-up all bone values were lower in women, except cortical volumetric bone mineral density (vBMD) inferiorly. The relative losses in all bone values estimated in the superior region were substantially (about threefold) and significantly greater compared to those estimated in the inferior region in both sexes. Women lost cortical thickness and cortical vBMD more rapidly than men in both regions; and this was only weakly reflected in total femoral neck dual-energy X-ray absorptiometry (DXA)-like results. The higher rate of bone loss in women at critical locations may contribute materially to the greater femoral neck fracture incidence among women than men.

Trabecular bone score is associated with volumetric bone density and microarchitecture as assessed by central QCT and HRpQCT in Chinese American and white women

Although high-resolution peripheral quantitative computed tomography (HRpQCT) and central quantitative computed tomography (QCT) studies have shown bone structural differences between Chinese American (CH) and white (WH) women, these techniques are not readily available in the clinical setting. The trabecular bone score (TBS) estimates trabecular microarchitecture from dual-energy X-ray absorptiometry spine images. We assessed TBS in CH and WH women and investigated whether TBS is associated with QCT and HRpQCT indices. Areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry, lumbar spine (LS) TBS, QCT of the LS and hip, and HRpQCT of the radius and tibia were performed in 71 pre- (37 WH and 34 CH) and 44 postmenopausal (21 WH and 23 CH) women. TBS did not differ by race in either pre- or postmenopausal women. In the entire cohort, TBS positively correlated with LS trabecular volumetric bone mineral density (vBMD) (r = 0.664), femoral neck integral (r = 0.651), trabecular (r = 0.641) and cortical vBMD (r = 0.346), and cortical thickness (C/I; r = 0.540) by QCT (p < 0.001 for all). TBS also correlated with integral (r = 0.643), trabecular (r = 0.574) and cortical vBMD (r = 0.491), and C/I (r = 0.541) at the total hip (p < 0.001 for all). The combination of TBS and LS aBMD predicted more of the variance in QCT measures than aBMD alone. TBS was associated with all HRpQCT indices (r = 0.20-0.52) except radial cortical thickness and tibial trabecular thickness. Significant associations between TBS and measures of HRpQCT and QCT in WH and CH pre- and postmenopausal women demonstrated here suggest that TBS may be a useful adjunct to aBMD for assessing bone quality.

A comparison of bone quality at the distal radius between Asian and white adolescents and young adults: an HR-pQCT study

Paradoxically, Asians have lower areal bone mineral density (aBMD), but their rates of hip and wrist fractures are lower than whites. Therefore, we used high-resolution pQCT (HR-pQCT) to determine whether differences in bone macrostructure and microstructure, BMD, and bone strength at the distal radius were apparent in Asian (n = 91, 53 males, 38 females, [mean ± SD] 17.3 ± 1.5 years) and white (n = 89, 46 males, 43 females, 18.1 ± 1.8 years) adolescents and young adults. HR-pQCT outcomes included total BMD (Tt.BMD), trabecular bone volume fraction (BV/TV), and trabecular number (Tb.N), thickness (Tb.Th), and separation (Tb.Sp). We used an automated segmentation algorithm to determine total bone area (Tt.Ar), and cortical BMD (Ct.BMD), porosity (Ct.Po), and thickness (Ct.Th), and we applied finite element (FE) analysis to HR-pQCT scans to estimate bone strength. We fit sex-specific multivariable regression models to compare bone outcomes between Asians and whites, adjusting for age, age at menarche (girls), lean mass, ulnar length, dietary calcium intake, and physical activity. In males, after adjusting for covariates, Asians had 11% greater Tt.BMD, 8% greater Ct.BMD, and 25% lower Ct.Po than whites (p < 0.05). Also, Asians had 9% smaller Tt.Ar and 27% greater Ct.Th (p < 0.01). In females, Asians had smaller Tt.Ar than whites (16%, p < 0.001), but this difference was not significant after adjusting for covariates. Asian females had 5% greater Ct.BMD, 12% greater Ct.Th, and 11% lower Tb.Sp than whites after adjusting for covariates (p < 0.05). Estimated bone strength did not differ between Asian and white males or females. Our study supports the notion of compensatory elements of bone structure that sustain bone strength; smaller bones as observed between those of Asian origin compared with white origin have, on average, more dense, less porous, and thicker cortices. Longitudinal studies are needed to determine whether ethnic differences in bone structure exist in childhood, persist into old age, and whether they influence fracture risk.

Bone turnover and bone mineral density in HIV-1 infected Chinese taking highly active antiretroviral therapy -a prospective observational study

Background

Low bone mass and high bone turnover have been reported in HIV-infected individuals, both as a consequence of HIV infection itself, as well as from treatment with highly active antiretroviral therapy (HAART). The purpose of this study is to evaluate the impact of HAART on bone mineral density and bone turnover in HIV-1 infected Chinese patients.

Methods

Forty HIV-1 infected patients were enrolled in this study; all patients were followed through 48 weeks, and 17 patients completed 96 weeks. Bone mineral density (BMD), procollagen type 1 N-terminal propeptide (P1NP), collagen type 1 cross-linked C-telopeptide (β-CTX), parathyroid hormone (PTH), and 25-OH vitamin D levels were measured at baseline, 48 and 96 weeks. Baseline measurements were compared with an age-, gender-, and BMI-matched healthy control population.

Results

At baseline, raw BMD in the lumbar spine of HIV-1 infected patients was significantly lower than that of healthy controls (1.138 ± 0.112 g/cm² vs. 1.195 ± 0.139 g/cm², p = 0.047). During the first 48 weeks after initiating HAART, BMD of lumbar spine, femoral neck, and total hip decreased significantly in HIV-1 infected patients, with annual percent decline ranging from 1.78-3.28%. However, from week 48 to 96, BMD remained stable. Baseline levels of β-CTX (0.31 ± 0.16 ng/mL vs. 0.42 ± 0.19 ng/mL, p = 0.008) and P1NP (32.96 ± 14.00 ng/mL vs. 55.82 ± 26.87 ng/mL, p = 0.05) were lower in HIV-infected patients compared with controls, respectively. Both β-CTX and P1NP levels increased after onset of HAART until week 48, and remained elevated during the next 48 weeks. 25-OH vitamin D in HIV-infected patients was lower at baseline compared to healthy controls, but this difference was not statistically significant. PTH, however, was higher in HIV patients at baseline, and showed a significant increase throughout the study.

Conclusions

Chinese adults with HIV-1 infection have low bone turnover prior to HAART as well as lower raw BMD of the lumbar spine compared with healthy controls, with further bone loss occurring following the initiation of HAART. The long-term clinical implications of these findings remain unclear at this time.

Adaptations in tibial cortical thickness and total volumetric bone density in postmenopausal South Asian women with small bone size

There is some evidence that South Asian women may have an increased risk of osteoporosis compared with Caucasian women, although whether South Asians are at increased risk of fracture is not clear. It is unknown whether older South Asian women differ from Caucasian women in bone geometry. This is the first study, to the authors' knowledge, to use peripheral Quantitative Computed Tomography (pQCT) to measure radial and tibial bone geometry in postmenopausal South Asian women. In comparison to Caucasian women, Asian women had smaller bone size at the 4% (-18% p<0.001) and 66% radius (-15% p=0.04) as well as increased total density at the 4% (+13% p=0.01) radius. For the tibia, they had a smaller bone size at the 4% (-16% p=0.005) and 14% (-38% p=0.002) sites. Also, Asians had increased cortical thickness (-17% p=0.04) at the 38% tibia, (in proportion to bone size (-30% p=0.003)). Furthermore, at the 4% and 14% tibia there were increased total densities (+12% to +29% p<0.01) and at the 14% tibia there was increased cortical density (+5% p=0.005) in Asians. These differences at the 14% and 38% (but not 4%) remained statistically significant after adjustment for Body Mass Index (BMI). These adaptations are similar to those seen previously in Chinese women. Asian women had reduced strength at the radius and tibia, evidenced by the 20-40% reduction in both polar Strength Strain Index (SSIp) and fracture load (under bending). Overall, the smaller bone size in South Asians is likely to be detrimental to bone strength, despite some adaptations in tibial cortical thickness and tibial and radial density which may partially compensate for this.

Premenopausal and postmenopausal differences in bone microstructure and mechanical competence in Chinese-American and white women

Compared to white women, premenopausal Chinese-American women have more plate-like trabecular (Tb) bone. It is unclear whether these findings are relevant to postmenopausal women and if there are racial differences in the deterioration of bone microarchitecture with aging. We applied individual trabecula segmentation and finite element analysis to high-resolution peripheral quantitative computed tomography images in premenopausal and postmenopausal Chinese-American and white women to quantify within-race age-related differences in Tb plate-versus-rod microarchitecture and bone stiffness. Race-menopause status interactions were assessed. Comparisons between races within menopause status were adjusted for age, height and weight. Comparisons between premenopausal and postmenopausal women were adjusted for height and weight. Adjusted analyses at the radius indicated that premenopausal Chinese-Americans had a higher plate bone volume fraction (pBV/TV), Tb plate-to-rod ratio (P-R ratio), and greater plate-plate junction densities (P-P Junc.D) versus white women (all p < 0.01), resulting in 27% higher Tb stiffness (p < 0.05). Greater cortical thickness and density (Ct.Th and Dcort) and more Tb plates led to 19% greater whole bone stiffness (p < 0.05). Postmenopausal Chinese-Americans had similar pBV/TV and P-P Junc.D, yet a higher P-R ratio versus white women. Postmenopausal Chinese-American versus white women had greater Ct.Th, Dcort, and relatively intact Tb plates, resulting in similar Tb stiffness but 12% greater whole bone stiffness (p < 0.05). In both races, Ct.Th and Dcort were lower in postmenopausal versus premenopausal women and there were no differences between races. Tb plate parameters were also lower in postmenopausal versus premenopausal women, but age-related differences in pBV/TV, P-R ratio, and P-P Junc D were greater (p < 0.05) in Chinese-Americans versus white women. There are advantages in cortical and Tb bone in premenopausal Chinese-American women. Within-race cross-sectional differences between premenopausal and postmenopausal women suggest greater loss of plate-like Tb bone with aging in Chinese-Americans, though thicker cortices and more plate-like Tb bone persists.

Clinical review: Ethnic differences in bone mass--clinical implications

CONTEXT

Differences in bone mineral density (BMD) as assessed with dual-energy x-ray absorptiometry are observed between geographic and ethnic groups, with important implications in clinical practice.

EVIDENCE ACQUISITION

PubMed was employed to identify relevant studies. A review of the literature was conducted, and data were summarized and integrated.

EVIDENCE SYNTHESIS

The available data highlight the complex ethnic variations in BMD, which only partially account for observed variations in fracture rates. Factors contributing to ethnic differences include genetics, skeletal size, body size and composition, lifestyle, and social determinants. Despite BMD differences, the gradient of risk for fracture from BMD and other clinical risk factors appears to be similar across ethnic groups. Furthermore, BMD variation is greater within an ethnic population than between ethnic populations. New imaging technologies have identified ethnic differences in bone geometry, volumetric density, microarchitecture, and estimated bone strength that may contribute to a better understanding of ethnic differences in fracture risk.

CONCLUSIONS

Factors associated with ethnicity affect BMD and fracture risk through direct and indirect mechanisms.

Volumetric bone mineral density at the spine and hip in Chinese American and White women

This study evaluated racial differences in bone size and volumetric density at the spine and hip in pre- and postmenopausal Chinese American and White women. Compared with White women, Chinese American women have greater cortical volumetric bone density (vBMD) at the hip, congruent with the results at the peripheral skeleton.

INTRODUCTION

Chinese American women have lower rates of fracture than White women despite lower areal bone density. At the forearm and tibia, however, Chinese American women have higher cortical vBMD as well as greater trabecular and cortical thickness, but smaller bone area as measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) compared with White women. Since HR-pQCT data are obtained at peripheral sites, it is unclear whether these differences are relevant to the clinically important lumbar spine and hip. This study assesses racial differences in bone size and vBMD at the spine and hip in Chinese American and White women.

METHODS

QCT of the spine and hip was measured to assess racial differences in bone size, structure, and vBMD in pre- (n = 83) and postmenopausal (n = 50) Chinese American and White women. Data were adjusted for weight, height, physical activity, total calcium intake, parathyroid hormone, and 25-hydroxyvitamin D levels.

RESULTS

Among premenopausal women, lumbar spine trabecular vBMD was 5.8% greater in Chinese American versus White women (p = 0.01). At the hip, cortical vBMD was 3% greater at the femoral neck (p = 0.05) and 3.6% greater at the total hip (p = 0.01) in premenopausal Chinese American compared with White women. Among postmenopausal women, there was no difference in lumbar spine trabecular vBMD. Cortical vBMD was 4% greater at the total hip (p = 0.02) and tended to be greater at the femoral neck (p = 0.058) in Chinese American versus White women.

CONCLUSIONS

Consistent with earlier findings in the peripheral skeleton, cortical vBMD is greater at the hip in Chinese American versus White women.