Ethnic variability in bone geometry as assessed by hip structure analysis: findings from the hip strength across the menopausal transition study

Disparities in Osteoporosis Prevention and Care: Understanding Gender, Racial, and Ethnic Dynamics

PURPOSE

Osteoporosis, the most prevalent metabolic bone disease, significantly impacts global public health by increasing fracture risks, particularly among post-menopausal women and the elderly. Osteoporosis is characterized by decreased bone mineral density (BMD) and deterioration of bone tissue, which leads to enhanced fragility. The disease is predominantly diagnosed using dual X-ray absorptiometry (DXA) and is significantly influenced by demographic factors such as age and hormonal changes. This chapter delves into the condition's complex nature, emphasizing the pervasive gender and racial disparities in its screening, diagnosis, and treatment.

RECENT FINDINGS

Recent findings highlight a substantial gap in the management of osteoporosis, with many individuals remaining under-screened and under-treated. Factors contributing to this include the asymptomatic early stages of the disease, lack of awareness, economic barriers, and inconsistent screening practices, especially in under-resourced areas. These challenges are compounded by disparities that affect different genders and races unevenly, influencing both the prevalence of the disease and the likelihood of receiving adequate healthcare services. The summary of this chapter underscores the urgent need for targeted strategies to overcome these barriers and improve health equity in osteoporosis care. Proposed strategies include enhancing public and healthcare provider awareness of osteoporosis, broadening access to diagnostic screenings, and integrating personalized treatment approaches. These efforts aim to align with global health objectives to mitigate the impacts of osteoporosis and ensure equitable health outcomes across all demographic groups.

Extended offset stems are infrequently required in anterior approach total hip arthroplasty and low usage does not compromise stability

INTRODUCTION

Extended offset (EO) stems are commonly used in posterior approach (PA) total hip arthroplasty (THA), but usage rates and complications are not well studied with anterior approach (AA) THA. This study evaluated usage rates, radiographic outcomes and complications following AA THA between patients receiving EO stems and a matched cohort receiving standard offset (SO) stems.

MATERIALS AND METHODS

This retrospective review evaluated 1515 consecutive AA THA performed between 2014 and 2021. The recent 100 EO were included in radiographic and complication analysis and were matched to 100 SO stems based on stem size, procedure (unilateral/bilateral), sex, body mass index (BMI), and age. Data collection included patient demographics; pre- and postoperative radiographic measurements of leg length difference (LLD) and global hip offset difference (GHOD); and complications within 1 year. Independent t-tests and Chi-squared analyses compared EO and SO groups.

RESULTS

EO was utilized in 8% of all AA THA. Despite matching procedures, the distribution of racial groups was different between EO and SO groups, respectively: Caucasian (75% vs. 43%), Asian (12% vs. 35%), Native Hawaiian/Pacific Islander (NHPI) (9% vs. 13%), and other (4% vs. 9%) (p < 0.001). No fractures, dislocations, or revisions occurred within 1 year after surgery in either group. One deep infection was noted in the SO group. The proportions of patients following surgery who had a GHOD < 6 mm (76% vs. 82%; p = 0.193) and LLD < 6 mm (81% vs. 86%; p = 0.223) were not significantly different between EO and SO groups, respectively.

CONCLUSIONS

Prioritizing hip symmetry over stability results in a high proportion of patients achieving hip symmetry without high usage of EO stems in AA THA. Furthermore, low use of EO stems did not result in increased dislocations. Due to racial anatomical differences, Caucasian patients required EO stems to achieve hip symmetry more frequently than Asian and NHPI patients.

Bone Density Screening Rates Among Medicare Beneficiaries: An Analysis with a focus on Asian Americans

PURPOSE

To report osteoporosis screening utilization rates among Asian American (AsA) populations in the USA.

METHODS

We retrospectively assessed the use of dual-energy X-ray absorptiometry (DXA) screening using the Medicare 5% Research Identifiable Files. Using Current Procedural Terminology (CPT) codes indicative of a DXA scan, we identified patients recommended for DXA screening according to the ACR-SPR-SSR Practice Parameters (females ≥ 65 years, males ≥ 70 years). Sociodemographic factors and their association with screening were evaluated using chi-square tests.

RESULTS

There were 80,439 eligible AsA beneficiaries, and 12,102 (15.1%) received osteoporosis screening. DXA rate for women was approximately four times greater than the rate for men (19.8% vs. 5.0%; p < 0.001). AsA beneficiaries in zip codes with higher mean household income (MHI) were more likely to have DXA than those in lower MHI areas (17.6% vs. 14.3%, p < 0.001). AsA beneficiaries aged < 80 were more likely to receive DXA (15.5%) than those aged ≥ 80 (14.1%, p < 0.001). There were 2,979,801 eligible non-AsA beneficiaries, and 496,957 (16.7%) received osteoporosis screening during the study period. Non-Hispanic white beneficiaries had the highest overall screening rate (17.5%), followed by North American Native (13.0%), Black (11.8%), and Hispanic (11.1%) beneficiaries. Comparing AsA to non-AsA populations, there were significantly lower DXA rates among AsA beneficiaries when controlling for years of Medicare eligibility, patient age, sex, location, and mean income (p < 0.001).

CONCLUSION

We found lower than expected DXA screening rates for AsA patients. A better understanding of the barriers and facilitators to AsA osteoporosis screening is needed to improve patient care.

Femora of women with premature ovarian insufficiency exhibit reduced strength and misalignment with the transmitted vertical forces from the upper body

BACKGROUND

Women with premature ovarian insufficiency (POI) lack oestrogen, which is a key determinant of bone growth, epiphyseal closure, and bone tissue organisation. Although dual-energy X-ray absorptiometry (DXA)-derived areal bone mineral density (BMD) remains the gold standard for fracture risk evaluation, it does not fully characterise the skeletal abnormalities present in these women. Hence, we aimed to assess hip/femur anatomy, strength, and geometry and femoral alignment using advanced hip analysis (AHA).

METHODS

We conducted a cross-sectional, case-control study including 89 women with spontaneous normal karyotype POI (s-POI) or iatrogenic POI (i-POI), aged 20-50 years compared with 89 age- and body mass index (BMI)-matched population-based female controls. Hip anatomy, strength, geometrical parameters, and femur alignment were measured using hip DXA images and Lunar AHA software. Femoral orientation angle (FOA) was quantified as the overall orientation of the femur with respect to the axis of the forces transmitted from the upper body.

RESULTS

The median age of POI diagnosis was 35 (18-40) years; the mean POI duration at the time of DXA was 2.07 (range 0-13) years, and 84% of POI women received oestrogen therapy. Areal BMD at all sites was significantly lower in the POI group (all P < .05). Indices of compressive and bending strength were lower in women with POI compared with controls, specifically the cross-sectional area (CSA, mm2) and section modulus (SM, mm3) (139.30 ± 29.08 vs 157.29 ± 22.26, P < .001 and 665.21 ± 129.54 vs 575.53 ± 150.88, P < .001, respectively). The FOA was smaller (124.99 ± 3.18) in women with POI as compared with controls (128.04 ± 3.80; P < .001) at baseline and after adjusting for height and femoral neck BMD.

CONCLUSION

Alongside lower BMD at multiple sites, the femora of women with POI demonstrate reduced strength and a misalignment with forces transmitted from the upper body. Further research is needed to establish the role of these newly identified features and their role in fracture risk prediction in this population.

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.

Sex- and ethnic-specific patterns in the incidence of hip fracture among older US Asian and non-Hispanic White adults

BACKGROUND

Asian and Pacific Islander (Asian/PI) adults have lower hip fracture incidence than non-Hispanic White (NHW) adults, but data regarding Asian/PI subgroups are limited. We compared hip fracture incidence among older US Asian/PI and NHW populations, including ethnic subgroup differences.

METHODS

Using observational data from a California healthcare system, we identified Asian/PI and NHW adults aged ≥50 years (2000-2019) and followed subjects to 2021 for hip fracture determined by principal/primary hospital diagnosis or by secondary hospital diagnosis with hip/femur procedure codes. Age-adjusted hip fracture incidence was calculated with 95% confidence intervals (CIs). Log-Poisson regression was used to determine fracture incidence rate ratios (IRRs, [CI]; NHW or Chinese as reference) adjusting for age and year.

RESULTS

Among 215,359 Asian/PI and 776,839 NHW women, hip fracture incidence was 1.34 (1.28-1.40) and 2.97 (2.94-3.01) per 1000 person-years, respectively, with IRR 0.45 (0.43-0.47). Among 188,328 Asian/PI and 697,046 NHW men, hip fracture incidence was 0.62 (0.58-0.67) and 1.81 (1.78-1.84) per 1000 person-years, respectively, with IRR 0.34 (0.32-0.37). For the four largest Asian/PI subgroups, Filipina women (IRR 0.85 [0.75-0.96]) had lower, and Japanese (IRR 1.36 [1.20-1.54]) and South Asian (IRR 1.36 [1.07-1.72]) women had higher hip fracture incidence compared to Chinese women. Hip fracture incidence was only higher among South Asian (IRR 1.61 [1.21-2.14]) compared to Chinese men.

CONCLUSION

Hip fracture incidence among US Asian/PI adults was 55% (women) and 66% (men) lower than NHW adults, but incidence varied by Asian/PI subgroup. The heterogeneity among Asian/PI adults highlights the importance of examining fracture risk by ethnic subgroup.

Associations Among Hip Structure, Bone Mineral Density, and Strength Vary With External Bone Size in White Women

Bone mineral density (BMD) is heavily relied upon to reflect structural changes affecting hip strength and fracture risk. Strong correlations between BMD and strength are needed to provide confidence that structural changes are reflected in BMD and, in turn, strength. This study investigated how variation in bone structure gives rise to variation in BMD and strength and tested whether these associations differ with external bone size. Cadaveric proximal femurs (n = 30, White women, 36-89+ years) were imaged using nanocomputed tomography (nano-CT) and loaded in a sideways fall configuration to assess bone strength and brittleness. Bone voxels within the nano-CT images were projected onto a plane to create pseudo dual-energy X-ray absorptiometry (pseudo-DXA) images consistent with a clinical DXA scan. A validation study using 19 samples confirmed pseudo-DXA measures correlated significantly with those measured from a commercially available DXA system, including bone mineral content (BMC) (R ²  = 0.95), area (R ²  = 0.58), and BMD (R ²  = 0.92). BMD-strength associations were conducted using multivariate linear regression analyses with the samples divided into narrow and wide groups by pseudo-DXA area. Nearly 80% of the variation in strength was explained by age, body weight, and pseudo-DXA BMD for the narrow subgroup. Including additional structural or density distribution information in regression models only modestly improved the correlations. In contrast, age, body weight, and pseudo-DXA BMD explained only half of the variation in strength for the wide subgroup. Including bone density distribution or structural details did not improve the correlations, but including post-yield deflection (PYD), a measure of bone material brittleness, did increase the coefficient of determination to more than 70% for the wide subgroup. This outcome suggested material level effects play an important role in the strength of wide femoral necks. Thus, the associations among structure, BMD, and strength differed with external bone size, providing evidence that structure-function relationships may be improved by judiciously sorting study cohorts into subgroups. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Preoperative Vitamin D Deficiency is Associated with Increased One-Year Mortality in Chinese Geriatric Hip Fracture Patients - A Propensity Score Matching Study

BACKGROUND

Vitamin D deficiency is a common comorbidity in geriatric hip fracture patients. However, there is still an ongoing debate regarding the influence of preoperative Vitamin D status on postoperative mortality in hip fracture patients.

METHODS

Elderly patients (≥60 years) who underwent surgical interventions for unilateral hip fracture from 2015 to 2020 in our center were included. We retrospectively retrieved the demographic data from the electronic medical database. Preoperative serum total 25-hydroxy-Vitamin D was set as the independent variable and patients were classified as the Vitamin D deficiency (<20ng/mL) and the control groups consequently. Clinical outcomes include all-cause mortality, walking ability, and major postoperative complications in the first postoperative year. Propensity score matching (PSM) was performed in a ratio of 1:1 in the two groups for further comparison.

RESULTS

A total of 210 patients were included and 121 patients (57.6%) were diagnosed with Vitamin D deficiency. Patients in the Vitamin D deficiency group were much older and therefore preferred peripheral nerve block, and had significantly higher proportions of females, preoperative dementia, higher ASA grade, and lower baseline serum albumin level. Overall, 79 patients were identified in the Vitamin D deficiency and control groups after PSM, respectively. Patients diagnosed with Vitamin D deficiency showed a significantly higher one-year mortality (21.5% vs 6.3%, P=0.011) and a much lower one-year independent walking rate (67.1% vs.84.8%, P=0.016) after the matching. Regarding the dataset before PSM and after PSM, the AUC for serum Vitamin D for predicting one-year mortality was 0.656 (P=0.006) and 0.695 (P=0.002), respectively.

CONCLUSION

Our retrospective PSM-design study provides new evidence that Vitamin D deficiency was associated with a significantly higher mortality and poor walking ability in the first year after surgical intervention based on southern Chinese populations.

Triglyceride Glucose-Body Mass Index Is a Reliable Indicator of Bone Mineral Density and Risk of Osteoporotic Fracture in Middle-Aged and Elderly Nondiabetic Chinese Individuals

(1) Background: This study aimed to investigate the relationship of triglyceride glucose−body mass index (TyG-BMI) with bone mineral density (BMD), femoral neck geometry, and risk of fracture in middle-aged and elderly Chinese individuals. (2) Methods: A total of 832 nondiabetic individuals were selected from the prospective population-based HOPE cohort. All individuals underwent DXA for assessment of BMD at the lumbar spine, femoral neck, and total hip, as well as femoral neck geometry. The 10-year probabilities of both major osteoporotic (MOFs) and hip fractures (HFs) were calculated. (3) Results: Cortical thickness, compression strength index, cross-sectional moment of inertia, cross-sectional area, section modulus, and 25(OH)D levels were significantly lower in women (all p < 0.001). The presence of osteoporosis was related to age, BMI, BMD and femoral neck geometry, TyG-BMI, MOF, and HF. TyG-BMI was positively correlated with BMD. In men, TyG-BMI showed significant negative correlation with HF but not with MOF, the correlation exists only after adjusting for other variables in women. Femoral neck geometries were significantly impaired in individuals with low TyG-BMI. (4) Conclusion: TyG-BMI is positively associated with BMD and geometry, and negatively associated with risk of fracture in nondiabetic middle-aged and elderly Chinese men and women.

Genetic loci implicated in meta-analysis of body shape in Africans

BACKGROUND AND AIMS

Obesity is one of the leading causes of non-communicable diseases (NCD). Thus, NCD risk varies in obese individuals based on the location of their fat depots; while subcutaneous adiposity is protective, visceral adiposity increases NCD risk. Although, previously anthropometric traits have been used to quantify body shape in low-income settings, there is no consensus on how it should be assessed. Hence, there is a growing interest to evaluate body shape derived from the principal component analysis (PCA) of anthropometric traits; however, this is yet to be explored in individuals of African ancestry whose body shape is different from those of Europeans. We set out to capture body shape in its multidimensional structure and examine the association between genetic variants and body shape in individuals of African ancestry.

METHOD AND RESULTS

We performed a genome-wide association study (GWAS) for body shape derived from PCA analysis of anthropometric traits in the Ugandan General Population Cohort (GPC, n = 6407) and the South African Zulu Cohort (SZC, n = 2595), followed by a GWAS meta-analysis to assess the genetic variants associated with body shape. We identified variants in FGF12, GRM8, TLX1NB and TRAP1 to be associated with body shape. These genes were different from the genes been associated with BMI, height, weight, WC and waist-hip ration in continental Africans. Notably, we also observed that a standard deviation change in body shape was associated with an increase in blood pressure and blood lipids.

CONCLUSION

Variants associated with body shape, as a composite variable might be different for those of individual anthropometric traits. Larger studies are required to further explore these phenomena.

Racial and Ethnic Disparities in Bone Health and Outcomes in the United States

Osteoporosis is a bone disease classified by deterioration of bone microarchitecture and decreased bone strength, thereby increasing subsequent risk of fracture. In the United States, approximately 54 million adults aged 50 years and older have osteoporosis or are at risk due to low bone mass. Osteoporosis has long been viewed as a chronic health condition affecting primarily non-Hispanic white (NHW) women; however, emerging evidence indicates racial and ethnic disparities in bone outcomes and osteoporosis management. The primary objective of this review is to describe disparities in bone mineral density (BMD), prevalence of osteoporosis and fracture, as well as in screening and treatment of osteoporosis among non-Hispanic black (NHB), Hispanic, and Asian adults compared with NHW adults living on the US mainland. The following areas were reviewed: BMD, osteoporosis prevalence, fracture prevalence and incidence, postfracture outcomes, DXA screening, and osteoporosis treatments. Although there are limited studies on bone and fracture outcomes within Asian and Hispanic populations, findings suggest that there are differences in bone outcomes across NHW, NHB, Asian, and Hispanic populations. Further, NHB, Asian, and Hispanic populations may experience suboptimal osteoporosis management and postfracture care, although additional population-based studies are needed. There is also evidence that variation in BMD and osteoporosis exists within major racial and ethnic groups, highlighting the need for research in individual groups by origin or background. Although there is a clear need to prioritize future quantitative and qualitative research in these populations, initial strategies for addressing bone health disparities are discussed. © 2021 American Society for Bone and Mineral Research (ASBMR).

Rapid preoperative predicting tools for 1-year mortality and walking ability of Asian elderly femoral neck fracture patients who planned for hip arthroplasty

BACKGROUND

Femoral neck fractures in elderly patients typically warrant operative treatment and are related to high risks of mortality and morbidity. As early hip arthroplasties for elderly femoral neck fractures are widely accepted, rapid predicting models that allowed quantitative and individualized prognosis assessments are strongly needed as references for orthopedic surgeons during preoperative conversations.

METHODS

Data of patients aged ≥ 65 years old who underwent primary unilateral hemiarthroplasty or total hip arthroplasty due to femoral neck fracture between January 1st, 2012 and June 30th, 2019 in our center were collected. Candidate variables included demographic data, comorbidities, and routine preoperative screening tests. The main outcomes included 1-year mortality and free walking rate after hip arthroplasty. Patients were randomly divided into derivation and validation groups in the ratio of three to one. Nomograms were developed based on multivariable logistic regressions of derivation group via R language. One thousand bootstraps were used for internal validation. Those models were further tested in the validation group for external validation.

RESULTS

The final analysis was performed on 702 patients after exclusion and follow-up. All-cause 1-year mortality of the entire data set was 23.4%, while the free walking rate was 57.3%. Preoperative walking ability showed the biggest impact on predicting 1-year mortality and walking ability. Static nomograms were created from the final multivariable models, which allowed simplified graphical computations for the risks of 1-year mortality and walking ability in a certain patient. The bias-corrected C index of those nomograms for predicting 1-year mortality in the derivation group and the validation group were 0.789 and 0.768, while they were 0.807 and 0.759 for predicting postoperative walking ability. The AUC of the mortality and walking ability predicting models were 0.791 and 0.818, respectively.

CONCLUSIONS

Our models enabled rapid preoperative 1-year mortality and walking ability predictions in Asian elderly femoral neck fracture patients who planned for hip arthroplasty, with adequate predictive discrimination and calibration. Those rapid assessment models could help surgeons in making more reasonable clinical decisions and subsequently reducing the risk of potential medical dispute via quantitative and individualized prognosis assessments.

Newly developed hip geometry parameters are associated with hip fracture

BACKGROUND

The conventional and newly developed geometry parameters at the femoral neck have formed a large geometry profile and their relationship with hip fracture was largely unknown. We aimed to evaluate the relationship between the geometry profile and hip fracture in Chinese.

METHODS

The hip geometry profile contains seven conventional geometry parameters at femoral neck (FN) and thirty newly developed parameters at three sub-regions (Narrow Neck, NN; Intertrochanter, IT; Femoral shaft, FS) of the total hip. Based on 6294 recruited Chinese (≥65 years), 97 subjects with osteoporotic fracture (OF) history and 388 matched controls were selected. The t test, Chi-square statistic, conditional logistic regression model were used.

RESULTS

Three geometric parameters (endocortical diameter, ED; cortical thickness, CT; buckling ratio, BR) have consistent differences at all the sites between the cases and controls (p < 0.01). Conventional geometry parameters (e.g., cross-sectional area, CSA; BR) and the newly developed parameters (e.g., NN_ED, NN_Outer Diameter, IT_ED) were identified as the risk factors of hip fracture independent of BMD. The additional predictive ability of the hip geometric parameters, over BMD alone, (receiver operating characteristic curve (ROC) analysis) was improved. Especially at NN, the area of ROC used single NN_BMD is only 0.596, but increased rapidly at 0.705 when combined with the hip geometric parameters.

CONCLUSIONS

This study found that three newly developed hip geometry parameters are associated with hip fracture. The results will increase our understanding of the determinants of fracture and provide potential clue for future prevention of fracture in Chinese Population.

Current Applications and Selected Technical Details of Dual-Energy X-Ray Absorptiometry

The application of dual-energy X-ray absorptiometry (DXA) examinations in the assessment of bone mineral density (BMD) in the lumbar spine, hip, and forearm is the basic diagnostic method for recognition of osteoporosis. The constant development of DXA technique is due to the aging of societies and the increasing importance of osteoporosis as a public health problem. In order to assess the degree of bone demineralization in patients with hyperparathyroidism, forearm DXA examination is recommended. The vertebral fracture assessment (VFA) of the thoracic and lumbar spine, performed by a highly-skilled technician, is an interesting alternative to the X-ray examination. The DXA total body examination can be useful in the evaluation of fat redistribution among patients after bariatric surgery, in patients infected with HIV and receiving antiretroviral therapy, and in patients with metabolic diseases and suspected to have sarcopenia. The assessment of visceral adipose tissue (VAT) and detection of abdominal aortic calcifications may be useful in the prediction of cardiovascular events. The positive effect of anti-resorptive therapy may affect some parameters of DXA hip structure analysis (HSA). Long-term anti-resorptive therapy, especially with the use of bisphosphonates, may result in changes in the DXA image, which may herald atypical femur fractures (AFF). Reduction of the periprosthetic BMD in the DXA measurements can be used to estimate the likelihood of loosening the prosthesis and periprosthetic fractures. The present review aims to present current applications and selected technical details of DXA.

Using Z-score to optimize population-specific DDH screening: a retrospective study in Hangzhou, China

BACKGROUND

DDH (Developmental Dysplasia of the Hip) screening can potentially avert many morbidities and reduce costs. The debate about universal vs. selective DDH ultrasonography screening in different countries revolves to a large extent around effectiveness, cost, and the possibility of overdiagnosis and overtreatment. In this study, we proposed and evaluated a Z-score enhanced Graf method to optimize population-specific DDH screening.

METHODS

A total of 39,710 history ultrasonography hip examinations were collected to establish a sex, side specific and age-based Z-scores model using the local regression method. The correlation between Z-scores and classic Graf types was analyzed. Four thousand two hundred twenty-nine cases with follow-up ultrasonographic examinations and 5284 cases with follow-up X-ray examinations were used to evaluate the false positive rate of the first examination based on the subsequent examinations. The results using classic Graf types and the Z-score enhanced types were compared.

RESULTS

The Z-score enhanced Graf types were highly correlated with the classic Graf's classification (R = 0.67, p < 0.001). Using the Z-scores ≥2 as a threshold could reduce by 86.56 and 80.44% the false positives in the left and right hips based on the follow-up ultrasonographic examinations, and reduce by 78.99% false-positive cases based on the follow-up X-ray examinations, respectively.

CONCLUSIONS

Using an age, sex and side specific Z-scores enhanced Graf's method can better control the false positive rate in DDH screening among different populations.

Hip Structural Analysis Reveals Impaired Hip Geometry in Girls With Type 1 Diabetes

CONTEXT

Among patients with type 1 diabetes (T1D), the risk of hip fracture is up to 6-fold greater than that of the general population. However, the cause of this skeletal fragility remains poorly understood.

OBJECTIVE

To assess differences in hip geometry and imaging-based estimates of bone strength between youth with and without T1D using dual-energy x-ray absorptiometry (DXA)-based hip structural analysis.

DESIGN

Cross-sectional comparison.

PARTICIPANTS

Girls ages 10 to 16 years, including n = 62 with T1D and n = 61 controls.

RESULTS

The groups had similar age, bone age, pubertal stage, height, lean mass, and physical activity. Bone mineral density at the femoral neck and total hip did not differ in univariate comparisons but was lower at the femoral neck in T1D after adjusting for bone age, height, and lean mass. Subjects with T1D had significantly lower cross-sectional area, cross-sectional moment of inertia, section modulus, and cortical thickness at the narrow neck, with deficits of 5.7% to 10.3%. Cross-sectional area was also lower at the intertrochanteric region in girls with T1D. Among those T1D subjects with HbA1c greater than the cohort median of 8.5%, deficits in hip geometry and strength estimates were more pronounced.

CONCLUSIONS

DXA-based hip structural analysis revealed that girls with T1D have unfavorable geometry and lower estimates of bone strength at the hip, which may contribute to skeletal fragility and excess hip fracture risk in adulthood. Higher average glycemia may exacerbate effects of T1D on hip geometry.

Effect of vitamin D on bone strength in older African Americans: a randomized controlled trial

There is controversy over whether African Americans have higher vitamin D requirements than recommended by the Institute of Medicine. We previously reported that maintaining serum 25(OH)D above 30 ng/mL does not prevent age-related bone loss. Herein, we report that bone strength is also unaffected by maintaining this level in this population.

INTRODUCTION

The role of vitamin D in bone strength has not been investigated in the African American (AA) population.

METHODS

A 3-year randomized controlled trial was designed to examine the effect of vitamin D supplementation on physical performance, bone loss, and bone strength in healthy older AA women. A total of 260 postmenopausal AA women, ages ≥ 60 years were randomized to a vitamin D₃ or placebo arm. Vitamin D₃ dose was adjusted to maintain serum 25OHD > 30 ng/mL. Bone mineral density, femoral axis length, and femoral neck (FN) width were measured by dual-energy X-ray absorptiometry. Composite indices of FN strength [compression strength index (CSI), bending strength index (BSI), and impact strength index (ISI)] were computed.

RESULTS

The mean age of participants was 68.2 ± 4.9 years. Baseline characteristics between groups were similar. The average dose of vitamin D₃ was 3490 ± 1465 IU/day in the active group. The mean serum 25OHD was 46.8 ± 1.2 ng/mL versus 20.7 ± 1.1 ng/mL in the active versus placebo group. Serum 25OHD did not correlate with any composite indices. The longitudinal differences observed in FN width, CSI, BSI, and ISI in both groups were not statistically significant (all p values > 0.05). Further, there was no group × time interaction effect for any of the composite indices (all p values > 0.05).

CONCLUSION

Maintaining serum 25OHD > 30 ng/mL (75 nmol/L) does not affect bone strength in older AA women. There is no evidence to support vitamin D intake greater than the recommended RDA by the Institute of Medicine in this population for bone strength.

Altered topological blueprint of trabecular bone associates with skeletal pathology in humans

Bone is a hierarchically organized biological material, and its strength is usually attributed to overt factors such as mass, density, and composition. Here we investigate a covert factor – the topological blueprint, or the network organization pattern of trabecular bone. This generally conserved metric of an edge-and-node simplified presentation of trabecular bone relates to the average coordination/valence of nodes and the equiangular 3D offset of trabeculae emanating from these nodes. We compare the topological blueprint of trabecular bone in presumably normal, fractured osteoporotic, and osteoarthritic samples (all from human femoral head, cross-sectional study). We show that bone topology is altered similarly in both fragility fracture and in joint degeneration. Decoupled from the morphological descriptors, the topological blueprint subjected to simulated loading associates with an abnormal distribution of strain, local stress concentrations and lower resistance to the standardized load in pathological samples, in comparison with normal samples. These topological effects show no correlation with classic morphological descriptors of trabecular bone. The negative effect of the altered topological blueprint may, or may not, be partly compensated for by the morphological parameters. Thus, naturally occurring optimization of trabecular topology, or a lack thereof in skeletal disease, might be an additional, previously unaccounted for, contributor to the biomechanical performance of bone, and might be considered as a factor in the life-long pathophysiological trajectory of common bone ailments.

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Mechanical performance of the skeleton results from many factors and their interplay.

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Topological blueprint as a basic trabecular design plan is an understudied factor.

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Topological blueprint deviation undermines mechanical properties of trabecular bone.

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Higher bone mass or thicker trabeculae do not compensate for deviant topology.

Longitudinal changes in hip geometry in relation to the final menstrual period: Study of Women's Health Across the Nation (SWAN)

BACKGROUND

In SWAN, we showed that accelerated loss of bone mineral density (BMD) begins 1 year before the final menstrual period (FMP) to 2 years after the FMP and slows thereafter. However, the risk of fracture depends on both BMD and bone geometry. The hip structural analysis (HSA) measures important geometric properties of bone. Changes in HSA parameters across the menopausal transition have not been previously assessed.

METHODS

The current analysis uses data from SWAN, 5 years before to 5 years after FMP (N = 900, Age (mean(SD)) = 46.85(2.60), 44% White). HSA parameters at the femoral narrow neck were obtained from 2D DXA scans and normalized to baseline values. FMP was determined from annual interviews. Changes in HSA were assessed over 3 periods, 5 to 2 years before FMP (pre-transmenopausal), 2 years before to 1 years after FMP (transmenopausal), 1 to 5 years after FMP (postmenopausal). Mixed linear models with random slopes were used to estimate the rate of change in HSA parameters relative to FMP.

RESULTS

Loss of BMD, cross-sectional area (CSA), and section modulus (SM) and increases in outer diameter (OD) were greatest in the transmenopausal period (p for all<0.05). Changes continued in the postmenopausal period but were not statistically significant. The cumulative percentage changes over 10 years in BMD (-10.67%), CSA (-9.01), SM (-7.03) and OD (+1.95) were statistically significant.

CONCLUSION

Changes in hip geometry across the menopause transition parallel changes in BMD and provide insight into mechanisms that may increase risk of fragility fracture.

Trabecular Bone Score and Hip Structural Analysis in Patients With Atypical Femur Fractures

Bisphosphonate use has declined dramatically in recent years, partly because of fear of rare side effects like atypical femur fractures (AFFs). It is therefore desirable to have a diagnostic method to identify those at risk of AFF to prevent this serious complication. We compared trabecular microarchitecture and hip geometry between 30 patients with AFF and 141 controls of similar age and sex, using bisphosphonates. Trabecular bone score (TBS) and hip structural analysis (HSA) were used to assess trabecular microarchitecture and macroscopic hip geometry from dual-energy X-ray absorptiometry images of the lumbar spine and hip, respectively. General characteristics, TBS, and HSA were compared between patients with AFF and controls using Student's t tests and chi-square statistics. Associations between AFF and TBS and femur geometric characteristics by HSA were adjusted for sex, age, height, weight, ethnicity, duration of bisphosphonate use, and glucocorticoid use. Additionally, the analysis of TBS was adjusted for lumbar spine bone mineral density and the time difference between dual-energy X-ray absorptiometry scanning and the diagnosis of AFF. Patients with AFF had significantly higher body mass index than controls, had used bisphosphonates longer, and glucocorticoids and proton pump inhibitors more frequently. Sex-specific T-score was significantly higher in patients with AFF at the lumbar spine (p = 0.004), but not at the femoral neck (p = 0.190) after adjustment for age, height, and weight. TBS did not differ significantly between patients with AFF and controls. Neither neck shaft angle nor any geometric variables at the femoral shaft measured by HSA differed between patients with AFF and controls. At the narrow neck, patients with AFF had lower buckling ratio and higher centroid position, consistent with a lower risk of classical fragility hip fractures. The findings at narrow neck and higher bone mineral density might be explained by the fact that the majority of patients with AFF used bisphosphonates to prevent glucocorticoid-induced osteoporosis. Based on our results, TBS and HSA do not appear to have value in detecting patients at risk of AFF.

Bone Health During the Menopause Transition and Beyond

The menopause transition is a critical period for bone health, with rapid losses in bone mass and strength occurring in a 3-year window bracketing the date of the final menstrual period. Declines in bone mass are accompanied by deleterious changes in bone macrostructure and microarchitecture, which may be captured by changes in composite strength indices and indices of trabecular thickness and connectivity. The onset of the rapid bone loss phase is preceded by changes in sex steroid hormones and increases in markers of bone resorption, measurements of which may be clinically useful in predicting the onset of the rapid loss phase and in identifying the women who will lose the most bone strength over the menopause transition.

Influence of Different Reference Databases on Categorization of Bone Mineral Density: A Study on Rural Postmenopausal Women from Southern India

BACKGROUND AND OBJECTIVES

Currently available DXA (Dual energy X-ray Absorptiometry) scanners utilise bone mineral density (BMD) of Caucasian population to calculate T scores and categorise BMD. We studied the influence of various databases on classification of BMD in south-Indian postmenopausal women aged above 50 years.

METHODOLOGY

This was a cross-sectional study. Hologic DXA scanner was used to estimate BMD at lumbar spine (LS) and femoral neck (FN). T scores of ≤-2.5, -2.4 to -1, -0.9 to +1 were diagnostic of osteoporosis, osteopenia and normal respectively. Three reference databases(Italian, Korean and north Indian) were used to recalculate T scores. The agreement (K=kappa) between manufacturer provided database and the other databases was studied. The impact of different databases in diagnosing osteoporosis in subjects with FN fracture was assessed.

RESULTS

A total of 1956 postmenopausal women with mean (SD) age of 62 (4.3) years and 211 femoral neck(FN) fracture subjects with mean(SD) age of 68 (7.2) years were recruited. In subjects with fracture, osteoporosis at FN was found in 72% with Caucasian, 88% with North Indian, 56% with Italian, and 45% with Korean database. On comparing manufacturer provided database with the other population-specific reference, there was perfect agreement with north Indian (κ = 0.81 [FN], κ = 0.82 [LS]) and good agreement with the Italian database (κ = 0.78 [FN], κ = 0.74 [LS]).

CONCLUSION

North-Indian database identified most of the participants with FN fracture as having osteoporosis and had perfect agreement with the manufacturer's database. Follow up studies will further validate the impact of utilizing this database in clinical practice.

Differences in femoral neck structure between elderly Caucasian and Chinese populations: a cross-sectional study of Perth-Beijing cohorts

Structural skeletal differences of the femoral neck of older Beijing-Chinese and Perth-Caucasian women were compared; adjusting for frame size-related differences, Beijing-Chinese have lower periosteal width; however, indices of internal bone distribution suggest that Beijing-Chinese may exhibit increased resistance to fracture that may relate to the reduced hip fracture incidence.

INTRODUCTION

Ethnic differences in skeletal structure may relate to differences in hip fracture risk in Chinese and Caucasian populations. 2D mass, size, and structural biomechanics were compared in the two populations.

METHODS

Quantitative computed tomography-derived geometric variables were compared in age-matched community-derived female populations, 196 Beijing-Chinese 76.5 ± 4.8 (mean ± SD) years and 237 Perth-Caucasians 77.1 ± 5.0 years. These included scanned area (A), periosteal width (W), bone mineral content (BMC), aBMD, bone cross-sectional area (bCSA), section modulus (Z) and buckling ratio (BR). Assumption-free measures included sigma (σ), related to the distribution of bone in the scanned image previously identified as a predictor of hip fracture, and delta (δ), the center-of-mass displacement from the geometric center.

RESULTS

Compared to Beijing-Chinese, Perth-Caucasians were heavier (Beijing-Chinese 58.7 ± 11.8; Perth-Caucasians 66.1 ± 11.0 kg), taller (154.9 ± 16.7 vs 158.9 ± 6.0 cm), and had higher BMC, A, and W. After adjustment for frame size, BMC was not significantly different but W remained higher in Perth-Caucasians. Differences in variables aBMD, Z, BR, and σ favored higher resistance to failure with Beijing-Chinese before and after adjustment for frame size. δ was similar in both populations; bCSA was higher in Beijing-Chinese before adjustment for frame size but not after.

CONCLUSIONS

Bone mass differences in two populations were related to frame size differences. However, femoral neck width remained smaller in Beijing-Chinese suggesting effects of local genetic and environmental factors. In Beijing-Chinese participants compared to Perth-Caucasians, internal bone distribution suggests increased resistance to deformation if exposed to same force that may, in-part, relate to reduced incidence of hip fracture in Beijing-Chinese.

Femoral Neck External Size but not aBMD Predicts Structural and Mass Changes for Women Transitioning Through Menopause

The impact of adult bone traits on changes in bone structure and mass during aging is not well understood. Having shown that intracortical remodeling correlates with external size of adult long bones led us to hypothesize that age-related changes in bone traits also depend on external bone size. We analyzed hip dual-energy X-ray absorptiometry images acquired longitudinally over 14 years for 198 midlife women transitioning through menopause. The 14-year change in bone mineral content (BMC, R²  = 0.03, p = 0.015) and bone area (R²  = 0.13, p = 0.001), but not areal bone mineral density (aBMD, R²  = 0.00, p = 0.931) correlated negatively with baseline femoral neck external size, adjusted for body size using the residuals from a linear regression between baseline bone area and height. The dependence of the 14-year changes in BMC and bone area on baseline bone area remained significant after adjusting for race/ethnicity, postmenopausal hormone use, the 14-year change in weight, and baseline aBMD, weight, height, and age. Women were sorted into tertiles using the baseline bone area-height residuals. The 14-year change in BMC (p = 0.009) and bone area (p = 0.001) but not aBMD (p = 0.788) differed across the tertiles. This suggested that women showed similar changes in aBMD for different structural and biological reasons: women with narrow femoral necks showed smaller changes in BMC but greater increases in bone area compared to women with wide femoral necks who showed greater losses in BMC but without large compensatory increases in bone area. This finding is opposite to expectations that periosteal expansion acts to mechanically offset bone loss. Thus, changes in femoral neck structure and mass during menopause vary widely among women and are predicted by baseline external bone size but not aBMD. How these different structural and mass changes affect individual strength-decline trajectories remains to be determined. © 2017 American Society for Bone and Mineral Research.

Applying ethnic-specific bone mineral density T-scores to Chinese women in the USA

Caucasian reference data are used to classify bone mineral density in US women of all races. However, use of Chinese American reference data yields lower osteoporosis prevalence in Chinese women. The reduction in osteoporosis labeling may be relevant for younger Chinese women at low fracture risk.

INTRODUCTION

Caucasian reference data are used for osteoporosis classification in US postmenopausal women regardless of race, including Asians who tend to have lower bone mineral density (BMD) than women of white race. This study examines BMD classification by ethnic T-scores for Chinese women.

METHODS

Using BMD data in a Northern California healthcare population, Chinese women aged 50-79 years were compared to age-matched white women (1:5 ratio), with femoral neck (FN), total hip (TH), and lumbar spine (LS) T-scores calculated using Caucasian versus Chinese American reference data.

RESULTS

Comparing 4039 Chinese and 20,195 white women (44.8 % age 50-59 years, 37.5 % age 60-69 years, 17.7 % age 70-79 years), Chinese women had lower BMD T-scores at the FN, TH, and LS (median T-score 0.29-0.72 units lower across age groups, p < 0.001) using Caucasian reference data. Using Chinese American BMD reference data resulted in an average +0.47, +0.36, and +0.48 units higher FN, TH, and LS T-scores, respectively, reducing the prevalence of osteoporosis (T-score ≤ -2.5) in Chinese women at the FN (16.7 to 6.6 %), TH (9.8 to 3.2 %), and LS (23.2 to 8.9 %); osteoporosis prevalence at any one of three sites fell from 29.6 to 12.6 % (22.4 to 8.1 % for age 50-64 years and 43.2 to 21.0 % for age 65-79 years).

CONCLUSION

Use of Chinese American BMD reference data yields higher (ethnic) T-scores by 0.4-0.5 units, with a large proportion of Chinese women reclassified from osteoporosis to osteopenia. The reduction in osteoporosis labeling with ethnic T-scores may be relevant for younger Chinese women at low fracture risk.

Ethnic differences in heterotopic ossification following total hip arthroplasty

Aims

We aimed to assess the influence of ethnicity on the incidence of heterotopic ossification (HO) after total hip arthroplasty (THA).

Patients and Methods

We studied the six-month post-operative anteroposterior radiographs of 1449 consecutive primary THAs (1324 patients) and retrospectively graded them for the presence of HO, using the Brooker Classification.

Results

Based on multivariate analysis, African-American ethnicity was an independent risk factor for HO formation following THA with an adjusted odds ratio (OR) of 2.6 (95% confidence interval (CI) 1.3 to 5.2, p = 0.007) for severe HO and 1.9 (95% CI 1.3 to 2.7, p < 0.001) for any grade of HO.

Conclusion

Given the increased risk of HO formation, particularly high grade HO, and the potentially poorer outcomes associated with HO, it is important to consider using prophylaxis against HO in patients of African-American ethnicity undergoing THA. Take home message: African Americans are at an increased risk for developing heterotopic ossification and thus may benefit from HO prophylaxis. Cite this article: Bone Joint J 2016;98-B:761–6.

A biomechanical sorting of clinical risk factors affecting osteoporotic hip fracture

Osteoporotic fracture has been found associated with many clinical risk factors, and the associations have been explored dominantly by evidence-based and case-control approaches. The major challenges emerging from the studies are the large number of the risk factors, the difficulty in quantification, the incomplete list, and the interdependence of the risk factors. A biomechanical sorting of the risk factors may shed lights on resolving the above issues. Based on the definition of load-strength ratio (LSR), we first identified the four biomechanical variables determining fracture risk, i.e., the risk of fall, impact force, bone quality, and bone geometry. Then, we explored the links between the FRAX clinical risk factors and the biomechanical variables by looking for evidences in the literature. To accurately assess fracture risk, none of the four biomechanical variables can be ignored and their values must be subject-specific. A clinical risk factor contributes to osteoporotic fracture by affecting one or more of the biomechanical variables. A biomechanical variable represents the integral effect from all the clinical risk factors linked to the variable. The clinical risk factors in FRAX mostly stand for bone quality. The other three biomechanical variables are not adequately represented by the clinical risk factors. From the biomechanical viewpoint, most clinical risk factors are interdependent to each other as they affect the same biomechanical variable(s). As biomechanical variables must be expressed in numbers before their use in calculating LSR, the numerical value of a biomechanical variable can be used as a gauge of the linked clinical risk factors to measure their integral effect on fracture risk, which may be more efficient than to study each individual risk factor.

Effects of load-bearing exercise on skeletal structure and mechanics differ between outbred populations of mice

Effects of load-bearing exercise on skeletal structure and mechanical properties can vary between inbred strains of mice. Here, we examine whether such variation also exists at the population level. An experiment was performed with two outbred mouse stocks that have been reproductively isolated for >120 generations (Hsd:ICR, Crl:CD1). Growing females from each stock were either treated with a treadmill-running regimen for 1 month or served as controls. Limb forces were recorded with a force plate and cage activity monitored to verify that they were similar between stocks. After the experiment, femoral cortical and trabecular bone structure were quantified with micro-CT in the mid-diaphysis and distal metaphysis, respectively, and diaphyseal structural strength was determined with mechanical testing. Among Hsd:ICR mice, running led to significant improvements in diaphyseal bone quantity, structural geometry, and mechanical properties, as well as enhanced trabecular morphology. In contrast, among Crl:CD1 mice, the same running regimen had little effect on cortical and trabecular structure and significantly reduced diaphyseal resistance to fracture. In neither stock was body mass, muscle mass, or cage activity level different between runners and controls. Given that most environmental variables were controlled in this study, the differential effects of exercise on Hsd:ICR and Crl:CD1 bones were likely due to genetic differences between stocks. These results suggest that the benefits of loading for bone may vary between human populations (e.g., ethnic groups), in which case exercise programs and technologies designed to promote bone health with mechanical signals may be more advantageous to certain populations than others.

Ethnic differences in bone health

There are differences in bone health between ethnic groups in both men and in women. Variations in body size and composition are likely to contribute to reported differences. Most studies report ethnic differences in areal bone mineral density (aBMD), which do not consistently parallel ethnic patterns in fracture rates. This suggests that other parameters beside aBMD should be considered when determining fracture risk between and within populations, including other aspects of bone strength: bone structure and microarchitecture, as well as muscle strength (mass, force generation, anatomy) and fat mass. We review what is known about differences in bone-densitometry-derived outcomes between ethnic groups and the extent to which they account for the differences in fracture risk. Studies are included that were published primarily between 1994 and 2014. A "one size fits all approach" should definitely not be used to understand better ethnic differences in fracture risk.

Thyrotropin levels within the lower normal range are associated with an increased risk of hip fractures in euthyroid women, but not men, over the age of 65 years

CONTEXT

The contemporary literature on the relationship between serum TSH levels and osteoporotic fractures in euthyroid individuals is limited by conflicting results and analyses conducted on a small number of fractures.

OBJECTIVE

Our objective was to examine the association between the normal range of variation of TSH and the incidence of hip fractures in male and female euthyroid patients aged 65 years or older.

DESIGN AND SETTING

We performed a population-based historical prospective cohort study within the Clalit Health Services population.

PARTICIPANTS

Clalit Health Services members aged ≥65 years with at least 1 TSH measurement during the year 2004. We excluded patients with preexisting hip fracture, thyroid disease, malignancy, or chronic kidney disease.

OUTCOME MEASURES

The primary outcome was hip fracture, and the secondary outcome was any other osteoporotic fracture.

STATISTICAL ANALYSIS

Adjusted odds ratios comparing episodes of each outcome across 3 TSH groups (low, 0.35-1.6 mIU/L; intermediate, 1.7-2.9 mIU/L; high, 3-4.2 mIU/L) were generated using logistic regression models.

RESULTS

The 14 325 included participants suffered from 514 hip fractures (mean follow-up, 102 ± 3 months). Women, but not men, in the lowest TSH group had a higher incidence of hip fractures (odds ratio = 1.28, 95% confidence interval = 1.03-1.59, P = .029) when compared with the intermediate group, after multivariate adjustment for age, comorbidities, and use of drugs affecting bone metabolism. There was no difference in hip fracture incidence between intermediate- and high-TSH groups. No association was found between TSH levels and other osteoporotic fractures.

CONCLUSIONS

TSH levels within the lower normal range are associated with an increased risk of hip fractures in euthyroid women, but not men, aged 65 years and more.

Race/ethnic differences in associations between bone mineral density and fracture history in older men

SUMMARY

To determine whether there are race/ethnic differences in bone mineral density (BMD) by fracture history in men aged 65 years and older, we performed cross-sectional analysis in five large independent cohorts. Low BMD was associated with a higher prevalence of fracture in all cohorts, and the magnitude of the BMD differences by fracture status was similar across groups.

INTRODUCTION

We aimed to determine whether there are race/ethnic and geographic differences in bone mineral density by fracture history in men aged 65 years and older.

METHOD

The datasets included the Osteoporotic Fractures in Men (MrOS) Study (5,342 White, 243 African-American, 190 Asian, and 126 Hispanic), MrOS Hong Kong (1,968 Hong Kong Chinese), Tobago Bone Health Study (641 Afro-Caribbean), Namwon Study (1,834 Korean), and Dong-gu Study (2,057 Korean). The two Korean cohorts were combined.

RESULTS

The prevalence of self-reported non-traumatic fracture was US white, 17.1 %; Afro-Caribbean, 5.5 %; US African-American, 15.1 %; US Hispanic, 13.7 %; US Asian, 10.5 %; Hong Kong Chinese, 5.6 %, and Korean, 5.1 %. The mean differences in hip and lumbar spine BMD between subjects with fracture and without fracture were statistically significant in all cohorts except US African American and US Asian men. There was a significant race/ethnic interaction for lumbar spine BMD by fracture status (p for interaction = 0.02), which was driven by the small number of Hispanic men. There was no interaction for femoral neck or total hip BMD. There were no significant race/ethnic differences in the odds ratio of fracture by BMD.

CONCLUSIONS

Low BMD was associated with a higher prevalence of fracture in all cohorts and the magnitude of the BMD differences by fracture status was similar across groups suggesting homogeneity in the BMD-fracture relationship among older men.

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.

Risk factors for fracture in middle-age and older-age men of African descent

Although fracture rates are lower in individuals of African descent compared to individuals of European ancestry, morbidity and mortality following a fracture may be greater in individuals of African ancestry. However, fracture risk and associated clinical risk factors have not been well-defined among African ancestry populations, especially among men of African ancestry. We used data collected from the Tobago Bone Health Study to examine potential clinical risk factors for incident fractures, including demographic information, anthropometric measurements, medical history, lifestyle factors, bone mineral density (BMD), and hip structural geometry. Among 1933 Afro-Caribbean men aged ≥40 years at study entry (mean age: 57.2 ± 11.0 years), 65 reported at least one new fracture during 10 years of subsequent follow-up. Younger age, mixed Afro-Caribbean ancestry, prior fracture history, BMD, and hip structural geometry were statistically significant risk factors for incident fractures. A 1-SD change in several skeletal parameters (hip BMD, cross-sectional area, outer diameter, cortical thickness, and buckling ratio) were each associated with a 35% to 56% increase in incident fracture risk after adjusting for age. Men with a prior fracture history were three times more likely to experience a new fracture during follow-up, and the association remained strong after adjusting for age, mixed Afro-Caribbean ancestry, and skeletal parameters (hazard ratios ranged from 2.72 to 2.82). Our findings suggest that except for age, risk factors for fracture in men of African ancestry are similar to established risk factors in white populations. Prior fracture history is a powerful and independent risk factor for incident fractures among men of African ancestry and could easily be incorporated into clinical risk evaluation.