Women with previous fragility fractures can be classified based on bone microarchitecture and finite element analysis measured with HR-pQCT

Automated micro-CT morphometry of femoral biopsies from hip arthroplasties: adaptive local thresholding, volume of interest wrapping and removal of debris

Bone biopsies are an important biological tool for investigating bone microarchitecture, which can be non-destructively imaged in 3D via micro-computed tomography (micro-CT). Image thresholding and delineation of a region of interest (ROI) are prerequisites for quantifying bone parameters. Validated automatic protocols enable quantification of biopsies that contain trabecular and cortical bone. However, irregularly shaped trabecular bone biopsies with peripheral and internal debris have required manual ROI delineation, which is time-intensive and subject to inter and intra-observer variance. We hypothesise that an automated workflow will be a suitable alternative to overcome these issues and objectively determine bone microarchitecture in surgical biopsies, at higher throughput suitable for clinical studies. Hence, the aim of this study was to develop an objective, reproducible and automated workflow to analyse microarchitecture of trabecular bone biopsies. To accomplish this aim, we tested six different methods of ROI delineation: a whole biopsy ROI, and both manual (slow) and automatically delineated (fast) reduced ROIs to remove peripheral debris, each with (adaptive thresholding and a set of morphological operations to remove debris) and without (global thresholding) processing in a subset (n = 8) of intertrochanteric femoral biopsies obtained from patients undergoing hip arthroplasty. Number of objects, bone volume to tissue volume (BV/TV), trabecular separation (Tb.Sp), structure model index (SMI) and Euler number and trabecular pattern factor (Tb.Pf) were compared between the six workflows using Friedman's test and post-hoc pairwise comparisons with Bonferroni correction was performed. The two most reproducible techniques were tested for validation in a larger cohort of arthroplasty patients (n = 60) and results were compared with appropriate t-test. Subset analysis indicated that the manual and automated ROI with processing increased the ability to resolve real differences between these groups in parameters BV/TV, Tb.Sp and Euler number compared to with no processing and whole biopsy ROI approach. A validation cohort consisted of thirty osteoarthritis patients with a mean age 68.25 ± 8.64 and thirty neck of femur fracture with a mean age 82.4 ± 8.9. The manual technique failed to detect differences in BV/TV, SMI and Tb.Pf between the two patient groups (p > 0.05, for all) while the automated workflow demonstrated significant differences in these parameters between the OA and the NOF patients (p < 0.05). This is probably due to irregularity in the reference VOI volume introduced by manual ROI delineation reducing morphometric precision, compared to the automated method. In conclusion, our automated workflow performed better than customary practice; it represents a user-independent, high throughput technique to measure bone microarchitecture accurately in surgical biopsies.

Strength and strain distributions obtained from digital wrist tomosynthesis discriminate patients with and without a history of fragility fracture

Bone fractures due to osteoporosis are a significant problem. Limited accuracy of standard bone mineral density (BMD) for fracture risk assessment, combined with low adherence to bone health screening precludes identification of those at risk of fracture. Because of the wide availability of digital breast tomosynthesis (DBT) imaging, bone screening using a DBT scanner at the time of breast screening has been proposed. Earlier studies have shown that BMD, microstructure, and stiffness of the distal radius can be calculated using digital tomosynthesis imaging of the wrist (DWT). However, strength and stress/strain parameters, which are more relevant to structural failure, and have the potential to enhance the utility of DWT, were not examined previously. Therefore, this study aimed to examine the ability of DWT to discriminate patients with and without fragility fracture using DWT based finite element (DWT-FE) derived strength and stress/strain distribution properties, and to determine in vivo repeatability of these biomechanical properties. Twenty-two postmenopausal women with any fragility fracture (included spine, hip, distal radius, humerus and tibia fractures) and 68 without were recruited. Each participant's nondominant arm (dominant arm if history of fracture in the nondominant arm) was scanned with DWT and compressive loading was simulated using FE modeling. Six additional patients were DWT-scanned thrice, with repositioning, to determine the repeatability of the study variables. Age and T-score were not different between fracture and nonfracture groups (p > 0.1), but strength and stress/strain parameters were significant predictors of fracture status (AUC = 0.64-0.74). Standard deviation of tensile strain was the most discriminatory variable for fracture status (AUC = 0.74) and was independent from stiffness. Repeatability error of DWT biomechanical properties was 0.7 % to 5.8 %. This study demonstrated that DWT-FE based strength and standard deviation of tensile strain were reproducible and predict fracture status independent from BMD and stiffness. The results suggest that the accuracy of fracture risk screening can be improved in the highly accessible environment of mammographic imaging.

Quantitative ultrasound imaging reveals distinct fracture-associated differences in tibial intracortical pore morphology and viscoelastic properties in aged individuals with and without diabetes mellitus - an exploratory study

Introduction

Diabetes mellitus (DM) is a chronic metabolic disorder that increases fragility fracture risk. Conventional DXA-based areal bone mineral density (aBMD) assessments often underestimate this risk. Cortical Backscatter (CortBS) ultrasound, a radiation-free technique, non-invasively analyzes cortical bone's viscoelastic and microstructural properties. This study aimed to evaluate CortBS's discriminative performance in DM patients compared to DXA and characterize changes in cortical bone microstructure in Type 1 and Type 2 DM (T1DM, T2DM) patients.

Methods

This in-vivo study included 89 DM patients (T1DM = 39, T2DM = 48) and 76 age- and sex-matched controls. DXA measured aBMD, while CortBS measurements were taken at the anteromedial tibia using a medical ultrasound scanner with custom software. Multivariate analysis of variance assessed the impact of DM type on CortBS and DXA measurement results. Partial least squares discriminant analyses with cross-validation were used to compare the discrimination performance for vertebral, non-vertebral, and any fragility fractures, adjusting for gender, age, and anthropometric parameters (weight, height, BMI).

Results

Fractures occurred in 8/23 T1DM, 17/18 T2DM, and 16/55 controls. DXA parameters were reduced in fracture patients, with significant diabetes impact. T2DM was associated with altered CortBS parameters, reduced scatterer density, and larger pores. CortBS outperformed DXA in discriminating fracture risk (0.61 ≤ AUC(DXA) ≤ 0.63, 0.68 ≤ AUC(CortBS) ≤ 0.69).

Conclusions

Both T1DM and T2DM showed altered bone metabolism, with T2DM linked to impaired tissue formation. CortBS provides insights into pathophysiological changes in diabetic bone and provided superior fracture risk assessment in DM patients compared to DXA.

Individual trabecula segmentation validation in first- and second-generation high-resolution peripheral computed tomography compared to micro-computed tomography in the distal radius and tibia

High-resolution peripheral quantitative computed tomography (HR-pQCT) has been used for in vivo 3D visualization of trabecular microstructure. Second-generation HR-pQCT (HR-pQCT II) has been shown to have good agreement with first generation HR-pQCT (HR-pQCT I). Advanced Individual Trabecula Segmentation (ITS) decomposes the trabecula network into individual plates and rods. ITS based on HR-pQCT I showed a strong correlation to ITS based on micro-computed tomography (μCT) and identified trabecular changes in metabolic bone diseases. ITS based on HR-pQCT II has new potential because of the enhanced resolution but has yet to be validated. The objective of this study was to assess the agreement between ITS based on HR-pQCT I, HR-pQCT II, and μCT to assess the capability of ITS on HR-pQCT images as a tool for studying bone structure. Freshly frozen tibia and radius bones were scanned in the distal region using HR-pQCT I at 82 μm, HR-pQCT II at 60.7 μm, and μCT at 37 μm. Images were registered, binarized, and ITS analysis was performed. Bone volume fraction (pBV/TV, rBV/TV), number density (pTb.N, rTb.N), thickness (pTb.Th, rTb.Th), and plate-to-rod (PR) ratio (pBV/rBV) of trabecular plates and rods were obtained. Paired Student's t-tests with post hoc Bonferroni analysis were used to examine the differences. Linear regression was used to determine the correlation coefficient. The HR-pQCT I parameters were different from the μCT measurements. The HR-pQCT II parameters were different from the μCT measurements except for rTb.N, and the HR-pQCT I parameters were different from the HR-pQCT II measurements except for pTb.Th. The strong correlation between HR-pQCT II and μCT microstructural analysis (R2 = 0.55-0.94) suggests that HR-pQCT II can be used to assess changes in plate and rod microstructure and that values from HR-pQCT I can be corrected.

Fixed and Relative Positioning of Scans for High Resolution Peripheral Quantitative Computed Tomography

INTRODUCTION

High resolution peripheral quantitative computed tomography (HR-pQCT) imaging protocol requires defining where to position the ∼1 cm thick scan along the bone length. Discrepancies between the use of two positioning methods, the relative and fixed offset, may be problematic in the comparison between studies and participants. This study investigated how bone landmarks scale linearly with length and how this scaling affects both positioning methods aimed at providing a consistent anatomical location for scan acquisition.

METHODS

Using CT images of the radius (N = 25) and tibia (N = 42), 10 anatomical landmarks were selected along the bone length. The location of these landmarks was converted to a percent length along the bone, and the variation in their location was evaluated across the dataset. The absolute location of the HR-pQCT scan position using both offset methods was identified for all bones and converted to a percent length position relative to the HR-pQCT reference line for comparison. A secondary analysis of the location of the scan region specifically within the metaphysis was explored at the tibia.

RESULTS

The location of landmarks deviated from a linear relationship across the dataset, with a range of 3.6 % at the radius sites, and 4.5 % at the tibia sites. The consequent variation of the position of the scan at the radius was 0.6 % and 0.3 %, and at the tibia 2.4 % and 0.5 %, for the fixed and relative offset, respectively. The position of the metaphyseal junction with the epiphysis relative to the scan position was poorly correlated to bone length, with R2 = 0.06 and 0.37, for the fixed and relative offset respectively.

CONCLUSION

The variation of the scan position by either method is negated by the intrinsic variation of the bone anatomy with respect both to total bone length as well as the metaphyseal region. Therefore, there is no clear benefit of either offset method. However, the lack of difference due to the inherent variation in the underlying anatomy implies that it is reasonable to compare studies even if they are using different positioning methods.

Predictive value of machine learning on fracture risk in osteoporosis: a systematic review and meta-analysis

OBJECTIVES

Early identification of fracture risk in patients with osteoporosis is essential. Machine learning (ML) has emerged as a promising technique to predict the risk, whereas its predictive performance remains controversial. Therefore, we conducted this systematic review and meta-analysis to explore the predictive efficiency of ML for the risk of fracture in patients with osteoporosis.

METHODS

Relevant studies were retrieved from four databases (PubMed, Embase, Cochrane Library and Web of Science) until 31 May 2023. A meta-analysis of the C-index was performed using a random-effects model, while a bivariate mixed-effects model was used for the meta-analysis of sensitivity and specificity. In addition, subgroup analysis was performed according to the types of ML models and fracture sites.

RESULTS

Fifty-three studies were included in our meta-analysis, involving 15 209 268 patients, 86 prediction models specifically developed for the osteoporosis population and 41 validation sets. The most commonly used predictors in these models encompassed age, BMI, past fracture history, bone mineral density T-score, history of falls, BMD, radiomics data, weight, height, gender and other chronic diseases. Overall, the pooled C-index of ML was 0.75 (95% CI: 0.72, 0.78) and 0.75 (95% CI: 0.71, 0.78) in the training set and validation set, respectively; the pooled sensitivity was 0.79 (95% CI: 0.72, 0.84) and 0.76 (95% CI: 0.80, 0.81) in the training set and validation set, respectively; and the pooled specificity was 0.81 (95% CI: 0.75, 0.86) and 0.83 (95% CI: 0.72, 0.90) in the training set and validation set, respectively.

CONCLUSIONS

ML has a favourable predictive performance for fracture risk in patients with osteoporosis. However, most current studies lack external validation. Thus, external validation is required to verify the reliability of ML models.

PROSPERO REGISTRATION NUMBER

CRD42022346896.

Digital wrist tomosynthesis (DWT)-based finite element analysis of ultra-distal radius differentiates patients with and without a history of osteoporotic fracture

Despite effective therapies for those at risk of osteoporotic fracture, low adherence to screening guidelines and limited accuracy of bone mineral density (BMD) in predicting fracture risk preclude identification of those at risk. Because of high adherence to routine mammography, bone health screening at the time of mammography using a digital breast tomosynthesis (DBT) scanner has been suggested as a potential solution. BMD and bone microstructure can be measured from the wrist using a DBT scanner. However, the extent to which biomechanical variables can be derived from digital wrist tomosynthesis (DWT) has not been explored. Accordingly, we measured stiffness from a DWT based finite element (DWT-FE) model of the ultra-distal (UD) radius and ulna, and correlate these to reference microcomputed tomography image based FE (μCT-FE) from five cadaveric forearms. Further, this method is implemented to determine in vivo reproducibility of FE derived stiffness of UD radius and demonstrate the in vivo utility of DWT-FE in bone quality assessment by comparing two groups of postmenopausal women with and without a history of an osteoporotic fracture (Fx; n = 15, NFx; n = 51). Stiffness obtained from DWT and μCT had a strong correlation (R2 = 0.87, p < 0.001). In vivo repeatability error was <5 %. The NFx and Fx groups were not significantly different in DXA derived minimum T-scores (p > 0.3), but stiffness of the UD radius was lower for the Fx group (p < 0.007). Logistic regression models of fracture status with stiffness of the nondominant arm as the predictor were significant (p < 0.01). In conclusion this study demonstrates the feasibility of fracture risk assessment in mammography settings using DWT imaging and FE modeling in vivo. Using this approach, bone and breast screening can be performed in a single visit, with the potential to improve both the prevalence of bone health screening and the accuracy of fracture risk assessment.

A Fracture Risk Assessment Tool for High Resolution Peripheral Quantitative Computed Tomography

Most fracture risk assessment tools use clinical risk factors combined with bone mineral density (BMD) to improve assessment of osteoporosis; however, stratifying fracture risk remains challenging. This study developed a fracture risk assessment tool that uses information about volumetric bone density and three-dimensional structure, obtained using high-resolution peripheral quantitative compute tomography (HR-pQCT), to provide an alternative approach for patient-specific assessment of fracture risk. Using an international prospective cohort of older adults (n = 6802) we developed a tool to predict osteoporotic fracture risk, called μFRAC. The model was constructed using random survival forests, and input predictors included HR-pQCT parameters summarizing BMD and microarchitecture alongside clinical risk factors (sex, age, height, weight, and prior adulthood fracture) and femoral neck areal BMD (FN aBMD). The performance of μFRAC was compared to the Fracture Risk Assessment Tool (FRAX) and a reference model built using FN aBMD and clinical covariates. μFRAC was predictive of osteoporotic fracture (c-index = 0.673, p < 0.001), modestly outperforming FRAX and FN aBMD models (c-index = 0.617 and 0.636, respectively). Removal of FN aBMD and all clinical risk factors, except age, from μFRAC did not significantly impact its performance when estimating 5-year and 10-year fracture risk. The performance of μFRAC improved when only major osteoporotic fractures were considered (c-index = 0.733, p < 0.001). We developed a personalized fracture risk assessment tool based on HR-pQCT that may provide an alternative approach to current clinical methods by leveraging direct measures of bone density and structure. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Fractal dimension, lacunarity, and cortical thickness in the mandible: Analyzing differences between healthy men and women with cone-beam computed tomography

Purpose

The objective of this study was to assess the fractal dimension, lacunarity, trabecular microarchitecture parameters, and cortical linear measurements in the mandibles of male and female individuals to identify differences between them.

Materials and Methods

In total, 116 cone-beam computed tomography scans of healthy individuals of different ages (57 men and 59 women, aged between 20 and 60 years) were selected. The following bone parameters were measured: 1) buccal, lingual, and basal cortical bone thickness in 5 standard parasagittal sections (the midline, the left and right sides of the lower lateral incisors, and the left and right sides of the lower canines); 2) the bone volume fraction of 10 sequential axial sections from each patient by creating a volume of interest in the area between the lower canines; and 3) fractal dimension and lacunarity using grayscale images of the same region of the volume of interest in the anterior mandible. Spearman correlation coefficients and the Mann-Whitney test were used.

Results

A significant and positive correlation was found between age and cortical thickness, especially in the region of the central incisors. Significant differences between sexes in terms of fractal dimension, lacunarity, and bone volume were found. Women revealed lower fractal dimension values and higher lacunarity and bone volume ratio values than men.

Conclusion

Fractal dimension, lacunarity, trabecular bone volume, and cortical thickness were different between men and women of different ages.

Bone parameters in T1D and T2D assessed by DXA and HR-pQCT - A cross-sectional study: The DIAFALL study

INTRODUCTION/AIM

People with type 1 diabetes(T1D) and type 2 diabetes(T2D) have an increased risk of fractures due to skeletal fragility. We aimed to compare areal bone mineral density(aBMD), volumetric BMD(vBMD), cortical and trabecular measures, and bone strength parameters in participants with diabetes vs. controls.

METHODS

In a cross-sectional study, we included participants with T1D(n = 111), T2D(n = 106) and controls(n = 328). The study comprised of whole-body DXA and HR-pQCT scans, biochemistry, handgrip strength(HGS), Timed Up and GO(TUG), vibration perception threshold (VPT), questionnaires, medical histories, alcohol use, and previous fractures. Group comparisons were performed after adjustment for sex, age, BMI, diabetes duration, HbA1c, alcohol, smoking, previous fractures, postmenopausal, HGS, TUG, and VPT.

RESULTS

We found decreased aBMD in participants with T1D at the femoral neck(p = 0.028), whereas T2D had significantly higher aBMD at peripheral sites(legs, arms, p < 0.01) vs. controls. In T1D we found higher vBMD(p < 0.001), cortical vBMD (p < 0.001), cortical area(p = 0.002) and thickness(p < 0.001), lower cortical porosity(p = 0.008), higher stiffness(p = 0.002) and failure load(p = 0.003) at radius and higher vBMD(p = 0.003), cortical vBMD(p < 0.001), bone stiffness(p = 0.023) and failure load(p = 0.044) at the tibia than controls. In T2D we found higher vBMD(p < 0.001), cortical vBMD(p < 0.001), trabecular vBMD(p < 0.001), cortical area (p < 0.001) and thickness (p < 0.001), trabecular number (p = 0.024), lower separation(p = 0.010), higher stiffness (p < 0.001) and failure load (p < 0.001) at the radius and higher total vBMD(p < 0.001), cortical vBMD(p < 0.011), trabecular vBMD(p = 0.001), cortical area(p = 0.002) and thickness(p = 0.021), lower trabecular separation(p = 0.039), higher stiffness(p < 0.001) and failure load(p = 0.034) at tibia compared with controls.

CONCLUSION

aBMD measures were as expected but favorable bone microarchitecture and strength parameters were seen at the tibia and radius for T1D and T2D.

Continuum finite element analysis generalizesin vivotrabecular bone microstructural strength measures between two CT scanners with different image resolution

Fragility of trabecular bone (Tb) microstructure is increased in osteoporosis, which is associated with rapid bone loss and enhanced fracture-risk. Accurate assessment of Tb strength usingin vivoimaging available in clinical settings will be significant for management of osteoporosis and understanding its pathogenesis. Emerging CT technology, featured with high image resolution, fast scan-speed, and wide clinical access, is a promising alternative forin vivoTb imaging. However, variation in image resolution among different CT scanners pose a major hurdle in CT-based bone studies. This paper presents nonlinear continuum finite element (FE) methods for computation of Tb strength fromin vivoCT imaging and evaluates their generalizability between two scanners with different image resolution. Continuum FE-based measures of Tb strength under different loading conditions were found to be highly reproducible (ICC ≥ 0.93) using ankle images of twenty healthy volunteers acquired on low- and high-resolution CT scanners 44.6 ± 2.7 days apart. FE stress propagation was mostly confined to Tb micro-network (2.3 ± 1.7 MPa) with nominal leakages over the marrow space (0.4 ± 0.5 MPa) complying with the fundamental principle of mechanics atin vivoimaging. In summary, nonlinear continuum FE-based Tb strength measures are reproducible among different CT scanners and suitable for multi-site longitudinal human studies.

Comparison of bone microstructures via high-resolution peripheral quantitative computed tomography in patients with different stages of chronic kidney disease before and after starting hemodialysis

Chronic kidney disease (CKD) negatively affects bone strength; however, the osteoporotic conditions in patients with CKD are not fully understood. Moreover, the changes in bone microstructure between pre-dialysis and dialysis are unknown. High-resolution peripheral quantitative computed tomography (HR-pQCT) reveals the three-dimensional microstructures of the bone. We aimed to evaluate bone microstructures in patients with different stages of CKD. This study included 119 healthy men and 40 men admitted to Nagasaki University Hospital for inpatient education or the initiation of hemodialysis. The distal radius and tibia were scanned with HR-pQCT. Patient clinical characteristics and bone microstructures were evaluated within 3 months of initiation of hemodialysis (in patients with CKD stage 5 D), patients with CKD stage 4-5, and healthy volunteers. Cortical bone parameters were lower in the CKD group than in healthy controls. Tibial cortical and trabecular bone parameters (cortical thickness, cortical area, trabecular volumetric bone mineral density, trabecular-bone volume fraction, and trabecular thickness) differed between patients with CKD stage 5 D and those with CKD stage 4-5 (p < 0.01). These differences were also observed between patients with CKD stage 5 and those with CKD stage 5 D (p < 0.017), but not between patients with CKD stage 4 and those with CKD stage 5, suggesting that the bone microstructure rapidly changed at the start of hemodialysis. Patients with CKD stage 5 D exhibited tibial microstructural impairment compared with those with CKD stage 4-5. HR-pQCT is useful for elucidation of the pathology of bone microstructures in patients with renal failure.

The clinician's guide to prevention and treatment of osteoporosis

Osteoporosis is the most common metabolic bone disease in the USA and the world. It is a subclinical condition until complicated by fracture(s). These fractures place an enormous medical and personal burden on individuals who suffer from them and take a significant economic toll. Any new fracture in an adult aged 50 years or older signifies imminent elevated risk for subsequent fractures, particularly in the year following the initial fracture. What a patient perceives as an unfortunate accident may be seen as a sentinel event indicative of bone fragility and increased future fracture risk even when the result of considerable trauma. Clinical or subclinical vertebral fractures, the most common type of osteoporotic fractures, are associated with a 5-fold increased risk for additional vertebral fractures and a 2- to 3-fold increased risk for fractures at other sites. Untreated osteoporosis can lead to a vicious cycle of recurrent fracture(s), often resulting in disability and premature death. In appropriate patients, treatment with effective antifracture medication prevents fractures and improves outcomes. Primary care providers and medical specialists are critical gatekeepers who can identify fractures and initiate proven osteoporosis interventions. Osteoporosis detection, diagnosis, and treatment should be routine practice in all adult healthcare settings. The Bone Health and Osteoporosis Foundation (BHOF) - formerly the National Osteoporosis Foundation - first published the Clinician's Guide in 1999 to provide accurate information on osteoporosis prevention and treatment. Since that time, significant improvements have been made in diagnostic technologies and treatments for osteoporosis. Despite these advances, a disturbing gap persists in patient care. At-risk patients are often not screened to establish fracture probability and not educated about fracture prevention. Most concerning, the majority of highest risk women and men who have a fracture(s) are not diagnosed and do not receive effective, FDA-approved therapies. Even those prescribed appropriate therapy are unlikely to take the medication as prescribed. The Clinician's Guide offers concise recommendations regarding prevention, risk assessment, diagnosis, and treatment of osteoporosis in postmenopausal women and men aged 50 years and older. It includes indications for bone densitometry as well as fracture risk thresholds for pharmacologic intervention. Current medications build bone and/or decrease bone breakdown and dramatically reduce incident fractures. All antifracture therapeutics treat but do not cure the disease. Skeletal deterioration resumes sooner or later when a medication is discontinued-sooner for nonbisphosphonates and later for bisphosphonates. Even if normal BMD is achieved, osteoporosis and elevated risk for fracture are still present. The diagnosis of osteoporosis persists even if subsequent DXA T-scores are above - 2.5. Ongoing monitoring and strategic interventions will be necessary if fractures are to be avoided. In addition to pharmacotherapy, adequate intake of calcium and vitamin D, avoidance of smoking and excessive alcohol intake, weight-bearing and resistance-training exercise, and fall prevention are included in the fracture prevention armamentarium. Where possible, recommendations in this guide are based on evidence from RCTs; however, relevant published data and guidance from expert clinical experience provides the basis for recommendations in those areas where RCT evidence is currently deficient or not applicable to the many osteoporosis patients not considered for RCT participation due to age and morbidity.

Intermuscular adipose tissue in Type 2 diabetes mellitus: Non-invasive quantitative imaging and clinical implications

Intermuscular adipose tissue (IMAT) is an ectopic fat depot found beneath the fascia and within the muscles. IMAT modulates muscle insulin sensitivity and triggers local and systemic chronic low-grade inflammation by producing cytokines and chemokines, which underlie the pathogenesis of Type 2 diabetes mellitus (T2DM). Imaging techniques have been increasingly used to non-invasively quantify IMAT in patients with diabetes in research and healthcare settings. In this study, we systematically reviewed the cell of origin and definition of IMAT, and the use of quantitative and functional imaging technology pertinent to the etiology, risk factors, lifestyle modification, and therapeutic treatment of diabetes. The purpose of this article is to provide important insight into the current understanding of IMAT and future prospects of targeting IMAT for T2DM control.

Why Aboriginal and Torres Strait Islander Australians fall and fracture: the codesigned Study of Indigenous Muscle and Bone Ageing (SIMBA) protocol

OBJECTIVES

Aboriginal and Torres Strait Islander Australians have a substantially greater fracture risk, where men are 50% and women are 26% more likely to experience a hip fracture compared with non-Indigenous Australians. Fall-related injuries in this population have also increased by 10%/year compared with 4.3%/year in non-Indigenous Australians. This study aims to determine why falls and fracture risk are higher in Aboriginal and Torres Strait Islander Australians.

SETTING

All clinical assessments will be performed at one centre in Melbourne, Australia. At baseline, participants will have clinical assessments, including questionnaires, anthropometry, bone structure, body composition and physical performance tests. These assessments will be repeated at follow-up 1 and follow-up 2, with an interval of 12 months between each clinical visit.

PARTICIPANTS

This codesigned prospective observational study aims to recruit a total of 298 adults who identify as Aboriginal and Torres Strait Islander and reside within Victoria, Australia. Stratified sampling by age and sex will be used to ensure equitable distribution of men and women across four age-bands (35-44, 45-54, 55-64 and 65+ years).

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome is within-individual yearly change in areal bone mineral density at the total hip, femoral neck and lumbar spine assessed by dual energy X-ray absorptiometry. Within-individual change in cortical and trabecular volumetric bone mineral density at the radius and tibia using high-resolution peripheral quantitative computed tomography will be determined. Secondary outcomes include yearly differences in physical performance and body composition.

ETHICAL APPROVAL

Ethics approval for this study has been granted by the Monash Health Human Research Ethics Committee (project number: RES-19-0000374A).

TRIAL REGISTRATION NUMBER

ACTRN12620000161921.

Bone Microarchitecture Phenotypes Identified in Older Adults Are Associated With Different Levels of Osteoporotic Fracture Risk

Prevalence of osteoporosis is more than 50% in older adults, yet current clinical methods for diagnosis that rely on areal bone mineral density (aBMD) fail to detect most individuals who have a fragility fracture. Bone fragility can manifest in different forms, and a "one-size-fits-all" approach to diagnosis and management of osteoporosis may not be suitable. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides additive information by capturing information about volumetric density and microarchitecture, but interpretation is challenging because of the complex interactions between the numerous properties measured. In this study, we propose that there are common combinations of bone properties, referred to as phenotypes, that are predisposed to different levels of fracture risk. Using HR-pQCT data from a multinational cohort (n = 5873, 71% female) between 40 and 96 years of age, we employed fuzzy c-means clustering, an unsupervised machine-learning method, to identify phenotypes of bone microarchitecture. Three clusters were identified, and using partial correlation analysis of HR-pQCT parameters, we characterized the clusters as low density, low volume, and healthy bone phenotypes. Most males were associated with the healthy bone phenotype, whereas females were more often associated with the low volume or low density bone phenotypes. Each phenotype had a significantly different cumulative hazard of major osteoporotic fracture (MOF) and of any incident osteoporotic fracture (p < 0.05). After adjustment for covariates (cohort, sex, and age), the low density followed by the low volume phenotype had the highest association with MOF (hazard ratio = 2.96 and 2.35, respectively), and significant associations were maintained when additionally adjusted for femoral neck aBMD (hazard ratio = 1.69 and 1.90, respectively). Further, within each phenotype, different imaging biomarkers of fracture were identified. These findings suggest that osteoporotic fracture risk is associated with bone phenotypes that capture key features of bone deterioration that are not distinguishable by aBMD. © 2021 American Society for Bone and Mineral Research (ASBMR).

Influence of loading conditions in finite element analysis assessed by HR-pQCT on ex vivo fracture prediction

Many fractures occur in individuals with normal areal Bone Mineral Density (aBMD) measured by Dual X-ray Absorptiometry (DXA). High Resolution peripheral Quantitative Computed Tomography (HR-pQCT) allows for non-invasive evaluation of bone stiffness and strength through micro finite element (μFE) analysis at the tibia and radius. These μFE outcomes are strongly associated with fragility fractures but do not provide clear enhancement compared with DXA measurements. The objective of this study was to establish whether a change in loading conditions in standard μFE analysis assessed by HR-pQCT enhance the discrimination of low-trauma fractured radii (n = 11) from non-fractured radii (n = 16) obtained experimentally throughout a mechanical test reproducing a forward fall. Micro finite element models were created using HR-pQCT images, and linear analyses were performed using four different types of loading conditions (axial, non-axial with two orientations and torsion). No significant differences were found between the failure load assessed with the axial and non-axial models. The different loading conditions tested presented the same area under the receiver operating characteristic (ROC) curves of 0.79 when classifying radius fractures with an accuracy of 81.5%. In comparison, the area under the curve (AUC) is 0.77 from DXA-derived ultra-distal aBMD of the forearm with an accuracy of 85.2%. These results suggest that the restricted HR-pQCT scanned region seems not sensitive to loading conditions for the prediction of radius fracture risk based on ex vivo experiments (n = 27).

Dairy Food Intake Is Not Associated with Measures of Bone Microarchitecture in Men and Women: The Framingham Osteoporosis Study

Previous studies reported that dairy foods are associated with higher areal bone mineral density (BMD) in older adults. However, data on bone strength and bone microarchitecture are lacking. We determined the association of dairy food intake (milk, yogurt, cheese, milk + yogurt, and milk + yogurt + cheese, servings/week) with high resolution peripheral quantitative computed tomography (HR-pQCT) measures of bone (failure load, cortical BMD, cortical thickness, trabecular BMD, and trabecular number). This cross-sectional study included participants with diet from a food frequency questionnaire (in 2005–2008 and/or 1998–2001) and measurements of cortical and trabecular BMD and microarchitecture at the distal tibia and radius (from HR-pQCT in 2012–2015). Sex-specific multivariable linear regression estimated the association of dairy food intake (energy adjusted) with each bone measure adjusting for covariates. Mean age was 64 (SD 8) years and total milk + yogurt + cheese intake was 10.0 (SD 6.6) and 10.6 (6.4) servings/week in men and women, respectively. No significant associations were observed for any of the dairy foods and bone microarchitecture measures except for cheese intake, which was inversely associated with cortical BMD at the radius (p = 0.001) and tibia (p = 0.002) in women alone. In this cohort of primarily healthy older men and women, dairy intake was not associated with bone microarchitecture. The findings related to cheese intake and bone microarchitecture in women warrant further investigation.

Volumetric Bone Mineral Density Measured by HR-pQCT in Patients with Psoriasis or Psoriatic Arthritis: A Systematic Review and Meta-Analysis with Trial Sequential Analysis

Bone health in psoriasis and psoriatic arthritis has been emphasized in recent years. Novel imaging modalities allow investigations into volumetric bone mineral density (vBMD) and bone microstructure in psoriatic patients. However, literature regarding vBMD measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) is inconclusive. We conducted a systematic review and meta-analysis to evaluate vBMD in patients with psoriatic disease. We searched PubMed, EMBASE, Web of Science, and Cochrane Library for relevant observational studies. A random-effects meta-analysis with trial sequential analysis (TSA) was performed. The pooled mean difference (MD) and 95% confidence interval (CI) were calculated. Five studies with 780 patients were included. Patients with psoriatic disease showed a lower average vBMD than controls (MD -14.90; 95% CI -22.90 to -6.89; TSA-adjusted CI -23.77 to -6.03; I² = 41%). Trabecular vBMD and cortical vBMD results were inconclusive because of the small sample size. Patients recruited in Asia and those whose vBMD were measured at the distal radius exhibited a lower average vBMD than controls. Further research should clarify the association of psoriasis with bone microstructure and the underlying pathophysiology.

The clinical application of high-resolution peripheral computed tomography (HR-pQCT) in adults: state of the art and future directions

High-resolution peripheral computed tomography (HR-pQCT) was developed to image bone microarchitecture in vivo at peripheral skeletal sites. Since the introduction of HR-pQCT in 2005, clinical research to gain insight into pathophysiology of skeletal fragility and to improve prediction of fractures has grown. Meanwhile, the second-generation HR-pQCT device has been introduced, allowing novel applications such as hand joint imaging, assessment of subchondral bone and cartilage thickness in the knee, and distal radius fracture healing. This article provides an overview of the current clinical applications and guidance on interpretation of results, as well as future directions. Specifically, we provide an overview of (1) the differences and reference data for HR-pQCT variables by age, sex, and race/ethnicity; (2) fracture risk prediction using HR-pQCT; (3) the ability to monitor response of anti-osteoporosis therapy with HR-pQCT; (4) the use of HR-pQCT in patients with metabolic bone disorders and diseases leading to secondary osteoporosis; and (5) novel applications of HR-pQCT imaging. Finally, we summarize the status of the application of HR-pQCT in clinical practice and discuss future directions. From the clinical perspective, there are both challenges and opportunities for more widespread use of HR-pQCT. Assessment of bone microarchitecture by HR-pQCT improves fracture prediction in mostly normal or osteopenic elderly subjects beyond DXA of the hip, but the added value is marginal. The prospects of HR-pQCT in clinical practice need further study with respect to medication effects, metabolic bone disorders, rare bone diseases, and other applications such as hand joint imaging and fracture healing. The mostly unexplored potential may be the differentiation of patients with only moderately low BMD but severe microstructural deterioration, which would have important implications for the decision on therapeutical interventions.

High-impact exercise stimulated localised adaptation of microarchitecture across distal tibia in postmenopausal women

We provided evidence that a 6-month regular hopping exercise intervention can increase trabecular number and possibly trabecular volume fraction of the distal tibia. Our novel localised analysis demonstrated region-specific changes, predominantly in the anterior region, in postmenopausal women.

INTRODUCTION

The localisation of bone remodelling and microarchitectural adaptation to exercise loading has not been demonstrated previously in vivo in humans. The aim of this study is to assess the feasibility of using 3D image registration and high-resolution peripheral quantitative computed tomography (HR-pQCT) to investigate the effect of high-impact exercise on human trabecular bone variables and remodelling rate across the distal tibia.

METHODS

Ten postmenopausal women were recruited for 6-month unilateral hopping exercises, with HR-pQCT scans taken of both exercise leg (EL) and control leg (CL) for each participant before and after the intervention. A 3D image registration was used to ensure measurements were taken at the same region. Short-term reproducibility tests were conducted prior to the assessment using identical setup. The results were assessed comparing CL and EL, and interaction (time × leg) using a two-way repeated measures analysis of variance (RM-ANOVA).

RESULTS

Across the whole tibia, we observed significant increases in trabecular number (Tb.N) (+ 4.4%) and trabecular bone formation rate (tBFR) (3.3%), and a non-significant increase in trabecular bone volume fraction (BV/TV) (+ 1%) in the EL. Regional resorption was higher in the CL than the EL, with this difference being statistically significant at the lateral tibia. In the EL, tBFR was significantly higher in the anterior region than the medial but a trabecular bone resorption rate (tBRR) showed no significant regional variation. Conversely in the CL, both tBFR and tBRR were significantly higher in the anterior and lateral than the medial region.

CONCLUSION

We demonstrated that it was possible to detect exercise-related bone adaptation with 3D registration of HR-pQCT scan data. Regular hopping exercise increased Tb.N and possibly BV/TV across the whole distal tibia. A novel finding of the study was that tBFR and tBRR responses to loading were localised: changes were achieved by formation rate exceeding resorption rate in the exercise leg, both globally and at the anterior region where turnover was greatest.

TRIAL REGISTRATION

clinicaltrials.gov : NCT03225703.

Higher Hand Grip Strength Is Associated With Greater Radius Bone Size and Strength in Older Men and Women: The Framingham Osteoporosis Study

Mechanical loading by muscles elicits anabolic responses from bone, thus age‐related declines in muscle strength may contribute to bone fragility in older adults. We used high‐resolution peripheral quantitative computed tomography (HR‐pQCT) to determine the association between grip strength and distal radius bone density, size, morphology, and microarchitecture, as well as bone strength estimated by micro–finite element analysis (μFEA), among older men and women. Participants included 508 men and 651 women participating in the Framingham Offspring Study with grip strength measured in 2011–2014 and HR‐pQCT scanning in 2012–2015. Separately for men and women, analysis of covariance was used to compare HR‐pQCT measures among grip strength quartiles and to test for linear trends, adjusting for age, height, weight, smoking, and physical activity. Mean age was 70 years (range, 50–95 years), and men had higher mean grip strength than the women (37 kg vs. 21 kg). Bone strength estimated by μFEA‐calculated failure load was higher with greater grip strength in both men (p < 0.01) and women (p = 0.04). Higher grip strength was associated with larger cross‐sectional area in both men and women (p < 0.01), with differences in area of 6% and 11% between the lowest to highest grip strength quartiles in men and women, respectively. Cortical thickness was positively associated with grip strength among men only (p = 0.03). Grip strength was not associated with volumetric BMD (vBMD) in men. Conversely, there was a trend for lower total vBMD with higher grip strength among women (p = 0.02), though pairwise comparisons did not reveal any statistically significant differences in total vBMD among grip strength quartiles. Bone microarchitecture (cortical porosity, trabecular thickness, trabecular number) was not associated with grip strength in either men or women. Our findings suggest that the positive association between hand grip strength and distal radius bone strength may be driven primarily by bone size. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

A new approach for quantifying localized bone loss by measuring void spaces

The application of high resolution peripheral quantitative computed tomography (HR-pQCT) for the study of bone health has provided valuable insight into the role bone microarchitecture has in determining bone strength and fracture risk. However, conventional density and morphological parameters struggle to distinguish whether localized bone loss is present, visible as heterogeneous deterioration in the trabecular network. This is because current HR-pQCT parameters quantify a global average of properties in the cortical or trabecular compartment. This study proposes a new metric we term "void space" that segments volumes of localized deterioration in the trabecular bone network from HR-pQCT scans and quantifies void space as the void space to total volume ratio (VS/TV, %). A simple and fully automated protocol for segmenting and quantifying void space in HR-pQCT scans is presented, along with the assessment of accuracy, precision, and cross-calibration between generations of HR-pQCT systems. Finally, prevalence of void space and the association with standard HR-pQCT parameters is demonstrated using a large population-based cohort (n = 1236). Void space detection was found to be highly reproducible (accuracy >95%, least significant change <1.76% VS/TV) and correlation between scanner generations was strong (R² = 0.87), although the first generation system struggled to identify small voids. Assessment of void space prevalence in the population-based cohort revealed that void spaces were more common in females than males, prevalence increased with age, and void spaces were typically systemic (occurring at both scan sites rather than only one). A comparison of group-wise differences between participants with and without void space demonstrated that individuals with void spaces had significantly worse trabecular properties for both sexes and at both scan sites. Specifically, the median trabecular bone mineral density, bone volume fraction, and trabecular number were below the 25th percentile of the population, while trabecular separation and inhomogeneity were above the 75th percentile of the population in participants with void spaces. Cortical bone characteristics did not differ between participants with and without void spaces. When the void space region was excluded from morphological analysis so that only the remaining "functional bone" was considered, trabecular properties of participants with void spaces were greatly improved, especially for those who were the greatest outliers. Void space is an intuitive morphological parameter that captures localized deterioration in the trabecular bone network, and has the potential to provide valuable insight into the assessment of bone fragility.

Consequences of Hyperthyroidism and Its Treatment for Bone Microarchitecture Assessed by High-Resolution Peripheral Quantitative Computed Tomography

Background: Hyperthyroidism is associated with bone mass reduction and increased fracture risk, but the effects on other important bone parameters have been sparsely examined. Therefore, we investigated bone microarchitecture and estimated bone strength by high-resolution peripheral quantitative computed tomography (HR-pQCT) in hyperthyroid patients at diagnosis and after being euthyroid for at least one year. Methods: Two approaches were used: (A) a case-control study comparing 61 hyperthyroid women with 61 euthyroid women matched for age and menopause status; (B) a follow-up study, in which 46 of the 61 women were re-examined after having been euthyroid for one year. HR-pQCT of the distal radius and tibia, and dual-energy X-ray absorptiometry (DXA) of the lumbar spine and the hip were performed. Results: In analysis A: In the radius, compared with the healthy controls, hyperthyroid patients had higher total area (16.9% ± 29.5%; p < 0.001), trabecular area (28.6% ± 45.7%; p < 0.001), and lower cortical area (-11.7% ± 23.2%; p < 0.001). Total volumetric bone mineral density (vBMD) (-13.9% ± 26.5%; p < 0.001), cortical vBMD (-5.8% ± 7.9%; p < 0.001), cortical thickness (-16.7% ± 26.0%; p < 0.001), and estimated bone strength (-6.6% ± 19.5%; p < 0.01) were lower. No significant differences were found in the tibia or in the DXA parameters. In analysis B: In the radius, significant improvements were observed in the cortical area (2.1% ± 4.6%; p < 0.01), cortical thickness (2.5% ± 5.1%; p < 0.001), and total vBMD (0.8% ± 3.0%; p < 0.05). Trabecular area decreased (-0.5% ± 1.0%; p < 0.01) and trabecular separation increased (2.0% ± 8.3%; p < 0.05). In the tibia, cortical area (3.6% ± 7.3%; p < 0.01) and cortical thickness (3.8% ± 7.6%; p < 0.01) increased, and trabecular area decreased (-0.5% ± 1.1%; p < 0.01). Areal BMD, measured by DXA, increased in the spine (1.1% ± 3.4%; p < 0.05) and in the hip (2.0% ± 3.8%; p < 0.01). Conclusions: Compared with the healthy control group, hyperthyroid women had lower vBMD, lower estimated bone strength, and compromised cortical microarchitecture in the radius. After restoration of euthyroidism, significant improvements in vBMD and cortical microarchitecture were observed, highlighting the importance of achieving and maintaining euthyroidism.

A comparative study of trabecular bone micro-structural measurements using different CT modalities

Osteoporosis, characterized by reduced bone mineral density and micro-architectural degeneration, significantly enhances fracture-risk. There are several viable methods for trabecular bone micro-imaging, which widely vary in terms of technology, reconstruction principle, spatial resolution, and acquisition time. We have performed an excised cadaveric bone specimen study to evaluate different computed tomography (CT)-imaging modalities for trabecular bone micro-structural analysis. Excised cadaveric bone specimens from the distal radius were scanned using micro-CT and fourin vivoCT imaging modalities: high-resolution peripheral quantitative computed tomography (HR-pQCT), dental cone beam CT (CBCT), whole-body multi-row detector CT (MDCT), and extremity CBCT. A new algorithm was developed to optimize soft thresholding parameters for individualin vivoCT modalities for computing quantitative bone volume fraction maps. Finally, agreement of trabecular bone micro-structural measures, derived from differentin vivoCT imaging, with reference measures from micro-CT imaging was examined. Observed values of most trabecular measures, including trabecular bone volume, network area, transverse and plate-rod micro-structure, thickness, and spacing, forin vivoCT modalities were higher than their micro-CT-based reference values. In general, HR-pQCT-based trabecular bone measures were closer to their reference values as compared to otherin vivoCT modalities. Despite large differences in observed values of measures among modalities, high linear correlation (rε [0.94 0.99]) was found between micro-CT andin vivoCT-derived measures of trabecular bone volume, transverse and plate micro-structural volume, and network area. All HR-pQCT-derived trabecular measures, except the erosion index, showed high correlation (rε [0.91 0.99]). The plate-width measure showed a higher correlation (rε [0.72 0.91]) amongin vivoand micro-CT modalities than its counterpart binary plate-rod characterization-based measure erosion index (rε [0.65 0.81]). Although a strong correlation was observed between micro-structural measures fromin vivoand micro-CT imaging, large shifts in their values forin vivomodalities warrant proper scanner calibration prior to adopting in multi-site and longitudinal studies.

Reference values and clinical predictors of bone strength for HR-pQCT-based distal radius and tibia strength assessments in women and men

Reference values for radius and tibia strength using multiple-stack high-resolution peripheral quantitative computed tomography (HR-pQCT) with homogenized finite element analysis are presented in order to derive critical values improving risk prediction models of osteoporosis. Gender and femoral neck areal bone mineral density (aBMD) were independent predictors of bone strength.

INTRODUCTION

The purpose was to obtain reference values for radius and tibia bone strength computed by using the homogenized finite element analysis (hFE) using multiple stacks with a HR-pQCT.

METHODS

Male and female healthy participants aged 20-39 years were recruited at the University Hospital of Bern. They underwent interview and clinical examination including hand grip, gait speed and DXA of the hip. The nondominant forearm and tibia were scanned with a double and a triple-stack protocol, respectively, using HR-pQCT (XCT II, SCANCO Medical AG). Bone strength was estimated by using the hFE analysis, and reference values were calculated using quantile regression. Multivariable analyses were performed to identify clinical predictors of bone strength.

RESULTS

Overall, 46 women and 41 men were recruited with mean ages of 25.1 (sd 5.0) and 26.2 (sd 5.2) years. Sex-specific reference values for bone strength were established. Men had significantly higher strength for radius (mean (sd) 6640 (1800) N vs. 4110 (1200) N; p < 0.001) and tibia (18,200 (4220) N vs. 11,970 (3150) N; p < 0.001) than women. In the two multivariable regression models with and without total hip aBMD, the addition of neck hip aBMD significantly improved the model (p < 0.001). No clinical predictors of bone strength other than gender and aBMD were identified.

CONCLUSION

Reference values for radius and tibia strength using multiple HR-pQCT stacks with hFE analysis are presented and provide the basis to help refining accurate risk prediction models. Femoral neck aBMD and gender were significant predictors of bone strength.

Spectrum of microarchitectural bone disease in inborn errors of metabolism: a cross-sectional, observational study

BACKGROUND

Patients diagnosed with inborn errors of metabolism (IBEM) often present with compromised bone health leading to low bone density, bone pain, fractures, and short stature. Dual-energy X-ray absorptiometry (DXA) is the current gold standard for clinical assessment of bone in the general population and has been adopted for monitoring bone density in IBEM patients. However, IBEM patients are at greater risk for scoliosis, short stature and often have orthopedic hardware at standard DXA scan sites, limiting its use in these patients. Furthermore, DXA is limited to measuring areal bone mineral density (BMD), and does not provide information on microarchitecture.

METHODS

In this study, microarchitecture was investigated in IBEM patients (n = 101) using a new three-dimensional imaging technology high-resolution peripheral quantitative computed tomography (HR-pQCT) which scans at the distal radius and distal tibia. Volumetric BMD and bone microarchitecture were computed and compared amongst the different IBEMs. For IBEM patients over 16 years-old (n = 67), HR-pQCT reference data was available and Z-scores were calculated.

RESULTS

Cortical bone density was significantly lower in IBEMs associated with decreased bone mass when compared to lysosomal storage disorders (LSD) with no primary skeletal pathology at both the radius and tibia. Cortical thickness was also significantly lower in these disorders when compared to LSD with no primary skeletal pathology at the radius. Cortical porosity was significantly greater in hypophosphatasia when compared to all other IBEM subtypes.

CONCLUSION

We demonstrated compromised bone microarchitecture in IBEMs where there is primary involvement of the skeleton, as well as IBEMs where skeletal complications are a secondary outcome. In conclusion, our findings suggest HR-pQCT may serve as a valuable tool to monitor skeletal disease in the IBEM population, and provides insight to the greatly varying bone phenotype for this cohort that can be used for clinical monitoring and the assessment of response to therapeutic interventions.

A novel mechanical parameter to quantify the microarchitecture effect on apparent modulus of trabecular bone: A computational analysis of ineffective bone mass

BACKGROUND

One of the characteristics of osteoporotic bone is the deterioration of trabecular microarchitecture. Previous studies have shown microarchitecture alone can vary the apparent modulus of trabecular bone significantly independent of bone volume fraction (BV/TV) from morphological and topological perspectives. However, modulus is a mechanical quantity and there is a lack of mechanical explanatory parameters. This study aims to propose a novel mechanical parameter to quantify the microarchitecture effect on the apparent modulus of trabecular bone.

MATERIALS AND METHODS

Fourteen human female cadaveric vertebrae were scanned with a dual-energy X-ray (DXA) equipment followed by a micro-CT (μCT) system at 18 μm isotropic resolution. Four trabecular bone specimens (3.46 × 3.46 × 3.46 mm) were obtained from each vertebral body and converted to voxel-based micro finite element (μFE) models. The apparent modulus (E) of the μFE model was computed using a linear micro finite element analysis (μFEA). The normalized apparent modulus (E*) was computed as E divided by BV/TV. The relationship between E and BV/TV was analyzed by linear, power-law and exponential regressions. Linear regression was performed between E* and BV/TV. Ineffective bone mass (InBM) was defined as the bone mass with a negligible contribution to the load-resistance and represented by elements with von Mises stress less than a certain stress threshold. InBM was quantified as the low von Mises stress ratio (LS_VMR), which is the ratio of the number of InBM elements to the total number of elements in the μFE model. An incremental search technique with coarse and fine search intervals of 10 and 1 MPa, respectively, was adopted to determine the stress threshold for calculating LS_VMR of the μFE model. Correlation between E* and LS_VMR was analyzed using linear and power-law models for each stress threshold. The threshold producing the highest coefficient of determination (R²) in the correlation between E* and LS_VMR was taken as the optimal stress threshold for calculating LS_VMR. Linear regression was performed between E and LS_VMR. Multiple linear regression of E against both BV/TV and LS_VMR was further analyzed.

RESULTS

E significantly (p < .001) correlates to BV/TV whereas E* has no significant (p = .75) correlation with BV/TV. Incremental search suggests 59 MPa to be the optimal stress threshold for calculating LS_VMR. BV/TV alone can explain 59% of the variation in E using power-law regression model (E = 2254.64BV/TV^1.04, R² = 0.59, p < .001). LS_VMR alone can explain 48% of the variation in E using linear regression model (E = 1696.4-1647.1LS_VMR, R² = 0.48, p < .001). With these two predictors taken into consideration, 95% of the variation in E can be explained in a multiple linear regression model (E = 1364.89 + 2184.37BV/TV - 1605.38LS_VMR, adjusted R² = 0.95, p < .001).

CONCLUSION

LS_VMR can be adopted as the mechanical parameter to quantify the microarchitecture effect on the apparent modulus of trabecular bone.

Impact on bone microarchitecture and failure load in a patient with type I Gaucher disease who switched from Imiglucerase to Eliglustat

Gaucher disease (GD; OMIM 230800) is a lysosomal storage disorder caused by a deficiency in acid beta-glucosidase as a result of mutation in the GBA gene. Type 1 GD (GD1) is the most common form and its clinical manifestations include severe hematological, visceral and bone disease. The goal of disease-modifying treatments for GD1 is to reduce substrate storage and hence toxicity from the disease. The two common therapeutic routes for managing GD1 are enzyme replacement therapy (ERT) and substrate reduction therapy (SRT). These therapies have shown to improve hematological and visceral aspects of the disease. However, quantitative investigations into how these therapies may help prevent or improve the progression of bone disease is limited. This case involves a patient diagnosed with GD1 in childhood, who began ERT in young adulthood. Following over 20 years of treatment with ERT, the patient switched to SRT. This case report examined the novel application of high-resolution peripheral quantitative computed tomography (HR-pQCT) in a patient who switched from ERT to SRT. Using bone microarchitecture measurements from HR-pQCT, we applied finite element analysis techniques to calculate the failure load which estimates the resistance to fracture. Over the course of one year following the switch from ERT to SRT therapy, failure load improved in the patient's lower limb. In conclusion, failure load can be computed in the short term in a patient who made a switch from ERT to SRT. Further exploration of failure load in study design to look at interventions that impact bone quality in GD may be considered.

Update on Imaging-Based Measurement of Bone Mineral Density and Quality

PURPOSE OF REVIEW

Patients with inflammatory arthropathies have a high rate of fragility fractures. Diagnostic assessment and monitoring of bone density and quality are therefore critically important. Here, we review standard and advanced techniques to measure bone density and quality, specifically focusing on patients with inflammatory arthropathies.

RECENT FINDINGS

Current standard procedures are dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). DXA-based newer methods include trabecular bone score (TBS) and vertebral fracture assessment (VFA). More advanced imaging methods to measure bone quality include high-resolution peripheral quantitative computed tomography (HR-pQCT) as well as multi-detector CT (MD-CT) and magnetic resonance imaging (MRI). Quantitative ultrasound has shown promise but is not standard to assess bone fragility. While there are limitations, DXA remains the standard technique to measure density in patients with rheumatological disorders. Newer modalities to measure bone quality may allow better characterization of bone fragility but currently are not standard of care procedures.

MRI-based assessment of proximal femur strength compared to mechanical testing

Half of the women who sustain a hip fracture would not qualify for osteoporosis treatment based on current DXA-estimated bone mineral density criteria. Therefore, a better approach is needed to determine if an individual is at risk of hip fracture from a fall. The objective of this study was to determine the association between radiation-free MRI-derived bone strength and strain simulations compared to results from direct mechanical testing of cadaveric femora. Imaging was conducted on a 3-Tesla MRI scanner using two sequences: one balanced steady-state free precession sequence with 300 μm isotropic voxel size and one spoiled gradient echo with anisotropic voxel size of 234 × 234 × 1500 μm. Femora were dissected free of soft-tissue and 4350-ohm strain-gauges were securely applied to surfaces at the femoral shaft, inferior neck, greater trochanter, and superior neck. Cadavers were mechanically tested with a hydraulic universal test frame to simulate loading in a sideways fall orientation. Sideways fall forces were simulated on MRI-based finite element meshes and bone stiffness, failure force, and force for plastic deformation were computed. Simulated bone strength metrics from the 300 μm isotropic sequence showed strong agreement with experimentally obtained values of bone strength, with stiffness (r = 0.88, p = 0.0002), plastic deformation point (r = 0.89, p < 0.0001), and failure force (r = 0.92, p < 0.0001). The anisotropic sequence showed similar trends for stiffness, plastic deformation point, and failure force (r = 0.68, 0.70, 0.84; p = 0.02, 0.01, 0.0006, respectively). Surface strain-gauge measurements showed moderate to strong agreement with simulated magnitude strain values at the greater trochanter, superior neck, and inferior neck (r = -0.97, -0.86, 0.80; p ≤0.0001, 0.003, 0.03, respectively). The findings from this study support the use of MRI-based FE analysis of the hip to reliably predict the mechanical competence of the human femur in clinical settings.

Peripheral quantitative computed tomography (pQCT)-based finite element analysis provides enhanced diagnostic performance in identifying non-vertebral fracture patients compared with dual-energy X-ray absorptiometry

Due to limitations of the predominant clinical method for diagnosing osteoporosis, an engineering model based on a dedicated CT scanner for bone density and structure was applied in fracture patients and controls. Improved diagnostic performance was observed, which supports its potential use in future research and clinical practice.

INTRODUCTION

Dual-energy X-ray absorptiometry (DXA), the predominant clinical method for diagnosing osteoporosis, has limitations in identifying individuals with increased fracture risk. Peripheral quantitative computed tomography (pQCT) provides additional information and can be used to generate finite element (FE) models from which bone strength properties can be estimated. We investigated the ability of pQCT-FE properties to distinguish peripheral low-trauma fracture patients from healthy controls, by comparison with DXA and standard pQCT.

METHODS

One hundred and eight fracture patients (77 females aged 67.7 ± 7.9 years, 31 males aged 69.7 ± 8.9 years) were recruited from a hospital fracture liaison service. One hundred and twenty healthy community controls (85 females aged 69.8 ± 8.5 years, 35 males aged 68.9 ± 7.2 years) were recruited.

RESULTS

Significant differences between groups were observed in pQCT-FE properties, especially at the 4% tibia site. Fracture odds increased most per standard deviation decrease in pQCT-FE at this location [shear stiffness estimate, k_shear, in females, OR = 10.34, 95% CI (1.91, 43.98); bending stiffness estimate, k_bend, in males, OR = 8.32, 95% CI (4.15, 33.84)]. Area under the receiver operating characteristics curve (AUROC) was observed to be highest with pQCT-FE properties at 4% the tibia site. In females, this was 0.83 for the pQCT-FE variable k_shear, compared with 0.72 for DXA total hip bone density (TH aBMD) and 0.76 for pQCT tibia trabecular density (Trb vBMD); in males, this was 0.81 for the pQCT-FE variable k_bend at the 4% tibia site, compared with 0.62 for TH aBMD and 0.71 for Trb vBMD. There were significant differences in AUROC between DXA and pQCT-FE variables in both females (p = 0.02) and males (p = 0.03), while no difference was observed in AUROC between primary pQCT and pQCT-FE variables.

CONCLUSIONS

pQCT-FE modeling can provide enhanced diagnostic performance compared with DXA and, given its moderate cost, may be useful in clinical settings.

Ultrasound-Based Estimates of Cortical Bone Thickness and Porosity Are Associated With Nontraumatic Fractures in Postmenopausal Women: A Pilot Study

Recent ultrasound (US) axial transmission techniques exploit the multimode waveguide response of long bones to yield estimates of cortical bone structure characteristics. This pilot cross-sectional study aimed to evaluate the performance at the one-third distal radius of a bidirectional axial transmission technique (BDAT) to discriminate between fractured and nonfractured postmenopausal women. Cortical thickness (Ct.Th) and porosity (Ct.Po) estimates were obtained for 201 postmenopausal women: 109 were nonfractured (62.6 ± 7.8 years), 92 with one or more nontraumatic fractures (68.8 ± 9.2 years), 17 with hip fractures (66.1 ± 10.3 years), 32 with vertebral fractures (72.4 ± 7.9 years), and 17 with wrist fractures (67.8 ± 9.6 years). The areal bone mineral density (aBMD) was obtained using DXA at the femur and spine. Femoral aBMD correlated weakly, but significantly with Ct.Th (R = 0.23, p < 0.001) and Ct.Po (R = -0.15, p < 0.05). Femoral aBMD and both US parameters were significantly different between the subgroup of all nontraumatic fractures combined and the control group (p < 0.05). The main findings were that (1) Ct.Po was discriminant for all nontraumatic fractures combined (OR = 1.39; area under the receiver operating characteristic curve [AUC] equal to 0.71), for vertebral (OR = 1.96; AUC = 0.84) and wrist fractures (OR = 1.80; AUC = 0.71), whereas Ct.Th was discriminant for hip fractures only (OR = 2.01; AUC = 0.72); there was a significant association (2) between increased Ct.Po and vertebral and wrist fractures when these fractures were not associated with any measured aBMD variables; (3) between increased Ct.Po and all nontraumatic fractures combined independently of aBMD neck; and (4) between decreased Ct.Th and hip fractures independently of aBMD femur. BDAT variables showed comparable performance to that of aBMD neck with all types of fractures (OR = 1.48; AUC = 0.72) and that of aBMD femur with hip fractures (OR = 2.21; AUC = 0.70). If these results are confirmed in prospective studies, cortical BDAT measurements may be considered useful for assessing fracture risk in postmenopausal women. © 2019 American Society for Bone and Mineral Research.

Cluster Analysis of Finite Element Analysis and Bone Microarchitectural Parameters Identifies Phenotypes with High Fracture Risk

High-resolution peripheral quantitative computed tomography (HRpQCT) is increasingly used for exploring associations between bone microarchitectural and finite element analysis (FEA) parameters and fracture. We hypothesised that combining bone microarchitectural parameters, geometry, BMD and FEA estimates of bone strength from HRpQCT may improve discrimination of fragility fractures. The analysis sample comprised of 359 participants (aged 72-81 years) from the Hertfordshire Cohort Study. Fracture history was determined by self-report and vertebral fracture assessment. Participants underwent HRpQCT scans of the distal radius and DXA scans of the proximal femur and lateral spine. Poisson regression with robust variance estimation was used to derive relative risks for the relationship between individual bone microarchitectural and FEA parameters and previous fracture. Cluster analysis of these parameters was then performed to identify phenotypes associated with fracture prevalence. Receiver operating characteristic analysis suggested that bone microarchitectural parameters improved fracture discrimination compared to aBMD alone, whereas further inclusion of FEA parameters resulted in minimal improvements. Cluster analysis (k-means) identified four clusters. The first had lower Young modulus, cortical thickness, cortical volumetric density and Von Mises stresses compared to the wider sample; fracture rates were only significantly greater among women (relative risk [95%CI] compared to lowest risk cluster: 2.55 [1.28, 5.07], p = 0.008). The second cluster in women had greater trabecular separation, lower trabecular volumetric density and lower trabecular load with an increase in fracture rate compared to lowest risk cluster (1.93 [0.98, 3.78], p = 0.057). These findings may help inform intervention strategies for the prevention and management of osteoporosis.

The Correction of Systematic Error due to Plaster and Fiberglass Casts on HR-pQCT Bone Parameters Measured In Vivo at the Distal Radius

Due to difficulty assessing healing of distal radius fractures using conventional radiography, there is interest in using high resolution peripheral quantitative computed tomography (HR-pQCT) to track healing at the microarchitectural level. Unfortunately, the plaster-of-Paris and fiberglass casts used to immobilize fractures affect HR-pQCT measurements due to beam hardening, and increased noise. The challenge is compounded because casts have variable thickness, and an individual patient will often have their cast changed 2-3 times during the course of treatment. This study quantifies the effect of casts within a clinically relevant range of thicknesses on measured bone parameters at the distal radius, and establishes conversion equations to correct for systematic error in due to cast presence. Eighteen nonfractured participants were scanned by HR-pQCT in three conditions: no cast, plaster-of-Paris cast, and fiberglass cast. Measured parameters were compared between the baseline scan (no cast) and each cast scan to evaluate if systematic error exists due to cast presence. A linear regression model was used to determine an appropriate conversion for parameters that were found to have systematic error. Plaster-of-Paris casts had a greater range of thicknesses (3.2-9.5 mm) than the fiberglass casts (3.0-5.4 mm), and induced a greater magnitude of systematic error overall. Key parameters of interest were bone mineral density (total, cortical, and trabecular) and trabecular bone volume fraction, all of which were found to have systematic error due to presence of either cast type. Linear correlations between baseline and cast scans for these parameters were excellent (R² > 0.98), and appropriate conversions could be determined within a margin of error less than a ±6% for the plaster-of-Paris cast, and ±4% for the fiberglass cast. We have demonstrated the effects of cast presence on bone microarchitecture measurements, and presented a method to correct for systematic error, in support of future use of HR-pQCT to study fracture healing.

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.

Accurate and Efficient Plate and Rod Micro Finite Element Whole Bone Models Based on High-Resolution Peripheral Computed Tomography

The high-resolution peripheral quantitative computed tomography (HRpQCT) provides unprecedented visualization of bone microstructure and the basis for constructing patient-specific micro-finite element (µFE) models. Based on HRpQCT images, we have developed a plate rod µFE (PRµFE) method for whole bone segments using individual trabecula segmentation (ITS) and an adaptive cortical meshing technique. In contrast to the conventional voxel approach, the complex microarchitecture of the trabecular compartment is simplified into shell and beam elements based on the trabecular plate-and-rod configuration. Compared to voxel-based µFE models of µCT and mechanical testing, nonlinear analyses of stiffness and yield strength using the HRpQCT-based PRµFE models demonstrated high correlation and accuracy, indicating that the combination of segmented trabecular plate-rod morphology and adjusted cortical mesh adequately captures mechanics of the whole bone segment. Meanwhile, the PRµFE approach reduced model size by nearly 300-fold and shortened computation time for nonlinear analysis from days to within hours, permitting broader clinical application of HRpQCT-based nonlinear µFE modeling. Furthermore, the presented approach was tested using a subset of radius and tibia HRpQCT scans of patients with prior vertebral fracture from a previous study. Results indicated that yield strength for radius and tibia predicted by the PRµFE model was effective in discriminating vertebral fracture subjects from non-fractured controls. In conclusion, the PR µFE model of HRpQCT images accurately predicted mechanics for whole bone segments and can serve as a valuable clinical tool to evaluate musculoskeletal diseases.

Cortical and trabecular bone microarchitecture as an independent predictor of incident fracture risk in older women and men in the Bone Microarchitecture International Consortium (BoMIC): a prospective study

BACKGROUND

Although areal bone mineral density (aBMD) assessed by dual-energy x-ray absorptiometry (DXA) is the clinical standard for determining fracture risk, most older adults who sustain a fracture have T scores greater than -2·5 and thus do not meet the clinical criteria for osteoporosis. Importantly, bone fragility is due to low BMD and deterioration in bone structure. We assessed whether indices of high-resolution peripheral quantitative CT (HR-pQCT) were associated with fracture risk independently of femoral neck aBMD and the Fracture Risk Assessment Tool (FRAX) score.

METHODS

We assessed participants in eight cohorts from the USA (Framingham, Mayo Clinic), France (QUALYOR, STRAMBO, OFELY), Switzerland (GERICO), Canada (CaMos), and Sweden (MrOS). We used Cox proportional hazard ratios (HRs) to estimate the association between HR-pQCT bone indices (per 1 SD of deficit) and incident fracture, adjusting for age, sex, height, weight, and cohort, and then additionally for femoral neck DXA aBMD or FRAX.

FINDINGS

7254 individuals (66% women and 34% men) were assessed. Mean baseline age was 69 years (SD 9, range 40-96). Over a mean follow-up of 4·63 years (SD 2·41) years, 765 (11%) participants had incident fractures, of whom 633 (86%) had femoral neck T scores greater than -2·5. After adjustment for age, sex, cohort, height, and weight, peripheral skeleton failure load had the greatest association with risk of fracture: tibia HR 2·40 (95% CI 1·98-2·91) and radius 2·13 (1·77-2·56) per 1 SD decrease. HRs for other bone indices ranged from 1·12 (95% CI 1·03-1·23) per 1 SD increase in tibia cortical porosity to 1·58 (1·45-1·72) per 1 SD decrease in radius trabecular volumetric bone density. After further adjustment for femoral neck aBMD or FRAX score, the associations were reduced but remained significant for most bone parameters. A model including cortical volumetric bone density, trabecular number, and trabecular thickness at the distal radius and a model including these indices plus cortical area at the tibia were the best predictors of fracture.

INTERPRETATION

HR-pQCT indices and failure load improved prediction of fracture beyond femoral neck aBMD or FRAX scores alone. Our findings from a large international cohort of men and women support previous reports that deficits in trabecular and cortical bone density and structure independently contribute to fracture risk. These measurements and morphological assessment of the peripheral skeleton might improve identification of people at the highest risk of fracture.

FUNDING

National Institutes of Health National Institute of Arthritis Musculoskeletal and Skin Diseases.

The application of finite element modelling based on clinical pQCT for classification of fracture status

Fracture risk assessment using dual-energy X-ray absorptiometry (DXA) frequently fails to diagnose osteoporosis amongst individuals who later experience fragility fractures. Hence, more reliable techniques that improve the prediction of fracture risk are needed. In this study, we evaluated a finite element (FE) modelling framework based on clinical peripheral quantitative computed tomography (pQCT) imaging of the tibial epiphysis and diaphysis to predict the stiffness at these locations in compression, shear, torsion and bending. The ability of these properties to identify a group of women who had recently sustained a low-trauma fracture from an age- and weight-matched control group was determined and compared to clinical pQCT and DXA properties and structural properties based on composite beam theory. The predicted stiffnesses derived from the FE models and composite beam theory were significantly different (p < 0.05) between the control and fracture groups, whereas no meaningful differences were observed using DXA and for the stress-strain indices (SSIs) derived using pQCT. The diagnostic performance of each property was assessed by the odds ratio (OR) and the area under the receiver operating curve (AUC), and both were greatest for the FE-predicted shear stiffness (OR 16.09, 95% CI 2.52-102.56, p = 0.003) (AUC: 0.80, 95% CI 0.67-0.93). The clinical pQCT variable total density (ρ_tot) and a number of structural and FE-predicted variables had a similar probability of correct classification between the control and fracture groups (i.e. ORs and AUCs with mean values greater than 5.00 and 0.80, respectively). In general, the diagnostic characteristics were lower for variables derived using DXA and for the SSIs (i.e. ORs and AUCs with mean values of 1.65-2.98 and 0.64-0.71, respectively). For all properties considered, the trabecular-dominant tibial epiphysis exhibited enhanced classification characteristics, as compared to the cortical-dominant tibial diaphysis. The results of this study demonstrate that bone properties may be derived using FE modelling that have the potential to enhance fracture risk assessment using conventional pQCT or DXA instruments in clinical settings.

Long-Term and Recent Weight Change Are Associated With Reduced Peripheral Bone Density, Deficits in Bone Microarchitecture, and Decreased Bone Strength: The Framingham Osteoporosis Study

Weight loss in older adults is associated with increased bone loss and fracture. Little is known about the potential impact of weight loss on cortical and trabecular bone density, microarchitecture, and strength. In this study, participants were members of the Framingham Offspring Cohort (769 women, 595 men; mean age 70 ± 8 years), who underwent high-resolution peripheral quantitative computed tomography (HR-pQCT) scanning at the tibia and radius in 2012 to 2016. Weight measurements taken every 4 to 6 years were used to assess recent weight change over 6 years and long-term change over 40 years. General linear models, adjusting for age, sex, height, smoking, and diabetes, were used to evaluate the association between HR-pQCT indices and relative long-term and recent weight change. We found that long-term and recent weight loss were associated with lower cortical density and thickness, higher cortical porosity, and lower trabecular density and number. Associations were stronger for the tibia than radius. Failure load was lower in those individuals with long-term but not short-term weight loss. Deterioration in both cortical and trabecular indices, especially at the weight-bearing skeleton, characterizes bone fragility associated with long-term and recent weight loss in older adults. © 2018 American Society for Bone and Mineral Research.

Trabecular bone microarchitecture predicts fragility fractures in postmenopausal women on denosumab treatment

BACKGROUND

High-resolution peripheral quantitative computed tomography (HR-pQCT) represents a three-dimensional tool for the screening of osteoporosis patients i.e., regarding fracture risk. The purpose of this study was to determine the baseline and follow-up bone microarchitecture in relation to incident fracture risk in postmenopausal women on denosumab treatment.

METHODS

We have retrospectively evaluated data from 182 postmenopausal women treated with denosumab that underwent an initial HR-pQCT scan before the initiation of the treatment; and at least one second HR-pQCT after 12 months. Women were assigned to two groups based on documented fragility fractures for the following 2.9 ± 1.1 years: fracture (n = 22) and no fracture (n = 160). Baseline parameters from DXA, HR-pQCT and bone turnover were compared between the two groups. Furthermore, ROC and multiple regression analyses of the baseline and follow-up data were performed to evaluate the predictive value regarding incident fractures.

RESULTS

At baseline, trabecular parameters were significantly reduced in the fracture group and showed the best predictive value for new fractures, while DXA results could not predict fractures. A multiple regression model identified BV/TV and age as the best baseline parameters for incident fracture risk. At 12 months, cortical and trabecular parameters increased in the non-fracture group, while no significant increase was noted in the fracture group. However, no significant differences regarding the changes of these parameters could be detected between the non-fracture and fracture cohort.

CONCLUSIONS

Trabecular bone microstructure at baseline is crucial for incident fracture risk in postmenopausal women on denosumab treatment, especially in comparison to DXA values. In this context, the microstructural follow-up results seemed to be of lesser importance regarding fracture risk. The results of this exploratory study should be validated in independent populations.

Prediction of Fractures in Men Using Bone Microarchitectural Parameters Assessed by High-Resolution Peripheral Quantitative Computed Tomography-The Prospective STRAMBO Study

Areal bone mineral density (aBMD) poorly identifies men at high fracture risk. Our aim was to assess prediction of fractures in men by bone microarchitectural measures. At baseline, 825 men aged 60 to 87 years had the assessment of bone microarchitecture at distal radius and distal tibia by high-resolution peripheral QCT (HR-pQCT; XtremeCT-I, Scanco Medical, Brüttisellen, Switzerland). Bone strength was estimated by micro-finite element analysis. During the prospective 8-year follow-up, 105 men sustained fractures (59 vertebral fractures in 49 men and 70 nonvertebral fractures in 68 men). After adjustment for age, body mass index (BMI), prior falls, and fractures, most HR-pQCT measures at both skeletal sites predicted fractures. After further adjustment for aBMD, low distal radius trabecular number (Tb.N) was most strongly associated with higher fracture risk (hazard ratio [HR] = 1.63 per SD, 95% confidence interval [CI] 1.31-2.03, p < 0.001). In similar models, low Tb.N was associated with higher risk of major osteoporotic fracture (HR = 1.80 per SD, p < 0.001), vertebral fracture (HR = 1.78 per SD, p < 0.01) and nonvertebral fracture (HR = 1.46 per SD, p < 0.01). In comparison with the reference model (age, BMI, falls, fractures, aBMD), the adjustment for distal radius Tb.N increased the estimated fracture probability in men who sustained fractures versus those who did not have ones (difference = 4.1%, 95% CI 1.9-6.3%, p < 0.001). However, the adjustment for distal radius Tb.N did not increase the area under the curve (AUC, p = 0.37). Similar results were found for distal radius trabecular separation (Tb.Sp) and connectivity density (Conn. D). They were predictive of all fracture types and increased the estimated fracture risk, but not AUC, in men who had incident fractures. Thus, poor distal radius trabecular microarchitecture is predictive of fracture after adjustment for age, BMI, falls, fractures, and aBMD. Although distal radius Tb.N, Conn. D, and Tb.Sp improve the discrimination between men who will or who will not have fracture, they do not provide clinically relevant improvement of fracture prediction in older men. © 2018 American Society for Bone and Mineral Research.

Urinary Pentosidine levels negatively associates with trabecular bone scores in patients with type 2 diabetes mellitus

Pentosidine levels were higher in diabetic patients with vertebral fractures. Trabecular bone scores were negatively associated with pentosidine levels in diabetic patients only. Our results provide further evidence that AGEs are associated with the pathogenesis of bone fragility in patients with T2DM.

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is associated with fracture risk. Pentosidine, an advanced glycation end product (AGE), is associated with prevalent vertebral fractures (VFs) in patients with T2DM. Trabecular bone score (TBS) has been proposed as an index of bone microarchitecture associated with bone quality. This study evaluated the associations of urine pentosidine and TBS in T2DM and non-T2DM groups.

METHODS

A total of 112 T2DM patients and 62 non-T2DM subjects were enrolled. TBS was calculated using TBS insight® software (version 2.1). Pentosidine levels were measured using high-performance liquid chromatography method. We compared the BMD, TBS, and pentosidine levels between those with and without VFs with or without adjustment for age and sex. The association with TBS, lumbar spine BMD, and pentosidine levels were also evaluated in both T2DM and non-T2DM groups.

RESULTS

Pentosidine levels were significantly higher in T2DM patients with VFs. TBSs were significantly lower in patients with T2DM and VFs. In non-diabetic patients, there were no significant differences in TBS and pentosidine levels for those with and without VFs after adjustment for age and sex. Pentosidine levels were negatively associated with TBS only in patients with T2DM. In multivariate stepwise regression analysis, pentosidine levels were significantly associated with TBS in patients with T2DM.

CONCLUSIONS

TBS and pentosidine could be used as a method to assess bone quality to identify T2DM patients at risk of VFs. Our results also provide further evidence that AGEs are associated with the pathogenesis of bone fragility in patients with T2DM.

Lower Bone Density, Impaired Microarchitecture, and Strength Predict Future Fragility Fracture in Postmenopausal Women: 5-Year Follow-up of the Calgary CaMos Cohort

The aim of this prospective study was to use high-resolution peripheral quantitative computed tomography (HR-pQCT) to determine if baseline skeletal parameters can predict incident fragility fracture in women and, secondly, to establish if women that fracture lose bone at a faster rate than those who do not fracture. Women older than 60 years who experienced a fragility fracture during the 5-year follow-up period (incident fracture group, n = 22) were compared with those who did not experience a fragility fracture during the study (n = 127). After image registration between baseline and follow-up measures, standard and cortical morphological analyses were conducted. Odds ratios were calculated for baseline values and annualized percent change of HR-pQCT and finite element variables. At the radius, baseline HR-pQCT results show women who fractured had lower total bone mineral density (Tt.BMD; 19%), trabecular bone mineral density (Tb.BMD; 25%), and trabecular number (Tb.N; 14%), with higher trabecular separation (Tb.Sp; 19%) than women who did not fracture. At the tibia, women with incident fracture had lower Tt.BMD (15%), Tb.BMD (12%), cortical thickness (Ct.Th; 14%), cortical area (Ct.Ar; 12%), and failure load (10%) with higher total area (Tt.Ar; 7%) and trabecular area (Tb.Ar; 10%) than women who did not fracture. Odds ratios (ORs) at the radius revealed every SD decrease of Tt.BMD (OR = 2.1), Tb.BMD (OR = 2.0), and Tb.N (OR = 1.7) was associated with a significantly increased likelihood of fragility fracture. At the tibia, every SD decrease in Tt.BMD (OR = 2.1), Tb.BMD (OR = 1.7), Ct.Th (OR = 2.2), Ct.Ar (OR = 1.9), and failure load (OR = 1.7) were associated with a significantly increased likelihood of fragility fracture. Irrespective of scanning modality, the annualized percent rate of bone loss was not different between fracture groups. The results suggest baseline bone density, microarchitecture, and strength rather than change in these variables are associated with incident fragility fractures in women older than 60 years. Furthermore, irrespective of fragility fracture status, women experienced changes in skeletal health at a similar rate. © 2017 American Society for Bone and Mineral Research.

3-T MR Imaging of Proximal Femur Microarchitecture in Subjects with and without Fragility Fracture and Nonosteoporotic Proximal Femur Bone Mineral Density

Purpose To determine if 3-T magnetic resonance (MR) imaging of proximal femur microarchitecture can allow discrimination of subjects with and without fragility fracture who do not have osteoporotic proximal femur bone mineral density (BMD). Materials and Methods Sixty postmenopausal women (30 with and 30 without fragility fracture) who had BMD T scores of greater than -2.5 in the hip were recruited. All subjects underwent dual-energy x-ray absorptiometry to assess BMD and 3-T MR imaging of the same hip to assess bone microarchitecture. World Health Organization Fracture Risk Assessment Tool (FRAX) scores were also computed. We used the Mann-Whitney test, receiver operating characteristics analyses, and Spearman correlation estimates to assess differences between groups, discriminatory ability with parameters, and correlations among BMD, microarchitecture, and FRAX scores. Results Patients with versus without fracture showed a lower trabecular plate-to-rod ratio (median, 2.41 vs 4.53, respectively), lower trabecular plate width (0.556 mm vs 0.630 mm, respectively), and lower trabecular thickness (0.114 mm vs 0.126 mm) within the femoral neck, and higher trabecular rod disruption (43.5 vs 19.0, respectively), higher trabecular separation (0.378 mm vs 0.323 mm, respectively), and lower trabecular number (0.158 vs 0.192, respectively), lower trabecular connectivity (0.015 vs 0.027, respectively) and lower trabecular plate-to-rod ratio (6.38 vs 8.09, respectively) in the greater trochanter (P < .05 for all). Trabecular plate-to-rod ratio, plate width, and thickness within the femoral neck (areas under the curve [AUCs], 0.654-0.683) and trabecular rod disruption, number, connectivity, plate-to-rod ratio, and separation within the greater trochanter (AUCs, 0.662-0.694) allowed discrimination of patients with fracture from control subjects. Femoral neck, total hip, and spine BMD did not differ between and did not allow discrimination between groups. FRAX scores including and not including BMD allowed discrimination between groups (AUCs, 0.681-0.773). Two-factor models (one MR imaging microarchitectural parameter plus a FRAX score without BMD) allowed discrimination between groups (AUCs, 0.702-0.806). There were no linear correlations between BMD and microarchitectural parameters (Spearman ρ, -0.198 to 0.196). Conclusion 3-T MR imaging of proximal femur microarchitecture allows discrimination between subjects with and without fragility fracture who have BMD T scores of greater than -2.5 and may provide different information about bone quality than that provided by dual-energy x-ray absorptiometry. ^© RSNA, 2018.

Diabetes and Deficits in Cortical Bone Density, Microarchitecture, and Bone Size: Framingham HR-pQCT Study

Older adults with type 2 diabetes (T2D) tend to have normal or greater areal bone mineral density (aBMD), as measured by DXA, than those who do not have diabetes (non-T2D). Yet risk of fracture is higher in T2D, including 40% to 50% increased hip fracture risk. We used HR-pQCT to investigate structural mechanisms underlying skeletal fragility in T2D. We compared cortical and trabecular bone microarchitecture, density, bone area, and strength in T2D and non-T2D. In secondary analyses we evaluated whether associations between T2D and bone measures differed according to prior fracture, sex, and obesity. Participants included 1069 members of the Framingham Study, who attended examinations in 2005 to 2008 and underwent HR-pQCT scanning in 2012 to 2015. Mean age was 64 ± 8 years (range, 40 to 87 years), and 12% (n = 129) had T2D. After adjustment for age, sex, weight, and height, T2D had lower cortical volumetric BMD (vBMD) (p < 0.01), higher cortical porosity (p = 0.02), and smaller cross-sectional area (p = 0.04) at the tibia, but not radius. Trabecular indices were similar or more favorable in T2D than non-T2D. Associations between T2D and bone measures did not differ according to sex or obesity status (all interaction p > 0.05); however, associations did differ in those with a prior fracture and those with no history of fracture. Specifically, cortical vBMD at the tibia and cortical thickness at the radius were lower in T2D than non-T2D, but only among those individuals with a prior fracture. Cortical porosity at the radius was higher in T2D than non-T2D, but only among those who did not have a prior fracture. Findings from this large, community-based study of older adults suggest that modest deterioration in cortical bone and reductions in bone area may characterize diabetic bone disease in older adults. Evaluation of these deficits as predictors of fracture in T2D is needed to develop prevention strategies in this rapidly increasing population of older adults. © 2017 American Society for Bone and Mineral Research.

Bone Quality in Chronic Kidney Disease: Definitions and Diagnostics

PURPOSE OF REVIEW

In this paper, we review the epidemiology, diagnosis, and pathogenesis of fractures and renal osteodystrophy.

RECENT FINDINGS

The role of bone quality in the pathogenesis of fracture susceptibility in chronic kidney disease (CKD) is beginning to be elucidated. Bone quality refers to bone material properties, such as cortical and trabecular microarchitecture, mineralization, turnover, microdamage, and collagen content and structure. Recent data has added to our understanding of the effects of CKD on alterations to bone quality, emerging data on the role of abnormal collagen structure on bone strength, the potential of non-invasive methods to inform our knowledge of bone quality, and how we can use these methods to inform strategies that protect against bone loss and fractures. However, more prospective data is required. CKD is associated with abnormal bone quality and strength which results in high fracture incidence.