Bone density, geometry, microstructure, and stiffness: Relationships between peripheral and central skeletal sites assessed by DXA, HR-pQCT, and cQCT in premenopausal women

Photon-counting CT Spectral Localizer Radiographs for Lumbar Areal Bone Mineral Density Quantification: A Clinical Study on Accuracy, Reliability, and Diagnostic Performance for Osteoporosis

RATIONALE AND OBJECTIVES

To explore the accuracy, reliability, and diagnostic performance of photon-counting CT (PCCT) spectral localizer radiographs (SLRs) for quantifying lumbar areal bone mineral density (BMD) and detecting osteoporosis (T-score ≤-2.5).

MATERIALS AND METHODS

This prospective study recruited consecutive participants from April to July 2024. Participants each underwent a dual-energy X-ray absorptiometry (DXA) examination serving as the gold-standard reference for aBMD (aBMDDXA) and a PCCT scan to obtain SLR. The SLRs were reconstructed into hydroxyapatite (HA) and water maps. Lumbar vertebrae (L1 to L4) and soft tissue were blindly and semiautomatically segmented on HA and water maps to calculate aBMDSLR. The agreement and relative absolute error (RAE) between aBMDSLR and aBMDDXA were calculated. Factors that might influence the RAE were evaluated. Using DXA results as the reference, the diagnostic performance of PCCT-SLRs for osteoporosis was assessed.

RESULTS

A total of 159 participants (88 females) with a median age of 66 years (interquartile range [IQR], 55-72 years) were included. The median (IQR) aBMDDXA and aBMDSLR values were 1.095 (0.936-1.261) g/cm2 and 1.086 (0.932-1.255) g/cm2, respectively. There was excellent agreement between the two methods (mean bias=-0.57%). The median (IQR) RAE was 2.65% (1.23-4.07%). The RAE was unaffected by age, body mass index, aBMD, sex, tube voltage, or tube current. The sensitivity and specificity of PCCT-SLRs for osteoporosis diagnosis were 92.31% (12/13) and 98.63% (144/146), respectively.

CONCLUSION

The PCCT-SLR is an accurate and reliable approach for lumbar aBMD quantification in humans, with high diagnostic performance for osteoporosis.

Textural and geometric measures derived from digital tomosynthesis discriminate women with and without vertebral fracture

Vertebral fractures are a common and debilitating consequence of osteoporosis. Bone mineral density (BMD), measured by dual energy x-ray absorptiometry (DXA), is the clinical standard for assessing overall bone quantity but falls short in accurately predicting vertebral fracture. Fracture risk prediction may be improved by incorporating metrics of microstructural organization from an appropriate imaging modality. Digital tomosynthesis (DTS)-derived textural and microstructural parameters have been previously correlated to vertebral bone strength in vitro, but the in vivo utility has not been explored. Therefore, the current study sought to establish the extent to which DTS-derived measurements of vertebral microstructure and size discriminate patients with and without vertebral fracture. In a cohort of 93 postmenopausal women with or without history of vertebral fracture, DTS-derived microstructural parameters and vertebral width were calculated for T12 and L1 vertebrae, as well as lumbar spine BMD and trabecular bone score (TBS) from DXA images. Fracture patients had lower BMD and TBS, while DTS-derived degree of anisotropy and vertebral width were higher, compared to nonfracture (p < 0.02 to p < 0.003) patients. The addition of DTS-derived parameters (fractal dimension, lacunarity, degree of anisotropy and vertebral width) improved discriminative capability for models of fracture status (AUC = 0.79) compared to BMD alone (AUC = 0.67). For twelve additional participants who were imaged twice, in vivo repeatability errors for DTS parameters were low (0.2 % - 7.3 %). The current results support the complementary use of DTS imaging for assessing bone quality and improving the accuracy of fracture risk assessment beyond that achievable by DXA alone.

Choose your mother wisely: the familial resemblance of bone adaptation

This study demonstrates how complex bone microarchitectural features can be summarized to describe bone adaptations seen with aging in women, which are consistent with the stages of osteoporosis. Additionally, we showed familial resemblance in these bone microarchitectural traits between mothers and daughters that can be used to predict bone adaptations.

INTRODUCTION

Patient-specific characterization of bone quality can reduce complex microarchitectural features to common combinations of bone characteristics, known as bone phenotypes. This study investigated whether there is a general trend in bone phenotype change over time seen with aging in females and whether there is a familial resemblance to phenotype membership between mothers and daughters.

METHODS

Bone phenotype membership was calculated on biological mother and daughter pairs (Participants = 101), scanned using high resolution peripheral quantitative computed tomography, to the three pre-defined phenotypes (healthy, low volume, and low density). The trajectory of bone phenotype with age was explored using all participant's data. Linear regression models were used to assess the familial resemblance of phenotyping in the mother-daughter pairs.

RESULTS

When stratified for age, the trajectory of the phenotype membership transitioned from healthy (20-40 years), to low volume (40-60 years), to low density (60-80 years), which similarly aligns with the stages of osteoporosis observed in females. Familial resemblance (½h2) was observed in the healthy phenotype (β = 0.432, p < 0.01). Predictive modelling showed a significant association in phenotype membership between mothers and daughters in the healthy (R2 = 0.347, p = 0.04) and low volume (R2 = 0.416, p < 0.01) phenotypes, adjusted for age, height, and weight.

CONCLUSION

Our results suggest that phenotype membership in females changes with age in a pattern that is consistent with the stages of osteoporosis. Additionally, we showed familial resemblance in bone phenotype, which can be used to predict bone adaptations between mothers and daughters that are associated with bone loss with aging.

Diabetes Risk Factors and Bone Microarchitecture as Assessed by High-Resolution Peripheral Quantitative Computed Tomography in Adults With Long-standing Type 1 Diabetes

OBJECTIVE

To determine whether type 1 diabetes and its complications are associated with bone geometry and microarchitecture.

RESEARCH DESIGN AND METHODS

This cross-sectional study was embedded in a long-term observational study. High-resolution peripheral quantitative computed tomography (HR-pQCT) scans of the distal radius and distal and diaphyseal tibia were performed in a subset of 183 participants with type 1 diabetes from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study and 94 control participants without diabetes. HbA1c, skin advanced glycation end products (AGEs), and diabetes-related complications were assessed in EDIC participants with >30 years of follow-up.

RESULTS

Compared with control participants (aged 60 ± 8 years, 65% female), EDIC participants (aged 60 ± 7 years, diabetes duration 38 ± 5 years, 51% female) had lower total bone mineral density (BMD) at the distal radius (-7.9% [95% CI -15.2%, -0.6%]; P = 0.030) and distal tibia (-11.3% [95% CI -18.5%, -4.2%]; P = 0.001); larger total area at all sites (distal radius 4.7% [95% CI 0.5%, 8.8%; P = 0.030]; distal tibia 5.9% [95% CI 2.1%, 9.8%; P = 0.003]; diaphyseal tibia 3.4% [95% CI 0.8%, 6.1%; P = 0.011]); and poorer radius trabecular and cortical microarchitecture. Estimated failure load was similar between the two groups. Among EDIC participants, higher HbA1c, AGE levels, and macroalbuminuria were associated with lower total BMD. Macroalbuminuria was associated with larger total area and lower cortical thickness at the distal radius. Higher HbA1c and AGE levels and lower glomerular filtration rate, peripheral neuropathy, and retinopathy were associated with deficits in trabecular microarchitecture.

CONCLUSIONS

Type 1 diabetes is associated with lower BMD, larger bone area, and poorer trabecular microarchitecture. Among participants with type 1 diabetes, suboptimal glycemic control, AGE accumulation, and microvascular complications are associated with deficits in bone microarchitecture and lower BMD.

Bone mineral density in osseointegration implant surgery: A review of current studies (Review)

Osseointegration implant (OI) surgery is the latest rehabilitation technology for amputees, where a bone-anchored implant obviates the limitations of traditional socket prostheses. The bone mineral density (BMD) in the periprosthetic and other anatomical regions can be used to assess bone remodelling following OI surgery. Currently, limited studies have used BMD measurements in reporting post-operative OI outcomes and the association between the maintenance of BMD and implant efficacy has remained elusive. This review captured and analysed all studies that have reported the BMD as an objective outcome measure in patients with trans-femoral or trans-tibial OI. The PubMed, Medline, Scopus and Web of Science databases were searched using the terms 'amputation', 'osseointegration' and 'bone mineral density'. A total of 6 studies involving human participants were included for analysis. All studies used dual X-ray absorptiometry and/or X-rays for measuring BMD. Rehabilitation of trans-femoral or trans-tibial amputation using OI may help restore healthy BMD by enabling physiological bone loading. However, there is a low correlation between the BMD around the OI and the success of OI surgery or the risk of periprosthetic fractures. This review summarises the current evidence on BMD assessment in OI for lower limb amputee rehabilitation. Despite the great variability in the results, the available evidence suggests that OI may help restore BMD following surgery. The limited evidence calls for further investigation, as well as the development of a standard BMD measurement protocol.

Familial Resemblance of Bone Health in Maternal Lineage Pairs and Triads: A Scoping Review

INTRODUCTION

Female bone health is influenced by familial resemblance, health parameters and maturational periods (puberty and menopause); this combination has been researched using familial multi-generational cross-sectional studies.

AIM

This scoping review aimed to compile bone health research which uses sexually mature (grandmother-) mother-daughter pairs (and triads) and to determine the trends in its methodologies and familial comparisons.

METHODS

The Joanna Briggs Institute methodology for scoping reviews was used. Extraction included study and population characteristics, methodology (with an emphasis on imaging) and family-based results.

RESULTS

Twenty-nine studies were included, and their generations were categorized into four developmental categories: late adolescent to young adult, pre-menopause, mixed-menopause, and post-menopause. Eleven different pair/triad combinations were observed; the most common was pre-menopausal daughters and post-menopausal mothers. Dual-energy X-ray absorptiometry (DXA) was the most utilized imaging modality, and the hip was the most imaged region of interest (ROI). Regardless of pairing, imaging modality and ROI, there was often a trend toward significant familial resemblance and heritability (h2 and h2L).

CONCLUSION

This scoping review highlights the trends in bone health linked to familial resemblance, as well as the importance of menopause and late adolescence. This review compiles the commonalities and challenges within these studies to inform future research.

TBS correlates with bone density and microstructure at trabecular and cortical bone evaluated by HR-pQCT

INTRODUCTION

Trabecular bone score (TBS) estimates bone microstructure, which is directly measured by high-resolution peripheral quantitative computed tomography (HRpQCT). We evaluated the correlation between these methods and TBS influence on fracture risk assessed by FRAX.

MATERIALS AND METHODS

We evaluated 129 individuals (82 women, 43 postmenopausal) 20 to 82.3 years without prevalent clinical or non-clinical morphometric vertebral fractures, using DXA (spine and hip), HR-pQCT at distal radius (R) and tibia (T) and TBS which classifies bone microarchitecture as normal (TBS ≥ 1.350), partially degraded (1.200 < TBS < 1.350), or degraded (TBS ≤ 1.200).

RESULTS

Spine and hip BMD and HR-pQCT parameters at cortical bone: area (T), density (R,T) thickness (T) and trabecular bone: density (R,T), number (T) and thickness (R) were significantly better in the 78 individuals with normal TBS (group 1) versus the 51 classified as partially degraded (n = 42) or degraded microarchitecture (n = 9) altogether (group 2). TBS values correlated with age (r = - 0.55), positively with spine and hip BMD and all cortical and trabecular bone density and microstructure parameters evaluated, p < 0.05 all tests. Binary logistic regression defined age (p = 0.008) and cortical thickness (p = 0.018) as main influences on TBS, while ANCOVA demonstrated that HR-pQCT data corrected for age were not different between TBS groups 1 and 2. TBS adjustment increased FRAX risk for major osteoporotic fractures and hip fractures.

CONCLUSION

We describe significant association between TBS and both trabecular and cortical bone parameters measured by HR-pQCT, consistent with TBS influence on fracture risk estimation by FRAX, including hip fractures, where cortical bone predominates.

Assessment of bovine cortical bone fracture behavior using impact microindentation as a surrogate of fracture toughness

The fracture behavior of bone is critically important for evaluating its mechanical competence and ability to resist fractures. Fracture toughness is an intrinsic material property that quantifies a material's ability to withstand crack propagation under controlled conditions. However, properly conducting fracture toughness testing requires the access to calibrated mechanical load frames and the destructive testing of bone samples, and therefore fracture toughness tests are clinically impractical. Impact microindentation mimicks certain aspects of fracture toughness measurements, but its relationship with fracture toughness remains unknown. In this study, we aimed to compare measurements of notched fracture toughness and impact microindentation in fresh and boiled bovine bone. Skeletally mature bovine bone specimens (n = 48) were prepared, and half of them were boiled to denature the organic matrix, while the other half remained preserved in frozen conditions. All samples underwent a notched fracture toughness test to determine their resistance to crack initiation (KIC) and an impact microindentation test using the OsteoProbe to obtain the Bone Material Strength index (BMSi). Boiling the bone samples increased the denatured collagen content, while mineral density and porosity remained unaffected. The boiled bones also showed significant reduction in both KIC (P < .0001) and the average BMSi (P < .0001), leading to impaired resistance of bone to crack propagation. Remarkably, the average BMSi exhibited a high correlation with KIC (r = 0.86; P < .001). A ranked order difference analysis confirmed the excellent agreement between the 2 measures. This study provides the first evidence that impact microindentation could serve as a surrogate measure for bone fracture behavior. The potential of impact microindentation to assess bone fracture resistance with minimal sample disruption could offer valuable insights into bone health without the need for cumbersome testing equipment and sample destruction.

Theoretical and experimental study of attenuation in cancellous bone

Significance

Photoacoustic (PA) technology shows great potential for bone assessment. However, the PA signals in cancellous bone are complex due to its complex composition and porous structure, making such signals challenging to apply directly in bone analysis.

Aim

We introduce a photoacoustic differential attenuation spectrum (PA-DAS) method to separate the contribution of the acoustic propagation path to the PA signal from that of the source, and theoretically and experimentally investigate the propagation attenuation characteristics of cancellous bone.

Approach

We modified Biot's theory by accounting for the high frequency and viscosity. In parallel with the rabbit osteoporosis model, we build an experimental PA-DAS system featuring an eccentric excitation differential detection mechanism. Moreover, we extract a PA-DAS quantization parameter-slope-to quantify the attenuation of high- and low-frequency components.

Results

The results show that the porosity of cancellous bone can be evaluated by fast longitude wave attenuation at different frequencies and the PA-DAS slope of the osteoporotic group is significantly lower compared with the normal group (**p < 0.01 ).

Conclusions

Findings demonstrate that PA-DAS effectively differentiates osteoporotic bone from healthy bone, facilitating quantitative assessment of bone mineral density, and osteoporosis diagnosis.

Bone erosions associated with systemic bone loss on HR-pQCT in women with longstanding polyarticular juvenile idiopathic arthritis

OBJECTIVES

To analyze longstanding polyarticular juvenile idiopathic arthritis (pJIA) for possible associations between localized bone damage (erosions), and systemic bone loss. Besides, to compare the systemic bone mass of pJIA with healthy controls.

METHODS

Thirty-four pJIA women and 99 healthy controls (HC) were included. Radius and tibia of all subjects were scanned by HR-pQCT. Volumetric bone mineral density (vBMD), bone microarchitecture, and -finite element parameters were analyzed. Patients underwent HR-pQCT of 2nd and 3rd metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of the dominant hand, for bone erosions quantification.

RESULTS

The mean age of patients was 31.5 ± 7.4yrs with a mean disease duration of 21.7 ± 9.2yrs. Bone erosions were detectable in 79% of patients. The number of bone erosions was positively correlated with cortical porosity (Ct.Po) at tibia (r = 0.575, p = 0.001), and radius (r = 0.423, p = 0.018); and negatively correlated with cortical vBMD at tibia (r=-0.420, p = 0.015). In a logistic regression analysis, adjusted for anti-CCP, the presence of bone erosions was independently associated with Ct.Po at radius (p = 0.018) and cortical vBMD at tibia (p = 0.020). Moreover, cortical and trabecular vBMD, trabecular number, and μ-finite element parameters were decreased in patients compared to HC (p < 0.05).

CONCLUSION

Bone erosions in longstanding pJIA women were associated with decreased cortical bone parameters, and these patients showed systemic bone impairment at peripheral sites compared with healthy controls.

The role of genetic and epigenetic factors in determining the risk of spinal fragility fractures: new insights in the management of spinal osteoporosis

Osteoporosis predisposes patients to spinal fragility fractures. Imaging plays a key role in the diagnosis and prognostication of these osteoporotic vertebral fractures (OVF). However, the current imaging knowledge base for OVF is lacking sufficient standardisation to enable effective risk prognostication. OVF have been shown to be more prevalent in Caucasian patient cohorts in comparison to the Eastern Asian population. These population-based differences in risk for developing OVF suggest that there could be genetic and epigenetic factors that drive the pathogenesis of osteoporosis, low bone mineral density (BMD) and OVF. Several genetic loci have been associated with a higher vertebral fracture risk, although at varying degrees of significance. The present challenge is clarifying whether these associations are specific to vertebral fractures or osteoporosis more generally. Furthermore, these factors could be exploited for diagnostic interpretation as biomarkers [including novel long non-coding (lnc)RNAs, micro (mi)RNAs and circular (circ)RNAs]. The extent of methylation of genes, alongside post-translational histone modifications, have shown to affect several interlinked pathways that converge on the regulation of bone deposition and resorption, partially through their influence on osteoblast and osteoclast differentiation. Lastly, in addition to biomarkers, several exciting new imaging modalities could add to the established dual-energy X-ray absorptiometry (DXA) method used for BMD assessment. New technologies, and novel sequences within existing imaging modalities, may be able to quantify the quality of bone in addition to the BMD and bone structure; these are making progress through various stages of development from the pre-clinical sphere through to deployment in the clinical setting. In this mini review, we explore the literature to clarify the genetic and epigenetic factors associated with spinal fragility fractures and delineate the causal genes, pathways and interactions which could drive different risk profiles. We also outline the cutting-edge imaging modalities which could transform diagnostic protocols for OVF.

Association Between Papillary Thyroid Carcinoma and Vertebral Fracture

Suppression of TSH levels associated with levothyroxine treatment is a known risk factor for fracture. However, it is unclear whether patients with papillary thyroid carcinoma (PTC) have a higher risk of vertebral fracture (VF) before TSH suppression. The aim of the study was to examine whether the risk of VF is higher in PTC than in healthy subjects. A hospital-based, matched case-control study was conducted comparing PTC and healthy individuals. We enrolled 43 postoperative patients with PTC scheduled for radioiodine therapy and 43 age- and sex-matched healthy controls. Serum and urinary biological parameters, bone mineral density (BMD), and presence of VFs were evaluated in both groups. We compared these indices using χ2 and Mann-Whitney U-test and analyzed the association between PTC and VF by logistic regression analysis. The PTC group had higher BMI, HbA1c and phosphorus, and lower intact PTH than the control group. Lumbar and femoral neck BMD did not differ between the two groups. Prevalence of VFs was significantly higher in the PTC group (44.1%) than in the control group (16.3%). Multivariate logistic regression analyses adjusted for age, sex, and BMI identified PTC as being associated with the presence of VFs (odds ratio, 5.63; 95% confidence interval: 1.82 to 17.5). This relationship remained significant after additional adjustment for HbA1c and BMD. There is an association between PTC and a risk of VF independent of sex, BMI, glucose metabolism, and BMD, suggesting the importance of fracture risk assessment before TSH suppression.

Assessment of bovine cortical bone fracture behavior using impact microindentation as a surrogate of fracture toughness

The fracture behavior of bone is critically important for assessing its mechanical competence and ability to resist fractures. Fracture toughness, which quantifies a material's resistance to crack propagation under controlled geometry, is regarded as the gold standard for evaluating a material's resistance to fracture. However properly conducting this test requires access to calibrated mechanical load frames the destruction of the bone samples, making it impractical for obtaining clinical measurement of bone fracture. Impact microindentation offers a potential alternative by mimicking certain aspects of fracture toughness measurements, but its relationship with mechanistic fracture toughness remains unknown. In this study, we aimed to compare measurements of notched fracture toughness and impact microindentation in fresh and boiled bovine bone. Skeletally mature bovine bone specimens (n=48) were prepared, and half of them were boiled to denature the organic matrix, while the other half remained preserved in frozen conditions. Notched fracture toughness tests were conducted on all samples to determine Initiation toughness (KIC), and an impact microindentation test using the OsteoProbe was performed to obtain the Bone Material Strength index. Boiling the bone samples resulted increased the denatured collagen without affecting mineral density or porosity. The boiled bones also showed significant reduction in both KIC (p < 0.0001) and the average Bone Material Strength index (p < 0.0001), leading to impaired resistance of bone to crack propagation. Remarkably, the average Bone Material Strength index exhibited a high correlation with KIC (r = 0.86; p < 0.001). The ranked order difference analysis confirmed excellent agreement between the two measures. This study provides the first evidence that impact microindentation could serve as a surrogate measure for bone fracture behavior. The potential of impact microindentation to non-destructively assess bone fracture resistance could offer valuable insights into bone health without the need for elaborate testing equipment and sample destruction.

Dual-Energy CT-based Opportunistic Volumetric Bone Mineral Density Assessment of the Distal Radius

Background In patients with distal radius fractures (DRFs), low bone mineral density (BMD) is associated with bone substitute use during surgery and bone nonunion, but BMD information is not regularly available. Purpose To evaluate the feasibility of dual-energy CT (DECT)-based BMD assessment from routine examinations in the distal radius and the relationship between the obtained BMD values, the occurrence of DRFs, bone nonunion, and use of surgical bone substitute. Materials and Methods Scans in patients who underwent routine dual-source DECT in the distal radius between January 2016 and December 2021 were retrospectively acquired. Phantomless BMD assessment was performed using the delineated trabecular bone of a nonfractured segment of the distal radius and both DECT image series. CT images and health records were examined to determine fracture severity, surgical management, and the occurrence of bone nonunion. Associations of BMD with the occurrence of DRFs, bone nonunion, and bone substitute use at surgical treatment were examined with generalized additive models and receiver operating characteristic analysis. Results This study included 263 patients (median age, 52 years; IQR, 36-64 years; 132 female patients), of whom 192 were diagnosed with fractures. Mean volumetric BMD was lower in patients who sustained a DRF (93.9 mg/cm3 vs 135.4 mg/cm3; P < .001), required bone substitutes (79.6 mg/cm3 vs 95.5 mg/cm3; P < .001), and developed bone nonunion (71.1 mg/cm3 vs 96.5 mg/cm3; P < .001). Receiver operating characteristic curve analysis identified these patients with an area under the curve of 0.71-0.91 (P < .001). Lower BMD increased the risk to sustain DRFs, develop bone nonunion, and receive bone substitutes at surgery (P < .001). Conclusion DECT-based BMD assessment at routine examinations is feasible and could help predict surgical bone substitute use and the occurrence of bone nonunion in patients with DRFs. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Carrino in this issue.

Comparison of bone microstructure and strength in the distal radius and tibia between the different types of primary hypertrophic osteoarthropathy: an HR-pQCT study

Primary hypertrophic osteoarthropathy (PHO) is a hereditary bone disease that is grouped into PHO autosomal recessive 1 (PHOAR1) and PHO autosomal recessive 2 (PHOAR2) due to different causative genes. Data comparing bone microstructure between the two subtypes are scarce. This is the first study to find that PHOAR1 patients had inferior bone microstructure compared with PHOAR2 patients.

PURPOSE

The primary goal of this study was to assess bone microarchitecture and strength in PHOAR1 and PHOAR2 patients and to compare them with age- and sex-matched healthy controls (HCs). The secondary goal was to assess the differences between PHOAR1 and PHOAR2 patients.

METHODS

Twenty-seven male Chinese PHO patients (PHOAR1 = 7; PHOAR2 = 20) were recruited from Peking Union Medical College Hospital. The areal bone mineral density (aBMD) was assessed by dual-energy X-ray absorptiometry (DXA). Peripheral bone microarchitecture at the distal radius and tibia were evaluated by high-resolution peripheral quantitative computed tomography (HR-pQCT). Biochemical markers of PGE2, bone turnover, and Dickkopf-1 (DKK1) were investigated.

RESULTS

Compared with HCs, PHOAR1 and PHOAR2 patients had distinctively larger bone geometry, substantially lower vBMD at the radius and tibia, and compromised cortical microstructure at the radius. For trabecular bone, PHOAR1 and PHOAR2 patients showed different changes at the tibia. PHOAR1 patients had significant deficits in the trabecular compartment, resulting in lower estimated bone strength. Conversely, PHOAR2 patients showed a higher trabecular number, narrower trabecular separation, and lower trabecular network inhomogeneity than HCs, translating into preserved or slightly high estimated bone strength.

CONCLUSION

PHOAR1 patients had inferior bone microstructure and strength compared with PHOAR2 patients and HCs. Additionally, this study was the first to find differences in the bone microstructure between PHOAR1 and PHOAR2 patients.

Teriparatide Followed by Denosumab in Premenopausal Idiopathic Osteoporosis: Bone Microstructure and Strength by HR-pQCT

Premenopausal women with idiopathic osteoporosis (PreMenIOP) have marked deficits in skeletal microstructure. We have reported that sequential treatment with teriparatide and denosumab improves central skeletal bone mineral density (BMD) by dual-energy X-ray absorptiometry and central QCT in PreMenIOP. We conducted preplanned analyses of high-resolution peripheral quantitative computed tomography (HR-pQCT) scans from teriparatide and denosumab extension studies to measure effects on volumetric BMD (vBMD), microarchitecture, and estimated strength at the distal radius and tibia. Of 41 women enrolled in the parent teriparatide study (20 mcg daily), 34 enrolled in the HR-pQCT study. HR-pQCT participants initially received teriparatide (N = 24) or placebo (N = 10) for 6 months; all then received teriparatide for 24 months. After teriparatide, 26 enrolled in the phase 2B denosumab extension (60 mg q6M) for 24 months. Primary outcomes were percentage change in vBMD, microstructure, and stiffness after teriparatide and after denosumab. Changes after sequential teriparatide and denosumab were secondary outcomes. After teriparatide, significant improvements were seen in tibial trabecular number (3.3%, p = 0.01), cortical area and thickness (both 2.7%, p < 0.001), and radial trabecular microarchitecture (number: 6.8%, thickness: 2.2%, separation: -5.1%, all p < 0.02). Despite increases in cortical porosity and decreases in cortical density, whole-bone stiffness and failure load increased at both sites. After denosumab, increases in total (3.5%, p < 0.001 and 3.3%, p = 0.02) and cortical vBMD (1.7% and 3.2%; both p < 0.01), and failure load (1.1% and 3.6%; both p < 0.05) were seen at tibia and radius, respectively. Trabecular density (3.5%, p < 0.001) and number (2.4%, p = 0.03) increased at the tibia, while thickness (3.0%, p = 0.02) increased at the radius. After 48 months of sequential treatment, significant increases in total vBMD (tibia: p < 0.001; radius: p = 0.01), trabecular microstructure (p < 0.05), cortical thickness (tibia: p < 0.001; radius: p = 0.02), and whole bone strength (p < 0.02) were seen at both sites. Significant increases in total vBMD and bone strength parameters after sequential treatment with teriparatide followed by denosumab support the use of this regimen in PreMenIOP. © 2022 American Society for Bone and Mineral Research (ASBMR).

Fat, adipokines, bone structure and bone regulatory factors associations in obesity

CONTEXT

Obese (OB) adults (BMI ≥ 30) have a higher bone mineral density (BMD) and more favourable bone microarchitecture than normal-weight (NW) adults (BMI 18.5-24.9).

OBJECTIVE

The objective of this study was to identify which fat compartments have the strongest association with bone density and bone turnover and whether biochemical factors (adipokines, hormones and bone regulators) are likely to be important mediators of the effect of obesity on bone.

DESIGN

This was a cross-sectional, observational, matched case-control study.

SETTING

Participants were recruited from the local community.

PARTICIPANTS

Two hundred healthy men and women aged 25-40 or 55-75 were recruited in individually matched OB and NW pairs. Body composition, BMD and bone microarchitecture were determined by dual-energy X-ray absorptiometry (DXA), computed tomography (CT) and high-resolution peripheral CT (HR-pQCT). Bone turnover and potential regulators such as C-terminal cross-linking telopeptide (CTX), type 1 procollagen N-terminal peptide (PINP), sclerostin, periostin, parathyroid hormone (PTH), 25-hydroxyvitamin D (25OHD), insulin-like growth factor 1 (IGF1), adiponectin, leptin and insulin were assessed.

MAIN OUTCOME

Planned exploratory analysis of the relationships between fat compartments, areal and volumetric BMD, bone microarchitecture, bone turnover markers and bone regulators.

RESULTS

Compared with NW, OB had lower CTX, PINP, adiponectin, IGF1, and 25OHD and higher leptin, PTH and insulin (all P < 0.05). CTX and subcutaneous adipose tissue (SAT) were the bone marker and fat compartment most consistently associated with areal and volumetric BMD. In regression models, SAT was negatively associated with CTX (P < 0.001). When leptin was added to the model, SAT was no longer associated with CTX, but leptin (P < 0.05) was negatively associated with CTX.

CONCLUSIONS

SAT is associated with lower bone resorption and properties favourable for bone strength in obesity. Leptin may be an important mediator of the effects of SAT on the skeleton.

Spine Volumetric BMD and Strength in Premenopausal Idiopathic Osteoporosis: Effect of Teriparatide Followed by Denosumab

CONTEXT

Premenopausal women with idiopathic osteoporosis (PreMenIOP) have marked deficits in bone density, microstructure, and strength.

OBJECTIVE

To define effects of treatment with teriparatide followed by denosumab on lumbar spine (LS) volumetric bone mineral density (vBMD) and stiffness by finite element analysis assessed on central quantitative computed tomography (cQCT) scans.

DESIGN, SETTINGS, AND PARTICIPANTS

Ancillary analysis of baseline, post-teriparatide, and post-denosumab cQCT scans from a randomized trial of 41 women allocated to teriparatide (20 mcg daily; n = 28) or placebo (n = 11). After 6 months, those on teriparatide continued for 18 months, and those on placebo switched to teriparatide for 24 months. After completing teriparatide, 33 enrolled in a Phase 2B extension with denosumab (60 mg every 6 months) for 12 months.

MAIN OUTCOME MEASURES

Primary outcomes were percentage change from baseline in LS trabecular vBMD and stiffness after teriparatide and between end of teriparatide and completing denosumab. Percentage change from baseline in LS trabecular vBMD and stiffness after sequential teriparatide and denosumab were secondary outcomes.

FINDINGS

There were large increases (all Ps < 0.001) in trabecular vBMD (25%), other vBMD parameters, and stiffness (21%) after teriparatide. Statistically significant increases in trabecular vBMD (10%; P < 0.001) and other vBMD parameters (P = 0.03-0.001) were seen after denosumab, while stiffness increased by 7% (P = 0.068). Sequential teriparatide and denosumab led to highly significant (all Ps < 0.001) increases LS trabecular vBMD (43%), other vBMD parameters (15-31%), and stiffness (21%).

CONCLUSIONS

The large and statistically significant increases in volumetric density and stiffness after sequential treatment with teriparatide followed by denosumab are encouraging and support use of this regimen in PreMenIOP.

M. Assessment of trabecular and cortical parameters using high-resolution peripheral quantitative computed tomography, histomorphometry and microCT of iliac crest bone core in hemodialysis patients

Patients with end-stage renal disease develop changes in bone quality and quantity, which can be assessed using different methods. This study aimed to compare and to correlate bone parameters obtained in vivo using high-resolution peripheral quantitative computed tomography (HR-pQCT) with those obtained by bone biopsy using histomorphometry and microcomputed tomography (microCT) analysis of the iliac crest core, and to evaluate if HR-pQCT is helpful in aiding with categorization of those with high turnover. Twenty hemodialysis patients, 13 females (7 postmenopausal), underwent bone biopsy from 2018 to 2020. The mean age was 48.5 ± 10.6 years, and the mean hemodialysis vintage was 15 years. Histomorphometry identified mineralization defects, low turnover, and high turnover in 65%, 45%, and 35% of the patients, respectively. The highest values of trabecular bone volume (BV/TV) were obtained by histomorphometry, while the highest values of cortical thickness (Ct.Th) were obtained by HR-pQCT at the distal tibia. Moderate correlations were found between BV/TV values obtained by microCT of the bone core and HR-pQCT at the distal radius (r = 0.531, p = 0.016) and at the distal tibia (r = 0.536, p = 0.015). BV/TV values obtained from the bone core by histomorphometry and microCT were also significantly correlated (r = 0.475, p = 0.04). Regarding Ct.Th, there was a strong correlation between the radius and tibia HR-pQCT (r = 0.800, p < 0.001), between bone core microCT and the distal radius HR-pQCT (r = 0.610, p < 0.01), as between histomorphometry and microCT (r = 0.899, p < 0.01). In groups classified by bone turnover, patients with high turnover presented lower BV/TV, Tb.N, Tb.Th, and Ct.Th than those with low turnover in peripheral sites using HR-pQCT. By this method, it was possible to identify low turnover from tibia BV/TV > 12,4% plus Tb.Sp ≤ 0.667 mm (AUC 0.810, 95% CI 0.575 to 0.948) and high turnover from total bone mineral density (BMD) ≤ 154.2 mg HA/cm³ (AUC 0.860, 95% CI 0.633 to 0.982, p < 0.001) and cortical BMD ≤ 691.6 mg HA/cm³ (AUC 0.840, 95% CI 0.609 to 0.963, p < 0.001). In conclusion, HR-pQCT had significant correlation with iliac crest bone in BV/TV and Ct.Th, which are known to provide bone strength. This method is quick and non-invasive and may be helpful in categorizing those with high versus low turnover in hemodialysis patients.

•

Bone structure in hemodialysis patients can be assessed using different methods.

•

There was correlation of BV/TV and Ct.Th between histomorphometry and bone core microCT.

•

BV/TV and Ct.Th values obtained by radius HR-pQCT and bone core microCT were correlated.

•

High turnover patients had lower BV/TV, Tb.N, Tb.Th, and Ct.Th by HR-pQCT.

•

HR-pQCT was able to discriminate low and high turnover in hemodialysis patients.

Impact of Adolescent Pregnancy on Bone Density in Underprivileged Pre-Menopausal Indian Women

High prevalence (31.5%) of adolescent pregnancies (AP) have been reported in India. Reports suggest that pregnancy during adolescence may have deleterious effects on peak bone mass. Very few studies have described the long-term effects of a history of AP on bone mass. The objective of this study was to compare bone mineral density (BMD) and bone geometry of premenopausal women with first childbirth during adolescence (i.e., before age of 19 years) or after 20 years. A cross-sectional study was conducted in 242 women (age 28.0-54.5 years) from Pune, India (November, 2015 to November, 2017). Women were divided into 2-groups: Group-1: women-who had 1st-pregnancy and childbirth before 19 years of age (AP n = 131) and Group-2: women-who had 1st pregnancy after 20 years of age (non-AP n = 111). Demographic data, anthropometric measurements, and biochemical tests were performed using standard protocols. Physical activity and nutrient intakes were recorded using validated questionnaires. Areal BMD and bone geometry were measured using Dual-Energy-Absorptiometry-DXA (Lunar-iDXA, GE Healthcare) and peripheral-quantitative-computed-tomography-pQCT (XCT2000, Stratec Inc.). Mean age of the study group was 37 ± 4.6 years; in women from group-1 mean age at first delivery was 16.9 ± 1.6 years as against 22.6 ± 3.1 years in group-2. Both groups were similar in body mass index and socioeconomic status. pQCT measured radial diaphyseal cortical thickness (1.97 ± 0.3 mm vs 1.88 ± 0.3 mm resp., p = 0.016, periosteal circumference (38.0 ± 3.6 mm vs 36.7 ± 2.5 mm, resp. p = 0.016), total bone area (114.3 ± 24.8 mm2 vs 108.7 ± 14.7 mm2 resp. p = 0.026) and stress-strain index (SSI = 217 ± 75 vs 201 ± 40 mm3 resp. p = 0.042) were significantly higher in group-1 than group-2. After adjusting for anthropometric and lifestyle parameters, pQCT measured cortical thickness (1.98 ± 0.03 mm in group-1, 1.87 ± 0.03 mm group-2, p = 0.01, mean ± SE) and iDXA derived aBMD at forearm were still significantly higher (0.599 ± 0.006 g/cm3 vs 0.580 ± 0.006 g/cm3, p = 0.023) in Group-1. Our data suggest that women with a history of adolescent pregnancy had better bone geometry and higher aBMD at radius in later years. We speculate that early exposure to pregnancy resulted in higher aBMD at the radius and induced changes at radial diaphysis with bones becoming thicker and wider among these women.

Association of androgen excess and bone mineral density in women with classical congenital adrenal hyperplasia with 21-hydroxylase deficiency

The relationship between androgen excess and bone health in patients with congenital adrenal hyperplasia (CAH) with 21-hydroxylase (21-OH) deficiency is not fully understood. This study demonstrated positive correlations between androgen hormones and bone mineral density (BMD) in CAH women with 21-OH deficiency.

PURPOSE

This study aims to assess BMD and its association with androgen excess in women with CAH.

METHODS

We enrolled 92 women with CAH with 21-OH deficiency and retrospectively reviewed their clinical features, hormone concentrations, body composition, glucocorticoid (GC) dose, and BMD.

RESULTS

BMD was not different according to the subtypes of CAH. BMD at the lumbar spine was lower in women with CAH with regular menstruation than those with irregular menstruation (1.081 vs. 1.165 g/cm², P < 0.05). BMD was lower in women with CAH with 17-hydroxyprogesterone (17-OHP) < 10 ng/mL than in those with ≥ 10 ng/mL (lumbar spine, 1.019 vs. 1.150 g/cm²; femur neck, 0.806 vs. 0.899 g/cm²; total hip, 0.795 vs. 0.943 g/cm²; all P < 0.05). After adjusting for age and BMI in correlation analyses, testosterone concentrations were positively correlated with lumbar spine, femur neck, and total hip BMD (r = 0.46, r = 0.38, and r = 0.35, respectively; all P < 0.05), while 17-OHP was positively correlated with lumbar spine BMD (r = 0.38, P < 0.01). In subgroup analysis, 17-OHP was positively correlated with BMD (lumbar spine, r = 0.22; femur neck, r = 0.22; total hip, r = 0.24; all P < 0.05) only in the group with a total cumulative dose of GC ≥ 156.0 g/m².

CONCLUSION

Androgen excess may have a protective effect on BMD in women with classic CAH and high cumulative doses of GC.

Bone Geometry, Density, Microstructure, and Biomechanical Properties in the Distal Tibia in Patients With Primary Hypertrophic Osteoarthropathy Assessed by Second-Generation High-Resolution Peripheral Quantitative Computed Tomography

Periosteosis refers to pathological woven bone formation beneath the cortical bone of the long bones. It is an imaging hallmark of primary hypertrophic osteoarthropathy (PHO) and also considered as one of the major diagnostic criteria of PHO patients. Up to date, detailed information on bone quality changes in long bones of PHO patients is still missing. This study aimed to evaluate bone microarchitecture and bone strength in PHO patients by using high-resolution peripheral quantitative computed tomography (HR-pQCT). The study comprised 20 male PHO patients with the average age of 27.0 years and 20 age- and sex-matched healthy controls. The areal bone mineral density (aBMD) was assessed at the lumbar spine (L₁ -L₄ ) and hip (total hip and femoral neck) by dual-energy X-ray absorptiometry (DXA). Bone geometry, volumetric bone mineral density (vBMD), and microstructure parameters at the distal tibia were evaluated by using HR-pQCT. Bone strength was evaluated by finite element analysis (FEA) based on HR-pQCT screening at distal tibia. Urinary prostaglandin E₂ (PGE₂ ), serum phosphatase (ALP), beta-C-telopeptides of type I collagen (β-CTX), soluble receptor activator of nuclear factor-κB ligand (sRANKL), osteoprotegerin (OPG), and neuronal calcitonin gene-related peptide (CGRP) were investigated. As compared with healthy controls, PHO patients had larger bone cross-sectional areas; lower total, trabecular, and cortical vBMD; compromised bone microstructures with more porous cortices, thinned trabeculae, reduced trabecular connectivity, and relatively more significant resorption of rod-like trabeculae at distal tibia. The apparent Young's modulus was significantly lower in PHO patients. The concentration of PGE₂ , biomarkers of bone resorption (β-CTX and sRANKL/OPG ratio), and the neuropeptide CGRP were higher in PHO patients versus healthy controls. PGE₂ level correlated negatively with vBMD and estimated bone strength and positively with bone geometry at distal tibia. The present HR-pQCT study is the first one illustrating the microarchitecture and bone strength features in long bones. © 2021 American Society for Bone and Mineral Research (ASBMR).

Examining effects of habitual physical activity and body composition on bone structure in early post-menopausal women: a pQCT analysis

After menopause, bones decline in structure and can break more easily. Physical activity can strengthen bones. This study investigated how activity and body composition can impact bone structure in post-menopausal women. Higher levels of physical activity were positively associated with bone structure at the lower leg.

PURPOSE

The menopausal transition is characterized by dramatic bone loss, leading to an increased risk of fracture. Few studies have examined how modifiable risk factors influence bone structure. Thus, the objective of this cross-sectional study was to examine the relationship between habitual physical activity (PA), body composition, and bone structure in post-menopausal women with low bone mass.

METHODS

Data was analyzed from 276 post-menopausal women with low bone mass enrolled in the Heartland Osteoporosis Prevention Study. Body composition and bone structure measures were collected using dual X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) at the tibia. Habitual PA was collected using the Human Activity Profile questionnaire. Multiple regression analysis was used to determine the relative impact of habitual PA and body composition on bone structure measures (density, area, and strength). Direct and/or indirect effects of PA on bone outcomes were assessed by path analysis.

RESULTS

Mean (± SD) age of participants was 54.5 (± 3.2) years and average BMI was 25.7 (± 4.7). Mean T-score of the total lumber spine and hip were - 1.5 (± .6) and - 0.8 (± .59), respectively, with all women classified with low bone mass. Habitual PA had a significant positive effect on bone area and strength measures at the 66% site, and trend effects at the 4% site. Lean mass had a significant positive effect on area and strength at the 66% site and 4% site. Fat mass showed no effect at the 66% site, with a positive effect on density and strength at the 4% site.

CONCLUSION

Increased habitual activity was related to improved bone structure of the tibia. Our results in post-menopausal women emphasize that PA and lean mass preservation are important for maintaining bone structure in the years following menopause.

Best Performance Parameters of HR-pQCT to Predict Fragility Fracture: Systematic Review and Meta-Analysis

Osteoporosis is a systemic skeletal disease characterized by low bone mass and bone structural deterioration that may result in fragility fractures. Use of bone imaging modalities to accurately predict fragility fractures is always an important issue, yet the current gold standard of dual-energy X-ray absorptiometry (DXA) for diagnosis of osteoporosis cannot fully satisfy this purpose. The latest high-resolution peripheral quantitative computed tomography (HR-pQCT) is a three-dimensional (3D) imaging device to measure not only volumetric bone density, but also the bone microarchitecture in a noninvasive manner that may provide a better fracture prediction power. This systematic review and meta-analysis was designed to investigate which HR-pQCT parameters at the distal radius and/or distal tibia could best predict fragility fractures. A systematic literature search was conducted in Embase, PubMed, and Web of Science with relevant keywords by two independent reviewers. Original clinical studies using HR-pQCT to predict fragility fractures with available full text in English were included. Information was extracted from the included studies for further review. In total, 25 articles were included for the systematic review, and 16 articles for meta-analysis. HR-pQCT was shown to significantly predict incident fractures and/or major osteoporotic fractures (MOFs). Of all the HR-pQCT parameters, our meta-analysis revealed that cortical volumetric bone mineral density (Ct.vBMD), trabecular thickness (Tb.Th), and stiffness were better predictors. Meanwhile, HR-pQCT parameters indicated better performance in predicting MOFs than incident fractures. Between the two standard measurement sites of HR-pQCT, the non-weight-bearing distal radius was a more preferable site than distal tibia for fracture prediction. Furthermore, most of the included studies were white-based, whereas very few studies were from Asia or South America. These regions should build up their densitometric databases and conduct related prediction studies. It is expected that HR-pQCT can be used widely for the diagnosis of osteoporosis and prediction of future fragility fractures. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Mechanical metric for skeletal biomechanics derived from spectral analysis of stiffness matrix

A new metric for the quantitative and qualitative evaluation of bone stiffness is introduced. It is based on the spectral decomposition of stiffness matrix computed with finite element method. The here proposed metric is defined as an amplitude rescaled eigenvalues of stiffness matrix. The metric contains unique information on the principal stiffness of bone and reflects both bone shape and material properties. The metric was compared with anthropometrical measures and was tested for sex sensitivity on pelvis bone. Further, the smallest stiffness of pelvis was computed under a certain loading condition and analyzed with respect to sex and direction. The metric complements anthropometrical measures and provides a unique information about the smallest bone stiffness independent from the loading configuration and can be easily computed by state-of-the-art subject specified finite element algorithms.

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

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

Management of bone fragility in type 2 diabetes: Perspective from an interdisciplinary expert panel

AIM

Bone fragility is increasingly recognized as a relevant complication of type 2 diabetes (T2D) and diabetic patients with fragility fractures have higher mortality rates than non diabetic individuals or diabetic patients without fractures. However, current diagnostic approaches for fracture risk stratification, such as bone mineral density measurement or the use of risk assessment algorithms, largely underestimate fracture risk in T2D patients. A multidisciplinary expert panel was established in order to in order to formulate clinical consensus recommendations on bone health assessment and management of fracture risk in patients with T2D.

DATA SYNTHESIS

The following key questions were addressed: a) which are the risk factors for bone fragility in T2D?, b) which diagnostic procedures can be currently used to stratify fracture risk in T2D patients?, c) which are the effects of antidiabetic treatments on bone?, and d) how to prevent and treat bone fragility in T2D patients? Based on the available data members of this panel suggest that the stratification of fracture risk in patients with diabetes should firstly rely on the presence of a previous fragility fracture and on the individual risk profile, with the inclusion of T2D-specific risk factors (namely T2D duration above 10 yrs, presence of chronic T2D complications, use of insulin or thiazolidinediones and persistent HbA1c levels above 8% for at least 1 year). Two independent diagnostic approaches were then suggested in the presence or the absence of a prevalent fragility fracture, respectively.

CONCLUSIONS

Clinical trials in T2D patients at risk for fragility fractures are needed to determine the efficacy and safety of available antiresorptive and anabolic agents in this specific setting.

Severe Bone Microarchitecture Impairment in Women With Pregnancy and Lactation-Associated Osteoporosis

Context

Pregnancy- and lactation-associated osteoporosis (PLO) is a rare condition characterized by fragility fractures, mostly vertebral, during the third trimester of pregnancy or the early postpartum period.

Objective

The aim of this study was to evaluate bone microarchitecture in women with PLO to better understand the pathophysiology of this disease.

Methods

In this retrospective study, we included women with PLO referred to our bone center between November 2007 and July 2012. We assessed bone mineral density (BMD) by dual-energy x-ray absorptiometry, bone turnover markers, and bone microarchitecture by high-resolution peripheral quantitative computed tomography. Results were compared with a control group of healthy lactating women.

Results

Of the 7 primiparous patients with PLO, 6 suffered vertebral fractures and 1 developed a hip fracture during the seventh month of gestation. Fractures occurred within the eighth month of pregnancy and the fourth month post partum; vertebral fractures were multiple in 85.7%. Major or minor risk factors for osteoporosis were present in 86% of our patients. Trabecular density, number, and thickness were 34%, 20% and 22% lower than controls (P < .01, P = .01, and P = .01, respectively). Cortical parameters were also deteriorated but to a lesser extent.

Conclusion

In comparison with healthy lactating women, patients with PLO presented severe deterioration of bone trabecular and cortical microarchitecture. This significant compromise may explain the occurrence of multiple fractures in these otherwise healthy young women. Further prospective studies are needed to determine whether bone microarchitecture might be able to be restored in the future.

Bone Microarchitecture, Volumetric or Areal Bone Mineral Density for Discrimination of Vertebral Deformity in Adults: A Cross-sectional Study

INTRODUCTION/BACKGROUND

Both areal bone mineral density (aBMD) and bone microarchitecture have been associated with vertebral deformity (VD), but there are limited data on the utility of bone microarchitecture measures in combination with aBMD in discriminating VD. This study aimed to describe whether radial bone microarchitecture measures alone or in combinations with radial volumetric bone mineral density (vBMD) or spine aBMD can improve discrimination of VD in adults.

METHODS

Data on 196 subjects (mean age (standard deviation, SD) = 72 (7) years, female 46%) were utilized. VD of T4-L4 and spine aBMD were measured using dual-energy X-ray absorptiometry. VD was defined if anterior to posterior height ratio was more than 3-SD, 4-SD below, or >25% decrease compared with the sex-matched normal means. Bone microarchitecture parameters at distal radius were collected using high-resolution peripheral quantitative computed tomography and analyzed using StrAx.

RESULTS

The strongest associations were seen for the cortical thickness (odds ratios (ORs): 2.63/SD decrease for 25% and 2.38/SD decrease for 3-SD criterion) and compact cortical area (OR: 3.33/SD decrease for 4-SD criterion). The area under the receiver operating characteristic curve (AUC) for spine aBMD for VD was 0.594, 0.597, and 0.634 for 25%, 3-SD and 4-SD criteria, respectively (all p < 0.05). Compact cortical area, cortical thickness and compact cortical thickness alone had the largest AUCs for VD (0.680-0.685 for 25% criterion, 0.659-0.674 for 3-SD criterion, and 0.699-0.707 for 4-SD criterion). Adding spine aBMD or radial vBMD to each cortical measure did not improve VD discrimination (∆ AUC 0.8%-2.1%).

CONCLUSIONS

Cortical measures had the best utility for discriminating VD when used alone. Adding either spine aBMD or radial vBMD did not improve the utility of cortical measures.

MRI-derived porosity index is associated with whole-bone stiffness and mineral density in human cadaveric femora

Ultrashort echo time (UTE) magnetic resonance imaging (MRI) measures proton signals in cortical bone from two distinct water pools, bound water, or water that is tightly bound to bone matrix, and pore water, or water that is freely moving in the pore spaces in bone. By isolating the signal contribution from the pore water pool, UTE biomarkers can directly quantify cortical bone porosity in vivo. The Porosity Index (PI) is one non-invasive, clinically viable UTE-derived technique that has shown strong associations in the tibia with μCT porosity and other UTE measures of bone water. However, the efficacy of the PI biomarker has never been examined in the proximal femur, which is the site of the most catastrophic osteoporotic fractures. Additionally, the loads experienced during a sideways fall are complex and the femoral neck is difficult to image with UTE, so the usefulness of the PI in the femur was unknown. Therefore, the aim of this study was to examine the relationships between the PI measure in the proximal cortical shaft of human cadaveric femora specimens compared to (1) QCT-derived bone mineral density (BMD) and (2) whole bone stiffness obtained from mechanical testing mimicking a sideways fall. Fifteen fresh, frozen whole cadaveric femora specimens (age 72.1 ± 15.0 years old, 10 male, 5 female) were scanned on a clinical 3-T MRI using a dual-echo UTE sequence. Specimens were then scanned on a clinical CT scanner to measure volumetric BMD (vBMD) and then non-destructively mechanically tested in a sideways fall configuration. The PI in the cortical shaft demonstrated strong correlations with bone stiffness (r = -0.82, P = 0.0014), CT-derived vBMD (r = -0.64, P = 0.0149), and with average cortical thickness (r = -0.60, P = 0.0180). Furthermore, a hierarchical regression showed that PI was a strong predictor of bone stiffness which was independent of the other parameters. The findings from this study validate the MRI-derived porosity index as a useful measure of whole-bone mechanical integrity and stiffness.

Bone erosion in the 2nd metacarpophalangeal head: association with its bone mineral density by HR-pQCT in rheumatoid arthritis patients

Background

Rheumatoid arthritis (RA) is a chronic autoimmune disease depicted by synovial inflammation leading to local and systemic bone loss. The aim of this study was to evaluate by a HR-pQCT (High Resolution Peripheral Quantitative Computed Tomography) study which parameters are associated with volume of bone erosions including bone mineral density (BMD) around erosions (VOI 1 to 4 = volume of interest), BMD of metacarpophalangeal (MCP) head, BMD of radius, presence of osteophytes and joint space width (JSW).

Methods

Fifty female RA patients (18–50 years) were enrolled in this study. Demographic and disease-specific data, laboratory inflammatory parameters and handgrip test were performed. All patients underwent HR-pQCT of 2nd and 3rd MCP joints and distal radius, according to established protocols. The volume of bone erosions was evaluated by MIAF (Medical Image Analysis Framework) software. Osteophytes were analyzed by manual method.

Results

The mean of age and disease duration were 40.0 ± 6.0 yrs. and 10.8 ± 4.8 yrs., respectively. According to DAS-28 (Disease Activity Score), 54% (27) of the sample were in remission. However, when SDAI (Simplified Disease Activity Index) was used, only 18% (9) were under remission. The mean of HAQ (Health Assessment Questionnaire), ESR (Erythrocyte sedimentation rate) and CRP (C reactive protein) were 0.9 ± 0.7, 13.9 ± 12.2 mm and 5.6 ± 7.5 mg/mL, respectively. Forty-six bone erosions (0.9 ± 1.2 erosion/patient) and 14 osteophytes (0.3 ± 0.7 osteophyte/patient) were found in 2nd MCP head. The median (IQR-Interquartile range) of volume of erosion and volume of osteophytes were 14.9 (5.7;35.9)mm³ and 3.1 (2.1, 4.3)mm³, respectively. The mean of JSW was 80.5 ± 34.2 mm³. The volume of bone erosions was negatively correlated with BMD of 2nd MCP head, VOI-4 and JSW; and it was positively correlated with osteophytes number. Regarding absence or presence of erosion in 2nd MCP head, a significant difference was found between BMD of MCP head, osteophyte number and JSW. Multiple linear regression analysis showed that only BMD of 2nd MCP head was independently associated with volume of bone erosions.

Conclusion

BMD of MCP head was independently associated with volume of bone erosion, suggesting that this parameter should be used to analyze and monitoring bone destruction, as well as to evaluate treatment response in RA patients.

Performance of HR-pQCT, DXA, and FRAX in the discrimination of asymptomatic vertebral fracture in postmenopausal Chinese women

Volumetric bone density (vBMD) and trabecular microarchitecture measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) can discriminate the patients with high risk of asymptomatic vertebral fracture (VF) in postmenopausal Chinese women. These findings suggested that HR-pQCT could provide additional information on bone quality of the patients with asymptomatic VF.

INTRODUCTION

Although there were several studies using HR-pQCT to investigate asymptomatic VF, it remains uncertain if HR-pQCT parameters can discriminate asymptomatic VF patients, especially in Chinese population. The purpose of this study was to investigate whether bone quality measured by HR-pQCT could discriminate asymptomatic VF independent of hip areal bone mineral density (aBMD) measured by dual-energy x-ray absorptiometry (DXA) and fracture risks evaluated using built-in Fracture Risk Assessment Tool (FRAX_BMD).

METHODS

This is a nested case-control study. One hundred seventy-five ambulatory Chinese postmenopausal women aged 60-79 years were retrieved from Normative Reference Standards (NRS) cohort in Hong Kong. DXA was used to identify VF from lateral spine images (VFA) using Genant's semi-quantitative method. Major osteoporotic fracture risk was calculated using FRAX tool. HR-pQCT was used to assess vBMD, microarchitecture, and estimated strength at both distal radius and tibia. Comparison of HR-pQCT parameters between asymptomatic VF and control was performed using covariance analysis. Logistic regression analysis was performed for calculating the adjusted odds ratio (OR) with 95% confidence intervals (CI) of fracture status as per SD decrease in HR-pQCT parameters.

RESULTS

Women with asymptomatic VF were older than those of the control in our NRS cohort. Nevertheless, after adjusted for covariance, asymptomatic VF showed significantly lower trabecular vBMD (Tb.vBMD) at radius but higher SMI at tibia as compared with those of the control. Tb.vBMD at radius yielded the highest value of area under the curve (AUC) as compared with total hip aBMD and FRAX_BMD. However, no significant difference was found among each other.

CONCLUSION

Tb.vBMD at the radius and SMI at the tibia provided by HR-pQCT can discriminate asymptomatic VF independent of hip aBMD and FRAX_BMD by DXA in postmenopausal women.

Cortical parameters predict bone strength at the tibial diaphysis, but are underestimated by HR-pQCT and μCT compared to histomorphometry

Cortical bone and its microstructure are crucial for bone strength, especially at the long bone diaphysis. However, it is still not well‐defined how imaging procedures can be used as predictive tools for mechanical bone properties. This study evaluated the capability of several high‐resolution imaging techniques to capture cortical bone morphology and assessed the correlation with the bone's mechanical properties. The microstructural properties (cortical thickness [Ct.Th], porosity [Ct.Po], area [Ct.Ar]) of 11 female tibial diaphysis (40–90 years) were evaluated by dual‐energy X‐ray absorptiometry (DXA), high‐resolution peripheral‐quantitative‐computed‐tomography (HR‐pQCT), micro‐CT (μCT) and histomorphometry. Stiffness and maximal torque to failure were determined by mechanical testing. T‐Scores determined by DXA ranged from 0.6 to −5.6 and a lower T‐Score was associated with a decrease in Ct.Th (p ≤ 0.001) while the Ct.Po (p ≤ 0.007) increased, and this relationship was independent of the imaging method. With decreasing T‐Score, histology showed an increase in Ct.Po from the endosteal to the periosteal side (p = 0.001) and an exponential increase in the ratio of osteons at rest to those after remodelling. However, compared to histomorphometry, HR‐pQCT and μCT underestimated Ct.Po and Ct.Th. A lower T‐Score was also associated with significantly reduced stiffness (p = 0.031) and maximal torque (p = 0.006). Improving the accuracy of Ct.Po and Ct.Th did not improve prediction of the mechanical properties, which was most closely related to geometry (Ct.Ar). The ex‐vivo evaluation of mechanical properties correlated with all imaging modalities, with Ct.Th and Ct.Po highly correlated with the T‐Score of the tibial diaphysis. Cortical microstructural changes were underestimated with the lower resolution of HR‐pQCT and μCT compared to the histological ‘gold standard’. The increased accuracy did not result in an improved prediction for local bone strength in this study, which however might be related to the limited number of specimens and thus needs to be evaluated in a larger collective.

Estimation of mass apparent density and Young's modulus of femoral neck-head region

The purpose of this study is to estimate mass apparent density and Young's modulus to investigate biomechanical properties of the proximal femur bone. In this study eleven specimens of sheep femur bone having age between 1-1.25 years and human femur bone having age between 14 and 81years are used. In the present study, the first technique attempts to estimate the density from the image-based Hounsfield unit which is obtained directly from a computed tomography image. The modulus of elasticity is estimated from density-elasticity relation which is available in the literature. Another technique is used to develop a correlation between computed apparent density and greyscale based coefficient obtained by material mapping method using commercial Simpleware ScanIP software. Estimated mean deviation in apparent mass density and Young's modulus is 4.34% and 4.69% in sheep bone and 4.35% and 4.94% in human bone respectively. It is found that apparent density and Young's modulus obtained shows close agreement with values reported in the literature. Moreover, the study attempts to build up a new material model between human and sheep for orthopaedics clinical trials and research in Indian context. In addition, it is also observed that bone mass density of sheep is 1.60 times human. This method can also be useful to study and analyse biomechanical properties of the human femur bone.

Bone Evaluation by High-Resolution Peripheral Quantitative Computed Tomography in Patients With Adrenal Incidentaloma

CONTEXT

Data regarding high-resolution peripheral quantitative computed tomography (HR-pQCT) in patients with adrenal incidentaloma (AI) are unknown.

PURPOSE

To evaluate the areal bone mineral density (aBMD), microstructure, and fractures in patients with nonfunctioning AI (NFAI) and autonomous cortisol secretion (ACS).

METHODS

We evaluated 45 patients with NFAI (1 mg dexamethasone suppression test [DST] ≤1.8 µg/dL) and 30 patients with ACS (1 mg DST 1.9-5.0 µg/dL). aBMD was measured using dual-energy X-ray absorptiometry; vertebral fracture by spine X-ray; and bone geometry, volumetric bone mineral density (vBMD), and microstructure by HR-pQCT.

RESULTS

Patients with ACS showed lower aBMD values at the spine, femoral neck, and radius 33% than those with NFAI. Osteoporosis was frequent in both groups: NFAI (64.9%) and ACS (75%). Parameters at the distal radius by HR-pQCT were decreased in patients with ACS compared to those with NFAI: trabecular vBMD (Tb.vBMD, P = 0.03), inner zone of the trabecular region (Inn.Tb.vBMD, P = 0.01), the bone volume/tissue volume ratio (BV/TV, P = 0.03) and trabecular thickness (P = 0.04). As consequence, a higher ratio of the outer zone of the trabecular region/inner zone vBMD (Meta/Inn.vBMD, P = 0.003) was observed. A correlation between the cortisol levels after 1 mg DST and Meta/Inn.vBMD ratio was found (r = 0.29; P = 0.01). The fracture frequency was 73.7% in patients with ACS vs 55.6% in patients with NFAI (P = 0.24).

CONCLUSION

Our findings point to an association between trabecular bone microarchitectural derangement at the distal radius and ACS. Our data suggest that AI have a negative impact on bone when assessed by HR-pQCT, probably associated to subclinical hypercortisolism.

Low volumetric bone density is a risk factor for early complications after spine fusion surgery

This study aims to investigate lumbar spine (LS) volumetric bone density (vBMD) as a risk factor for complications (pseudoarthrosis, instrumentation failure, adjacent fractures), re-operation, and time to complication after fusion.

INTRODUCTION

Lumbar spine (LS) fusion surgery is increasingly performed worldwide. Complications after fusion result in significant morbidity and healthcare costs. Multiple factors, including osteoporosis, have been suggested to contribute to risk of complications and re-operation. However, most studies have used DXA, which is subject to artifact in patients with spine pathology, and none have investigated the relationship between BMD and timing of post-operative complications. This study aims to investigate LS volumetric bone density (vBMD) as a risk factor for complications (pseudoarthrosis, instrumentation failure, adjacent fractures), re-operation, and time to complication after fusion.

METHODS

We evaluated a cohort of 359 patients who had initial LS fusion surgery at our institution, had pre-operative LS CTs and post-operative imaging available for review. Demographic factors, smoking status, vBMD, and details of surgical procedure were related to likelihood and timing of post-operative complications.

RESULTS

Mean age was 60 ± 14 years, vBMD 122 ± 37 g/cm³. Median follow-up was 11 months. Skeletal complications occurred in 47 patients (13%); 34 patients (10%) required re-operation. Low vBMD (directly measured and estimated using HU) and smoking were associated with increased risk of skeletal complications. Each increase in baseline vBMD of 10 g/cm³ decreased the complication hazard and increased the complication-free duration in time-to-event analysis (hazard ratio 0.91, 95% CI 0.83-0.98, p < 0.02).

CONCLUSIONS

Low vBMD was a significant risk factor for early post-operative complications in patients undergoing LS fusion. Prospective studies are needed to confirm these findings and to elucidate the optimal timing for follow-up and strategies for prevention of post-operative complications in this population.

Abnormal microarchitecture and stiffness in postmenopausal women with isolated osteoporosis at the 1/3 radius

BACKGROUND

Postmenopausal women with isolated osteoporosis at the 1/3 radius (1/3RO) present a therapeutic dilemma. Little is known about whether these patients have generalized skeletal fragility, and whether this finding warrants treatment. The aim of this study was to investigate the biochemical and microarchitectural phenotype of women with 1/3RO compared to women with classic postmenopausal osteoporosis by DXA at the spine and hip (PMO), and controls without osteoporosis at any site.

METHODS

This cross-sectional study enrolled 266 postmenopausal women, who were grouped according to densitometric pattern. Subjects had serum biochemistries, areal BMD (aBMD) measured by DXA, trabecular and cortical vBMD, microarchitecture, and stiffness by high resolution peripheral QCT (HR-pQCT, voxel size ~82 μm) of the distal radius and tibia.

RESULTS

Mean age was 68 ± 7 years. DXA T-Scores reflected study design. By HR-pQCT, 1/3RO had abnormalities at both radius and tibia compared to controls: lower total, cortical and trabecular vBMD, cortical thickness and trabecular number, higher trabecular separation and heterogeneity, and lower whole bone stiffness. In contrast, the magnitude and pattern of abnormalities in vBMD, microarchitecture and stiffness in 1/3RO were similar to those in PMO; the difference compared to controls was similar among the two groups. Serum calcium, creatinine, parathyroid hormone, 25-hydroxyvitamin D, and 24-hour urine calcium did not differ.

CONCLUSIONS

Although aBMD appeared relatively preserved at the spine and hip by DXA, women with 1/3RO had significant microarchitectural and biomechanical deficits comparable to those in women with typical PMO. Further study is required to guide treatment decisions in this population.

Distal radius bone microarchitecture: what are the differences between age 25 and old age?

This study reported that the transitional zones in older adults were enlarged at the expense of the compact-appearing cortex with a greater porosity in all cortical sub-compartments. The magnitude of differences in areal and volumetric bone mineral density (aBMD, vBMD) between older and younger groups was similar.

INTRODUCTION

Aging is strongly associated with bone loss, but little is known about magnitudes of differences in bone microarchitectures, aBMD, and vBMD from peak bone mass (PBM) to senescence. We aimed to describe differences in aBMD, vBMD, and bone microarchitecture parameters at the distal radius between older and young adults.

METHODS

We compared 201 participants, aged 62-89 years (female 47%) and 196 participants, aged 24-28 years (female 38%). Bone microarchitecture parameters at distal radius were measured using high-resolution peripheral computed tomography (HRpQCT). aBMD was measured using dual-energy X-ray absorptiometry (DXA). Unpaired t tests and chi-square tests were used to compare differences in means and proportions as appropriate.

RESULTS

Older adults had thinner compact-appearing cortices with larger (cross-sectional area: outer 30.96 mm² vs. 28.38 mm², inner 36.34 mm² vs. 32.93 mm²) and thicker (outer 0.57 mm vs. 0.54 mm, inner 0.71 mm vs. 0.65 mm) transitional zones compared with young adults (all p < 0.05). Cortical porosity was modestly higher in older adults than in young adults (54% vs. 49%, p < 0.001). The magnitude of the difference in hip aBMD between older and young adults was slightly lower than of total radial vBMD (- 0.51 SD vs. - 0.78 SD).

CONCLUSION

Compared with young adults at the time of PBM, the transitional zones in older adults were enlarged at the expense of the compact-appearing cortex with a greater porosity in all cortical sub-compartments. The similar SD differences in aBMD and vBMD between older and younger groups suggest that the differences in bone area are not leading to major artefactual change in aBMD.

Bone Mineral Density in Adults With Congenital Adrenal Hyperplasia: A Systematic Review and Meta-Analysis

Background: Decreased bone mineral density (BMD) is a concern in patients with congenital adrenal hyperplasia (CAH) due to lifelong glucocorticoid replacement. Studies till date have yielded conflicting results. We wanted to systematically evaluate the available evidence regarding BMD in adult patients with CAH. Methods: We searched Medline, Embase and Cochrane Central Register of Controlled Trials to identify eligible studies. Studies comparing BMD in CAH patients with age- and sex-matched controls were included. Age <16 years and absence of controls were exclusion criteria. Two authors independently reviewed abstracts, read full-text articles, extracted data, assessed risk of bias using Newcastle-Ottawa scale, and determined level of evidence using Grading of Recommendations Assessment, Development, and Evaluation methodology. Results: Nine case-control studies with a total sample of 598 (cases n = 254, controls n = 344) met eligibility criteria. Median age was 31 years (IQR 23.9-37) and 65.7% were female. Total body BMD (Mean Difference [MD]-0.06; 95%CI -0.07, -0.04), lumbar spine BMD (MD -0.05; 95%CI -0.07, -0.03) and femoral neck BMD (MD -0.07; 95%CI -0.10, -0.05) was lower in cases compared to controls. Lumbar spine T-scores (MD -0.86; 95%CI -1.16, -0.56) and Z-scores (MD -0.66; 95%CI -0.99, -0.32) and femoral neck T-scores (MD -0.75 95%CI -0.95, -0.56) and Z-scores (MD -0.27 95%CI -0.58, 0.04) were lower in cases. Conclusion: BMD in adult patients with CAH was lower compared to controls. Although insufficient data precludes a dose-response relationship between glucocorticoid dose and BMD, it would be prudent to avoid overtreatment with glucocorticoids.

MDCT-QCT, QUS, and DXA in healthy adults: An intermodality comparison

Background: Cortical deceleration is the main reason for bone loss at peripheral sites. It was suggested that when peripheral bones were assessed for osteoporosis, management and therapy can be administered early. The main aim of this study was to assess the relationships between the central and peripheral measurements at different skeleton bone sites (spine, femur, forearm, tibia, and calcaneus) with available modalities: DXA, QUS, and MDCT-QCT. Methods: The volunteers recruited in this study did not have any history or evidence of metabolic bone disease. Blood test and DXA measurements were used as inclusion criteria to select 40 healthy participants. The selected volunteers underwent 3 imaging modalities: QCT, DXA, and QUS. DXA-based measurements were made on 3 sites, including spine, femur, and forearm. QCT and QUS measurements were done for distal of tibia and calcaneus bones, respectively. The extracted parameters from the 3 modalities were analyzed using a bivariate (Pearson) correlation (r) in statistical software. Results: The results showed moderate to good correlations between spongy bones in central and peripheral sites from all the modalities. However, there was no correlation between MDCT measures and central bone values. According to correlations between different peripheral sits, aBMD of 33% radius and trabecular vBMD in 38% distal tibia showed weak but significant relationship between peripheral bones (r=-0.342, p=0.044). Conclusion: The findings demonstrated how bones in central and peripheral sites were correlated. Multimodality imaging was used in this group of healthy volunteers. Also, it was found that QCT-based MDCT needs more optimization and requires further investigations.

Effects of FES-Rowing Exercise on the Time-Dependent Changes in Bone Microarchitecture After Spinal Cord Injury: A Cross-Sectional Investigation

Disuse osteoporosis is a serious, secondary consequence of spinal cord injury (SCI). Numerous pharmacological and exercise therapies have been implemented to mitigate bone loss after SCI. However, these therapies have not been shown to improve bone density, potentially because of insufficient duration and magnitude of loading and/or inability of imaging modalities to capture changes in bone microarchitecture. In this cross‐sectional study, we evaluated bone microstructure of the distal tibia and radius using HR‐pQCT in men with SCI (N = 13) who regularly trained with functional electrical stimulation‐ (FES‐) rowing. We aimed to determine whether the amount of FES‐rowing (total distance rowed and peak foot force) and/or time since injury (TSI) predict bone loss after SCI. We assessed volumetric density of the total, cortical, and trabecular compartments, cortical thickness, and trabecular thickness. Using linear regression analysis, we found that TSI was not associated with any of the tibial bone metrics. In fact, none of the variables (TSI, total distance rowed, and peak foot force) independently predicted bone loss. Using stepwise regression, when all three variables were considered together, we found a strong prediction for trabecular microstructure (trabecular vBMD: R² = 0.53; p = 0.06; trabecular thickness: R² = 0.72; p < 0.01), but not cortical bone metrics. In particular, trabecular vBMD and thickness were negatively associated with TSI and positively associated with distance rowed. Foot force contributed markedly less to trabecular bone than distance rowed or TSI. Our results suggest that regular FES‐rowing may have the capacity to alter the time‐dependent bone negative effects of SCI on trabecular bone density and microstructure. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Bone measurements at multiple skeletal sites in adolescent idiopathic scoliosis-an in vivo correlation study using DXA, HR-pQCT and QCT

Significant correlations for bone mineral density and bone microstructure between spinal and non-spinal skeletal sites (distal radius and proximal femur) in adolescent idiopathic scoliosis (AIS) patients were observed, indicating that proximal femoral DXA and distal radial HR-pQCT could provide valid clinical assessments in patients with AIS.

PURPOSE

Low bone mass is an important feature of adolescent idiopathic scoliosis (AIS), which is a complex 3D spinal deformity that affects girls during puberty. However, no clinical imaging modality is suitable for regular monitoring on their spinal bone qualities in rapid growth period. Therefore, we investigated whether bone mineral density (BMD) and bone microstructure at non-spinal sites correlated with BMD and mechanical property in the spine in AIS patients.

METHODS

Thirty-two AIS girls (16.7 ± 3.5 years old with mean Cobb angle of 67 ± 11°) who underwent pre-operative spine CT examination for navigation surgery were recruited. Volumetric BMD (vBMD) of lumbar spine (LS) was measured by quantitative computed tomography (QCT), vBMD and bone microstructure of distal radius (DR) by high-resolution peripheral QCT (HR-pQCT) and areal BMDs of total hip (TH) and femoral necks (FN) by dual-energy X-ray absorptiometry (DXA). Biomechanical properties of the DR and LS were estimated by finite element analysis (FEA). Pearson correlation was performed to study the correlation between bone parameters at these three sites.

RESULTS

LS vBMD correlated significantly with both FN and TH aBMD (R = 0.663-0.725, both p < 0.01) and with DR microstructural parameters (R = 0.380-0.576, all p < 0.05). Mechanical properties of LS and DR were also correlated (R = 0.398, p = 0.039).

CONCLUSIONS

Bone measurement at proximal femur and distal radius could provide an additional predictive power in estimating the bone changes at spine, which is the primary site of deformity in AIS patients. Our result indicated that DXA and HR-pQCT could provide a valid surrogate for spine bone measurements in AIS patients.

Association between 25-Hydroxyvitamin D, Parathyroid Hormone, Vitamin D and Calcium Intake, and Bone Density in Healthy Adult Women: A Cross-Sectional Analysis from the D-SOL Study

There is still limited data on the association between 25-hydroxyvitamin D (25(OH)D), parathyroid hormone (PTH), and bone health in healthy younger adults, particularly in Latin America. This cross-sectional analysis aimed to investigate the associations of 25(OH)D and plasma PTH concentrations with bone parameters, and potential confounders, in women living in a high (England) or low (Brazil) latitude country. Bone was assessed by either peripheral quantitative computed tomography (pQCT) (England) or dual-energy x-ray absorptiometry (DXA) scan (Brazil), serum 25(OH)D concentrations by high performance liquid chromatography tandem mass spectrometry (HPLC-MS) and PTH by the chemiluminescent method. In participants living in England, total volumetric bone mineral density (vBMD) was significantly higher in women <29 years compared to ≥30 years, and total and cortical vBMD values at the 66% site were negatively correlated with weight and body mass index (BMI). In participants living in Brazil, age was positively correlated with bone mineral density (BMD) at the femur and bone mineral content (BMC), and weight, BMI, and body fat were correlated with BMD (lumbar spine and femur) and BMC. PTH concentrations were negatively correlated with 25(OH)D concentrations, and the prevalence of secondary hyperparathyroidism was 28.6% (n = 14) in participants with concentrations <25 nmol/L and 12.2% (n = 41) with concentrations between 25 and 49.9 nmol/L, compared to 6.3% (n = 79) in those with concentrations ≥50 nmol/L. In conclusion, weight and BMI were significantly correlated with bone parameters in both groups and age was significantly correlated with BMD at the femoral neck for women living in Brazil only. Although 25(OH)D concentrations were not correlated to bone parameters at any sites, in either country, PTH concentrations showed a significant correlation with total vBMD at the 66% site for women living in England. Secondary hyperparathyroidism was more common amongst those with deficient and insufficient vitamin D status.

Impact of Weight Loss With Intragastric Balloon on Bone Density and Microstructure in Obese Adults

The historical concept that obesity protects against bone fractures has been questioned. Weight loss appears to reduce bone mineral density (BMD); however, the results in young adults are inconsistent, and data on the effects of weight loss on bone microstructure are limited. This study aimed to evaluate the impact of weight loss using an intragastric balloon (IGB) on bone density and microstructure. Forty obese patients with metabolic syndrome (mean age 35.1 ± 7.3 yr) used an IGB continuously for 6 mo. Laboratory tests, areal BMD, and body composition measurements via dual-energy X-ray absorptiometry, and volumetric BMD and bone microstructure measurements via high-resolution peripheral quantitative computed tomography were conducted before IGB placement and after IGB removal. The mean weight loss was 11.5%. After 6 mo, there were significant increases in vitamin D and carboxyterminal telopeptide of type 1 collagen levels. After IGB use, areal BMD increased in the spine but decreased in the total femur and the 33% radius. Cortical BMD increased in the distal radius but tended to decrease in the distal tibia. The observed trabecular bone loss in the distal tibia contributed to the decline in the total volumetric BMD at this site. There was a negative correlation between the changes in leptin levels and the measures of trabecular quality in the tibia on high-resolutionperipheral quantitative computed tomography. Weight loss may negatively impact bone microstructure in young patients, especially for weight-bearing bones, in which obesity has a more prominent effect.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Characterising variability and regional correlations of microstructure and mechanical competence of human tibial trabecular bone: An in-vivo HR-pQCT study

OBJECTIVE

Quantifying spatial distribution of trabecular bone mechanical competence and microstructure is important for early diagnosis of skeletal disorders and potential risk of fracture. The objective of this study was to determine a spatial distribution of trabecular mechanical and morphological properties in human distal tibia and examine the contribution of regional variability of trabecular microarchitecture to mechanical competence.

METHODS

A total of 340 representative volume elements at five anatomic regions of trabecular bone - anterior, posterior, lateral, medial and centre - from ten white European-origin postmenopausal women were studied. Region-specific trabecular parameters such as trabecular volume fraction, trabecular thickness, trabecular number, trabecular surface area, trabecular separation, plate-like structure fraction and finite element analysis of trabecular stiffness were determined based on in-vivo high resolution peripheral quantitative computed tomographic (HR-pQCT) images of distal tibiae from ten postmenopausal women. Mean values were compared using analysis of variance. The correlations between morphological parameters and stiffness were calculated.

RESULTS

Significant regional variation in trabecular microarchitecture of the human distal tibia was observed (p < 0.05), with up to 106% differences between lowest (central and anterior) and highest (medial and posterior) regions. Higher proportion of plate-like trabecular morphology (63% and 53%) was found in medial and posterior regions in the distal tibia. Stiffness estimated from finite element models also differed significantly (p < 0.05), with stiffness being 4.5 times higher in the highest (medial) than lowest (central) regions. The bone volume fraction was the strongest correlate of stiffness in all regions.

CONCLUSION

A novel finding of this study is the fact that significant regional variation of stiffness derived from two-phased FEA model with individual trabecula representation correlated highly to regional morphology obtained from in-vivo HR-pQCT images at the distal tibia. The correlations between regional morphological parameters and mechanical competence of trabecular bone were consistent at all regions studied, with regional BV/TV showing the highest correlation. The method developed for regional analysis of trabecular mechanical competence may offer a better insight into the relationship between mechanical behaviour and microstructure of bone. The findings provide evidence needed to further justify a larger-cohort feasibility study for early detection of bone degenerative diseases: examining regional variations in mechanical competence and trabecular specifications may allow better understanding of fracture risks in addition to others contributing factors.

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.

The relationship between whole bone stiffness and strength is age and sex dependent

Accurately estimating whole bone strength is critical for identifying individuals that may benefit from prophylactic treatments aimed at reducing fracture risk. Strength is often estimated from stiffness, but it is not known whether the relationship between stiffness and strength varies with age and sex. Cadaveric proximal femurs (44 Male: 18-78 years; 40 Female: 24-95 years) and radial (36 Male: 18-89 years; 19 Female: 24-95 years) and femoral diaphyses (34 Male: 18-89 years; 19 Female: 24-95 years) were loaded to failure to evaluate how the stiffness-strength relationship varies with age and sex. Strength correlated significantly with stiffness at all sites and for both sexes, as expected. However, females exhibited significantly less strength for the proximal femur (58% difference, p < 0.001). Multivariate regressions revealed that stiffness, age and PYD were significant negative independent predictors of strength for the proximal femur (Age: M: p = 0.005, F: p < 0.001, PYD: M: p = 0.022, F: p = 0.025), radial diaphysis (Age: M = 0.055, PYD: F = 0.024), and femoral diaphysis (Age: M: p = 0.014, F: p = 0.097, PYD: M: p = 0.003, F: p = 0.091). These results indicated that older bones tended to be significantly weaker for a given stiffness than younger bones. These results suggested that human bones exhibit diminishing strength relative to stiffness with aging and with decreasing PYD. Incorporating these age- and sex-specific factors may help to improve the accuracy of strength estimates.