Alterations of cortical and trabecular architecture are associated with fractures in postmenopausal women, partially independent of decreased BMD measured by DXA: the OFELY study

Characterization of trabecular bone density with ultra-short echo-time MRI at 1.5, 3.0 and 7.0 T--comparison with micro-computed tomography

The goal of this study was to test the potential of ultra-short echo-time (UTE) MRI at 1.5, 3.0 and 7.0 T for depiction of trabecular bone structure (of the wrist bones), to evaluate whether T2* relaxation times of bone water and parametric maps of T2* of trabecular bone could be obtained at all three field strengths, and to compare the T2* relaxation times with structural parameters obtained from micro-computed tomography (micro-CT) as a reference standard. Ex vivo carpal bones of six wrists were excised en bloc and underwent MRI at 1.5, 3.0 and 7.0 T in a whole-body MR imager using the head coil. A three-dimensional radial fat-suppressed UTE sequence was applied with subsequent acquisitions, with six different echo times TE of 150, 300, 600, 1200, 3500 and 7000 µs. The T2* relaxation time and pixel-wise computed T2* parametric maps were compared with a micro-computed-tomography reference standard providing trabecular bone structural parameters including porosity (defined as the bone-free fraction within a region of interest), trabecular thickness, trabecular separation, trabecular number and fractal dimension (Dk). T2* relaxation curves and parametric maps could be computed from datasets acquired at all field strengths. Mean T2* relaxation times of trabecular bone were 4580 ± 1040 µs at 1.5 T, 2420 ± 560 µs at 3.0 T and 1220 ± 300 µs at 7.0 T, when averaged over all carpal bones. A positive correlation of T2* with trabecular bone porosity and trabecular separation, and a negative correlation of T2* relaxation time with trabecular thickness, trabecular number and fractal dimension, was detected (p < 0.01 for all field strengths and micro-CT parameters). We conclude that UTE MRI may be useful to characterize the structure of trabecular bone, comparable to micro-CT.

Diminished bone strength is observed in adult women and men who sustained a mild trauma distal forearm fracture during childhood

Children and adolescents who sustain a distal forearm fracture (DFF) owing to mild, but not moderate, trauma have reduced bone strength and cortical thinning at the distal radius and tibia. Whether these skeletal deficits track into adulthood is unknown. Therefore, we studied 75 women and 75 men (age range, 20 to 40 years) with a childhood (age < 18 years) DFF and 150 sex-matched controls with no history of fracture using high-resolution peripheral quantitative computed tomography (HRpQCT) to examine bone strength (ie, failure load) by micro-finite element (µFE) analysis, as well as cortical and trabecular bone parameters at the distal radius and tibia. Level of trauma (mild versus moderate) was assigned using a validated classification scheme, blind to imaging results. When compared to sex-matched, nonfracture controls, women and men with a mild trauma childhood DFF (eg, fall from standing height) had significant reductions in failure load (p < 0.05) of the distal radius, whereas women and men with a moderate trauma childhood DFF (eg, fall while riding a bicycle) had values similar to controls. Consistent findings were observed at the distal tibia. Furthermore, women and men with a mild trauma childhood DFF had significant deficits in distal radius cortical area (p < 0.05), and significantly lower dual-energy X-ray absorptiometry (DXA)-derived bone density at the radius, hip, and total body regions compared to controls (all p < 0.05). By contrast, women and men with a moderate trauma childhood DFF had bone density, structure, and strength that did not differ significantly from controls. These findings in young adults are consistent with our observations in children/adolescents with DFF, and they suggest that a mild trauma childhood DFF may presage suboptimal peak bone density, structure, and strength in young adulthood. Children and adolescents who suffer mild trauma DFFs may need to be targeted for lifestyle interventions to help achieve improved skeletal health.

Compromised bone microarchitecture and estimated bone strength in young adults with cystic fibrosis

CONTEXT

Young adults with cystic fibrosis (CF) are at risk for low bone density and fractures, but the underlying alterations in bone microarchitecture that may contribute to their increased fracture risk are currently unknown.

OBJECTIVE

The main goal of this study was to use high-resolution peripheral quantitative computed tomography (HR-pQCT) to characterize the bone microarchitecture, volumetric bone mineral density (vBMD), and estimated strength of the radius and tibia in young adults with CF compared with healthy volunteers.

DESIGN AND SETTING

This was a cross-sectional study at an outpatient clinical research center within a tertiary academic medical center.

PARTICIPANTS

Thirty young adults with CF, 18 to 40 years of age, were evaluated and compared with 60 healthy volunteers matched by age (±2 years), gender, and race.

MAIN OUTCOME MEASURES

The primary outcomes were HR-pQCT-derived cortical and trabecular vBMD, bone microarchitecture, and estimates of bone strength.

RESULTS

At the radius and tibia, young adults with CF had smaller bone cross-sectional area and lower vBMD. Cortical and trabecular microarchitecture were compromised at both sites, most notably involving the trabecular bone of the tibia. These differences translated into lower estimated bone strength both at the radius and tibia. After accounting for body mass index differences, young adults with CF had lower bone area and estimated bone strength at the radius and had compromised trabecular microarchitecture and lower total and trabecular vBMD and estimated bone strength at the tibia. Alterations in trabecular bone density and microarchitecture and estimated strength measures of the tibia were also greater than expected based on dual-energy x-ray absorptiometry-derived areal BMD differences.

CONCLUSIONS

Young adults with CF have compromised bone microarchitecture and lower estimated bone strength at both the radius and tibia, even after accounting for their smaller body size. These skeletal deficits likely explain the higher fracture risk observed in young adults with CF.

Alterations of bone density, microstructure, and strength of the distal radius in male patients with rheumatoid arthritis: a case-control study with HR-pQCT

In this cross-sectional study, we investigated volumetric bone mineral density (vBMD), bone microstructure, and biomechanical competence of the distal radius in male patients with rheumatoid arthritis (RA). The study cohort comprised 50 male RA patients of average age of 61.1 years and 50 age-matched healthy males. Areal BMD (aBMD) of the hip, lumbar spine, and distal radius was measured by dual-energy X-ray absorptiometry. High-resolution peripheral quantitative computed tomography (HR-pQCT) of the distal radius provided measures of cortical and trabecular vBMD, microstructure, and biomechanical indices. aBMD of the hip but not the lumbar spine or ultradistal radius was significantly lower in RA patients than controls after adjustment for body weight. Total, cortical, and trabecular vBMD at the distal radius were, on average, -3.9% to -23.2% significantly lower in RA patients, and these differences were not affected by adjustment for body weight, testosterone level, or aBMD at the ultradistal radius. Trabecular microstructure indices were, on average, -8.1% (trabecular number) to 28.7% (trabecular network inhomogeneity) significantly inferior, whereas cortical pore volume and cortical porosity index were, on average, 80.3% and 63.9%, respectively, significantly higher in RA patients. RA patients also had significantly lower whole-bone stiffness, modulus, and failure load, with lower and more unevenly distributed cortical and trabecular stress. Density and microstructure indices significantly correlated with disease activity, severity, and levels of pro-inflammatory cytokines (interleukin [IL] 12p70, tumor necrosis factor, IL-6 and IL-1β). Ten RA patients had focal periosteal bone apposition most prominent at the ulnovolar aspect of the distal radius. These patients had shorter disease duration and significantly higher cortical porosity. In conclusion, HR-pQCT reveals significant alterations of bone density, microstructure, and strength of the distal radius in male RA patients and provides new insight into the microstructural basis of bone fragility accompanying chronic inflammation.

Characterizing microarchitectural changes at the distal radius and tibia in postmenopausal women using HR-pQCT

Limited prospective evidence exists regarding bone microarchitectural deterioration. We report annual changes in trabecular and cortical bone microarchitecture at the distal radius and tibia in postmenopausal women. Lost trabeculae with corresponding increase in trabecular thickness at the radius and thinning tibial cortex indicated trabecularization of the cortex at both sites.

INTRODUCTION

Osteoporosis is characterized by low bone mass and the deterioration of bone microarchitecture. However, limited prospective evidence exists regarding bone microarchitectural changes in postmenopausal women: a population prone to sustaining osteoporotic fractures. Our primary objective was to characterize the annual change in bone area, density, and microarchitecture at the distal radius and distal tibia in postmenopausal women.

METHODS

Distal radius and tibia were measured using high-resolution peripheral quantitative computed tomography (HR-pQCT) at baseline and 1 year later in 51 women (mean age ± SD, 77 ± 7 years) randomly sampled from the Saskatoon cohort of the Canadian Multicentre Osteoporosis Study (CaMos). We used repeated measures analysis of variance (ANOVA) with Bonferroni adjustment for multiple comparisons to characterize the mean annual change in total density, cortical perimeter, trabecular and cortical bone area, density, content, and microarchitecture. Significant changes were accepted at P < 0.05.

RESULTS

At the distal radius in women without bone-altering drugs, total density (-1.7%) and trabecular number (-6.4%) decreased, while trabecular thickness (+6.0%), separation (+8.6%), and heterogeneity (+12.1%) increased. At their distal tibia, cortical area (-4.5%), density (-1.9%), content (-6.3%), and thickness (-4.4%) decreased, while trabecular area (+0.4%) increased.

CONCLUSIONS

The observed loss of trabeculae with concomitant increase in trabecular size at the distal radius and the declined cortical thickness, density, and content at the distal tibia indicated a site-specific trabecularization of the cortical bone in postmenopausal women.

Fracture risk and areal bone mineral density in adolescent females with anorexia nervosa

OBJECTIVE

To (i) compare fracture prevalence in adolescent females with anorexia nervosa (AN) versus normal-weight controls and (ii) examine whether reductions in areal bone mineral density (aBMD) predict fracture risk in females with AN.

METHOD

Four-hundred eighteen females (310 with active AN and 108 normal-weight controls) 12- to 22-years-old were studied cross-sectionally. Lifetime fracture history was recorded by a physician during participant interviews. Body composition and aBMD measurements of the whole body, whole body less head, lumbar spine, and hip were assessed by dual-energy X-ray absorptiometry, and bone mineral apparent density (BMAD) was calculated for the lumbar spine.

RESULTS

Participants with AN and normal-weight controls did not differ for chronological age, sexual maturity, or height. The lifetime prevalence of prior fracture was 59.8% higher in those with AN as compared to controls (31.0% vs. 19.4%, p = 0.02), and the fracture incidence rate peaked in our cohort after the diagnosis of AN. Lower aBMD and lumbar BMAD were not associated with a higher prevalence of fracture in the AN or control group on univariate or multivariate analyses. Compared to controls, fracture prevalence was significantly higher in the subgroup of girls with AN who had normal aBMD or only modest reductions of aBMD (Z-scores > -1 or -1.5).

DISCUSSION

This is the first study to show that the risk of fracture during childhood and adolescence is significantly higher in patients with AN than in normal-weight controls. Fracture prevalence is increased in this cohort of participants with AN even without significant reductions in aBMD.

Osteoporosis update: proceedings of the 2013 Santa Fe Bone Symposium

The 2013 Santa Fe Bone Symposium included plenary sessions on new developments in the fields of osteoporosis and metabolic bone disease, oral presentations of abstracts, and faculty panel discussions of common clinical conundrums: scenarios of perplexing circumstances where treatment decisions are not clearly defined by current medical evidence and clinical practice guidelines. Controversial issues in the care of osteoporosis were reviewed and discussed by faculty and participants. This is a review of the proceedings of the Santa Fe Bone Symposium, constituting in its entirety an update of advances in the understanding of selected bone disease topics of interest and the implications for managing patients in clinical practice. Topics included the associations of diabetes and obesity with skeletal fragility, the complexities and pitfalls in assessing the benefits and potential adverse effects of nutrients for treatment of osteoporosis, uses of dual-energy X-ray absorptiometry beyond measurement of bone mineral density, challenges in the care of osteoporosis in the very elderly, new findings on the role of osteocytes in regulating bone remodeling, and current concepts on the use of bone turnover markers in managing patients with chronic kidney disease who are at high risk for fracture.

Challenges in longitudinal measurements with HR-pQCT: evaluation of a 3D registration method to improve bone microarchitecture and strength measurement reproducibility

Definition of identical regions between repeated computed tomography (CT) scans is a key factor to monitor changes in bone microarchitecture. In longitudinal studies, accurate determination of the volume of interest (VOI), using three dimensional (3D) registration may improve precision. Therefore, the aim of our study was to investigate the short-term reproducibility of bone geometry, density, microstructure and biomechanical parameters assessed by HR-pQCT and micro-finite element (μFE) derived analyses, using the cross-sectional area (CSA) registration method in comparison with the use of 3D registration, to find overlapping regions between scans. Fifteen healthy individuals (aged 21-47 years) underwent 3 separate scans at the distal radius and tibia, within a one-month interval. Reproducibility was assessed after double contouring the cortical compartment and after applying three different methods to determine the common region between repeated scans: (i) the VOI was determined with no registration, i.e., on 110 slices, (ii) the VOI was determined after CSA-based registration, and (iii) the VOI was determined after 3D registration. Both pre- and post-registration short-term reproducibility for each subject was determined. With no registration, CVrms of geometry parameters ranged from 0.5 to 3.7%, showing a slight variation in the CSA between scans. When the CSA registration method was employed, the variability of geometry (CVrms<1.8%) and density parameters (CVrms<1.8%), was better than that obtained without registration. By removing the effect of repositioning, the 3D registration further improved the reproducibility of cortical bone measurements compared to other methods. Indeed, significant improvements were found for cortical geometry and microstructure measurements (CVrms ranged from 0.4% to 10.7% at both sites; p<0.05), whereas the impact on trabecular bone measurements was restricted to its geometry parameter. The repositioning error was significantly reduced, most markedly at the radius compared to the tibia. For μFE measures, the impact of 3D registration on whole bone stiffness was negligible, indicating adequate assessment of longitudinal changes in estimated biomechanical properties, even without registration. In conclusion, we have shown that the 3D registration improved the identification of the common region retained for longitudinal analysis, contributing to improve the reproducibility of cortical bone parameter measurements. We also quantified the minimally detectable bone changes to help designing future studies with HR-pQCT.

The influence of disuse on bone microstructure and mechanics assessed by HR-pQCT

Numerous clinical cohorts are exposed to reduced skeletal loading and associated bone loss, including surgical patients, stroke and spinal cord injury victims, and women on bed rest during pregnancy. In this context, understanding disuse-related bone loss is critical to developing interventions to prevent fractures and the associated morbidity, mortality, and cost to the health care system. The aim of this pilot study was to use high-resolution peripheral QCT (HR-pQCT) to examine changes in trabecular and cortical microstructure and biomechanics during a period of non weight bearing (WB) and during recovery following return to normal WB. Surgical patients requiring a 6-week non WB period (n=12, 34.8±7.7 yrs) were scanned at the affected and contralateral tibia prior to surgery, after the 6-week non WB period, and 6 and 13 weeks after returning to full WB. At the affected ultradistal tibia, integral vBMD (including both trabecular and cortical compartments) decreased with respect to baseline (-1.2%), trabecular number increased (+5.6%), while trabecular thickness (-5.4%), separation (-4.6%), and heterogeneity (-7.2%) decreased (all p<0.05). Six weeks after return to full WB, trabecular structure measures reverted to baseline levels. In contrast, integral vBMD continued to decrease after 6 (-2.0%, p<0.05) and 13 weeks (-2.5%, p=0.07) of full WB. At the affected distal site, the disuse period resulted in increased porosity (+16.1%, p<0.005), which remained elevated after 6 weeks (+16.8%, p<0.01) and after 13 weeks (+16.2%, p<0.05). A novel topological analysis applied to the distal tibia cortex demonstrated increased number of canals with surface topology ("slabs" +21.7%, p<0.01) and curve topology ("tubes" +15.0%, p<0.05) as well as increased number of canal junctions (+21.4%, p<0.05) following the disuse period. Porosity increased uniformly through increases in both pore size and number. Finite element analysis at the ultradistal tibia showed decreased stiffness and failure load (-2.8% and -2.4%, p<0.01) following non WB. These biomechanical predictions remained depressed following 6 and 13 weeks of full WB. Finite element analysis at the distal site followed similar trends. Our results suggest that detectable microstructural and biomechanical degradation occurs--particularly within the cortical compartment--as a result of non WB and persists following return to normal loading. A better understanding of these microstructural changes and their short- and long-term influence on biomechanics may have clinical relevance in the context of disuse-related fracture prevention.

Cortical measurements of the tibia from high resolution peripheral quantitative computed tomography images: a comparison with synchrotron radiation micro-computed tomography

High resolution-peripheral quantitative computed tomography (HR-pQCT) measurements are carried out in clinical research protocols to analyze cortical bone. Micro-computed tomography (micro-CT) is a standard tool for ex vivo examination of bone in 3D. The aim of this work was to evaluate cortical measurements derived from HR-pQCT images compared to those from synchrotron radiation (SR) micro-CT in a distal position (4.2 cm from the distal pilon). Twenty-nine tibia specimens were scanned with HR-pQCT using protocols provided by the manufacturer. The standard measured outcomes included volumetric bone density (gHA/cm(3)) of the cortical region (Dcomp), and the cortical thickness (Ct.Th, mm). New features, such as cortical porosity (Ct.Po) and mean pore diameter (Ct.Po.Dm), were measured by an auto-contouring process. All tibias were harvested from the posterior region and imaged with SR micro-CT (voxel size=7.5 μm). The cortical thickness, (Ct.Thmicro-CT), porosity (PoV/TV), pore diameter, pore spacing, pore number, and degree of mineralization of bone (DMB) were obtained for SR micro-CT images. For standard measurements on HR-pQCT images, site matched analyses with micro-CT were completed to obtain Dcomplocal and Ct.Thlocal. Dcomp was highly correlated to PoV/TV (r=-0.84, p<10(-4)) but not to DMB. Dcomplocal was correlated to PoV/TV (r=-0.72, p<10(-4)) and to DMB (r=0.40, p>0.05). Ct.Thlocal and Ct.Thmicro-CT were moderately correlated (r=0.53, p<0.01). Ct.Th and Ct.Po results from the autocontouring process are influenced by the level of trabecularization of the cortical bone and need manual correction of the endosteal contour. Distal tibia is a reliable region to study cortical bone with Dcomp as the best parameter because it reflects both the micro-porosity (Havers canals) and macro-porosity (resorption lacunae) of the cortical bone.

Bisphosphonates and bone quality

Bisphosphonates (BPs) are bone-avid compounds used as first-line medications for the prevention and treatment of osteoporosis. They are also used in other skeletal pathologies such as Paget's and metastatic bone disease. They effectively reduce osteoclast viability and also activity in the resorptive phase of bone remodelling and help preserve bone micro-architecture, both major determinants of bone strength and ultimately of the susceptibility to fractures. The chemically distinctive structure of each BP used in the clinic determines their unique affinity, distribution/penetration throughout the bone and their individual effects on bone geometry, micro-architecture and composition or what we call 'bone quality'. BPs have no clinically significant anabolic effects. This review will touch upon some of the components of bone quality that could be affected by the administration of BPs.

Accuracy of trabecular structure by HR-pQCT compared to gold standard μCT in the radius and tibia of patients with osteoporosis and long-term bisphosphonate therapy

Despite an increasing use of high-resolution peripheral quantitative computed tomography (HR-pQCT) to evaluate bone morphology in vivo, there are reservations about its applicability in patients with osteoporosis and antiresorptive therapy. This study shows that HR-pQCT provides acceptable in vivo accuracy for bone volume fraction (BV/TV) in patients with osteoporosis and bisphosphonate (BP) treatment.

INTRODUCTION

The primary aim was to analyze agreement of trabecular structure between HR-pQCT and gold standard microtomography (μCT) in patients with osteoporosis and long-term BP therapy.

METHODS

In the BioAsset study, we analyzed cadaver radii and tibiae of 34 postmenopausal females (81.1 ± 7.1 years) with osteoporosis (no BP n = 22, 1-5 years BP n = 5, >5 years BP n = 7). Two HR-pQCT protocols (patient-mode and μCT-mode) were compared with gold standard μCT after image registration. Undecalcified histological sections were obtained to quantify nonmineralized bone matrix. Bland-Altman plots illustrated methodological agreement. Multiple regression analysis was used to test for variables associated with method agreement.

RESULTS

In the radius and tibia, patient-mode HR-pQCT derived indices including bone volume fraction, trabecular number, and trabecular separation correlated well with gold standard μCT (R(2) = 0.78 - 0.88) except for trabecular thickness (R(2) = 0.11). Bland-Altman plots illustrated adequate agreement for bone volume fraction. Lower agreement of trabecular number and trabecular separation improved with decreasing structural impairment at the tibia only. Trabecular thickness was not appropriately assessed with HR-pQCT at both skeletal sites. Higher agreement for bone volume fraction was associated with increasing tissue mineral density in the tibia.

CONCLUSIONS

HR-pQCT provides acceptable in vivo accuracy for BV/TV in patients with osteoporosis and BP treatment. Higher TMD was associated with higher BV/TV accuracy in vivo. Overall, methodological agreement got less accurate with increasing structural impairment in the tibia.

Mandibular bone structure, bone mineral density, and clinical variables as fracture predictors: a 15-year follow-up of female patients in a dental clinic

OBJECTIVE

To compare three mandibular trabeculation evaluation methods, clinical variables, and osteoporosis as fracture predictors in women.

STUDY DESIGN

One hundred and thirty-six female dental patients (35-94 years) answered a questionnaire in 1996 and 2011. Using intra-oral radiographs from 1996, five methods were compared as fracture predictors: (1) mandibular bone structure evaluated with a visual radiographic index, (2) bone texture, (3) size and number of intertrabecular spaces calculated with Jaw-X software, (4) fracture probability calculated with a fracture risk assessment tool (FRAX), and (5) osteoporosis diagnosis based on dual-energy-X-ray absorptiometry. Differences were assessed with the Mann-Whitney test and relative risk calculated.

RESULTS

Previous fracture, gluco-corticoid medication, and bone texture were significant indicators of future and total (previous plus future) fracture. Osteoporosis diagnosis, sparse trabeculation, Jaw-X, and FRAX were significant predictors of total but not future fracture.

CONCLUSION

Clinical and oral bone variables may identify individuals at greatest risk of fracture.

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

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

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

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

Vertebral deformities and fractures are associated with MRI and pQCT measures obtained at the distal tibia and radius of postmenopausal women

SUMMARY

We investigated the association of postmenopausal vertebral deformities and fractures with bone parameters derived from distal extremities using MRI and pQCT. Distal extremity measures showed variable degrees of association with vertebral deformities and fractures, highlighting the systemic nature of postmenopausal bone loss.

INTRODUCTION

Prevalent vertebral deformities and fractures are known to predict incident further fractures. However, the association of distal extremity measures and vertebral deformities in postmenopausal women has not been fully established.

METHODS

This study involved 98 postmenopausal women (age range 60-88 years, mean 70 years) with DXA BMD T-scores at either the hip or spine in the range of -1.5 to -3.5. Wedge, biconcavity, and crush deformities were computed on the basis of spine MRI. Vertebral fractures were assessed using Eastell's criterion. Distal tibia and radius stiffness was computed using MRI-based finite element analysis. BMD at the distal extremities were obtained using pQCT.

RESULTS

Several distal extremity MRI and pQCT measures showed negative association with vertebral deformity on the basis of single parameter correlation (r up to 0.67) and two-parameter regression (r up to 0.76) models involving MRI stiffness and pQCT BMD. Subjects who had at least one prevalent vertebral fracture showed decreased MRI stiffness (up to 17.9 %) and pQCT density (up to 34.2 %) at the distal extremities compared to the non-fracture group. DXA lumbar spine BMD T-score was not associated with vertebral deformities.

CONCLUSIONS

The association between vertebral deformities and distal extremity measures supports the notion of postmenopausal osteoporosis as a systemic phenomenon.

Bone microarchitecture and estimated strength in 499 adult Danish women and men: a cross-sectional, population-based high-resolution peripheral quantitative computed tomographic study on peak bone structure

High-resolution peripheral quantitative computed tomography (HR-pQCT) allows in vivo assessment of cortical and trabecular bone mineral density (BMD), geometry, and microarchitecture at the distal radius and tibia in unprecedented detail. In this cross-sectional study, we provide normative and descriptive HR-pQCT data from a large population-based sample of Danish Caucasian women and men (n = 499) aged 20-80 years. In young adults (<35 years), women (n = 100) compared to men (n = 64) had smaller total and cortical areas, inferior metric trabecular indices, higher network inhomogeneity, lower cortical porosity, and lower finite element estimated bone strength. The changes in parameters with age were estimated from multiple regression analyses. In men, with age the greatest changes (from parameter minimum or maximum) until 80 years were found for cortical porosity (1.91 IQR), BV/TV (-1.09 IQR), and trabecular thickness (-0.87 IQR) in the radius and BV/TV (-1.55 IQR), cortical BMD (-1.25 IQR), and cortical porosity (1.25 IQR) in the tibia. In women changes were most pronounced for cortical porosity (4.76 IQR), trabecular inhomogeneity (3.84 IQR), and cortical BMD (-2.86 IQR) in the radius and cortical BMD (-5.06 IQR), cortical porosity (3.86 IQR), and cortical area (-1.64 IQR) in the tibia. These findings emphasize the age- and sex-related differences in bone morphology, with men having a structural advantage over women from early adult life translating into superior indices of bone strength. With age women are further disadvantaged compared to men by greater decrements in cortical and trabecular architecture in the radius and cortical architecture in the tibia.

Microstructural parameters of bone evaluated using HR-pQCT correlate with the DXA-derived cortical index and the trabecular bone score in a cohort of randomly selected premenopausal women

Background

Areal bone mineral density is predictive for fracture risk. Microstructural bone parameters evaluated at the appendicular skeleton by high-resolution peripheral quantitative computed tomography (HR-pQCT) display differences between healthy patients and fracture patients. With the simple geometry of the cortex at the distal tibial diaphysis, a cortical index of the tibia combining material and mechanical properties correlated highly with bone strength ex vivo. The trabecular bone score derived from the scan of the lumbar spine by dual-energy X-ray absorptiometry (DXA) correlated ex vivo with the micro architectural parameters. It is unknown if these microstructural correlations could be made in healthy premenopausal women.

Methods

Randomly selected women between 20–40 years of age were examined by DXA and HR-pQCT at the standard regions of interest and at customized sub regions to focus on cortical and trabecular parameters of strength separately. For cortical strength, at the distal tibia the volumetric cortical index was calculated directly from HR-pQCT and the areal cortical index was derived from the DXA scan using a Canny threshold-based tool. For trabecular strength, the trabecular bone score was calculated based on the DXA scan of the lumbar spine and was compared with the corresponding parameters derived from the HR-pQCT measurements at radius and tibia.

Results

Seventy-two healthy women were included (average age 33.8 years, average BMI 23.2 kg/m²). The areal cortical index correlated highly with the volumetric cortical index at the distal tibia (R  =  0.798). The trabecular bone score correlated moderately with the microstructural parameters of the trabecular bone.

Conclusion

This study in randomly selected premenopausal women demonstrated that microstructural parameters of the bone evaluated by HR-pQCT correlated with the DXA derived parameters of skeletal regions containing predominantly cortical or cancellous bone. Whether these indexes are suitable for better predictions of the fracture risk deserves further investigation.

Lean mass as a predictor of bone density and microarchitecture in adult obese individuals with metabolic syndrome

The effects of obesity and metabolic syndrome (MS) on bone health are controversial. Furthermore, the relationship between body composition and bone quality has not yet been determined in this context. The aim of this study was to investigate the correlations between body composition and bone mineral density (BMD) and bone microstructure in obese individuals with MS. This cross-sectional study assessed 50 obese individuals with MS with respect to their body composition and BMD, both assessed using dual X-ray absorptiometry, and bone microarchitecture, assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT) of the distal tibia and radius. Several HR-pQCT measurements exhibited statistically significant correlations with lean mass. Lean mass was positively correlated with parameters of better bone quality (r: 0.316-0.470) and negatively correlated with parameters of greater bone fragility (r: -0.460 to -0.310). Positive correlations were also observed between lean mass and BMD of the total femur and radius 33%. Fat mass was not significantly correlated with BMD or any HR-pQCT measurements. Our data suggest that lean mass might be a predictor of bone health in obese individuals with MS.

Lower peak bone mass and abnormal trabecular and cortical microarchitecture in young men infected with HIV early in life

INTRODUCTION

HIV infection and antiretroviral therapy (ART) early in life may interfere with acquisition of peak bone mass, thereby increasing fracture risk in adulthood.

METHODS

We conducted a cross-sectional study of dual-energy X-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HR-pQCT) in 30 HIV-infected African-American or Hispanic Tanner stage 5 men aged 20-25 on ART (15 perinatally infected and 15 infected during adolescence) and 15 HIV-uninfected controls.

RESULTS

HIV-infected men were similar in age and BMI, but were more likely to be African-American (P = 0.01) than uninfected men. DXA-derived areal bone mineral density (aBMD) Z-scores were 0.4-1.2 lower in HIV-infected men at the spine, hip, and radius (all P < 0.05). At the radius and tibia, total and trabecular volumetric BMD (vBMD), and cortical and trabecular thickness were between 6 and 19% lower in HIV-infected than uninfected men (P <0.05). HIV-infected men had dramatic deficiencies in plate-related parameters by individual trabeculae segmentation (ITS) analyses and 14-17% lower bone stiffness by finite element analysis. Differences in most HR-pQCT parameters remained significant after adjustment for race/ethnicity. No DXA or HR-pQCT parameters differed between men infected perinatally or during adolescence.

CONCLUSION

At an age by which young men have typically acquired peak bone mass, HIV-infected men on ART have lower BMD, markedly abnormal trabecular plate and cortical microarchitecture, and decreased whole bone stiffness, whether infected perinatally or during adolescence. Reduced bone strength in young adults infected with HIV early in life may place them at higher risk for fractures as they age.

Correlation of X-ray vector radiography to bone micro-architecture

Besides the overall mass density, strength of trabecular bone depends significantly on its microstructure. However, due to dose constraints in medical CT imaging, it is impossible to gain sufficient information about very fine bone structures in vivo on the micrometer scale. Here we show that a recently developed method of X-ray vector radiography (XVR), an imaging method which uses X-ray scattering information to form an image, allows predictions on the bone microstructure without the explicit need to spatially resolve even individual trabeculae in the bone. We investigated thick human femoral bone samples and compared state-of-the-art μCT data with XVR imaging. A model is presented which proves that XVR imaging yields information directly correlated with the trabecular microstructure. This opens up possibilities of using XVR as a tool to help early diagnosis of bone diseases, such as osteoporosis.

Cortical bone loss at the tibia in postmenopausal women with osteoporosis is associated with incident non-vertebral fractures: results of a randomized controlled ancillary study of HORIZON

BACKGROUND

In postmenopausal women, yearly intravenous zoledronate (ZOL) compared to placebo (PLB) significantly increased bone mineral density (BMD) at lumbar spine (LS), femoral neck (FN), and total hip (TH) and decreased fracture risk. The effects of ZOL on BMD at the tibial epiphysis (T-EPI) and diaphysis (T-DIA) are unknown.

METHODS

A randomized controlled ancillary study of the HORIZON trial was conducted at the Department of Osteoporosis of the University Hospital of Berne, Switzerland. Women with ≥1 follow-up DXA measurement who had received ≥1 dose of either ZOL (n=55) or PLB (n=55) were included. BMD was measured at LS, FN, TH, T-EPI, and T-DIA at baseline, 6, 12, 24, and 36 months. Morphometric vertebral fractures were assessed. Incident clinical fractures were recorded as adverse events.

RESULTS

Baseline characteristics were comparable with those in HORIZON and between groups. After 36 months, BMD was significantly higher in women treated with ZOL vs. PLB at LS, FN, TH, and T-EPI (+7.6%, +3.7%, +5.6%, and +5.5%, respectively, p<0.01 for all) but not T-DIA (+1.1%). The number of patients with ≥1 incident non-vertebral or morphometric fracture did not differ between groups (9 ZOL/11 PLB). Mean changes in BMD did not differ between groups with and without incident fracture, except that women with an incident non-vertebral fracture had significantly higher bone loss at predominantly cortical T-DIA (p=0.005).

CONCLUSION

ZOL was significantly superior to PLB at T-EPI but not at T-DIA. Women with an incident non-vertebral fracture experienced bone loss at T-DIA.

Are patterns of bone loss in anorexic and postmenopausal women similar? Preliminary results using high resolution peripheral computed tomography

This study intended to compare bone density and architecture in three groups of women: young women with anorexia nervosa (AN), an age-matched control group of young women, and healthy late postmenopausal women. Three-dimensional peripheral quantitative high resolution computed-tomography (HR-pQCT) at the ultradistal radius, a technology providing measures of cortical and trabecular bone density and microarchitecture, was performed in the three cohorts. Thirty-six women with AN aged 18-30 years (mean duration of AN: 5.8 years), 83 healthy late postmenopausal women aged 70-81 as well as 30 age-matched healthy young women were assessed. The overall cortical and trabecular bone density (D100), the absolute thickness of the cortical bone (CTh), and the absolute number of trabecules per area (TbN) were significantly lower in AN patients compared with healthy young women. The absolute number of trabecules per area (TbN) in AN and postmenopausal women was similar, but significantly lower than in healthy young women. The comparison between AN patients and post-menopausal women is of interest because the latter reach bone peak mass around the middle of the fertile age span whereas the former usually lose bone before reaching optimal bone density and structure. This study shows that bone mineral density and bone compacta thickness in AN are lower than those in controls but still higher than those in postmenopause. Bone compacta density in AN is similar as in controls. However, bone inner structure in AN is degraded to a similar extent as in postmenopause. This last finding is particularly troubling.

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

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

Bone disease in anorexia nervosa

Anorexia nervosa is a serious psychiatric disorder accompanied by high morbidity and mortality. It is characterized by emaciation due to self-starvation and displays a unique hormonal profile. Alterations in gonadal axis, growth hormone resistance with low insulin-like growth factor I levels, hypercortisolemia and low triiodothyronine levels are almost universally present and constitute an adaptive response to malnutrition. Bone metabolism is likewise affected resulting in low bone mineral density, reduced bone accrual and increased fracture risk. Skeletal deficits often persist even after recovery from the disease with serious implications for future skeletal health. The pathogenetic mechanisms underlying bone disease are quite complicated and treatment is a particularly challenging task.

Skeletal structure in postmenopausal women with osteopenia and fractures is characterized by abnormal trabecular plates and cortical thinning

The majority of fragility fractures occur in women with osteopenia rather than osteoporosis as determined by dual‐energy X‐ray absorptiometry (DXA). However, it is difficult to identify which women with osteopenia are at greatest risk. We performed this study to determine whether osteopenic women with and without fractures had differences in trabecular morphology and biomechanical properties of bone. We hypothesized that women with fractures would have fewer trabecular plates, less trabecular connectivity, and lower stiffness. We enrolled 117 postmenopausal women with osteopenia by DXA (mean age 66 years; 58 with fragility fractures and 59 nonfractured controls). All had areal bone mineral density (aBMD) measured by DXA. Trabecular and cortical volumetric bone mineral density (vBMD), trabecular microarchitecture, and cortical porosity were measured by high‐resolution peripheral computed tomography (HR‐pQCT) of the distal radius and tibia. HR‐pQCT scans were subjected to finite element analysis to estimate whole bone stiffness and individual trabecula segmentation (ITS) to evaluate trabecular type (as plate or rod), orientation, and connectivity.Groups had similar age, race, body mass index (BMI), and mean T‐scores. Fracture subjects had lower cortical and trabecular vBMD, thinner cortices, and thinner, more widely separated trabeculae. By ITS, fracture subjects had fewer trabecular plates, less axially aligned trabeculae, and less trabecular connectivity. Whole bone stiffness was lower in women with fractures. Cortical porosity did not differ. Differences in cortical bone were found at both sites, whereas trabecular differences were more pronounced at the radius.In summary, postmenopausal women with osteopenia and fractures had lower cortical and trabecular vBMD; thinner, more widely separated and rodlike trabecular structure; less trabecular connectivity; and lower whole bone stiffness compared with controls,despite similar aBMD by DXA. Our results suggest that in addition to trabecular and cortical bone loss, changes in plate and rod structure may be important mechanisms of fracture in postmenopausal women with osteopenia.

Quantification of lower leg arterial calcifications by high-resolution peripheral quantitative computed tomography

Vascular calcifications and bone health seem to be etiologically linked via common risk factors such as aging and subclinical chronic inflammation. Epidemiologic studies have shown significant associations between low bone mineral density (BMD), fragility fractures and calcifications of the coronary arteries and the abdominal aorta. In the last decade, high-resolution peripheral quantitative computed tomography (HR-pQCT) has emerged as in-vivo research tool for the assessment of peripheral bone geometry, density, and microarchitecture. Although vascular calcifications are frequently observed as incidental findings in HR-pQCT scans, they have not yet been incorporated into quantitative HR-pQCT analyses. We developed a semi-automated algorithm to quantify lower leg arterial calcifications (LLACs), captured by HR-pQCT. The objective of our study was to determine validity and reliability of the LLAC measure. HR-pQCT scans were downscaled to a voxel size of 250μm. After subtraction of bone volumes from the scans, LLACs were detected and contoured by a semi-automated, dual-threshold seed-point segmentation. LLAC mass (in mg hydroxyapatite; HA) was calculated as the product of voxel-based calcification volume (mm(3)) and mean calcification density (mgHA/cm(3))/1000. To determine validity, we compared LLACs to coronary artery calcifications (CACs), as quantified by multi-detector computed tomography (MDCT) and Agatston scoring in forty-six patients on chronic hemodialysis. Moreover, we investigated associations of LLACs with age, time on dialysis, type-2 diabetes mellitus, history of stroke, and myocardial infarction. In a second step, we determined intra- and inter-reader reliability of the LLAC measure. In the validity study, LLACs were present (>0mgHA) in 76% of patients, 78% of patients had CACs (>0mgHA). Median LLAC was 6.65 (0.08-24.40)mgHA and median CAC as expressed by Agatston score was 266.3 (15.88-1877.28). We found a significant positive correlation between LLAC and CAC (rho=0.6; p<0.01). Dialysis patients with type-2 diabetes mellitus (DM; 35%) and history of stroke (13%) had higher median LLAC than patients without those conditions (DM 20.0 fold greater, p=0.006; Stroke 5.1 fold greater, p=0.047). LLAC was positively correlated with time on dialysis (rho=0.337, p=0.029), there was a trend towards a positive association of LLAC and age (rho=0.289, p=0.053). The reliability study yielded excellent intra- and inter-reader agreement of the LLAC measure (intra-reader ICC=0.999, 95% CI=0.998-1.000; inter-reader ICC=0.998, 95% CI=0.994-0.999). Our study indicates that the LLAC measure has good validity and excellent reliability. The use of HR-pQCT for the simultaneous evaluation of arterial calcifications, peripheral bone geometry, bone density, and bone microarchitecture should facilitate future research on osteo-vascular interactions and potential associations with cardiovascular events.

Improved fracture risk assessment based on nonlinear micro-finite element simulations from HRpQCT images at the distal radius

More accurate techniques to estimate fracture risk could help reduce the burden of fractures in postmenopausal women. Although micro-finite element (µFE) simulations allow a direct assessment of bone mechanical performance, in this first clinical study we investigated whether the additional information obtained using geometrically and materially nonlinear µFE simulations allows a better discrimination between fracture cases and controls. We used patient data and high-resolution peripheral quantitative computed tomography (HRpQCT) measurements from our previous clinical study on fracture risk, which compared 100 postmenopausal women with a distal forearm fracture to 105 controls. Analyzing these data with the nonlinear µFE simulations, the odds ratio (OR) for the factor-of-risk (yield load divided by the expected fall load) was marginally higher (1.99; 95% confidence interval [CI], 1.41-2.77) than for the factor-of-risk computed from linear µFE (1.89; 95% CI, 1.37-2.69). The yield load and the energy absorbed up to the yield point as computed from nonlinear µFE were highly correlated with the initial stiffness (R(2)  = 0.97 and 0.94, respectively) and could therefore be derived from linear simulations with little loss in precision. However, yield deformation was not related to any other measurement performed and was itself a good predictor of fracture risk (OR, 1.89; 95% CI, 1.39-2.63). Moreover, a combined risk score integrating information on relative bone strength (yield load-based factor-of-risk), bone ductility (yield deformation), and the structural integrity of the bone under critical loads (cortical plastic volume) improved the separation of cases and controls by one-third (OR, 2.66; 95% CI, 1.84-4.02). We therefore conclude that nonlinear µFE simulations provide important additional information on the risk of distal forearm fractures not accessible from linear µFE nor from other techniques assessing bone microstructure, density, or mass.

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

CONTEXT

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

OBJECTIVE

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

DESIGN AND SETTING

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

PARTICIPANTS

We studied 138 women.

RESULTS

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

CONCLUSIONS

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

[Indication for primary fracture prosthesis of the shoulder]

Although fractures of the proximal humerus are one of the most common osteoporotic fracture types, no generally accepted treatment algorithm exists in the current literature. For young patients with high functional demands and good rehabilitation potential, we recommend humeral head salvage therapy. If symptomatic humeral head necrosis occurs, the implantation of an anatomic endoprothesis is possible on a secondary basis. For patients with a biological age > 70 years suffering from a persisting defect of the rotator cuff along with a humeral head fracture or from a multiple fragment fracture of the humeral head, we increasingly prefer implantation of a reverse shoulder prosthesis due to good clinical results. However, because of technical aspects and a high complication rate, treatment using the reverse fracture prosthesis should be reserved for surgeons with expertise in this particular field. After analyzing the fracture- and patient-specific risk factors and performance expectations, the trauma surgeon can select the best individual therapy with the patient.

Postmenopausal women treated with combination parathyroid hormone (1-84) and ibandronate demonstrate different microstructural changes at the radius vs. tibia: the PTH and Ibandronate Combination Study (PICS)

SUMMARY

In postmenopausal women receiving combination parathyroid hormone (PTH) (1-84) therapy and ibandronate, we evaluated bone microarchitecture and biomechanics using high-resolution peripheral quantitative computed tomography (HR-pQCT). Cortical and trabecular changes were different at the nonweight-bearing radius vs. the weight-bearing tibia, with more favorable overall changes at the tibia.

INTRODUCTION

PTH therapy and bisphosphonates decrease fracture risk in postmenopausal osteoporosis, but their effects on bone microstructure and strength have not been fully characterized, particularly during combination therapy. PTH increases trabecular bone mineral density (BMD) substantially but may decrease cortical BMD, possibly by stimulating intracortical remodeling. We evaluated bone microarchitecture and biomechanics with HR-pQCT at the radius (a nonweight-bearing site) and tibia (weight bearing) in women receiving combination PTH(1-84) and ibandronate.

METHODS

Postmenopausal women with low bone mass (n = 43) were treated with 6 months of PTH(1-84) (100 μg/day), either as one 6- or two 3-month courses, in combination with ibandronate (150 mg/month) over 2 years. HR-pQCT was performed before and after therapy.

RESULTS

Because changes in HR-pQCT parameters did not differ between treatment arms, groups were pooled into one cohort for analysis. Trabecular BMD increased at both radius and tibia (p < 0.01 for each). Cortical thickness and BMD decreased at the radius (p < 0.01), consistent with changes in dual-energy X-ray absorptiometry, while these parameters did not change at the tibia (p ≤ 0.02 for difference between radius and tibia). In contrast, cortical porosity increased at the tibia (p < 0.01) but not radius. Stiffness and failure load decreased at the radius (p < 0.0001) but did not change at the tibia.

CONCLUSIONS

Cortical and trabecular changes in response to the PTH/ibandronate treatment combinations utilized in this study were different at the nonweight-bearing radius vs. the weight-bearing tibia, with more favorable overall changes at the tibia. Our findings support the possibility that weight bearing may optimize the effects of osteoporosis therapy.

Radiographical texture analysis improves the prediction of vertebral fracture: an ex vivo biomechanical study

STUDY DESIGN

Compression biomechanical tests using fresh cadaveric thoracolumbar motion segments.

OBJECTIVE

The purpose of this study was to determine if the combination of bone texture parameters using bone microarchitecture, and bone mineral density (BMD) measurement by dual-energy x-ray absorptiometry provided a better prediction of vertebral fracture than BMD evaluation alone.

SUMMARY OF BACKGROUND DATA

Bone strength is routinely evaluated using BMD, as measured by dual-energy x-ray absorptiometry. Currently, there is an ongoing debate about the strengths and limitations of bone densitometry in clinical practice. To assess the fracture risk properly, other factors are important to be taken into account such as the macro- and microarchitecture of the bone. Recently, a new high-resolution x-ray device with direct digitization, named bone microarchitecture (BMA, D3A Medical Systems), has been developed to provide a better precision of texture parameters than those previously obtained on digitized films.

METHODS

Twenty-seven 3-level thoracolumbar motion segments (T11, T12, L1, and L2, L3, L4) of excised spines, obtained at the Anatomy Department of Marseille, were studied using bone microarchitecture to estimate 3 textural parameters: fractal parameter Hmean, co-occurrence matrix, and run-length matrix, dual-energy x-ray absorptiometry to measure BMD, and mechanical compression tests to failure. All specimens were examined by computed tomography before and after compression. The prediction of the vertebral failure load was evaluated using multiple regression analyses.

RESULTS

Twenty-seven vertebral fractures were observed with a mean failure load of 2636.3 N (standard deviation, 996 N). Fractal parameter Hmean, co-occurrence matrix, and run-length matrix were each significantly correlated with BMD (P< 0.01) and bone strength (P< 0.01). Combining bone texture parameters and BMD significantly improved the fracture load prediction from adjusted r = 0.701 to adjusted r = 0.806 (P< 0.01).

CONCLUSION

In these excised vertebrae, the combination of bone texture parameters with BMD demonstrated a better performance in the failure load prediction than that of BMD alone.

LEVEL OF EVIDENCE

N/A.

The role of bone intrinsic properties measured by infrared spectroscopy in whole lumbar vertebra mechanics: organic rather than inorganic bone matrix?

Whole bone strength is determined by bone mass, microarchitecture and intrinsic properties of the bone matrix. However, few studies have directly investigated the contribution of bone tissue material properties to whole bone strength in humans. This study assessed the role of bone matrix composition on whole lumbar vertebra mechanics. We obtained 17 fresh frozen human lumbar spines (8 W, 9 M, aged 76±11years). L3 bone mass was measured by DXA and microarchitecture by μ-CT with a 35 μm-isotropic resolution. Microarchitectural parameters were directly measured: Tb.BV/TV, SMI, Tb.Th, DA, Ct.Th, Ct.Po and radius of anterior cortical curvature. Failure load (N), stiffness (N/mm) and work to failure (N.mm) were extracted from quasi-static uniaxial compressive testing performed on L3 vertebral bodies. FTIRM analysis was performed on 2 μm-thick sections from L2 trabecular cores, with a Perkin-Elmer GXII Auto-image Microscope equipped with a wide band detector. Twenty measurements per sample were performed at 30∗100 μm of spatial resolution. Each spectrum was collected at 4 cm(-1) resolution and 50 scans in transmission mode. Mineral and collagen maturity, and mineralization and crystallinity index were measured. There was no association between the bone matrix characteristics and bone mass or microarchitecture. Mineral maturity, mineralization and crystallinity index were not related to whole vertebra mechanics. However, collagen maturity was positively correlated with whole vertebra failure load and stiffness (r=0.64, p=0.005 and r=0.54, p=0.025, respectively). The collagen maturity (3rd step) in combination with bone mass (i.e., BMC, 1st step) and microarchitecture (i.e., Tb.Th, 2nd step) improved the prediction of whole vertebra mechanical properties in forward stepwise multiple regression models, together explaining 71% of the variability in whole vertebra stiffness (p=0.001). In conclusion, we demonstrated a substantial contribution of collagen maturity, but not mineralization parameters, to whole bone strength of human lumbar vertebrae that was independent of bone mass and microarchitecture.

Advanced CT based in vivo methods for the assessment of bone density, structure, and strength

Based on spiral 3D tomography a large variety of applications have been developed during the last decade to asses bone mineral density, bone macro and micro structure, and bone strength. Quantitative computed tomography (QCT) using clinical whole body scanners provides separate assessment of trabecular, cortical, and subcortical bone mineral density (BMD) and content (BMC) principally in the spine and hip, although the distal forearm can also be assessed. Further bone macrostructure, for example bone geometry or cortical thickness can be quantified. Special high resolution peripheral CT (hr-pQCT) devices have been introduced to measure bone microstructure for example the trabecular architecture or cortical porosity at the distal forearm or tibia. 3D CT is also the basis for finite element analysis (FEA) to determine bone strength. QCT, hr-pQCT, and FEM are increasingly used in research as well as in clinical trials to complement areal BMD measurements obtained by the standard densitometric technique of dual x-ray absorptiometry (DXA). This review explains technical developments and demonstrates how QCT based techniques advanced our understanding of bone biology.

The predictive value of trabecular bone score (TBS) on whole lumbar vertebrae mechanics: an ex vivo study

We investigated the association of trabecular bone score (TBS) with microarchitecture and mechanical behavior of human lumbar vertebrae. We found that TBS reflects vertebral trabecular microarchitecture and is an independent predictor of vertebral mechanics. However, the addition of TBS to areal BMD (aBMD) did not significantly improve prediction of vertebral strength.

INTRODUCTION

The trabecular bone score (TBS) is a gray-level measure of texture using a modified experimental variogram which can be extracted from dual-energy X-ray absorptiometry (DXA) images. The current study aimed to confirm whether TBS is associated with trabecular microarchitecture and mechanics of human lumbar vertebrae, and if its combination with BMD improves prediction of fracture risk.

METHODS

Lumbar vertebrae (L3) were harvested fresh from 16 donors. The anteroposterior and lateral bone mineral content (BMC) and areal BMD (aBMD) of the vertebral body were measured using DXA; then, the TBS was extracted using TBS iNsight software (Medimaps SA, France). The trabecular bone volume (Tb.BV/tissue volume, TV), trabecular thickness (Tb.Th), degree of anisotropy, and structure model index (SMI) were measured using microcomputed tomography. Quasi-static uniaxial compressive testing was performed on L3 vertebral bodies to assess failure load and stiffness.

RESULTS

The TBS was significantly correlated to Tb.BV/TV and SMI (r = 0.58 and -0.62; p = 0.02, 0.01), but not related to BMC and BMD. TBS was significantly correlated with stiffness (r = 0.64; p = 0.007), independently of bone mass. Using stepwise multiple regression models, we failed to demonstrate that the combination of BMD and TBS was better at explaining mechanical behavior than either variable alone. However, the combination TBS, Tb.Th, and BMC did perform better than each parameter alone, explaining 79% of the variability in stiffness.

CONCLUSIONS

In our study, TBS was associated with microarchitecture parameters and with vertebral mechanical behavior, but TBS did not improve prediction of vertebral biomechanical properties in addition to aBMD.

Fracture history of healthy premenopausal women is associated with a reduction of cortical microstructural components at the distal radius

OBJECTIVES

The objective of this study is to determine in healthy premenopausal women with a history of fracture which bone structural components of the distal radius are the most closely associated with a risk of fracture.

METHODS AND PARTICIPANTS

The method was as follows: measurement of radial areal bone mineral density (aBMD) by DXA, microstructural components by high-resolution quantitative peripheral computerized tomography (HR-pQCT) and strength variables by micro Finite Element Analysis (μFEA) in 196 healthy premenopausal women aged 45.9 ± 3.7 (± SD) years with (FX, n = 96) and without (NO-FX, n = 100) a history of fracture. We evaluated differences in T-scores between FX and NO-FX and risk of fracture by Odds ratios (OR with 95% confidence intervals, CI) per one SD decrease, using logistic regression analysis after adjustment for age, height, weight, menarcheal age, calcium and protein intakes, and physical activity.

RESULTS

In the whole group the mean radial metaphysis aBMD T-score was not significantly different from zero. In the FX as compared to the NO-FX group, the differences in T-scores were as follows: for radial metaphysis: aBMD, -0.24 (P = 0.005); for distal radius microstructure components: cortical volumetric BMD, -0.38 (P = 0.0009); cortical thickness, -0.37 (P = 0.0001); cross-sectional area (CSA), +0.24 (P=0.034); and endosteal perimeter, +0.28 (P = 0.032); and for strength estimates: stiffness, -0.15 (P = 0.030); failure load, -0.14 (P = 0.044); and apparent modulus, -0.28 (P = 0.006). T-scores of trabecular volumetric BMD and thickness did not significantly differ between the FX and the NO-FX group. Accordingly, the risk of fracture (OR, 95% CI) for 1 SD decrease in radius bone parameters was as follows: radial metaphysis aBMD: 1.70 (1.18-2.44), P = 0.004; cortical volumetric BMD: 1.86 (1.28-2.71), P = 0.001; and cortical thickness: 2.36 (1.53-3.63), P = 0.0001. The corresponding fracture risk for the strength estimates was as follows: stiffness: 1.66 (1.06-2.61), P = 0.028; failure load: 1.59 (1.02-2.47), P = 0.041; and apparent modulus: 1.76 (1.17-2.64), P = 0.006.

CONCLUSIONS

In healthy premenopausal women, a history of fracture is associated with reduced T-scores in the distal radius, with the cortical components showing the greatest deficit. A reduction of one SD in cortical thickness is associated with a nearly three-fold increased risk of fracture. This finding strengthens the notion that, in healthy women, a certain degree of bone structural fragility contributes to fractures before the menopause and therefore should be taken into consideration in the individual prevention strategy of postmenopausal osteoporosis.

Rapid cortical bone loss in patients with chronic kidney disease

Chronic kidney disease (CKD) patients may have high rates of bone loss and fractures, but microarchitectural and biochemical mechanisms of bone loss in CKD patients have not been fully described. In this longitudinal study of 53 patients with CKD Stages 2 to 5D, we used dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HRpQCT), and biochemical markers of bone metabolism to elucidate effects of CKD on the skeleton. Median follow-up was 1.5 years (range 0.9 to 4.3 years); bone changes were annualized and compared with baseline. By DXA, there were significant declines in areal bone mineral density (BMD) of the total hip and ultradistal radius: -1.3% (95% confidence interval [CI] -2.1 to -0.6) and -2.4% (95% CI -4.0 to -0.9), respectively. By HRpQCT at the distal radius, there were significant declines in cortical area, density, and thickness and increases in porosity: -2.9% (95% CI -3.7 to -2.2), -1.3% (95% CI -1.6 to -0.6), -2.8% (95% CI -3.6 to -1.9), and +4.2% (95% CI 2.0 to 6.4), respectively. Radius trabecular area increased significantly: +0.4% (95% CI 0.2 to 0.6), without significant changes in trabecular density or microarchitecture. Elevated time-averaged levels of parathyroid hormone (PTH) and bone turnover markers predicted cortical deterioration. Higher levels of serum 25-hydroxyvitamin D predicted decreases in trabecular network heterogeneity. These data suggest that significant cortical loss occurs with CKD, which is mediated by hyperparathyroidism and elevated turnover. Future investigations are required to determine whether these cortical losses can be attenuated by treatments that reduce PTH levels and remodeling rates.

Quantitative in vivo HR-pQCT imaging of 3D wrist and metacarpophalangeal joint space width in rheumatoid arthritis

In this technique development study, high-resolution peripheral quantitative computed tomography (HR-pQCT) was applied to non-invasively image and quantify 3D joint space morphology of the wrist and metacarpophalangeal (MCP) joints of patients with rheumatoid arthritis (RA). HR-pQCT imaging (82 μm voxel-size) of the dominant hand was performed in patients with diagnosed rheumatoid arthritis (RA, N = 16, age: 52.6 ± 12.8) and healthy controls (CTRL, N = 7, age: 50.1 ± 15.0). An automated computer algorithm was developed to segment wrist and MCP joint spaces. The 3D distance transformation method was applied to spatially map joint space width, and summarized by the mean joint space width (JSW), minimal and maximal JSW (JSW.MIN, JSW.MAX), asymmetry (JSW.AS), and distribution (JSW.SD)-a measure of joint space heterogeneity. In vivo precision was determined for each measure by calculating the smallest detectable difference (SDD) and root mean square coefficient of variation (RMSCV%) of repeat scans. Qualitatively, HR-pQCT images and pseudo-color JSW maps showed global joint space narrowing, as well as regional and focal abnormalities in RA patients. In patients with radiographic JSN at an MCP, JSW.SD was two-fold greater vs. CTRL (p < 0.01), and JSW.MIN was more than two-fold lower (p < 0.001). Similarly, JSW.SD was significantly greater in the wrist of RA patients vs. CTRL (p < 0.05). In vivo precision was highest for JSW (SDD: 100 μm, RMSCV: 2.1%) while the SDD for JSW.MIN and JSW.SD were 370 and 110 μm, respectively. This study suggests that in vivo quantification of 3D joint space morphology from HR-pQCT, could improve early detection of joint damage in rheumatological diseases.

Fast trabecular bone strength predictions of HR-pQCT and individual trabeculae segmentation-based plate and rod finite element model discriminate postmenopausal vertebral fractures

Although high-resolution peripheral quantitative computed tomography (HR-pQCT) has advanced clinical assessment of trabecular bone microstructure, nonlinear microstructural finite element (µFE) prediction of yield strength using a HR-pQCT voxel model is impractical for clinical use due to its prohibitively high computational costs. The goal of this study was to develop an efficient HR-pQCT-based plate and rod (PR) modeling technique to fill the unmet clinical need for fast bone strength estimation. By using an individual trabecula segmentation (ITS) technique to segment the trabecular structure into individual plates and rods, a patient-specific PR model was implemented by modeling each trabecular plate with multiple shell elements and each rod with a beam element. To validate this modeling technique, predictions by HR-pQCT PR model were compared with those of the registered high-resolution micro-computed tomography (HR-µCT) voxel model of 19 trabecular subvolumes from human cadaveric tibia samples. Both the Young's modulus and yield strength of HR-pQCT PR models strongly correlated with those of µCT voxel models (r²  = 0.91 and 0.86). Notably, the HR-pQCT PR models achieved major reductions in element number (>40-fold) and computer central processing unit (CPU) time (>1200-fold). Then, we applied PR model µFE analysis to HR-pQCT images of 60 postmenopausal women with (n = 30) and without (n = 30) a history of vertebral fracture. HR-pQCT PR model revealed significantly lower Young's modulus and yield strength at the radius and tibia in fracture subjects compared to controls. Moreover, these mechanical measurements remained significantly lower in fracture subjects at both sites after adjustment for areal bone mineral density (aBMD) T-score at the ultradistal radius or total hip. In conclusion, we validated a novel HR-pQCT PR model of human trabecular bone against µCT voxel models and demonstrated its ability to discriminate vertebral fracture status in postmenopausal women. This accurate nonlinear µFE prediction of the HR-pQCT PR model, which requires only seconds of desktop computer time, has tremendous promise for clinical assessment of bone strength.

Alterations of bone geometry, density, microarchitecture, and biomechanical properties in systemic lupus erythematosus on long-term glucocorticoid: a case-control study using HR-pQCT

Compared to controls, HR-pQCT at distal radius of SLE patients on chronic glucocorticoid (SLE/GC) revealed reduced bone area, vBMD, deteriorated microarchitecture, and unevenly distributed stresses limited to cortical bone. Despite similar trabecular quality, whole bone strength decreased in patients. These alterations may partly explain high fracture rates in SLE/GC.

INTRODUCTION

To assess bone geometric, densitometric, microarchitectural, and biomechanical properties in patients with systemic lupus erythematosus (SLE) on long-term glucocorticoid (GC) (SLE/GC) as compared with healthy controls.

METHODS

A total of 180 female SLE patients and 180 healthy controls were in this cross-sectional study to assess areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry. High-resolution peripheral quantitative computed tomography (HR-pQCT) and microfinite element analysis (μFEA) was performed at distal radius.

RESULTS

In addition to significantly lower aBMD at femoral neck, total hip and lumbar spine, cortical area, average volumetric BMD (vBMD) and cortical vBMD also significantly reduced by 5.3, 5.7, to 1.9 % in SLE patients, respectively. Deteriorations of cortical microarchitecture were pronounced in patients, with 6.3 % reduction in cortical thickness and 13.6 % higher in cortical porosity. Local stresses were more unevenly distributed through cortical bone in patients. SLE/GC patients had decreased whole bone stiffness, estimated failure load, and apparent modulus. Parameters related to trabecular bone density and microarchitecture were comparable between patients and controls.

CONCLUSION

In SLE/GC patients, despite a reduction in bone area, vBMD and deteriorated microarchitecture and unevenly distributed stresses limited to the cortical compartment, whole bone strength decreased. HR-pQCT and μFEA were promising in elucidating the potential underlying pathophysiology of bone loss and propensity to fracture in SLE/GC and provide us additional information about alterations of bone quality which might better predict fracture risk beyond aBMD in SLE/GC.

Clinical imaging of bone microarchitecture with HR-pQCT

Osteoporosis, a disease characterized by loss of bone mass and structural deterioration, is currently diagnosed by dual-energy x-ray absorptiometry (DXA). However, DXA does not provide information about bone microstructure, which is a key determinant of bone strength. Recent advances in imaging permit the assessment of bone microstructure in vivo using high-resolution peripheral quantitative computed tomography (HR-pQCT). From these data, novel image processing techniques can be applied to characterize bone quality and strength. To date, most HR-pQCT studies are cross-sectional comparing subjects with and without fracture. These studies have shown that HR-pQCT is capable of discriminating fracture status independent of DXA. Recent longitudinal studies present new challenges in terms of analyzing the same region of interest and multisite calibrations. Careful application of analysis techniques and educated clinical interpretation of HR-pQCT results have improved our understanding of various bone-related diseases and will no doubt continue to do so in the future.

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

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

Impaired trabecular and cortical microarchitecture in daughters of women with osteoporotic fracture: the MODAM study

We investigated the familial resemblance of bone microarchitecture parameters between postmenopausal mothers with fragility fracture and their premenopausal daughters using high-resolution peripheral quantitative computed tomography (HR-pQCT). We found that daughters of women with fracture have lower total volumetric bone mineral density (vBMD), thinner cortices, and impaired trabecular microarchitecture at the distal radius and tibia, compared to controls.

INTRODUCTION

Familial resemblance of areal bone mineral density (aBMD) in mothers and daughters has been widely studied, but not its morphological basis, including microarchitecture.

METHODS

We compared aBMD, vBMD, bone size, and bone microarchitecture at the distal radius and tibia assessed by HR-pQCT in mothers and their premenopausal daughters. We included 115 women aged 43 ± 8 years whose mothers had sustained a fragility fracture and 206 women aged 39 ± 9 years whose mothers had never sustained a fragility fracture.

RESULTS

Women whose mothers had fracture had significantly (p < 0.05) lower aBMD at the lumbar spine, total hip, femoral neck, mid-distal radius, and ultradistal radius compared to controls. In similar multivariable models, women whose mothers had a fracture had lower total vBMD at the distal radius (-5 %, 0.3 standard deviation [SD]; p < 0.005) and distal tibia (-7 %, 0.4 SD; p < 0.005). They also had lower cortical thickness and area at the distal radius (-5 %, 0.3 SD and -4 %, 0.2 SD, respectively; p < 0.005) and at the distal tibia (-6 %, 0.3 SD and -4 %, 0.3SD, respectively; p < 0.005). Trabecular vBMD was lower at the distal radius (-5 %, 0.3 SD; p < 0.05) and tibia (-8 %, 0.4 SD; p < 0.005), with a more spaced and heterogeneous trabecular network (4 and 7 % at the radius and 5 and 9 %, at the tibia, p < 0.05, for Tb.Sp and Tb.Sp.SD, respectively).

CONCLUSION

Premenopausal daughters of women who had sustained fragility fracture have lower total and trabecular vBMD, thinner cortices, as well as impaired trabecular microarchitecture at the distal radius and tibia, compared with premenopausal daughters of women without fracture.

Long-term HIV infection and antiretroviral therapy are associated with bone microstructure alterations in premenopausal women

We evaluated the influence of long-term HIV infection and its treatment on distal tibia and radius microstructure. Premenopausal eumenorrheic HIV-positive women displayed trabecular and cortical microstructure alterations, which could contribute to increased bone fragility in those patients.

INTRODUCTION

Bone fragility is an emerging issue in HIV-infected patients. Dual-energy X-ray absorptiometry (DXA) quantified areal bone mineral density (BMD) predicts fracture risk, but a significant proportion of fracture risk results from microstructural alterations.

METHODS

We studied the influence of long-term HIV infection on bone microstructure as evaluated by high-resolution peripheral quantitative computed tomography (HR-pQCT) in 22 HIV-positive (+ve) premenopausal eumenorrheic women and 44 age- and body mass index (BMI)-matched HIV-negative (-ve) controls. All subjects completed questionnaires regarding calcium/protein intakes and physical activity, and underwent DXA and HR-pQCT examinations for BMD and peripheral skeleton microstructure, respectively. A risk factor analysis of tibia trabecular density using linear mixed models was conducted.

RESULTS

In HIV+ve women on successful antiretroviral therapy (undetectable HIV-RNA, median CD4 cell count, 626), infection duration was 16.5 ± 3.5 (mean ± SD) years; median BMI was 22 (IQR, 21-26) kg/m². More HIV+ve women were smokers (82 versus 50 %, p = 0.013). Compared to controls, HIV+ve women had lower lumbar spine (spine T-score -0.70 vs -0.03, p = 0.014), but similar proximal femur BMD. At distal tibia, HIV+ve women had a 14.1 % lower trabecular density and a 13.2 % reduction in trabecular number compared to HIV-ve women (p = 0.013 and 0.029, respectively). HR-pQCT differences in distal radius were significant for cortical density (-3.0 %; p = 0.029).

CONCLUSIONS

Compared with HIV-ve subjects, premenopausal HIV+ve treated women had trabecular and cortical bone alterations. Adjusted analysis revealed that HIV status was the only determinant of between group tibia trabecular density differences. The latter could contribute to increased bone fragility in HIV+ve patients.

Trabecular and cortical microarchitecture in postmenopausal HIV-infected women

Our objective was to assess the effects of HIV infection and antiretroviral therapy on trabecular and cortical microarchitecture in postmenopausal minority women. A subgroup of 106 (46 HIV-infected, 60 uninfected) postmenopausal Hispanic and African American women from an established cohort had areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry and trabecular and cortical volumetric BMD (vBMD) and microarchitecture measured by high-resolution peripheral quantitative computed tomography (HRpQCT) at the radius and tibia. HIV-infected women were slightly younger (58 ± 1 vs. 61 ± 1 years, p = 0.08), and had lower body mass index (BMI; 28 ± 1 vs. 32 ± 1 kg/m(2), p < 0.01). BMI-adjusted aBMD Z scores were lower in HIV-infected women at the lumbar spine, total hip, and ultradistal radius. Serum N-telopeptide and C-telopeptide levels were also higher in HIV-infected women. Trabecular and cortical vBMD were similar at the radius, but cortical area (105.5 ± 2.4 vs. 120.6 ± 2.0 mm(2), p < 0.01) and thickness (956 ± 33 vs. 1,075 ± 28 μm, p < 0.01) at the tibia were approximately 11-12 % lower in HIV-infected women. Differences remained significant after adjusting for age, BMI, and race/ethnicity. In contrast, cortical porosity was similar in the two groups. Although HIV-infected postmenopausal women had lower aBMD at the spine, total hip, and ultradistal radius and higher levels of bone resorption markers, the only differences detected by HRpQCT were lower cortical thickness and area at the tibia.

High-resolution peripheral quantitative computed tomography for the assessment of bone strength and structure: a review by the Canadian Bone Strength Working Group

Bone structure is an integral determinant of bone strength. The availability of high resolution peripheral quantitative computed tomography (HR-pQCT) has made it possible to measure three-dimensional bone microarchitecture and volumetric bone mineral density in vivo, with accuracy previously unachievable and with relatively low-dose radiation. Recent studies using this novel imaging tool have increased our understanding of age-related changes and sex differences in bone microarchitecture, as well as the effect of different pharmacological therapies. One advantage of this novel tool is the use of finite element analysis modelling to non-invasively estimate bone strength and predict fractures using reconstructed three-dimensional images. In this paper, we describe the strengths and limitations of HR-pQCT and review the clinical studies using this tool.

Computational identification and quantification of trabecular microarchitecture classes by 3-D texture analysis-based clustering

High resolution peripheral quantitative computed tomography (HR-pQCT) permits the non-invasive assessment of cortical and trabecular bone density, geometry, and microarchitecture. Although researchers have developed various post-processing algorithms to quantify HR-pQCT image properties, few of these techniques capture image features beyond global structure-based metrics. While 3D-texture analysis is a key approach in computer vision, it has been utilized only infrequently in HR-pQCT research. Motivated by high isotropic spatial resolution and the information density provided by HR-pQCT scans, we have developed and evaluated a post-processing algorithm that quantifies microarchitecture characteristics via texture features in HR-pQCT scans. During a training phase in which clustering was applied to texture features extracted from each voxel of trabecular bone, three distinct clusters, or trabecular microarchitecture classes (TMACs) were identified. These TMACs represent trabecular bone regions with common texture characteristics. The TMACs were then used to automatically segment the voxels of new data into three regions corresponding to the trained cluster features. Regional trabecular bone texture was described by the histogram of relative trabecular bone volume covered by each cluster. We evaluated the intra-scanner and inter-scanner reproducibility by assessing the precision errors (PE), intra class correlation coefficients (ICC) and Dice coefficients (DC) of the method on 14 ultradistal radius samples scanned on two HR-pQCT systems. DC showed good reproducibility in intra-scanner set-up with a mean of 0.870±0.027 (no unit). Even in the inter-scanner set-up the ICC showed high reproducibility, ranging from 0.814 to 0.964. In a preliminary clinical test application, the TMAC histograms appear to be a good indicator, when differentiating between postmenopausal women with (n=18) and without (n=18) prevalent fragility fractures. In conclusion, we could demonstrate that 3D-texture analysis and feature clustering seems to be a promising new HR-pQCT post-processing tool with good reproducibility, even between two different scanners.