Distal skeletal tibia assessed by HR-pQCT is highly correlated with femoral and lumbar vertebra failure loads

The Influence of Hyponatremia and Hypokalemia on the Risk of Fractures in Various Anatomical Regions among Adult Trauma Patients: A Propensity Score-Matched Analysis

BACKGROUND

Hyponatremia and hypokalemia are common electrolyte imbalances in trauma patients and have been identified to be risk factors for a fall. In addition, hyponatremia was reported to be related to osteoporosis and fragility fractures, while the association between hypokalemia and osteoporosis has only been reported in rare case reports. This study investigated the impact of hyponatremia and hypokalemia on the incidence of fractures in various body regions of adult trauma patients, using the propensity score-matched patient cohort to reduce the influence of patients' baseline characteristics.

METHODS

The study analyzed data from 11,173 hospitalized adult trauma patients treated from 1 January 1998, to 31 December 2022. The study included 1968 patients with hyponatremia and 9205 without, and 1986 with hypokalemia and 9187 without. Different 1:1 propensity score-matched cohorts were generated to create the 1903 pairings of patients with or without hyponatremia, 1977 pairings of patients with or without hypokalemia, and 380 pairing of patients with both hyponatremia and hypokalemia vs. normal control patients. Analysis was conducted on the incidence of fracture in various anatomic regions.

RESULTS

Hyponatremic patients had increased odds of thoracic vertebral fracture [odds ratio (95% confidence interval) 1.63 (1.10-2.42), p = 0.014], pelvic fracture [2.29 (1.12-4.67), p = 0.019], and femoral fracture [1.28 (1.13-1.45), p < 0.001] but decreased odds of radial and patella fractures. Hypokalemic patients showed no significant differences in fracture risk except for a decreased likelihood of radial fractures. The patients with both hyponatremia and hypokalemia showed a decreased likelihood of radial fractures and patella fractures.

CONCLUSION

Hyponatremia may have a greater impact on the occurrence of bone fractures than hypokalemia in trauma patients who have suffered a fall. Electrolyte abnormalities should be taken into account while assessing the risk of fractures in trauma patients.

Self-reported Resistance Training Is Associated With Better HR-pQCT-derived Bone Microarchitecture in Vegan People

CONTEXT

A plant-based lifestyle is a global trend; lower bone mineral density and increased fracture risk in vegan people are reported.

OBJECTIVE

The primary objective was to assess trabecular and cortical bone microarchitecture in vegans and omnivores. Secondary objectives were to evaluate relationships between bone microarchitecture, nutrition parameters, and physical activity.

METHODS

This was an observational study at the Medical Department II, St. Vincent Hospital (tertiary referral center for gastrointestinal, metabolic, and bone diseases, and teaching hospital of the Medical University of Vienna), including 43 healthy nonobese female and male subjects on a plant-based diet for at least 5 years, and 45 healthy nonobese female and male subjects on an omnivore diet for at least 5 years. The main outcome measures were the parameters of trabecular and cortical bone microarchitecture (high-resolution peripheral quantitative computed tomography), serum markers of bone turnover, nutrient intake (nutrition protocol), and self-reported resistance training (physical activity questionnaires).

RESULTS

In the vegan group, trabecular and cortical structure were altered compared with omnivores. Vegans not reporting resistance training had diminished bone microarchitecture compared with omnivores not reporting resistance training. In vegans and omnivores reporting resistance training, bone structure was similar. In both vegan subgroups (resistance training and not resistance training), a small number of correlations between nutrient intake and bone microarchitecture were observed without a conclusive pattern.

CONCLUSION

Bone microarchitecture in vegans differed from matched omnivores but could not be explained solely by nutrient uptake. These differences were attenuated between the subgroups reporting resistance training. In addition to a well-planned diet, progressive resistance training on a regular basis should be part of the vegan lifestyle.

Meta-analyses of the quantitative computed tomography data in dialysis patients show differential impacts of renal failure on the trabecular and cortical bones

Dialysis patients have compromised bone health that increases their fracture risk due to low bone mass and deterioration in bone microarchitecture. Through meta-analyses of published studies, we conclude that dialysis patients suffer from impaired compartmental bone parameters compared with healthy controls.

INTRODUCTION

We performed meta-analyses to determine the effect of chronic kidney disease (CKD) patients under dialysis on the trabecular and cortical parameters of radius and tibia.

METHODS

This is a meta-analysis of cross-sectional and prospective clinical studies. PubMed, Web of Science, Google Scholar, and Scopus were searched using various permutation combinations. Dialysis patients were compared with non-CKD healthy controls using quantitative computed tomography. High-resolution peripheral quantitative computed tomography (HR-pQCT) and pQCT data of dialysis patients were dissected from eligible studies for pooled analysis of each parameter.

RESULTS

Ten studies met the inclusion criteria that included data from 457 dialysis patients and 2134 controls. Pooled analysis showed a significant decrease (a) in total vBMD at distal radius [standard deviation of the mean (SDM) = -0.842, p = 0.000] and tibia (SMD = -0.705, p = 0.000) and (b) in cortical vBMD (SDM = -1.037, p = 0.000) at radius of dialysis patients compared with control. There were strong correlations between total vBMD and microarchitecture parameters at tibia in dialysis patients.

CONCLUSIONS

At radius and tibia, bone mass, microarchitecture, and geometry at trabecular and cortical envelopes displayed impairments in dialysis patients compared with control. Tibial vBMD may have diagnostic value in dialysis. HR-pQCT and pQCT may be used to further understand the compartmental bones response to CKD-induced loss at different stages of CKD.

Factors associated with changes in volumetric bone mineral density and cortical area in men with ankylosing spondylitis: a 5-year prospective study using HRpQCT

Patients with ankylosing spondylitis (AS) have impaired volumetric bone mineral density (vBMD) assessed with high-resolution peripheral computed tomography (HRpQCT). This first longitudinal HRpQCT study in AS shows that cortical and trabecular vBMD decreased at tibia and that signs of inflammation were associated with cortical bone loss at tibia and radius.

INTRODUCTION

Patients with ankylosing spondylitis (AS) have reduced volumetric bone mineral density (vBMD) in the peripheral skeleton assessed with high-resolution peripheral quantitative computed tomography (HRpQCT). The aims were to investigate longitudinal changes in vBMD, cortical area, and microarchitecture and to assess factors associated with changes in vBMD and cortical area in men with AS.

METHODS

HRpQCT of radius and tibia was performed in 54 men with AS at baseline and after 5 years. Univariate and multivariable linear regression analyses were used.

RESULTS

At tibia, there were significant decreases exceeding least significant changes (LSC) in cortical and trabecular vBMD, mean (SD) percent change -1.0 (1.9) and -2.7 (5.0) respectively (p<0.001). In multivariable regression analyses, increase in disease activity measured by ASDAS_CRP from baseline to follow-up was associated with decreases in cortical vBMD (β -0.86, 95% CI -1.31 to -0.41) and cortical area (β -1.66, 95% CI -3.21 to -0.10) at tibia. At radius, no changes exceeded LSC. Nonetheless, increase in ASDAS_CRP was associated with decreases in cortical vBMD, and high time-averaged ESR was associated with decreases in cortical area. Treatment with TNF inhibitor ≥ 4 years during follow-up was associated with increases in cortical vBMD and cortical area at tibia, whereas exposure to bisphosphonates was associated with increases in cortical measurements at radius. No disease-related variables or treatments were associated with changes in trabecular vBMD.

CONCLUSION

The findings in this first longitudinal HRpQCT study in patients with AS strengthen the importance of controlling disease activity to maintain bone density in the peripheral skeleton.

Pore-Size Distribution and Frequency-Dependent Attenuation in Human Cortical Tibia Bone Discriminate Fragility Fractures in Postmenopausal Women With Low Bone Mineral Density

Osteoporosis is a disorder of bone remodeling leading to reduced bone mass, structural deterioration, and increased bone fragility. The established diagnosis is based on the measurement of areal bone mineral density by dual‐energy X‐ray absorptiometry (DXA), which poorly captures individual bone loss and structural decay. Enlarged cortical pores in the tibia have been proposed to indicate structural deterioration and reduced bone strength in the hip. Here, we report for the first time the in vivo assessment of the cortical pore‐size distribution together with frequency‐dependent attenuation at the anteromedial tibia midshaft by means of a novel ultrasonic cortical backscatter (CortBS) technology. We hypothesized that the CortBS parameters are associated with the occurrence of fragility fractures in postmenopausal women (n = 55). The discrimination performance was compared with those of DXA and high‐resolution peripheral computed tomography (HR‐pQCT). The results suggest a superior discrimination performance of CortBS (area under the receiver operating characteristic curve [AUC]: 0.69 ≤ AUC ≤ 0.75) compared with DXA (0.54 ≤ AUC ≤ 0.55) and a similar performance compared with HR‐pQCT (0.66 ≤ AUC ≤ 0.73). CortBS is the first quantitative bone imaging modality that can quantify microstructural tissue deteriorations in cortical bone, which occur during normal aging and the development of osteoporosis. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Deterioration of bone microstructure by aging and menopause in Japanese healthy women: analysis by HR-pQCT

INTRODUCTION

Second-generation high-resolution peripheral quantitative computed tomography (HR-pQCT) has provide higher quality of bone images with a voxel size of 61 µm, enabling direct measurements of trabecular thickness. In addition to the standard parameters, the non-metric trabecular parameters such as trabecular morphology (plate to rod-like structures), connectivity, and anisotropy can also be analyzed. The purpose of this study is to investigate deterioration of bone microstructure in healthy Japanese women by measuring standard and non-metric parameters using HR-pQCT.

MATERIALS AND METHODS

Study participants were 61 healthy Japanese women (31-70 years). The distal radius and tibia were scanned using second-generation HR-pQCT, and microstructures of trabecular and cortical bone were measured. Non-metric trabecular parameters included structure model index (SMI), trabecular bone pattern factor (TBPf), connectivity density (Conn.D), number of nodes (N.Nd/TV), degree of anisotropy (DA), and star volume of marrow space (V*ms). Estimated bone strength was evaluated by micro finite element analysis. Associations between bone microstructure, estimated bone strength, age, and menopause were analyzed.

RESULTS

Trabecular number declined with age, and trabecular separation increased. SMI and TBPf increased, Conn.D and N.Nd/TV declined, and V*ms increased. Cortical BMD and thickness declined with age, and porosity increased. Stiffness and failure load decreased with age. Cortical thickness and estimated bone strength were affected by menopause. Cortical thickness was most associated with estimated bone strength.

CONCLUSIONS

Trabecular and cortical bone microstructure were deteriorated markedly with age. Cortical thickness decreased after menopause and was most related to bone strength. Non-metric parameters give additional information about osteoporotic changes of trabecular bone.

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

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Guidelines for the assessment of bone density and microarchitecture in vivo using high-resolution peripheral quantitative computed tomography

INTRODUCTION

The application of high-resolution peripheral quantitative computed tomography (HR-pQCT) to assess bone microarchitecture has grown rapidly since its introduction in 2005. As the use of HR-pQCT for clinical research continues to grow, there is an urgent need to form a consensus on imaging and analysis methodologies so that studies can be appropriately compared. In addition, with the recent introduction of the second-generation HrpQCT, which differs from the first-generation HR-pQCT in scan region, resolution, and morphological measurement techniques, there is a need for guidelines on appropriate reporting of results and considerations as the field adopts newer systems.

METHODS

A joint working group between the International Osteoporosis Foundation, American Society of Bone and Mineral Research, and European Calcified Tissue Society convened in person and by teleconference over several years to produce the guidelines and recommendations presented in this document.

RESULTS

An overview and discussion is provided for (1) standardized protocol for imaging distal radius and tibia sites using HR-pQCT, with the importance of quality control and operator training discussed; (2) standardized terminology and recommendations on reporting results; (3) factors influencing accuracy and precision error, with considerations for longitudinal and multi-center study designs; and finally (4) comparison between scanner generations and other high-resolution CT systems.

CONCLUSION

This article addresses the need for standardization of HR-pQCT imaging techniques and terminology, provides guidance on interpretation and reporting of results, and discusses unresolved issues in the field.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

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

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

HR-pQCT Measures of Bone Microarchitecture Predict Fracture: Systematic Review and Meta-Analysis

High-resolution peripheral quantitative computed tomography (HR-pQCT) is a noninvasive imaging modality for assessing volumetric bone mineral density (vBMD) and microarchitecture of cancellous and cortical bone. The objective was to (1) assess fracture-associated differences in HR-pQCT bone parameters; and (2) to determine if HR-pQCT is sufficiently precise to reliably detect these differences in individuals. We systematically identified 40 studies that used HR-pQCT (39/40 used XtremeCT scanners) to assess 1291 to 3253 and 3389 to 10,687 individuals with and without fractures, respectively, ranging in age from 10.9 to 84.7 years with no comorbid conditions. Parameters describing radial and tibial bone density, microarchitecture, and strength were extracted and percentage differences between fracture and control subjects were estimated using a random effects meta-analysis. An additional meta-analysis of short-term in vivo reproducibility of bone parameters assessed by XtremeCT was conducted to determine whether fracture-associated differences exceeded the least significant change (LSC) required to discern measured differences from precision error. Radial and tibial HR-pQCT parameters, including failure load, were significantly altered in fracture subjects, with differences ranging from -2.6% (95% confidence interval [CI] -3.4 to -1.9) in radial cortical vBMD to -12.6% (95% CI -15.0 to -10.3) in radial trabecular vBMD. Fracture-associated differences reported by prospective studies were consistent with those from retrospective studies, indicating that HR-pQCT can predict incident fracture. Assessment of study quality, heterogeneity, and publication biases verified the validity of these findings. Finally, we demonstrated that fracture-associated deficits in total and trabecular vBMD and certain tibial cortical parameters can be reliably discerned from HR-pQCT-related precision error and can be used to detect fracture-associated differences in individual patients. Although differences in other HR-pQCT measures, including failure load, were significantly associated with fracture, improved reproducibility is needed to ensure reliable individual cross-sectional screening and longitudinal monitoring. In conclusion, our study supports the use of HR-pQCT in clinical fracture prediction. © 2019 American Society for Bone and Mineral Research.

Marrow adipose tissue in adolescent girls with obesity

BACKGROUND

Marrow adipose tissue (MAT) is increasingly recognized as an active and dynamic endocrine organ that responds to changes in nutrition and environmental milieu. Compared to normal weight controls, adolescent girls with anorexia nervosa have higher MAT content, which is associated with impaired skeletal integrity, but data are limited regarding MAT content in adolescents with obesity and how this interacts with bone endpoints.

OBJECTIVE

To evaluate (i) MAT content in adolescents with obesity compared to normal-weight controls, (ii) the association of MAT with bone endpoints, and (iii) whether these associations of MAT are affected by body weight.

METHODS

We assessed MAT, bone endpoints, and body composition in 60 adolescent girls 14-21 years old: 45 with obesity (OB) and 15 normal-weight controls (NW-C). We used (i) DXA to assess areal bone mineral density (aBMD) at the lumbar spine and total hip, and total body fat and lean mass, (ii) proton magnetic resonance spectroscopy (1H-MRS) to assess MAT at the 4th lumbar vertebra and femur, and MRI to assess visceral (VAT) and subcutaneous adipose tissue (SAT), (iii) high resolution peripheral quantitative CT (HR-pQCT) to assess volumetric BMD (vBMD), (iv) individual trabeculae segmentation to evaluate trabecular bone (plate-rod morphology), and (v) finite element analysis to assess stiffness (a strength estimate) at the distal radius and tibia.

RESULTS

Groups did not differ for age or height. Weight, BMI, and areal BMD Z-scores at all sites were higher in the OB group (p<0.0001). MAT was lower in OB at the femoral diaphysis (p= <0.0001) and the lumbar spine (p=0.0039). For the whole group, MAT at the lumbar spine and femoral diaphysis was inversely associated with BMI, total fat mass, lean mass, and VAT. Even after controlling for body weight, independent inverse associations were observed of femoral diaphyseal and lumbar MAT with total tibial vBMD, and of lumbar MAT with radial trabecular vBMD.

CONCLUSION

Adolescent girls with obesity have lower MAT than normal-weight controls despite having an excess of total body fat. These findings confirm that MAT is regulated uniquely from other adipose depots in obesity. MAT was inversely associated with vBMD, emphasizing an inverse relationship between MAT and bone even in adolescent girls with obesity.

Bone microarchitecture and bone turnover in hepatic cirrhosis

Liver cirrhosis leads to bone loss. To date, information on bone quality (three-dimensional microarchitecture) and, thus, bone strength is scarce. We observed decreased bone quality at both assessed sites, independent of disease severity. Therefore, all patients should undergo early-stage screening for osteoporosis.

INTRODUCTION

Recent studies found low bone mineral density in cirrhosis, but data on bone microstructure are scarce. This study assessed weight-bearing and non-weight-bearing bones in patients with cirrhosis and healthy controls. The primary objective was to evaluate trabecular and cortical microarchitecture.

METHODS

This was a single-center study in patients with recently diagnosed hepatic cirrhosis. Thirty-two patients and 32 controls participated in this study. After determining the type of cirrhosis, the parameters of bone microarchitecture were assessed by high-resolution peripheral quantitative computed tomography.

RESULTS

Both cortical and trabecular microarchitectures showed significant alterations. At the radius, trabecular bone volume fraction was 17% lower (corrected p = 0.028), and, at the tibia, differences were slightly more pronounced. Trabecular bone volume fraction was 19% lower (p = 0.024), cortical bone mineral density 7% (p = 0.007), and cortical thickness 28% (p = 0.001), while cortical porosity was 32% higher (p = 0.023), compared to controls. Areal bone mineral density was lower (lumbar spine - 13%, total hip - 11%, total body - 9%, radius - 17%, and calcaneus - 26%). There was no correlation between disease severity and microarchitecture. Areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) correlated well with parameters of cortical and trabecular microarchitecture.

CONCLUSIONS

Hepatic cirrhosis deteriorates both trabecular and cortical microarchitecture, regardless of disease severity. Areal bone mineral density is diminished at all sites as a sign of generalized affection. In patients with hepatic cirrhosis, regardless of its origin or disease severity, aBMD measurements are an appropriate tool for osteologic screening.

In Vivo Measurements of Cortical Thickness and Porosity at the Proximal Third of the Tibia Using Guided Waves: Comparison with Site-Matched Peripheral Quantitative Computed Tomography and Distal High-Resolution Peripheral Quantitative Computed Tomography

The aim of this study was to estimate cortical porosity (Ct.Po) and cortical thickness (Ct.Th) using 500-kHz bi-directional axial transmission (AT). Ct.Th_AT and Ct.Po_AT were obtained at the tibia in 15 patients from a 2-D transverse isotropic free plate model fitted to measured guided wave dispersion curves. The velocities of the first arriving signal (υ_FAS) and A₀ mode (υ_A0) were also determined. Site-matched peripheral quantitative computed tomography (pQCT) provided volumetric cortical bone mineral density (Ct.vBMD_pQCT) and Ct.Th_pQCT. Good agreement was found between Ct.Th_AT and Ct.Th_pQCT (R² = 0.62, root mean square error [RMSE] = 0.39 mm). Ct.vBMD_pQCT correlated with Ct.Po_AT (R² = 0.57), υ_FAS (R² = 0.43) and υ_A0 (R² = 0.28). Furthermore, a significant correlation was found between AT and distal high-resolution pQCT. The measurement ofcortical parameters at the tibia using guided waves might improve the prediction of bone fractures in a cost-effective and radiation-free manner.

Large cortical bone pores in the tibia are associated with proximal femur strength

Alterations of structure and density of cortical bone are associated with fragility fractures and can be assessed in vivo in humans at the tibia. Bone remodeling deficits in aging women have been recently linked to an increase in size of cortical pores. In this ex vivo study, we characterized the cortical microarchitecture of 19 tibiae from human donors (aged 69 to 94 years) to address, whether this can reflect impairments of the mechanical competence of the proximal femur, i.e., a major fracture site in osteoporosis. Scanning acoustic microscopy (12 μm pixel size) provided reference microstructural measurements at the left tibia, while the bone vBMD at this site was obtained using microcomputed tomography (microCT). The areal bone mineral density of both left and right femoral necks (aBMD_neck) was measured by dual‐energy X‐ray absorptiometry (DXA), while homogenized nonlinear finite element models based on high-resolution peripheral quantitative computed tomography provided hip stiffness and strength for one-legged standing and sideways falling loads. Hip strength was associated with aBMD_neck (r = 0.74 to 0.78), with tibial cortical thickness (r = 0.81) and with measurements of the tibial cross-sectional geometry (r = 0.48 to 0.73) of the same leg. Tibial vBMD was associated with hip strength only for standing loads (r = 0.59 to 0.65). Cortical porosity (Ct.Po) of the tibia was not associated with any of the femoral parameters. However, the proportion of Ct.Po attributable to large pores (diameter > 100 μm) was associated with hip strength in both standing (r = -0.61) and falling (r = 0.48) conditions. When added to aBMD_neck, the prevalence of large pores could explain up to 17% of the femur ultimate force. In conclusion, microstructural characteristics of the tibia reflect hip strength as well as femoral DXA, but it remains to be tested whether such properties can be measured in vivo.

The relationship between estimated bone strength by finite element analysis at the peripheral skeleton to areal BMD and trabecular bone score at lumbar spine

Bone strength, estimated by finite element (FE) analysis based on high resolution peripheral quantitative computed tomography (HR-pQCT) images is an important contributor to understanding risk of fracture. However, it is a peripheral device and cannot be evaluated in vivo at lumbar spine L1-L4. The aim of this study was to investigate if the axial bone quality can be predicted by strength measurements of peripheral bone. Peripheral bone microarchitecture, areal bone mineral density (aBMD) and trabecular bone score (TBS) were measured in adults individuals (n = 262, 60 years and older; 63% women). Stiffness and failure load were estimated by FE analysis at HR-pQCT images at radius and tibia. Areal BMD and TBS were measured by dual energy X-ray absorptiometry (DXA) at L1-L4. Correlations between peripheral and axial data were estimated for each gender adjusted by age, weight, and height. Areal BMD L1-L4 resulted in weak to moderate significant correlations with stiffness and failure load at radius (women: R² = 0.178, p < 0.05 and R² = 0.187, p < 0.001, respectively; men: R² = 0.454 and R² = 0.451, p < 0.001, respectively) and at tibia (women: R² = 0.211 and R² = 0.216, p < 0.001, respectively; men: R² = 0.488 and R² = 0.502, p < 0.001, respectively). TBS showed a very weak or no correlation with stiffness and failure load at radius (women: R² = 0.148 and R² = 0.150, p < 0.05, respectively; men: R² = 0.108 and R² = 0.106, p < 0.05, respectively) and at tibia (women: R² = 0.146 and R² = 0.150, p < 0.05, respectively; men: R² = 0.072 and R² = 0.078, respectively). These data suggest that aBMD L1-L4 was better explained by peripheral bone strength characteristics than the TBS, mainly in men and tibia is generally the site with a better relationship.

Atlases with Arcuate Foramen Present Cortical Bone Thickening That May Contribute to Lower Fracture Risk

BACKGROUND

To date, no information about the cortical bone microstructural properties in atlas vertebrae with arcuate foramen has been reported. As a result, we aimed to test in an experimental model if there is a cortical bone thickening in an atlas vertebra which has an arcuate foramen that may play a protective role against bone fracture.

METHODS

We analyzed by means of micro-computed tomography the cortical bone thickness, the cortical volume, and the medullary volume (SkyScan 1172 Bruker micro-CT NV, Kontich, Belgium) in cadaveric dry atlas vertebrae with arcuate foramen and without arcuate foramen. We also reviewed a case series of 31 posterior atlas arch fractures to correlate the possible presence in the same atlas of both fracture and arcuate foramen.

RESULTS

The micro-computed tomography study revealed significant differences in cortical bone thickness (P < 0.001), cortical volume (P < 0.004), and medullary volume (P = 0.013) values between the arcuate foramen vertebrae and the nonarcuate foramen vertebrae. The clinical series found no coexistence in the same vertebra of a posterior atlas arch fractures and the arcuate foramen.

CONCLUSIONS

An atlas with arcuate foramen presents cortical bone thickening. This advantage in bone microarchitecture seems to contribute to a lower fracture risk compared to subjects without arcuate foramen as no coexistence in the same vertebra of a posterior atlas arch fractures and arcuate foramen was found.

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

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