Changes in bone mineral density and microarchitecture in cosmonauts after a six-month space flight

The effect of microgravity on the bone tissue of cosmonauts has been studied after a six-month space flight. The volumetric bone mineral density (VBMD) and the bone structural characteristics of distal segments in the radius and tibia have been studied by means of peripheral quantitative computed tomography (pQCT). The changes in VBMD were found to correlate with the position of the bone relative to the vector of gravity. In the radius, reversible hypermineralization, together with thickening of the compact bone were recorded. In the tibia, reversible osteopenia was characterized by significant losses in both compact and trabecular bones. Irrespective of the position relative to the vector of gravity, there was a trend towards microarchitectural deterioration, such as a decrease in the trabecula number and increase in the bone tissue heterogeneity. Postflight dynamics of structural parameters showed an integrative character with nonlinear time dependence.     

Cadmium Is More Toxic on Volume Bone Mineral Density than Tissue Bone Mineral Density

It has been showed that Cd induces low areal bone mineral density, but we do not know the effect of Cd on cubic bone density. This study was aimed to investigate the effects of Cd on volumetric bone mineral density (VBMD) and tissue bone mineral density (TBMD) in male rats. Twenty-four Sprague-Dawley male rats were randomly divided into four groups that were given cadmium chloride by subcutaneous injection at doses of 0, 0.1, 0.5, and 1.5?mg/kg body weight for 8?weeks, respectively. Then, microcomputed tomography scanning was performed on the proximal tibia, and region of interest was reconstructed using microview software. The VBMD, bone volume fraction of rats treated with 1.5?mg Cd/kg, were significantly decreased compared to control (p?相似文献   

pQCT provides better prediction of canine femur breaking load than does DXA

Our study was designed to examine the validity of dual energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) measurements as predictors of whole bone breaking strength in beagle femora. DXA was used to determine the bone mineral content, bone area, and 'areal' bone mineral density. PQCT was used to determine the cross-sectional moments of inertia, volumetric densities of the bone, and to calculate bone strength indices based on bone geometry and density. A three-point bending mechanical test was used to determine maximal load. Three variables from the pQCT data set explained 88% of the variance in maximal load, with the volumetric bone mineral density explaining 32% of the variance. The addition of the volumetric cortical density increased the adjusted r(2) to 0.601 (p=0.001) and the addition of an index created by multiplying volumetric cortical bone density by the maximum cross-sectional moment of inertia made further significant (p<0.001) improvements to an adjusted r(2) of 0.877. In comparison, when only the DXA variables were considered in a multiple regression model, areal bone mineral density was the only variable entered and explained only 51% (p<0.001) of the variance in maximal load. These results suggest that pQCT can better predict maximal load in whole beagle femora since pQCT provides information on the bone's architecture in addition to its volumetric density.     

Hormone replacement therapy improves distal radius bone structure by endocortical mineral deposition

Hormone replacement therapy (HRT) produces a small increase in bone mineral density (BMD) when measured by dual energy X-ray absorptiometry (DXA). The corresponding decrease in fracture risk is more impressive, implying that other factors that contribute to bone strength are favourably modified by HRT. We investigated, using peripheral quantitated computed tomography (pQCT), the changes produced by HRT in both the distribution of mineral between cortical and trabecular bone and the changes produced by HRT in the apparent structure of trabecular bone, expressed as average hole area and apparent connectivity. Twenty-one postmenopausal women starting HRT and 32 control women were followed for 2 years, with distal radius pQCT measurements every 6 months. HRT prevented the loss of total bone mass seen in controls (p < 0.02). HRT also produced an apparent rapid loss of trabecular bone mass within the first 6 months of the study (p < 0.02), with an associated rapid loss in the apparent connectivity (p = 0.034). Average hole area also increased but not to a statistically significant extent. Exogenous estrogen apparently fills small marrow pores close to the endocortical surface, such that the pQCT-defined boundary between trabecular and cortical bone is shifted in favour of cortical bone. Trabecular bone structure indices are adversely affected, as the central, poorly interconnected trabecular bone with greater than average marrow spaces constitutes a greater fraction of the remaining trabecular bone. This study suggests that the improvements in fracture risk resulting from HRT are explained by a reversal of net endocortical resorption of bone.     

Reduced trabecular bone mineral density and cortical thickness accompanied by increased outer bone circumference in metacarpal bone of rheumatoid arthritis patients: a cross-sectional study

Introduction

The objective of this study was to assess three-dimensional bone geometry and density at the epiphysis and shaft of the third meta-carpal bone of rheumatoid arthritis (RA) patients in comparison to healthy controls with the novel method of peripheral quantitative computed tomography (pQCT).

Methods

PQCT scans were performed in 50 female RA patients and 100 healthy female controls at the distal epiphyses and shafts of the third metacarpal bone, the radius and the tibia. Reproducibility was determined by coefficient of varia-tion. Bone densitometric and geometric parameters were compared between the two groups and correlated to disease characteristics.

Results

Reproducibility of different pQCT parameters was between 0.7% and 2.5%. RA patients had 12% to 19% lower trabecular bone mineral density (BMD) (P ≤ 0.001) at the distal epiphyses of radius, tibia and metacarpal bone. At the shafts of these bones RA patients had 7% to 16% thinner cortices (P ≤ 0.03). Total cross-sectional area (CSA) at the metacarpal bone shaft of pa-tients was larger (between 5% and 7%, P < 0.02), and relative cortical area was reduced by 13%. Erosiveness by Ratingen score correlated negatively with tra-becular and total BMD at the epiphyses and shaft cortical thickness of all measured bones (P < 0.04).

Conclusions

Reduced trabecular BMD and thinner cortices at peripheral bones, and a greater bone shaft diameter at the metacarpal bone suggest RA spe-cific bone alterations. The proposed pQCT protocol is reliable and allows measuring juxta-articular trabecular BMD and shaft geometry at the metacarpal bone.     

Volumetric and projective bone mineral density

Projectional bone mineral density measurement so far used extensively in radiogrammetry and single and dual source absorptiometry is confronted with a serious limitation for the accurate evaluation of true density artifactually providing higher values along with the increase of body size and bone depth on account of the omission of one dimension. Computed tomography is capable of measuring true volumetric density and also accomplishes a separate measurement of trabecular and cortical bone especially on application to the distal and mid-radius with abundant cortical bone in peripheral computed tomography (pQCT). New lines of information may be obtained by such separate trabecular and cortical bone measurement in decreases of bone density due to various causes, estrogen withdrawal, corticosteroid, diabetes mellitus, renal failure, etc. Dynamic analysis of the result of pQCT may also make it possible to assess bone strength and resistance to fracture.     

Linking chronic tryptophan deficiency with impaired bone metabolism and reduced bone accrual in growing rats

There is increasing evidence that serotonin may regulate bone metabolism. However, its role remains to be clarified. Serotonin seems to be either beneficial or detrimental for bone tissues depending on the pharmacological manipulation used. In this study we evaluated the impact of a reduction of serotonergic stores induced by chronic tryptophan (TRP) depletion on various bone parameters in growing rats. For this purpose rats received a TRP‐free diet for 60 days. Bone mass, mineral content and density were measured by DXA and by pQCT in the appendicular skeleton. Bone metabolic markers included urinary deoxypyridinoline and serum osteocalcin measurements. IGF‐I levels were also evaluated. In TRP‐free diet rats, we found a decrease in body weight, a delayed femoral bone growth and bone mineral content as measured by DXA. pQCT analysis showed that these effects were related to a reduction of both cortical and trabecular bone and are associated with a reduction of bone strength. These effects are due to a negative shift in the balance between bone formation and resorption with a significant decrease in bone formation as evidenced by a reduction both in osteocalcin and IGF‐I levels. The present data extend our overall knowledge on the participation of serotonin in the regulation of growing bone and could be of interest in studying the impairment of bone growth in depressed subjects under particular condition of rapid bone accrual such as childhood and adolescence. J. Cell. Biochem. 107: 890–898, 2009. © 2009 Wiley‐Liss, Inc.     

A Piece of the Puzzle: The Bone Health Index of the BoneXpert Software Reflects Cortical Bone Mineral Density in Pediatric and Adolescent Patients

Introduction

Suspected osteopathology in chronically ill children often necessitates the assessment of bone mineral density. The most frequently used methods are dual-energy X-ray-absorption (DXA) and peripheral quantitative computed tomography (pQCT). The BoneXpert software provides an automated radiogrammatic method to assess skeletal age from digitalized X-rays of the left hand. Furthermore, the program calculates the Bone Health Index (BHI), a measure of cortical thickness and mineralization, which is obtained from indices of three metacarpal bones. In our study, we analyzed the manner in which BHI information provided by BoneXpert compares with DXA or pQCT measurements in youths.

Study Design

The BHI was retrospectively obtained using digitalized X-rays of the left hand and compared with the results of 203 corresponding DXA readings (Lunar Prodigy, GE Healthcare) of the lumbar vertebrae and femur as well as 117 pQCT readings (XCT 900, Stratec) of the distal radius.

Results

The BHI values showed a strong positive correlation with the DXA readings at each and all lumbar vertebrae (L1 –L4: r = 0.73; P < 0.0001). The age-adjusted Z-score of L1 –L4 and the height-adjusted score showed a positive correlation with the BHI-SDS (standard deviation score, r = 0.23; P < 0.002 and r = 0.27; P < 0.001, respectively). Total bone mineral density, as assessed via pQCT, also positively correlated with the BHI (r = 0.39; P < 0.0001), but the trabecular values displayed only a weak correlation.

Conclusions

The BHI obtained using BoneXpert can be a useful parameter in the assessment of bone health in children in most cases. This technique provides observer-independent information on cortical thickness and mineralization based on X-ray imaging of the hands.     

Variations in morphological and biomechanical indices at the distal radius in subjects with identical BMD

Determination of osteoporotic status is based primarily on areal bone mineral density (aBMD) obtained through dual X-ray absorptiometry (DXA). However, many fractures occur in patients with T-scores above the WHO threshold of osteoporosis, in part because DXA measures are insensitive to biomechanically important alterations in bone quality. The goal of this study was to determine--within groups of subjects with identical radius aBMD values--the extant variation in densitometric, geometric, microstructural, and biomechanical parameters. High resolution peripheral quantitative computed tomography (HR-pQCT) and DXA radius data from males and females spanning large ranges in age, osteoporotic status, and anthropometrics were compiled. 262 distal radius datasets were processed for this study. HR-pQCT scans were analyzed according to the manufacturer's standard clinical protocol to quantify densitometric, geometric, and microstructural indices. Micro-finite element analysis was performed to calculate biomechanical indices. Factor of risk of wrist fracture was calculated. Simulated aBMD calculated from HR-pQCT data was used to group scans for evaluation of variation in quantified indices. Indices reflecting the greatest variation within aBMD level were BMD in the central portion of the trabecular compartment (max CV 142), trabecular heterogeneity (max CV 90), and intra-cortical porosity (max CV 151). Of the biomechanical indices, cortical load fraction had the greatest variation (max CV 38). Substantial variations in indices reflecting density, structure, and biomechanical competence exist among subjects with identical aBMD levels. Overlap of these indices among osteoporotic status groups reflects the reported incidence of osteoporotic fracture in subjects classified as osteopenic or normal.     

Bone microarchitecture in ankylosing spondylitis and the association with bone mineral density,fractures, and syndesmophytes

Introduction

Osteoporosis of the axial skeleton is a known complication of ankylosing spondylitis (AS), but bone loss affecting the peripheral skeleton is less studied. This study on volumetric bone mineral density (vBMD) and bone microarchitecture in AS was conducted to compare peripheral vBMD in AS patients with that in healthy controls, to study vBMD in axial compared with peripheral bone, and to explore the relation between vertebral fractures, spinal osteoproliferation, and peripheral bone microarchitecture and density.

Methods

High-resolution peripheral quantitative computed tomography (HRpQCT) of ultradistal radius and tibia and QCT and dual-energy x-ray absorptiometry (DXA) of lumbar spine were performed in 69 male AS patients (NY criteria). Spinal radiographs were assessed for vertebral fractures and syndesmophyte formation (mSASSS). The HRpQCT measurements were compared with the measurements of healthy controls.

Results

The AS patients had lower cortical vBMD in radius (P = 0.004) and lower trabecular vBMD in tibia (P = 0.033), than did the controls. Strong correlations were found between trabecular vBMD in lumbar spine, radius (r_S = 0.762; P < 0.001), and tibia (r_S = 0.712; P < 0.001).When compared with age-matched AS controls, patients with vertebral fractures had lower lumbar cortical vBMD (-22%; P = 0.019), lower cortical cross-sectional area in radius (-28.3%; P = 0.001) and tibia (-24.0%; P = 0.013), and thinner cortical bone in radius (-28.3%; P = 0.001) and tibia (-26.9%; P = 0.016).mSASSS correlated negatively with trabecular vBMD in lumbar spine (r_S = -0.620; P < 0.001), radius (r_S = -0.400; p = 0.001) and tibia (r_S = -0.475; p < 0.001) and also with trabecular thickness in radius (r_S = -0.528; P < 0.001) and tibia (r_S = -0.488; P < 0.001).Adjusted for age, syndesmophytes were significantly associated with decreasing trabecular vBMD, but increasing cortical vBMD in lumbar spine, but not with increasing cortical thickness or density in peripheral bone. Estimated lumbar vBMD by DXA correlated with trabecular vBMD measured by QCT (r_S = 0.636; P < 0.001).

Conclusions

Lumbar osteoporosis, syndesmophytes, and vertebral fractures were associated with both lower vBMD and deteriorated microarchitecture in peripheral bone. The results indicate that trabecular bone loss is general, whereas osteoproliferation is local in AS.     

Disproportional skeletal growth and markedly decreased bone mineral content in growth hormone receptor -/- mice

Growth hormone (GH) is important for skeletal growth as well as for a normal bone metabolism in adults. The skeletal growth and adult bone metabolism was studied in mice with an inactivated growth hormone receptor (GHR) gene. The lengths of femur, tibia, and crown-rump were, as expected, decreased in GHR-/- mice. Unexpectedly, GHR-/- mice displayed disproportional skeletal growth reflected by decreased femur/crown-rump and femur/tibia ratios. GHR-/- mice demonstrated decreased width of the growth plates in the long bones and disturbed ossification of the proximal tibial epiphysis. Furthermore, the area bone mineral density (BMD) as well as the bone mineral content (BMC)/body weight were markedly decreased in GHR-/- mice. The decrease in BMC in GHR-/- mice was not due to decreased trabecular volumetric BMD but to a decreased cross-sectional cortical bone area In conclusion, GHR-/- mice demonstrate disproportional skeletal growth and markedly decreased bone mineral content.     

Bone Analysis Using Trabecular Bone Score and Dual-Energy X-Ray Absorptiometry-Based 3-Dimensional Modeling in Postmenopausal Women With Primary Hyperparathyroidism

ObjectivePredominance of bone loss in cortical sites with relative preservation of trabecular bone, even in postmenopausal women, has been described in primary hyperparathyroidism (PHPT). The aim of this study was to evaluate bone microarchitectural differences using dual-energy x-ray absorptiometry (DXA), trabecular bone score (TBS), and DXA-based 3-dimensional (3D) modeling (3D-DXA) between postmenopausal women diagnosed with PHPT (PM-PHPT) and healthy postmenopausal controls.MethodsThis retrospective study included 44 women with PM-PHPT (9 of whom had fractures) and 48 healthy women matched by age, body mass index, and years since menopause treated at Hospital Universitario Fundación Jiménez Díaz between 2008 and 2017. The bone mineral density (BMD) of the lumbar spine (LS), femoral neck, total hip (TH), and 1/3 radius was assessed using DXA, and trabecular volumetric BMD (vBMD), cortical vBMD, integral vBMD, cortical thickness, and cortical surface BMD at TH were assessed using a 3D-DXA software and TBS at LS.ResultsThe mean adjusted BMD values at LS, the femoral neck, and TH; TBS at LS; and TH 3D-DXA parameters (trabecular vBMD, integral vBMD, cortical thickness, and cortical surface BMD) were significantly reduced in women with PM-PHPT compared with those in the controls. However, differences in mean cortical vBMD were not statistically significant (P = .078). There were no significant differences in mean BMD, TBS, or the 3D-DXA parameters between patients with fractures and those without fractures. The 25-hydroxyvitamin D level appeared to be associated with TBS but not with DXA and 3D-DXA measurements.ConclusionPM-PHPT has significant involvement of the trabecular and cortical compartments of the bone, as determined by DXA, TBS, and 3D-DXA.     

Critical ages and stages of puberty in the accumulation of spinal and femoral bone mass: the validity of bone mass measurements

In growing children, lumbar and femoral areal bone mineral density (aBMD), as measured by dual-energy X-ray absorptiometry (DXA), is influenced by skeletal growth and bone size. Correction of lumbar bone mineral density (BMD) for bone volume (volumetric BMD [vBMD]), by the use of mathematical extrapolations, reduces the confounding effect of bone size, but vBMD remains dependent on age and bone size during growth. Femoral (neck and mid-shaft) vBMD, assessed by DXA, is independent of age prior to puberty, but a slight increase occurs in late puberty and after menarche. Femoral (mid-shaft) cortical bone density and radial cortical and trabecular bone densities, assessed by quantitative computed tomography (QCT), show no peak during childhood or adolescence. Bone strength index, calculated by peripheral QCT, increases with age and correlates with handgrip strength, bone cross-sectional area and cortical area. Puberty is one of the main factors that influences lumbar bone mineral content and aBMD accumulation, but a high incidence of fractures occurs during this period of life, which may be associated with a reduced aBMD.     

A comparison of the fatigue behavior of human trabecular and cortical bone tissue

The fatigue properties of trabecular bone tissue (single trabeculae) and similarly sized cortical bone specimens from human tibia were experimentally determined on a microstructural level using four-point bending cyclic tests, and they were compared based on modulus, mineral density, and microstructural characteristics. The results showed that trabecular specimens had significantly lower moduli and lower fatigue strength than cortical specimens, despite their higher mineral density values. Fracture surface and microdamage analyses illustrated different fracture and damage patterns between trabecular and cortical bone tissue, depending upon their microstructural characteristics. Based on the results from mechanical tests and qualitative observations, a possible mechanical role of the cement lines in trabecular tissue microfracture was suggested.     

Evaluation of trabecular mechanical and microstructural properties in human calcaneal bone of advanced age using mechanical testing, microCT, and DXA

Early detection of fracture risk is important for initiating treatment and improving outcomes from both physiologic and pathologic causes of bone loss. While bone mineral density (a quantity measure) has traditionally been used for this purpose, alternative structural imaging parameters (quality measures) are proposed to better predict bone's true mechanical properties. To further elucidate this, trabecular bone from cadaveric human calcanei were used to evaluate the interrelationship of mechanical and structural parameters using mechanical testing, dual energy X-ray absorptiometry (DXA) scanning, and micro computed tomography (microCT) imaging. Directional specific structural properties were assessed in three-dimensional (3-D) and correlated to mechanical testing and DXA. The results demonstrated that microCT-derived indices of bone quality (i.e., volume fraction and structural model index) are better than DXA-derived bone mineral density for the prediction of the mechanical parameters of bone (i.e., elastic modulus, yield stress, and ultimate stress). Diagnostically, this implies that future work on the early prediction of fracture risk should focus as much on bone quality as on quantity. Furthermore, the results of this study show that a loss of bone primarily affects the connectedness and overall number of trabeculae. Ultimate stress, however, is better correlated with trabecular number than thickness. As such, primary prevention of osteoporosis may be more important than later countermeasures for bone loss.     

Least significant changes and monitoring time intervals for high-resolution pQCT-derived bone outcomes in postmenopausal women

Background:

Least Significant Change (LSC) assists in determining whether observed bone change is beyond measurement precision. Monitoring Time Interval (MTI) estimates time required to reliably detect skeletal changes. MTIs have not been defined for bone outcomes provided by high resolution peripheral quantitative computed tomography (HR-pQCT). The purpose of this study was to determine the LSCs and MTIs for HR-pQCT derived bone area, density and micro-architecture with postmenopausal women.

Methods:

Distal radius and tibia of 33 postmenopausal women (mean age: 77, SD: ±7 years), from the Saskatoon cohort of the Canadian Multicentre Osteoporosis Study (CaMos), were measured using HR-pQCT at baseline and 1-year later. We determined LSC from precision errors and divided them by the median annual percent changes to define MTIs for bone area, density, and micro-architecture.

Results:

Distal radius: HR-pQCT LSCs indicated a 1-8% observed change was needed for reliable monitoring of bone area and density while a 3-18% change was needed for micro-architectural measures. The longest MTIs (>3 years) pertained to cortical and trabecular area and density measures, cortical thickness and bone volume fraction; the shortest MTIs (~2 years) pertained to bone micro-architectural measures (trabecular number, thickness, separation and heterogeneity). Distal tibia: LSCs indicated a <1-5% observed change was needed for reliable monitoring of bone area and density, while a 3-19% change was needed for micro-architectural measures. The longest MTIs (>3 years) pertained to trabecular density, bone volume fraction, number, separation and heterogeneity; the shortest MTIs (~1 year) pertained to cortical and trabecular area, cortical density and thickness.

Conclusion:

MTIs suggest that performing HR-pQCT follow-up measures in postmenopausal women every 2 years at the distal radius and every 1 year at the distal tibia to monitor true skeletal changes as indicated by the LSCs.     

Mineral heterogeneity affects predictions of intratrabecular stress and strain

Knowledge of the influence of mineral variations (i.e., mineral heterogeneity) on biomechanical bone behavior at the trabecular level is limited. The aim of this study is to investigate how this material property affects the intratrabecular distributions of stress and strain in human adult trabecular bone. Two different sets of finite element (FE) models of trabecular samples were constructed; tissue stiffness was either scaled to the local degree of mineralization of bone as measured with microCT (heterogeneous) or tissue stiffness was assumed to be homogeneous. The influence of intratrabecular mineral heterogeneity was analyzed by comparing both models. Interesting effects were seen regarding intratrabecular stress and strain distributions. In the homogeneous model, the highest stresses were found at the surface with a significant decrease towards the core. Higher superficial stresses could indicate a higher predicted fracture risk in the trabeculae. In the heterogeneous model this pattern was different. A significant increase in stress with increasing distance from the trabecular surface was found followed by a significant decrease towards the core. This suggests trabecular bending during a compression. In both models a decrease in strain values from surface to core was predicted, which is consistent with trabecular bending. When mineral heterogeneity was taken into account, the predicted intratrabecular patterns of stress and strain are more consistent with the expected biomechanical behavior as based on mineral variations in trabeculae. Our findings indicate that mineral heterogeneity should not be neglected when performing biomechanical studies on topics such as the (long-term or dose dependent) effects of antiresorptive treatments.     

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

Dual energy X-ray absorptiometry (DXA) is the standard for assessing fragility fracture risk using areal bone mineral density (aBMD), but only explains 60–70% of the variation in bone strength. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides 3D-measures of bone microarchitecture and volumetric bone mineral density (vBMD), but only at the wrist and ankle. Finite element (FE) models can estimate bone strength with 86–95% precision. The purpose of this study is to determine how well vBMD and FE bone strength at the wrist and ankle relate to fracture strength at the hip and spine, and to compare these relationships with DXA measured directly at those axial sites. Cadaveric samples (radius, tibia, femur and L4 vertebra) were compared within the same body. The radius and tibia specimens were assessed using HR-pQCT to determine vBMD and FE failure load. aBMD from DXA was measured at the femur and L4 vertebra. The femur and L4 vertebra specimens were biomechanically tested to determine failure load. aBMD measures of the axial skeletal sites strongly correlated with the biomechanical strength for the L4 vertebra (r = 0.77) and proximal femur (r = 0.89). The radius correlated significantly with biomechanical strength of the L4 vertebra for vBMD (r = 0.85) and FE-derived strength (r = 0.72), but not with femur strength. vBMD at the tibia correlated significantly with femoral biomechanical strength (r = 0.74) and FE-estimated strength (r = 0.83), and vertebral biomechanical strength for vBMD (r = 0.97) and FE-estimated strength (r = 0.91). The higher correlations at the tibia compared to radius are likely due to the tibia’s weight-bearing function.     

Comparison of HR-pQCT- and microCT-based finite element models for the estimation of the mechanical properties of the calcaneus trabecular bone

The calcaneus bone is formed of extensive trabecular bone and is therefore well suited to be used as an example of loaded bone to establish the ability of combining microfinite element (microFE) technique with high-resolution peripheral quantitative computed tomography (HR-pQCT) in determining its mechanical properties. HR-pQCT is increasingly used as a tool for in vivo bone clinical research, but its use has been limited to the distal radius and tibia. The goal of this study was to determine the applicability of HR-pQCT-derived microFE models of the calcaneus trabecular bone with 82 μm voxel size with reference to higher-resolution microCT-based models taken as gold standard. By comparing the outputs of microFE models generated from both HR-pQCT and microCT images of the trabecular bone of five calcaneus cadaveric specimens, it was found that the HR-pQCT-based models predicted mechanical properties for fracture load, total reaction force and von Mises stress are considerably different from microCT-based counterparts by 33, 64 and 70%, respectively. Also, the morphological analysis showed a comprehensive geometrical difference between HR-pQCT-based microFE models and their microCT-based equivalents. The results of the HR-pQCT-based models were found to have strong dependency on the threshold value chosen to binarise the images prior to finite element modelling. In addition, it was found that the voxel size has a strong impact on accuracy of imaged-based microFE models compared to other factors such as the presence of soft tissue and image scanning integration time. Therefore, although HR-pQCT has shown to be useful to predict overall structural and biomechanical changes, it is limited in providing local accurate biomechanical properties of trabecular bone and therefore should be used with caution when assessing bone remodelling through local changes of trabecular bone apposition and resorption in disease treatment monitoring.     

Effect of age on bone mineral density and micro architecture in the radius and tibia of horses: An Xtreme computed tomographic study

Background

The effect of age on the bone mineral density and microarchitecture of the equine radius and tibia was investigated. Fifty-six bones from 15 horses aged four to 21 years were used. There were nine geldings and six mares, and none of the horses had any disease influencing bone properties. Xtreme computed tomography was used to evaluate a 9-mm segment of the diaphysis and metaphysis of each bone. The following variables were determined: length of the bone, circumference and diameter in the frontal and sagittal planes in the middle of the bone.Diaphysis: total volume, bone volume, bone volume ratio, slice area, bone area, marrow area, cortical and marrow thickness, bone mineral density, polar moment of inertia of the cortex.Metaphysis: total area, bone area, cortical bone area, cortical thickness, bone mineral density, bone mineral density in the cortex, bone mineral density in the trabecular region, trabecular number, trabecular thickness, trabecular separation, polar moment of inertia of the metaphysis, polar moment of inertia of the cortex of the metaphysis.

Results

Bone density and microarchitecture were not affected by breed or gender. However, the microarchitecture varied with the age of the horse; the number of trabeculae decreased significantly and the distance between trabeculae increased significantly with increasing age. There were no significant differences between bones of the left and right limbs or between the radius and tibia.

Conclusion

The variables investigated did not differ between geldings and mares. However, there were age-related changes in the microstructure of the bones. Further experimental studies are necessary to determine whether these changes reduce bone strength. Age-related changes in the bones were seen and may explain the higher incidence of fractures and fissures in older horses.