Variation of trabecular architecture in proximal femur of postmenopausal women

This investigation of microstructure in the human proximal femur probes the relationship between the parameters of the FRAX index of fracture risk and the parameters of bone microstructure. The specificity of fracture sites at the proximal femur raises the question of whether trabecular parameters are site-specific during post-menopause, before occurrence of fragility fracture. The donated proximal femurs of sixteen post-menopausal women in the sixth and seventh decades of life, free of metabolic pathologies and therapeutic interventions that could have altered the bone tissue, constituted the material of the study. We assessed bone mineral density of the proximal femurs by dual energy X-ray absorptiometry and then sectioned the femurs through the center of the femoral head and along the femoral neck axis. For each proximal femur, morphometry of trabeculae was conducted on the plane of the section divided into conventional regions and sub-regions consistent with the previously identified trabecular families that provide regions of relatively homogeneous microstructure. Mean trabecular width and percent bone area were calculated at such sites. Our findings indicate that each of mean trabecular width and percent bone area vary within each proximal femur independently from each other, with dependence on site. Both trabecular parameters show significant differences between pairs of sites. We speculate that a high FRAX index at the hip corresponds to a reduced percent bone area among sites that gives a more homogeneous and less site-specific quality to the proximal femur. This phenomenon may render the local tissue less able to carry out the expected mechanical function.     

A microstructural finite element simulation of mechanically induced bone formation.

A finite element method to simulate the formation of an interconnected trabectular bone microstructure oriented with respect to applied in vivo mechanical forces is introduced and quantitatively compared to experimental data from a hydraulic bone chamber implant model. Randomly located 45 microm mineralized nodules were used as the initial condition for the model simulations to represent an early stage of intramembranous bone formation. Boundary conditions were applied consistent with the mechanical environment provided by the in vivo bone chamber model. A two-dimensional repair simulation algorithim that incorporated strain energy density (SED), SED gradient, principal strain, or principal strain gradient as the local objective criterion was utilized to simulate the formation of an oriented trabecular bone microstructure. The simulation solutions were convergent, unique, and relatively insensitive to the assumed initial distribution of mineralized nodules. Model predictions of trabecular bone morphology and anisotropy were quantitatively compared to experimental results. All simulations produced structures that qualitatively resembled oriented trabecular bone. However only simulations utilizing a gradient objective criterion yielded results quantitatively similar to in vivo observations. This simulation approach coupled with an experimental model that delivers controlled in vivo mechanical stimuli can be utilized to study the relationship between physical factors and microstructural adaptation during bone repair.     

Biomechanical aspects of bone microstructure in vertebrates: potential approach to palaeontological investigations

Biomechanical or biophysical principles can be applied to study biological structures in their modern or fossil form. Bone is an important tissue in paleontological studies as it is a commonly preserved element in most fossil vertebrates, and can often allow its microstructures such as lacuna and canaliculi to be studied in detail. In this context, the principles of Fluid Mechanics and Scaling Laws have been previously applied to enhance the understanding of bone microarchitecture and their implications for the evolution of hydraulic structures to transport fluid. It has been shown that the microstructure of bone has evolved to maintain efficient transport between the nutrient supply and cells, the living components of the tissue. Application of the principle of minimal expenditure of energy to this analysis shows that the path distance comprising five or six lamellar regions represents an effective limit for fluid and solute transport between the nutrient supply and cells; beyond this threshold, hydraulic resistance in the network increases and additional energy expenditure is necessary for further transportation. This suggests an optimization of the size of the bone’s building blocks (such as osteon or trabecular thickness) to meet the metabolic demand concomitant to minimal expenditure of energy. This biomechanical aspect of bone microstructure is corroborated from the ratio of osteon to Haversian canal diameters and scaling constants of several mammals considered in this study. This aspect of vertebrate bone microstructure and physiology may provide a basis of understanding of the form and function relationship in both extinct and extant taxa.     

Evolutionary Patterns of Bone Histology and Bone Compactness in Xenarthran Mammal Long Bones

Bone microstructure reflects physiological characteristics and has been shown to contain phylogenetic and ecological signals. Although mammalian long bone histology is receiving increasing attention, systematic examination of the main clades has not yet been performed. Here we describe the long bone microstructure of Xenarthra based on thin sections representing twenty-two species. Additionally, patterns in bone compactness of humeri and femora are investigated. The primary bone tissue of xenarthran long bones is composed of a mixture of woven, parallel-fibered and lamellar bone. The vascular canals have a longitudinal, reticular or radial orientation and are mostly arranged in an irregular manner. Concentric rows of vascular canals and laminar organization of the tissue are only found in anteater bones. The long bones of adult specimens are marked by dense Haversian bone, a feature that has been noted for most groups of mammals. In the long bones of armadillos, secondary osteons have an oblique orientation within the three-dimensional bone tissue, thus resulting in their irregular shape when the bones are sectioned transversely. Secondary remodeling is generally more extensive in large taxa than in small taxa, and this could be caused by increased loading. Lines of arrested growth are assumed to be present in all specimens, but they are restricted to the outermost layer in bones of armadillos and are often masked by secondary remodeling in large taxa. Parameters of bone compactness show a pattern in the femur that separates Cingulata and Pilosa (Folivora and Vermilingua), with cingulates having a lower compactness than pilosans. In addition, cingulates show an allometric relationship between humeral and femoral bone compactness.     

Application of homogenization theory to the study of trabecular bone mechanics.

It is generally accepted that the strength and stiffness of trabecular bone is strongly affected by trabecular microstructure. It has also been hypothesized that stress induced adaptation of trabecular bone is affected by trabecular tissue level stress and/or strain. At this time, however, there is no generally accepted (or easily accomplished) technique for predicting the effect of microstructure on trabecular bone apparent stiffness and strength or estimating tissue level stress or strain. In this paper, a recently developed mechanics theory specifically designed to analyze microstructured materials, called the homogenization theory, is presented and applied to analyze trabecular bone mechanics. Using the homogenization theory it is possible to perform microstructural and continuum analyses separately and then combine them in a systematic manner. Stiffness predictions from two different microstructural models of trabecular bone show reasonable agreement with experimental results, depending on metaphyseal region, (R2 greater than 0.5 for proximal humerus specimens, R2 less than 0.5 for distal femur and proximal tibia specimens). Estimates of both microstructural strain energy density (SED) and apparent SED show that there are large differences (up to 30 times) between apparent SED (as calculated by standard continuum finite element analyses) and the maximum microstructural or tissue SED. Furthermore, a strut and spherical void microstructure gave very different estimates of maximum tissue SED for the same bone volume fraction (BV/TV). The estimates from the spherical void microstructure are between 2 and 20 times greater than the strut microstructure at 10-20% BV/TV.     

Dependence of ultrasonic attenuation on bone mass and microstructure in bovine cortical bone

The development of the axial transmission technique now enables in vivo evaluation of cortical bone quality, which plays an important role in bone fragility. Cortical bone is a complex multiscale material, which may be made of different types of microstructure. The interaction between ultrasound and cortical bone remains unclear and most studies have been confined to wave speed analysis. The first aim of this study is to investigate the dependence of the frequency-dependent attenuation on the type of bone microstructure. The second goal is to determine whether broadband ultrasonic attenuation (BUA) is related to volumetric bone mineral density (vBMD) and mass density. Parallelepipedic samples of bovine cortical bone were cut from three specimens and tested in the axial, radial and tangential directions using an ultrasonic transmission device. BUA was evaluated over a 1-MHz wide bandwidth around 4MHz. In addition, the microstructure of each sample was determined using an optical microscope. BUA values measured in porotic microstructure are significantly higher than in Haversian microstructure. The lowest BUA values are obtained for plexiform microstructure. For all structures, BUA in the axial direction is significantly smaller than in the radial and tangential directions. Moreover, BUA is correlated with both vBMD and density (determination coefficient (R2) equal to 0.44 and 0.65, respectively, in the axial direction). BUA variations can be explained by scattering and viscoelastic mechanisms. This study suggests that BUA measurements have the potential to discriminate among different cortical bone microstructures in addition to providing material properties.     

Monochromatic synchrotron radiation muCT reveals disuse-mediated canal network rarefaction in cortical bone of growing rat tibiae.

The purpose of this study was to demonstrate the ability of computed microtomography based on monochromatic synchrotron radiation (SRmuCT) in microstructural analysis of cortical bone. Tibial diaphyses of growing rats (14 wk, n = 8) undergoing unilateral sciatic neurectomy 8 wk before study were imaged with spatial volume resolution of 5.83 x 5.83 x 5.83 microm3 by SRmuCT (20 keV) at the synchrotron radiation facility (SPring-8). Reconstructed image data were translated into local mineral densities by using a calibrated linear relationship between linear absorption coefficients and concentrations of homogeneous K2HPO4 solution. Pure bone three-dimensional images, produced by simple thresholding at a bone mineral density of 0.82 g/cm3, were analyzed for macro- and microscopic structural properties. In neurectomized hindlimbs, cortical canal network rarefaction as well as bone atrophy were found. The former was characterized by 30% smaller porosity, 11% smaller canal density in transverse section, and 38% smaller canal connectivity density than those in contralateral bone. On the other hand, no difference was found in bone mineral density between neurectomized and intact hindlimbs (1.37 vs. 1.36 g/cm3). In conclusion, SRmuCT is a promising method for the three-dimensional analysis of cortical microstructure and the degree of mineralization in small animals.     

Pullout strength of suture anchors: Effect of mechanical properties of trabecular bone

This study investigated the relationships between trabecular microstructure and elastic modulus, compressive strength, and suture anchor pullout strength. Twelve fresh-frozen humeri underwent mechanical testing followed by micro-computed tomography (μCT). Either compression testing of cylindrical bone samples or pullout testing using an Arthrex 5 mm Corkscrew was performed in synthetic sawbone or at specific locations in the humerus such as the greater tuberosity, lesser tuberosity, and humeral head. Synthetic sawbone underwent identical mechanical testing and μCT analysis. Bone volume fraction (BVF), structural model index (SMI), trabecular thickness (TbTh), trabecular spacing (TbSp), trabecular number (TbN), and connectivity density were compared against modulus, compressive strength, and pullout strength in both materials. In cadaveric bone, modulus showed correlations to all of the microstructural properties, while compressive and pullout strength were only correlated to BVF, SMI, and TbSp. The microstructure of synthetic bone differed from cadaveric bone as SMI and TbTh showed little variation across the densities tested. Therefore, SMI and TbTh were the only microstructural properties that did not show correlations to the mechanical properties tested in synthetic bone. This study helps identify key microstructure–property relationships in cadaveric and synthetic bone as well as illustrate the similarities and differences between cadaveric and synthetic bone as biomechanical test materials.     

Micromechanical modeling of elastic properties of cortical bone accounting for anisotropy of dense tissue

The paper analyzes the connection between microstructure of the osteonal cortical bone and its overall elastic properties. The existing models either neglect anisotropy of the dense tissue or simplify cortical bone microstructure (accounting for Haversian canals only). These simplifications (related mostly to insufficient mathematical apparatus) complicate quantitative analysis of the effect of microstructural changes – produced by age, microgravity, or some diseases – on the overall mechanical performance of cortical bone. The present analysis fills this gap; it accounts for anisotropy of the dense tissue and uses realistic model of the porous microstructure. The approach is based on recent results of Sevostianov et al. (2005) and Saadat et al. (2012) on inhomogeneities in a transversely-isotropic material. Bone?s microstructure is modeled according to books of Martin and Burr (1989), Currey (2002), and Fung (1993) and includes four main families of pores. The calculated elastic constants for porous cortical bone are in agreement with available experimental data. The influence of each of the pore types on the overall moduli is examined.     

Nonlinear hierarchical multiscale modeling of cortical bone considering its nanoscale microstructure

We have used a hierarchical multiscale modeling scheme for the analysis of cortical bone considering it as a nanocomposite. This scheme consists of definition of two boundary value problems, one for macroscale, and another for microscale. The coupling between these scales is done by using the homogenization technique. At every material point in which the constitutive model is needed, a microscale boundary value problem is defined using a macroscopic kinematical quantity and solved. Using the described scheme, we have studied elastic properties of cortical bone considering its nanoscale microstructural constituents with various mineral volume fractions. Since the microstructure of bone consists of mineral platelet with nanometer size embedded in a protein matrix, it is similar to the microstructure of soft matrix nanocomposites reinforced with hard nanostructures. Considering a representative volume element (RVE) of the microstructure of bone as the microscale problem in our hierarchical multiscale modeling scheme, the global behavior of bone is obtained under various macroscopic loading conditions. This scheme may be suitable for modeling arbitrary bone geometries subjected to a variety of loading conditions. Using the presented method, mechanical properties of cortical bone including elastic moduli and Poisson's ratios in two major directions and shear modulus is obtained for different mineral volume fractions.     

Bone microarchitecture at muscle attachment sites: The relationship between macroscopic scores of entheses and their cortical and trabecular microstructural design

The studies of entheses in bioarchaeology attempted to reconstruct the habitual physical activities of past populations. However, the studies of microarchitecture of the underlying bone are still lacking despite well‐known potential of bone internal microarchitecture to reflect mechanical loading. It is unknown whether different morphological expressions of entheseal changes (ECs) correlate with the microstructural characteristics of the underlining bone. This study analyzed bone microstructural characteristics at the entheses. Our focus was on examining the possible successive nature of the three‐stage scale of entheseal macroscopic changes by comparing EC scores with the microarchitectural features at the attachment sites. The study was based on the hypothesis that mechanical loading influences the microarchitecture of the bone at the attachment site. The bone samples were taken from 24 adult male skeletons from medieval cemeteries in Serbia, with different macroscopic expression score of EC. We evaluated the macroscopic and microscopic appearance of four entheses of the lower limbs (origin of the soleus muscle and the insertions of the adductor magnus, gluteus maximus, and iliopsoas muscles). The specimens were scanned using microcomputed tomography (Scanco µCT 40). Our data showed a lack of consistent correlation between stages of the macroscopic scoring systems with microarchitecture at the entheses, only cortical thickness was significantly different between EC stages. Analyzing relationship between trabecular and cortical bone microstructure we found correlations between cortical and trabecular variables only in Stage C. Results of our study suggest that macroscopic EC might not represent distinct successive phases in bone adaptation to mechanical loading. Am J Phys Anthropol 157:81–93, 2015. © 2014 Wiley Periodicals, Inc.     

Analysis of microstructural and mechanical alterations of trabecular bone in a simulated three-dimensional remodeling process

Bone remodeling is a complex dynamic process, which modulates both bone mass and bone microstructure. In addition to bone mass, bone microstructure is an important contributor to bone quality in osteoporosis and fragility fractures. However, the quantitative knowledge of evolution of three-dimensional (3D) trabecular microstructure in adaptation to the external forces is currently limited. In this study, a new 3D simulation method of remodeling of human trabecular bone was developed to quantitatively study the dynamic evolution of bone mass and trabecular microstructure in response to different external loading conditions. The morphological features of trabecular plate and rod, such as thickness and number density in different orientations were monitored during the remodeling process using a novel imaging analysis technique, namely Individual Trabecula Segmentation (ITS). We showed that the volume fraction and microstructures of trabecular bone including, trabecular type and orientation, were determined by the applied mechanical load. Particularly, the morphological parameters of trabecular plates were more sensitive to the applied load, indicating that they played the major role in the mechanical properties of the trabecular bone. Reducing the applied load caused severe microstructural deteriorations of trabecular bone, such as trabecular plate perforation, rod breakage, and a conversion from plates to rods.     

Bone microstructure and developmental plasticity in birds and other dinosaurs

Patterns of bone microstructure have frequently been used to deduce dynamics and processes of growth in extant and fossil tetrapods. Often, the various types of primary bone tissue have been associated with different bone deposition rates and more recently such deductions have extended to patterns observed in dinosaur bone microstructure. These previous studies are challenged by the findings of the current research, which integrates an experimental neontological approach and a paleontological comparison. We use tetracycline labeling and morphometry to study the variability of bone deposition rates in Japanese quail (Coturnix japonica) growing under different experimental conditions. We compare resulting patterns in bone microstructure with those found in fossil birds and other dinosaurs. We found that a single type of primary bone varies significantly in rates of growth in response to environmental conditions. Ranging between 10-50 microm per day, rates of growth overlap with the full range of bone deposition rates that were previously associated with different patterns of bone histology. Bone formation rate was significantly affected by environmental/experimental conditions, skeletal element, and age. In the quail, the experimental conditions did not result in formation of lines of arrested growth (LAGs). Because of the observed variation of bone deposition rates in response to variation in environmental conditions, we conclude that bone deposition rates measured in extant birds cannot simply be extrapolated to their fossil relatives. Additionally, we observe the variable incidence of LAGs and annuli among several dinosaur species, including fossil birds, extant sauropsids, as well as nonmammalian synapsids, and some extant mammals. This suggests that the ancestral condition of the response of bone to environmental conditions was variable. We propose that such developmental plasticity in modern birds may be reduced in association with the shortened developmental time during the later evolution of the ornithurine birds.     

Mimetization of the elastic properties of cancellous bone via a parameterized cellular material

Bone tissue mechanical properties and trabecular microarchitecture are the main factors that determine the biomechanical properties of cancellous bone. Artificial cancellous microstructures, typically described by a reduced number of geometrical parameters, can be designed to obtain a mechanical behavior mimicking that of natural bone. In this work, we assess the ability of the parameterized microstructure introduced by Kowalczyk (Comput Methods Biomech Biomed Eng 9:135–147, 2006. doi: 10.1080/10255840600751473) to mimic the elastic response of cancellous bone. Artificial microstructures are compared with actual bone samples in terms of elasticity matrices and their symmetry classes. The capability of the parameterized microstructure to combine the dominant isotropic, hexagonal, tetragonal and orthorhombic symmetry classes in the proportions present in the cancellous bone is shown. Based on this finding, two optimization approaches are devised to find the geometrical parameters of the artificial microstructure that better mimics the elastic response of a target natural bone specimen: a Sequential Quadratic Programming algorithm that minimizes the norm of the difference between the elasticity matrices, and a Pattern Search algorithm that minimizes the difference between the symmetry class decompositions. The pattern search approach is found to produce the best results. The performance of the method is demonstrated via analyses for 146 bone samples.     

Simulation of creep in non-homogenous samples of human cortical bone

Characterising the mechanisms causing viscoelastic mechanical properties of human cortical bone, as well as understanding sources of variation, is important in predicting response of the bone to creep and fatigue loads. Any better understanding, when incorporated into simulations including finite element analysis, would assist bioengineers, clinicians and biomedical scientists. In this study, we used an empirically verified model of creep strain accumulation, in a simulation of 10 non-homogeneous samples, which were created from micro-CT scans of human cortical bone of the femur midshaft obtained from a 74-year-old female cadaver. These non-homogeneous samples incorporate the presence of Haversian canals and resorption cavities. The influence of inhomogeneity on the response and variation in the samples in both creep and stress relaxation tests are examined. The relationship between steady-state creep rate, applied loads (stress relaxation and creep tests) and microstructure, that is bone apparent porosity, is obtained. These relations may provide insight into damage accumulation of whole human bones and be relevant to studies on osteoporosis.     

Combined Effects of Fluoride and Cadmium on Liver and Kidney Function in Male Rats

Although cadmium (Cd) and fluoride may both have adverse effects on bone, most studies focus on a single agent. In this study, we investigated the effects of cadmium and fluoride on bone at a relative low level. Sprague–Dawley male rats were assigned randomly into four groups which were given sodium chloride, cadmium (50mg/L), and fluoride (20mg/L) alone, or in combination via drinking water. At the 12th week, urine, blood, and bone tissues were collected for biomarker assay, biomechanical assay, and histological assay. Cadmium had significantly adverse effects on bone mineral density, bone biomechanical property, and bone microstructure. Fluoride slightly increased vertebral bone mineral density but negatively affected bone biomechanical property and bone microstructure. Fluoride could reverse the decrease of vertebral bone mineral density caused by cadmium but could not improve the damage of bone biomechanical property and microstructure caused by cadmium. Tartrate-resistant acid phosphatase 5b levels in rats treated with cadmium and fluoride or in combination were 1–2.5 folds higher than the control. Our data suggest that low level of fluoride could reverse the decrease of vertebral bone mineral density caused by cadmium exposure but has no influence on appendicular skeleton damage caused by cadmium.     

Simulation of creep in non-homogenous samples of human cortical bone

Characterising the mechanisms causing viscoelastic mechanical properties of human cortical bone, as well as understanding sources of variation, is important in predicting response of the bone to creep and fatigue loads. Any better understanding, when incorporated into simulations including finite element analysis, would assist bioengineers, clinicians and biomedical scientists. In this study, we used an empirically verified model of creep strain accumulation, in a simulation of 10 non-homogeneous samples, which were created from micro-CT scans of human cortical bone of the femur midshaft obtained from a 74-year-old female cadaver. These non-homogeneous samples incorporate the presence of Haversian canals and resorption cavities. The influence of inhomogeneity on the response and variation in the samples in both creep and stress relaxation tests are examined. The relationship between steady-state creep rate, applied loads (stress relaxation and creep tests) and microstructure, that is bone apparent porosity, is obtained. These relations may provide insight into damage accumulation of whole human bones and be relevant to studies on osteoporosis.     

Homogenization theory and digital imaging: A basis for studying the mechanics and design principles of bone tissue

Bone tissue is a complex multilevel composite which has the ability to sense ad respond to its mechanical environment. It is believed that bone cells called osteocytes within the bone matrix sense the mechanical environment and determine whether structural alterations are needed. At present it is not known, however, how loads are transferred from the whole bone level to cells. A computational procedure combining representative volume element (RVE) based homogenization theory with digital imaging is proposed to estimate strains at various levels of bone structure. Bone tissue structural organization and RVE based analysis are briefly reviewed. The digital image based computational procedure was applied to estimate strains in individual trabeculae (first-level microstructure). Homogenization analysis of an idealized model was used to estimate strains at one level of bone structure around osteocyte lacunae (second-level trabecular microstructure). The results showed that strain at one level of bone structure is amplified to a broad range at the next microstructural level. In one case, a zeor-level tensile principal strain of 495 muE engendered strains ranging between -1000 and 7000 muE in individual trabeculae (first-level microstructure). Subsequently, a first-level tensile principal strains of 1325 muE within an inidividual trabecula engendered strains ranging between 782 and 2530 muE around osteocyte lacunae. Lacunar orientation was found to influence strains around osteocyte lacunae much more than lacunar ellipticity. In conclusion, the computational procedure combining homogenization theory with digital imaging can proveide estimates of cell level strains within whole bones. Such results may be used to bridge experimental studies of bone adaptation at the whole bone and cell culture level. (c) 1994 John Wiley & Sons, Inc.     

Long bone microstructure gives new insights into the life of pachypleurosaurids from the Middle Triassic of Monte San Giorgio,Switzerland/Italy

The long bone microstructure of four pachypleurosaurid taxa from Monte San Giorgio (Switzerland/Italy) was studied. Pachypleurosaurids are secondarily aquatic reptiles that lived during the Middle Triassic in varying marine environments of the Tethys. All four pachypleurosaurids show high compactness values in their long bones based on a thick cortex and a calcified cartilaginous core, which remains in the medullary region throughout the ontogeny. Parts or even the entire embryonic bone layer composed of a mixture of woven-fibered bone tissue and parallel-fibered bone tissue is preserved in both pachypleurosaurid genera. The rest of the cortex consists of lamellar-zonal bone tissue type. Differences in the microstructure of the bones between the pachypleurosaurids are reflected in the occurrence of remodelling processes, which, if present, affect the innermost growth marks of the cortex or the calcified cartilaginous core. Further variation is present in the spacing pattern of the growth cycles, as well as in the degree of vascularisation of the lamellar-zonal bone tissue type. Our data on the microstructure of the long bones support previous studies on morphology and facies distribution, which indicated different habitats and adaptation to a secondary aquatic lifestyle for each pachypleurosaurid taxon. Life history data furthermore reflect different longevities and ages at sexual maturity. The bone histological data of the stratigraphically youngest and oldest pachypleurosaurid species might indicate possible climate-dependant reproductive seasons similar to Recent lacertilian squamates.     

镉染毒大鼠胫骨骨微结构的活体Micro-CT观察

目的应用Micro-CT研究不同剂量CdCl2染毒后大鼠胫骨松质骨骨小梁密度和骨微结构的差异。方法 24只3月龄雄性SD大鼠随机分成4组,对照组、低剂量组、中剂量组和高剂量组,分别背部皮下注射生理盐水(0.5 mL)和0.1、0.5、1.5 mg/(kg.bw)CdCl2,每周称体重,并根据体重调整注射量。染毒后第8周对所有大鼠左侧胫骨近端进行活体Micro-CT扫描及三维重建。选取距生长板远端0.8、1.2 mm厚的骨组织为感兴趣区域,进行骨形态计量分析。结果镉染毒组大鼠体重和对照组相比有不同程度下降,高剂量组和其他组相比差异有显著性(P<0.05);镉染毒组大鼠骨密度、骨体积分数及骨小梁数量较对照组明显减少,高剂量组与对照组相比差异有显著性(P<0.01);镉染毒组大鼠胫骨骨小梁分离度及骨结构模型指数都较对照组有明显增高,并且随着染毒剂量的增加而升高。二维及三维图象显示,镉作用后大鼠胫骨骨髓腔增宽,骨量、骨小梁数量及骨小梁连接明显减少,板状骨数量减少,杆状骨数量增加。结论镉染毒对大鼠胫骨骨量及骨微观结构有明显损害。