Apparent Bone Density Research Articles

Tibial subchondral trabecular volumetric bone density in medial knee joint osteoarthritis using peripheral quantitative computed tomography technology

Knee osteoarthritis (OA) is an organ-level failure of the joint involving pathologic changes in articular cartilage and bone. This cross-sectional study compared apparent volumetric bone mineral density (vBMD) of proximal tibial subchondral trabecular bone in people with and without knee OA, using peripheral quantitative computed tomography (pQCT). Seventy-five individuals with mild or moderate medial compartment knee OA and 41 asymptomatic controls were recruited. Peripheral QCT was used to measure vBMD of trabecular bone beneath medial and lateral tibiofemoral compartments at levels of 2% and 4% of tibial length, distal to the tibial plateau. There was no significant difference in vBMD beneath the overall medial and lateral compartments between the 3 groups. However, in the affected medial compartment of those with moderate OA, lower vBMD was seen in the 2 posterior subregions compared with controls and those with mild knee OA, while higher vBMD was seen in the anteromedial subregion. Beneath the unaffected or lesser affected lateral compartment, significantly lower vBMD was seen at the 2% level in the anterior and lateral subregions of those with moderate disease. Volumetric BMD ratios showed relatively higher vBMD in the medial compartment compared with the lateral compartment, but these ratios were not influenced by disease status. Subregional vBMD changes were evident beneath the medial and lateral compartments of those with moderate medial knee OA. Of import, the posterior subchondral trabecular regions of the medial tibial plateau have markedly lower vBMD.

Apparent density patterns in subchondral bone of the sloth and anteater forelimb

Vertebrate morphologists often are interested in inferring limb-loading patterns in animals characterized by different locomotor repertoires. Because bone apparent density (i.e. mass per unit volume of bone inclusive of porosities) is a determinant of compressive strength, and thus indicative of compressive loading, recent comparative studies in primates have proposed a structure-function relationship between apparent density of subchondral bone and locomotor behaviours that vary in compressive loading. If such patterns are found in other mammals, then these relationships would be strengthened further. Here, we examine the distal radius of suspensory sloths that generally load their forelimbs (FLs) in tension and of quadrupedal anteaters that generally load their FLs in compression. Computed tomography osteoabsorptiometry was used to visualize the patterns in subchondral apparent density. Suspensory sloths exhibit relatively smaller areas of high apparent density than quadrupedal anteaters. This locomotor-based pattern is analogous to the pattern observed in suspensory and quadrupedal primates. Similarity between xenarthran and primate trends suggests broad-scale applicability for analysing subchondral bone apparent density and supports the idea that bone functionally alters its material properties in response to locomotor behaviours.

Dependencies of Ultrasonic Properties on Apparent Bone Density in Trabecular Bone

The present study aims to provide insight into the dependencies of ultrasonic properties, such as speed of sound (SOS), broadband ultrasonic attenuation (BUA), and integrated reflection coefficient (IRC), on apparent bone density in trabecular bone. SOS, BUA, and IRC were measured in 19 bovine trabecular bone specimens with apparent densities from 0.411 to 0.928 g/cm3, using a matched pair of transducers with a diameter of 12.7 mm and a center frequency of 1.0 MHz. They were also compared with the predictions obtained from the modified Biot–Attenborough (MBA) model for propagation in fluid-saturated porous media.

RELATIONS OF ANISOTROPIC ELASTIC MODULI TO DENSITY AND CT NUMBER IN BOVINE CORTICAL BONE

It would be useful to be able to determine the mechanical properties of bone using a noninvasive technique such as computed tomography (CT). However, in contrast to cancellous bone tissue, quantifying the elastic modulus of cortical bone from bone density and CT number has not been investigated extensively. This study measured the elastic moduli of cortical bone from eight bovine femora in the longitudinal, circumferential, and radial directions using mechanical compressive testing. Before testing, the CT number and wet apparent bone density were obtained. The experimentally determined coefficient of determination between CT number and bone density was around 0.6. Bone density was a good predictor of the elastic modulus of cortical bone in the longitudinal direction (r2 > 0.79), but it could not be used to predict the elastic moduli in the circumferential (r2 < 0.4) and radial (r2 < 0.22) directions. The coefficient of determination between CT number and the elastic modulus in the longitudinal direction was higher than 0.41. However, the correlations between CT number and elastic moduli were weak in the circumferential (r2 < 0.21) and radial (r2 < 0.19) directions. Moreover, the elastic modulus was much higher in the longitudinal direction than the circumferential and radial directions, and hence cortical bone can be considered a transversely isotropic property.

A study of the viscoelastic effect in a bone remodeling model

The present paper addresses the following question can a simple regulatory bone remodeling model predict effects of viscosity on the trabecular morphology? For that, we propose an extension of a previous bone remodeling model by taking into account the viscosity properties of the tissue. Zener's law is used to describe the mechanical behavior of the bone and a specific law of the apparent bone density rate is proposed. Based on stability analysis, numerical simulations are then performed to investigate the viscosity role on simulations of the bone remodeling process. We show that the viscous contribution affects the evolution of the apparent bone density, by slowing down the adaptation process, which seems to be confirmed by simulations with real data obtained from rat tibia.

Knee Posture Predicted from Subchondral Apparent Density in the Distal Femur: An Experimental Validation

Spatial patterning in the apparent density of subchondral bone can be used to discriminate between species that differ in their joint loading conditions. This study provides an experimental test of two hypotheses that relate aspects of subchondral apparent density patterns to joint loading conditions. First, the region of maximum subchondral apparent density (RMD) will correspond to differences in joint posture at the time of peak locomotor loads; and second, differences in maximum density between individuals will correspond to differences in exercise level. These hypotheses were tested using three age-matched samples of juvenile sheep. Two groups of five sheep were exercised, at moderate walking speeds, twice daily for 45 days on a treadmill with either a 0% or 15% grade. The remaining sheep were not exercised. Sheep walking on the inclined treadmill used more flexed knee postures than those in the level walking group at the time of peak vertical ground reaction forces. Kinematic measurements of knee posture were compared with knee postures estimated from the spatial position of the RMD on the medial femoral condyle. Our results show that the difference in the position of the RMD between the incline and level walking groups corresponded to the difference in knee postures obtained kinematically; however, exercised and nonexercised sheep did not differ in the magnitude of apparent density. These results suggest that patterns of subchondral apparent density are good indicators of the experimental modifications in joint posture during locomotion and may, therefore, be used to investigate differences between species in habitual joint loading.

Influence of microarchitecture alterations on ultrasonic backscattering in an experimental simulation of bovine cancellous bone aging

An experimental model which can simulate physical changes that occur during aging was developed in order to evaluate the effects of change of mineral content and microstructure on ultrasonic properties of bovine cancellous bone. Timed immersion in hydrochloric acid was used to selectively alter the mineral content. Scanning electron microscopy and histological staining of the acid-treated trabeculae demonstrated a heterogeneous structure consisting of a mineralized core and a demineralized layer. The presence of organic matrix contributed very little to normalized broadband ultrasound attenuation (nBUA) and speed of sound. All three ultrasonic parameters, speed of sound, nBUA and backscatter coefficient, were sensitive to changes in apparent density of bovine cancellous bone. A two-component model utilizing a combination of two autocorrelation functions (a densely populated model and a spherical distribution) was used to approximate the backscatter coefficient. The predicted attenuation due to scattering constituted a significant part of the measured total attenuation (due to both scattering and absorption mechanisms) for bovine cancellous bone. Linear regression, performed between trabecular thickness values and estimated from the model correlation lengths, showed significant linear correlation, with R(2)=0.81 before and R(2)=0.80 after demineralization. The accuracy of estimation was found to increase with trabecular thickness.

Addition of a short central extension to surface cemented tibial trays in primary TKA: An in vitro study of the effect on initial fixation stability and its relationship to supporting bone density

Background Short central extensions which do not enter the tibial medullary canal are incorporated to cemented tibial components to increase initial stability in primary total knee arthroplasty. Their role in tibiae of differing preoperative mechanical quality has been little studied. Methods Twelve embalmed cadaveric tibiae were paired and divided into two groups, receiving a similar cemented tibial component with or without a non-cemented short central extension (10 mm diameter, 35 mm length). The specimens were subjected to 6000 cycles of a medially applied 1350 N load. Relative bone–tray displacements were measured and the evolution of inducible and permanent micromotions were computed. The apparent density of the cancellous bone under the tibial tray and at the area to support the extension was computed from computed tomography images of each specimen. Findings No significant differences between groups were detected for any parameters. For the group with extension, a significant negative linear correlation ( P = 0.009, r 2 = 0.849) was found between the inducible tilt of the tray and the bone density at the zone of the extension. Also a trend towards a negative linear relation ( P = 0.07, r 2 = 0.59) was observed for the same group between maximum subsidence and apparent density at the zone of the extension. Interpretation The study did not find that the addition of a non-cemented short central extension provides any overall improvement of the initial fixation stability. However, it was found that short extensions may enhance tilting stiffness of the bone–implant construct if bone of sufficient mechanical quality is located around its supporting area.

Orthogonal Properties of Human Trabecular Bone by Spherical Indentation Test

The elastic modulus and the apparent density of the trabecular bone were evaluated from spherical indentation tests and Computed Tomography and their relationship was quantified. After the femurs were prepared and embedded with respect to their anatomical orientation, the transverse planes of the trabecular bone specimens were scanned at 1mm intervals using a CT scanner. The metaphyseal regions were sectioned with a diamond-blade saw, producing 8mm cubes. Using a custom-made spherical indentation tester, the cubes were mechanically tested in the anteriorposterior (AP), medial-lateral (ML), and inferior-superior (IS) directions. After determination of modulus from the mechanical testing, the apparent densities of the specimens were measured. The results showed that the IS modulus was significantly greater than both the AP and ML moduli with the AP modulus greater than the ML modulus. This demonstrated that orthogonality was a structural characteristic of the trabecular bone. The power relationship between the modulus and the apparent density was also found to be statistically significant.

The response of bone, articular cartilage and tendon to exercise in the horse

Horses can gallop within hours of birth, and may begin training for athletic competition while still growing. This review cites studies on the effects of exercise on bone, tendon and articular cartilage, as detected by clinical and research imaging techniques, tissue biochemical analysis and microscopy of various kinds. For bone, alterations in bone mineral content, mineral density and the morphology of the mineralized tissue are the most common end-points. Apparent bone density increases slightly after athletic training in the cortex, but substantially in the major load paths of the epiphyses and cuboidal bones, despite the lower material density of the new bone, which is deposited subperiosteally and on internal surfaces without prior osteoclastic resorption. With training of greater intensity, adaptive change is supervened by patho-anatomical change in the form of microdamage and frank lesions. In tendon, collagen fibril diameter distribution changes significantly during growth, but not after early training. The exact amount and type of protracted training that does cause reduction in mass average diameter (an early sign of progressive microdamage) have not been defined. Training is associated with an increase in the cross-sectional area of some tendons, possibly owing to slightly greater water content of non-collagenous or newly synthesized matrix. Early training may be associated with greater thickness of hyaline but not calcified articular cartilage, at least in some sites. The age at which adaptation of cartilage to biomechanical influences can occur may thus extend beyond very early life. However, cartilage appears to be the most susceptible of the three tissues to pathological alteration. The effect of training exercise on the anatomical or patho-anatomical features of connective tissue structures is affected by the timing, type and amount of natural or imposed exercise during growth and development which precedes the training.

Un modèle viscoélastique de remodelage osseux : approche unidimensionnelle

A bone remodeling model taking into account the viscoelastic properties of the material is proposed. The nonlinear equations governing the evolution of the bone apparent density are solved by a finite difference method in the unidimensional case of a n-unit elements model. The results show the effects of the viscous damping on the structure for a controlled mechanical loading. To cite this article: S. Baïotto, M. Zidi, C. R. Mecanique 332 (2004).

Osteoarthritis and osteoporosis: clinical and research evidence of inverse relationship.

The etiology of osteoporosis (OP) and osteoarthritis (OA) is multifactorial: both constitutional and environmental factors, ranging from genetic susceptibility, endocrine and metabolic status, to mechanical and traumatic injury, are thought to be involved. When interpreting research data, one must bear in mind that pathophysiologic factors, especially in disorders associated with aging, must be regarded as either primary or secondary. Therefore, findings in end-stage pathology are not necessarily the evidence or explanation of the primary cause or event in the diseased tissue. Both aspects of research are important for potentially curative or preventive measures. These considerations, in the case of our topic--the inverse relationship of OP and OA--are of particular importance. Although the inverse relationship between two frequent diseases associated with aging, OA and OP, has been observed and studied for more than 30 years, the topic remains controversial for some and stimulating for many. The anthropometric differences of patients suffering from OA compared with OP are well established. OA cases have stronger body build and are more obese. There is overwhelming evidence that OA cases have increased BMD or BMC at all sites. This increased BMD is related to high peak bone mass, as shown in mother-daughter and twin studies. With aging, the bone loss in OA is lower, except when measured near an affected joint (hand, hip, knee). The lower degree of bone loss with aging is explained by lower bone turnover as measured by bone resorption-formation parameters. OA cases not only have higher apparent and real bone density, but also wider geometrical measures of the skeleton, diameters of long bones and trabeculae, both contributing positively to better strength and fewer fragility fractures. Not only is bone quantity in OA different but also bone quality, compared with controls and OP cases, with increased content of growth factors such as IGF and TGFbeta, factors required for bone repair. Furthermore, in vitro studies of osteoblasts recruited from OA bone have different differentiation patterns and phenotypes. These general bone characteristics of OA bone may explain the inverse relationship OA-OP and why OA cases have fewer fragility fractures. The role of bone, in particular subchondral bone, in the pathophysiology, initiation and progression of OA is not fully elucidated and is still controversial. In 1970, it was hypothesized that an increased number of microfractures lead to an increase in subchondral bone stiffness, which impairs its ability to act as a shock absorber, so that cartilage suffers more. Although subchondral bone is slightly hypomineralized because of local increased turnover, the increase in trabecular number and volume compensates for this, resulting in a stiffer structure. There is also some experimental evidence that osteoblasts themselves release factors such as metalloproteinases directly or indirectly from the matrix, which predispose cartilage to deterioration. Instead, the osteoblast regenerative capacity of bone in OP is compromised compared with OA, as suggested by early cell adhesion differences. The proposition that drugs which suppress bone turnover in OP, such as bisphosphonates, may be beneficial for OA is speculative. Although bone turnover in the subchondral region of established OA is increased, the general bone turnover is reduced. Further reduction of bone turnover, however, may lead to overmineralized (aged) osteons and loss of bone quality, resulting in increased fragility.

Les outils d'investigation du système squelettique: Informations quantitatives et qualitatives, intérêt dans le suivi des sportifs

When investigating physical activity and bone health, there is a surge of interest in the various imaging techniques as bone strength is influenced by the type of bone present, its size and shape, as well as the amount of mineral. Bone has many interesting attributes that need to be measured in order to preserve or reestablish its functions. Consequently, to study bone, investigators need to measure its complex properties. Bone anatomy and caracteristics can be studied using different forms of imaging, such as dual energy X-ray absorptiometry (DXA), quantitative ultrasound (QUS), quantitative computerized tomography (QCT) and peripheral QCT (pQCT). DXA is the most common measure of bone mineral content (BMC, g) and Bone Mineral Density (BMD, g/cm 2). The modality of QUS is said to reflect bone microarchitecture. QCT measures apparent volumetric density of trabecular or cortical bone, and QCTp permits evaluation of the peripheral squeleton. Eventually, bone biochemical markers provide information about bone metabolism. Imaging plays an important clinical role, for example, in predicting fracture risk. Bone measurements related to fracture risk include bone mineral content and density, cortical thickness, trabecular structure and its external geometry.

Increased femoral neck cancellous bone and connectivity in coxarthrosis (hip osteoarthritis)

Patients with coxarthrosis (cOA) have a reduced incidence of intracapsular femoral neck fracture, suggesting that cOA offers protection. The distribution of bone in the femoral neck was compared in cases of coxarthrosis and postmortem controls to assess the possibility that disease-associated changes might contribute to reduced fragility. Whole cross-section femoral neck biopsies were obtained from 17 patients with cOA and 22 age- and sex-matched cadaveric controls. Densitometry was performed using peripheral quantitated computed tomography (pQCT) and histomorphometry on 10-μm plastic-embedded sections. Cortical bone mass was not different between cases and controls ( P > 0.23), but cancellous bone mass was increased by 75% in cOA ( P = 0.014) and histomorphometric cancellous bone area by 71% ( P < 0.0001). This was principally the result of an increase of apparent density (mass/vol) of cancellous bone (+45%, P = 0.001). Whereas cortical porosity was increased in the cases ( P < 0.0001), trabecular width was also increased overall in the cases by 52% ( P < 0.001), as was cancellous connectivity measured by strut analysis ( P < 0.01). Where osteophytic bone was present ( n = 9) there was a positive relationship between the amount of osteophyte and the percentage of cancellous area ( P < 0.05). Since cancellous bone buttresses and stiffens the cortex so reducing the risk of buckling, the increased cancellous bone mass and connectivity seen in cases of cOA probably explain, at least in part, the ability of patients with cOA to resist intracapsular fracture of the femoral neck during a fall.

A unified model for the speed of sound in cranial bone based on genetic algorithm optimization

The density and structure of bone is highly heterogeneous, causing wide variations in the reported speed of sound for ultrasound propagation. Current research on the propagation of high intensity focused ultrasound through an intact human skull for non-invasive therapeutic action on brain tissue requires a detailed model for the acoustic velocity in cranial bone. Such models have been difficult to derive empirically due to the aforementioned heterogeneity of bone itself.We propose a single unified model for the speed of sound in cranial bone based upon the apparent density of bone by CT scan. This model is based upon the coupling of empirical measurement, theoretical acoustic simulation and genetic algorithm optimization. The phase distortion caused by the presence of skull in an acoustic path is empirically measured. The ability of a theoretical acoustic simulation coupled with a particular speed-of-sound model to predict this phase distortion is compared against the empirical data, thus providing the fitness function needed to perform genetic algorithm optimization. By performing genetic algorithm optimization over an initial population of candidate speed-of-sound models, an ultimate single unified model for the speed of sound in both the cortical and trabecular regions of cranial bone is produced.The final model produced by genetic algorithm optimization has a nonlinear dependency of speed of sound upon local bone density. This model is shown by statistical significance to be a suitable model of the speed of sound in bone. Furthermore, using a skull that was not part of the optimization process, this model is also tested against a published homogeneous speed-of-sound model and shown to return an improved prediction of transcranial ultrasound propagation.

Acoustic properties of bovine cancellous bone from 0.5 to 1.5 MHz

Most previous studies using ultrasound for the diagnosis of osteoporosis have employed ultrasound in the frequency range from 0.2 to 1 MHz. Acoustic properties of 14 defatted bovine cancellous bone specimens were investigated in vitro. Speed of sound (SOS) and broadband ultrasonic attenuation (BUA) were measured using two matched pairs of transducers with the center frequencies of 1 and 2.25 MHz, respectively, in order to cover a broad frequency range from 0.5 to 1.5 MHz. In this frequency range, SOS and BUA show significant linear positive correlations with apparent bone density. These results suggest that the frequency range from 0.5 to 1.5 MHz may also be useful in the diagnosis of osteoporosis. [Work supported by BK21 Program, KRF (KRF-2000-015-DP0718), and KOSEF (KOSEF-2000-0238-100) in Korea.] a)For (Biomedical Ultrasound/Bioresponse to Vibration) Best Student Paper Award.

Body composition, bone mass and microstructural analysis in GH-transgenic mice reveals that skeletal changes are specific to bone compartment and gender.

Experimental and clinical studies suggest that high serum levels of growth hormone (GH) increase cortical but not trabecular bone. We studied body composition and bone structure in transgenic mice (MT-bGH) with systemic overexpression of GH. Body composition was examined with dual-energy X-ray absorptiometry (DXA), ashing, and chemical analysis, and the femora with DXA and micro computerized tomography. The absolute fat and bone tissue contents were significantly higher in GH transgenic mice vs controls (P < or = 0.05), but no significant difference was noted when normalizing the values to body weight. Male transgenics displayed no change in apparent (volumetric) femoral bone density, relative cortical area and trabecular bone volume fraction. Female transgenic mice demonstrated an increase in apparent femoral density and in trabecular bone volume fraction (+130%; P < or = 0.01). The mineralized tissue matrix density was decreased in male and female transgenic mice (P < or = 0.05). The results show that chronic GH excess affects trabecular bone in a gender-specific manner and that bone changes depend on the compartment investigated.

Ultrasonic wave propagation in trabecular bone predicted by the stratified model.

The objective of this study was to investigate ultrasound propagation in trabecular bone by considering the wave reflection and transmission in a multilayered medium. The use of ultrasound to identify those at risk of osteoporosis is a promising diagnostic method providing a measure of bone mineral density (BMD). A stratified model was proposed to study the effect of transmission and reflection of ultrasound wave within the trabecular architecture on the relationship between ultrasound and BMD. The results demonstrated that ultrasound velocity in trabecular bone was highly correlated with the bone apparent density (r=0.97). Moreover, a consistent pattern of the frequency dependence of ultrasound attenuation coefficient has been observed between simulation using this model and experimental measurement of trabecular bone. The normalized broadband ultrasound attenuation (nBUA) derived from the simulation results revealed that nBUA was nonlinear with respect to trabecular porosity and BMD. The curve of the relationship between nBUA and BMD was parabolic in shape, and the peak magnitude of nBUA was observed at approximately 60% of bone porosity. These results agreed with the published experimental data and demonstrated that according to the stratified model, reflection and transmission were important factors in the ultrasonic propagation through the trabecular bone.

Prediction of mechanical behaviors at interfaces between bone and two interbody cages of lumbar spine segments.

The effects of mechanical parameters at bone-implant interfaces of the lumbar spine segments were investigated under various combined loadings using the finite element method. To investigate the mechanical behaviors at bone-cage interfaces of lumbar spine segments with two interbody cages (two thread inserts). It is known that among many factors, relative micromotion at bone-implant interfaces can hinder bone growth into the surface pores of an implant. Loading conditions, mechanical properties of the materials, friction coefficients at the interfaces, and geometry of spinal segments would affect relative micromotion and spinal stability. In particular, relative micromotion is related closely to friction at bone-implant interfaces after arthroplasty. A finite element model of human L3-L4 lumbar segments with two titanium interbody cages was constructed. This finite element model was used to investigate mechanical behavior at the bone-cage interface. Relative micromotion (slip distance on the contact surfaces), posterior axial displacement, and stress were predicted for changes of friction coefficients, loading conditions, and age-related material-geometric properties of the spinal segments. Relative micromotion (slip distance) at the interfaces was obvious at their edges under axial compression. The slip occurred primarily at the anterior edges under torsion with preload, whereas it occurred primarily at the edges of the left cage under lateral bending with preload. Relative micromotion at the interfaces increased significantly as the apparent density of cancellous bone or the friction coefficient of the interfaces decreased. A significant increase in slip distance at the anterior anulus occurred with an addition of torsion to the compressive preload. Relative micromotion is sensitive to the friction coefficient of the interfaces, the bone density, and the loading conditions. A reduction in age-related bone density is less likely to allow bone growth into surface pores of the cage. However, it is likely that the larger the disc area or pedicle diameter, the more stable the interbody fusion of the spinal segments.

Visualization and analysis of trabecular bone architecture in the limited spatial resolution regime of in vivo micro-MRI.

There is substantial evidence that besides the volume fraction of the bone (often quantified in terms of apparent bone density) the three-dimensional arrangement of the trabecular network is a major determinant of elastic modulus1-5and ultimate strength.6-8 KeywordsTrabecular BoneDistal RadiusTrabecular StructureBone Volume FractionTrabecular Bone StructureThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.