Validation of a novel microradiography device for characterization of bone mineralization

International audienceIn order to simplify bone mineralization measurements, a system using radiographic films has been updated with a digital detector. The objective of this paper was to validate this new device. Technologies and physical phenomena involved in both systems (radiographic films and digital detector) are different. The methodology used to compare the two systems was based on image quality and assessed on two main parameters: contrast to noise ratio and spatial resolution. Results showed that the contrast to noise ratio was similar between the two systems, provided that acquisition parameters were optimized. With regard to spatial resolution, a magnification factor of at least 4 or more was required to achieve the same resolution as films. A final validation was also shown on a real image of a bone sample. The results showed that both systems have similar image quality performances, and the system using digital detector has several advantages (easier to use than films, no consumables and faster acquisition time)

High resolution pQCT micro architectureal parameters to predict bone failure in the case of forward fall

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3D analysis of the osteonal and interstitial tissue in human radii cortical bone

International audienceHuman cortical bone has a complex hierarchical structure that is periodically remodelled throughout a lifetime. This microstructure dictates the mechanical response of the tissue under a critical load. If only some structural features, such as the different porosities observed in bone, are primarily studied, then investigations may not fully consider the osteonal systems in three-dimensions (3D). Currently, it is difficult to differentiate osteons from interstitial tissue using standard 3D characterization methods. Synchrotron radiation micro-computed tomography (SR-μCT) in the phase contrast mode is a promising method for the investigation of osteons. In the current study, SR-μCT imaging was performed on cortical bone samples harvested from eight human radii (female, 50–91 y.o.). The images were segmented to identify Haversian canals, osteocyte lacunae, micro-cracks, as well as osteons. The significant correlation between osteonal and Haversian canal volume fraction highlights the role of the canals as sites where bone remodelling is initiated. The results showed that osteocyte lacunae morphometric parameters depend on their distance to cement lines, strongly suggesting the evolution of biological activity from the beginning to the end of the remodelling process. Thus, the current study provides new data on 3D osteonal morphometric parameters and their relationships with other structural features in humans

Experiment on ex-vivo vertebrae for numeric model evaluation: bone metastasis cases

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Experiment on ex-vivo vertebrae for numeric model evaluation: bone metastasis cases

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Micromechanical behaviour of human cortical bone: elasticity is Related to mineral while plasticity is related to organic matrix

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Computed tomography, histological and ultrasonic measurements of adolescent scoliotic rib hump geometrical and material properties

International audienceIn Adolescent Idiopathic Scoliosis (AIS), numerical models can enhance orthopaedic or surgical treatments and provide reliable insights into the mechanism of progression. Computational methods require knowledge of relevant parameters, such as the specific geometrical or material properties of the AIS rib, about which there is currently a lack of information. The aim of our study was to determine the geometrical and material properties (Young's modulus [E ] and Poisson's ratio [νν]) for AIS rib bones. Twelve ribs extracted during gibbectomy on 15 and 17 year old girls were tested using computed tomography (CT) scanner, histology and ultrasonic scanner. The mean porosity (± standard deviation (SD)) is 1.35 (±0.52)% and the mean (±SD) bone mineral density is 2188 (±19) mmHA/cc. The cortical part of the AIS rib hump is found to be thicker than physiological values in the literature. To mimic the rib hump for an AIS girl, our results suggest that ribs should be modeled as hollow circular cylinders with a 10.40 (±1.02) mm external radius and 7.56 mm (±0.75) internal radius, and material properties with a mean E of 14.9 GPa (±2.6) and a mean νν of 0.26 (±0.08)

Determinants of microdamage in elderly human vertebral trabecular bone.

Previous studies have shown that microdamage accumulates in bone as a result of physiological loading and occurs naturally in human trabecular bone. The purpose of this study was to determine the factors associated with pre-existing microdamage in human vertebral trabecular bone, namely age, architecture, hardness, mineral and organic matrix. Trabecular bone cores were collected from human L2 vertebrae (n = 53) from donors 54-95 years of age (22 men and 30 women, 1 unknown) and previous cited parameters were evaluated. Collagen cross-link content (PYD, DPD, PEN and % of collagen) was measured on surrounding trabecular bone. We found that determinants of microdamage were mostly the age of donors, architecture, mineral characteristics and mature enzymatic cross-links. Moreover, linear microcracks were mostly associated with the bone matrix characteristics whereas diffuse damage was associated with architecture. We conclude that linear and diffuse types of microdamage seemed to have different determinants, with age being critical for both types

CORTICAL THICKNESS AND POROSITY ASSESSMENT USING GUIDED WAVES MEASURED BY AXIAL TRANSMISSION: AN EX VIVO STUDY

International audienceCortical loss has been shown to play a key role in fracture risk [1], but it still imperfectly assessed in vivo using X-ray imaging techniques. To overcome this limitation, quantitative ultrasound guided waves are developed for their potential to probe material and structural properties of cortical bone. The purpose of this study is to assess the feasibility of estimating both cortical thickness (Ct.Th, mm) and porosity (Ct.P, %) using ultrasonic guided waves and to contrast the obtained values with reference values derived from X-ray microcomputed tomography

Bone Micromechanical Properties Are Compromised During Long-Term Alendronate Therapy Independently of Mineralization

International audienceIn the treatment of postmenopausal osteoporosis (PMOP), the use of alendronate (ALN) leads to a decrease in the risk of vertebral and nonvertebral fractures. To explore the possible adverse effects of prolonged ALN therapy, we studied the effects of 8 AE 2 years (6– 10 years) of ALN treatment on the iliac cortical bone mineral and collagen quality and micromechanical properties; by design, our study examined these parameters, independent of the degree of mineralization. From six ALN-treated and five age-matched untreated PMOP women, 153 bone structural units have been chosen according their degree of mineralization to obtain the same distribution in each group. In those bone structural units, Fourier transform infrared spectroscopy, quantitative microradiography, and nanoindentation were used to assess bone quality. Irrespective of the degree of mineralization, ALN treatment was associated with higher collagen maturity (þ7%, p < 0.001, c.v. ¼ 13% and 16% in treated and untreated women, respectively) and lower mineral crystallinity than that observed in the untreated PMOP group (À2%, p < 0.0001, c.v. ¼ 3% in both groups). Bone matrix from ALN-treated women also had lower elastic modulus (À12%, p < 0.0001, c.v. ¼ 14% in both groups) and, contact hardness (À6%, p < 0.05, c.v. ¼ 14% in both groups) than that of untreated women. Crystallinity (which reflects the size and perfection of crystals) was associated with both elastic modulus and contact hardness in treated women exclusively (r ¼ 0.43 and r ¼ 0.54, p < 0.0001, respectively), even after adjustment for the amount of mineral. We infer that long-term ALN treatment compromises micromechanical properties of the bone matrix as assessed ex vivo. The strength deficits are in part related to difference in crystallinity, irrespective of the mineral amount and mineral maturity. These novel findings at local levels of bone structure will have to be taken into account in the study of the pathophysiology of bone fragilities associated with prolonged ALN treatment.