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)

Effet de la vitesse de déformation sur la ténacité d'os cortical de tibias humains

L'ostéoporose cause environ 25 000 fractures par jour en Europe. Les méthodes utilisées en clinique pour établir son diagnostic sont basées sur des mesures densitométriques. Cependant, les résultats obtenus à l'aide de cette technique ne sont pas assez discriminant, 50% des femmes ayant subi une fracture ostéoporotique ne sont pas diagnostiquées comme atteintes d'ostéoporose selon les mesures densitométriques. Dans le but d'améliorer les prédictions sur le risque de fracture, de nouvelles méthodes sont envisagées, notamment le développement de modèles numériques simulant le comportement mécanique de l'os face à la fracture. Les données utilisées dans ces simulations ont été déterminées à partir d'essais mécaniques sous chargement quasi-statique. Or une fracture ostéoporotique est généralement la conséquence d'une chute du sujet, équivalent à un chargement rapide. L'os étant un matériau viscoélastique, l'objectif de cette étude est de mesurer la ténacité de l'os cortical humain sous chargement quasi-statique et sous chargement rapide pour simuler un cas de chute. Les résultats montrent que la ténacité de l'os cortical humain est plus faible pour une vitesse de chargement rapide

Influence de l'hétérogénéité des propriétés mécaniques sur la résistance de l'os trabéculaire humain

Afin de mieux comprendre le comportement mécanique de l os trabéculaire et d améliorer la prédiction du risque de fracture, l objectif de cette thèse est de développer un modèle numérique bio-fidèle prenant en compte l hétérogénéité tissulaire, et de déterminer les contraintes mécaniques au sein des travées osseuses, dans le domaine de déformation élastique. À l échelle tissulaire, une étude par nanoindentation a permis de dissocier les comportements élastiques et plastiques de l os en fonction de sa composition (minéral/collagène). Ainsi, le comportement élastique du tissu osseux serait principalement lié à sa quantité de minéral alors que ses propriétés plastiques seraient davantage liées à la phase organique. Une loi reliant le degré de minéralisation de l os (DMB) au module élastique a été déterminée dans l os humain. La création d un modèle numérique reproduisant de manière rigoureuse le comportement élastique de l os trabéculaire, nécessite la prise en compte de l hétérogénéité de la quantité de minéral (DMB) et donc son acquisition en 3D. Grâce à une méthode de recalage d image 2D/3D, les acquisitions de microtomographie ont été comparées aux valeurs obtenues par microradiographie quantitative, méthode de référence de mesure du DMB. Sous certaines conditions, la microtomographie permet une évaluation correcte de l hétérogénéité minérale. La création et l analyse d un modèle numérique par éléments finis de l os trabéculaire, à partir des images de tomographie, a montré l importance des paramètres du modèle (taille et formulation des éléments) ainsi que le rôle de l hétérogénéité minérale sur l évaluation des contraintes locales appliquées aux travées osseuses.Finite element modeling has become more and more suitable to estimate the mechanical properties of trabecular bone. Such models tend to be used to evaluate bone fracture risk. The main goal of this study was to create a bio-faithful model of trabecular bone to evaluate elastic stresses fields in trabeculae. In a first part, a nanoindentation study lead to a dissociation of elastic and plastic behavior of bone tissue, depending of its composition (mineral/collagen). At osteon level, bone elastic behavior mainly depends on mineral quantity whereas its plastic behavior mainly depends on collagen maturity. The relation between degree of mineralization of bone (DMB) and elastic modulus have been determined for human bone. The purpose of second part of the study was to evaluate DMB heterogeneity inside a 3D model of trabecular bone. Using 2D/3D registration, we compare the results obtain with high resolution microtomography to those from quantitative microradiography, the goldstandard method used to measure DMB. We prove that it was possible to obtain a good evaluation of mineral heterogeneity in trabecular bone by tomography. The last part of this study, is dedicated to the creation of a finite element model of trabecular bone. After analyzing the influence of finite element modeling parameter on the assessment of mechanical response (size and element formulation), we showed that the integration of mineral heterogeneity at the tissue level lead to strong modifications of stress fields in bone trabeculae. The results of this study prove that bone mineral heterogeneity is an important parameter and should be taken into account when evaluating trabecular bone mechanical properties.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF

Methodological approach for the detection of both microdamage and fluorochrome labels in ewe bone and human trabecular bone

International audienceThe purpose of this study was to adapt various staining methods for the detection of microdamage in human bone, while preserving tetracycline labels. We describe two staining methods using calcein green and xylenol orange, first developed in ewe bone samples and validated in human tra-becular bone samples. In ewe bones, we found that calcein green at 0.5 mM concentration diluted in 100% ethanol as well as xylenol orange at 5 mM were the most adequate flu-orochromes both to detect microdamage and preserve the double tetracycline labeling. These results were verified in human trabecular bone (iliac crest for the tetracycline label, and vertebral bone for the double labeling). Results obtained in human bone samples were identical to those in ewes, so this combination of fluorochromes is now used in our laboratory

Respective roles of organic and mineral components of human cortical bone matrix in micromechanical behavior: An instrumented indentation study

International audienceBone is a multiscale composite material made of both a type I collagen matrix and a poorly crystalline apatite mineral phase. Due to remodeling activity, cortical bone is made of Bone Structural Units (BSUs) called osteons. Since osteon represents a fundamental level of structural hierarchy, it is important to investigate the relationship between mechanical behavior and tissue composition at this scale for a better understanding of the mechanisms of bone fragility. The aim of this study is to analyze the links between ultrastructural properties and the mechanical behavior of bone tissue at the scale of osteon. Iliac bone biopsies were taken from untreated postmenopausal osteoporotic women, embedded, sectioned and microradiographed to assess the degree of mineralization of bone (DMB). On each section, BSUs of known DMB were indented with relatively high load (∼500 mN) to determine local elastic modulus (E), contact hardness (Hc) and true hardness(H) of several bone lamellae. Crystallinity and collagen maturity were measured by Fourier Transform InfraRed Microspectroscopy (FTIRM) on the same BSUs. Inter-relationships between mechanical properties and ultrastructural components were analyzed using multiple regression analysis. This study showed that elastic deformation was only explained by DMB whereas plastic deformation was more correlated with collagen maturity. Contact hardness, reflecting both elastic and plastic behaviors, was correlated with both DMB and collagen maturity. Norelationship was found between crystallinity and mechanical properties at the osteon level

A New Method To Determine Volumetric Bone Mineral Density From Bi-Planar Dual Energy Radiographs Using A Finite Element Model: An Ex-Vivo Study

Finite element models (FEMs) derived from QCT-scans were developed to evaluate vertebral strength but QCT scanners limitations are restrictive for routine osteoporotic diagnosis. A new approach considers using bi-planar dual energy (BP2E) X-rays absorptiometry to build vertebral FEM. The purpose was to propose a FEM based on BP2E absorptiometry and to compare the vertebral strength predicted from this model to a QCT-based FEM. About 46 vertebrae were QCT scanned and imaged with BP2E X-rays. Subject-specific vertebral geometry and bone material properties were obtained from both medical imaging techniques to build FEM for each vertebra. Vertebral body volumetric bone mineral density (vBMD) distribution and vertebral strength prediction from the BP2E-based FEM and the QCT-based FEM were compared. A statistical error of 7[Formula: see text]mg/cm3 with a RMSE of 9.6% and a [Formula: see text] of 0.83 were found in the vBMD distribution differences between the BP2E-based and qCT-based FEM. The average vertebral strength was 3321[Formula: see text][Formula: see text] and 3768[Formula: see text][Formula: see text][Formula: see text for the qCT-based and BP2E-based FEM, respectively, with a RMSE of 641[Formula: see text]N and [Formula: see text] of 0.92. This method was developed to estimate vBMD distribution in lumbar vertebrae from a pair of 2D-BMD images and demonstrated to be accurate to personalize the mechanical properties in vitro

Compositional and mechanical properties of growing cortical bone tissue: a study of the human fibula

International audienc

Compositional and mechanical properties of growing cortical bone tissue: a study of the human fibula

International audienc

Séminaire e-DIADEM sur le thème TICE (Technologies de l\u27Information et de la Communication pour l\u27Enseignement) : usages en contexte

Le laboratoire Elico a organisé le 3 décembre 2007 le séminaire e-DIADEM sur le thème "TICE (Technologies de l\u27Information et de la Communication pour l\u27Enseignement) : usages en contexte". Organisé par les chercheurs du groupe e-DIADEM. Trois chercheurs externes au laboratoire Elico sont intervenus au cours du séminaire : Christine DEVELOTTE (INRP), Viviane GLIKMAN (CNAM), Hélène GODINET (INRP)

Study of the economic impact of cryptosporidiosis in calves after implementing good practices to manage the disease on dairy farms in Belgium, France, and the Netherlands

Cryptosporidium spp. are widespread parasitic protozoans causing enteric infections in humans and animals. The parasites cause neonatal diarrhoea in calves, leading to a high mortality rate in the first 3 weeks. Losses are significant for farmers, but the cost of cryptosporidiosis remains poorly documented. In the absence of a vaccine, only preventive measures are available to farmers to combat the infection. This study, conducted between 2018 and 2021, aimed to evaluate the economic impact of Cryptosporidium spp. on European dairy farms and monitor changes in costs after implementing disease management measures. First, a field survey was carried out and questionnaires administered to 57 farmers in Belgium, France, and the Netherlands. The aim of the survey was to assess the losses associated with the occurrence of diarrhoea in calves aged between 3 days and 3 weeks. The economic impact of diarrhoea was calculated based on mortality losses, health expenditures, and additional labour costs. To refine the cost estimation specifically for Cryptosporidium spp., stool samples were collected from 10 calves per farm. The prevalence of Cryptosporidium spp. was determined, and the economic impact of diarrhoea was adjusted accordingly. The assumption was made that a certain percentage of costs was attributed to cryptosporidiosis based on the prevalence. These protocols were repeated at the end of the study to observe changes in costs. In the three years, the cost of diarrhoea for the 28 farms that stayed in the panel all along the study improved from €140 in 2018 to €106 on average per diarrhoeic calf in 2021. With a stable prevalence at 40%, the cost of cryptosporidiosis per infected calf decreased from €60.62 to €45.91 in Belgium, from €43.83 to €32.14 in France, and from €58.24 to €39.48 in the Netherlands. This represented an average of €15 saved per infected calf. The methodology employed in this study did not allow us to conclude that the improvement is strictly due to the implementation of preventive measures. However, with 11 million calves raised in the Interreg 2 Seas area covered by the study, it provided valuable insights into the economic burden of Cryptosporidium spp