1,555 research outputs found

    Software-assisted morphometry and volumetry of the lumbar spine

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    The aim of the study was to measure volumes of the lumbar vertebral bodies with use dedicated Computed Tomography (CT) workstation software to predict expected volume of PMMA for vertebroplasty and supplement calculations using computed tomography scanogram. Quantitative CT scans of 87 women's (mean age 69.4 years; SD 10.9) and 15 men's (mean age 64.3 years; SD 11.8) lumbar spines were analyzed; this made a total of 379 vertebrae. The population of patients was divided into three groups depending on measured BMD value, in accordance with American College of Radiology Practice Parameter for the Performance of Quantitative Computed Tomography (QCT) Bone Densitometry. With the use of the general linear model and least squares means groups were compared regarding vertebral volume, anterior, middle, and posterior vertebral heights. Morphometric parameters tended to be greater in males than in females, in a population of diversified bone mineral density. BMD result should be considered as the modifying factor for preoperative planning of the bone cement volume to be deposited inside the vertebra. Vertebral body volumetry might prove to be a useful tool in pre-operative planning as well as an alternative for treatment monitoring after minimally invasive spinal procedures

    Relation of vertebral deformities to bone density, structure, and strength.

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    Because they are not reliably discriminated by areal bone mineral density (aBMD) measurements, it is unclear whether minimal vertebral deformities represent early osteoporotic fractures. To address this, we compared 90 postmenopausal women with no deformity (controls) with 142 women with one or more semiquantitative grade 1 (mild) deformities and 51 women with any grade 2-3 (moderate/severe) deformities. aBMD was measured by dual-energy X-ray absorptiometry (DXA), lumbar spine volumetric bone mineral density (vBMD) and geometry by quantitative computed tomography (QCT), bone microstructure by high-resolution peripheral QCT at the radius (HRpQCT), and vertebral compressive strength and load-to-strength ratio by finite-element analysis (FEA) of lumbar spine QCT images. Compared with controls, women with grade 1 deformities had significantly worse values for many bone density, structure, and strength parameters, although deficits all were much worse for the women with grade 2-3 deformities. Likewise, these skeletal parameters were more strongly associated with moderate to severe than with mild deformities by age-adjusted logistic regression. Nonetheless, grade 1 vertebral deformities were significantly associated with four of the five main variable categories assessed: bone density (lumbar spine vBMD), bone geometry (vertebral apparent cortical thickness), bone strength (overall vertebral compressive strength by FEA), and load-to-strength ratio (45-degree forward bending ÷ vertebral compressive strength). Thus significantly impaired bone density, structure, and strength compared with controls indicate that many grade 1 deformities do represent early osteoporotic fractures, with corresponding implications for clinical decision making

    Reporting guidelines, review of methodological standards, and challenges toward harmonization in bone marrow adiposity research. Report of the Methodologies Working Group of the International Bone Marrow Adiposity Society

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    The interest in bone marrow adiposity (BMA) has increased over the last decade due to its association with, and potential role, in a range of diseases (osteoporosis, diabetes, anorexia, cancer) as well as treatments (corticosteroid, radiation, chemotherapy, thiazolidinediones). However, to advance the field of BMA research, standardization of methods is desirable to increase comparability of study outcomes and foster collaboration. Therefore, at the 2017 annual BMA meeting, the International Bone Marrow Adiposity Society (BMAS) founded a working group to evaluate methodologies in BMA research. All BMAS members could volunteer to participate. The working group members, who are all active preclinical or clinical BMA researchers, searched the literature for articles investigating BMA and discussed the results during personal and telephone conferences. According to the consensus opinion, both based on the review of the literature and on expert opinion, we describe existing methodologies and discuss the challenges and future directions for (1) histomorphometry of bone marrow adipocytes, (2

    Radiation exposure in X-ray-based imaging techniques used in osteoporosis

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    Recent advances in medical X-ray imaging have enabled the development of new techniques capable of assessing not only bone quantity but also structure. This article provides (a) a brief review of the current X-ray methods used for quantitative assessment of the skeleton, (b) data on the levels of radiation exposure associated with these methods and (c) information about radiation safety issues. Radiation doses associated with dual-energy X-ray absorptiometry are very low. However, as with any X-ray imaging technique, each particular examination must always be clinically justified. When an examination is justified, the emphasis must be on dose optimisation of imaging protocols. Dose optimisation is more important for paediatric examinations because children are more vulnerable to radiation than adults. Methods based on multi-detector CT (MDCT) are associated with higher radiation doses. New 3D volumetric hip and spine quantitative computed tomography (QCT) techniques and high-resolution MDCT for evaluation of bone structure deliver doses to patients from 1 to 3 mSv. Low-dose protocols are needed to reduce radiation exposure from these methods and minimise associated health risks

    Biomechanical analysis of osteoporotic spines with diseases using CT-based finite element method

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    The eventuality of recurrent fractures on the adjacent level of fractured vertebra is becoming prevalent in this era. To date, the underlying cause of this phenomena is either due to low bone quality or adverse geometrical changes of the vertebral body, as a result of osteoporosis and vertebral compression fractures (VCFs). To further investigate the determinant factor of this phenomenon, an image based finite element analysis (FEA) was used to scrutinize the biomechanical response of spines that have been afflicted by different types of spinal deformities, namely; wedge-shaped, fish-shaped and plana-shaped vertebrae. The evaluation was made based on its structural integrity in accordance to stress and strain distributions, and fracture risks prediction. These findings were then further corroborated by evaluating other associating factors such as kyphotic deformity angle and bone density distribution in order to find the underlying cause of this symptom. The results showed that the low bone density due to osteoporosis has become the dominant factor in inciting the risks of subsequent fractures on the adjacent vertebrae. This is based on the contradictory relation between the number of the failure elements distributions and the degree of the kyphotic deformity angle, as described by the wedge-shaped vertebral fracture model. Obviously, the most highly structural deformed vertebra still could withstand any kinds of high input loads, provided that its structural formation is still intact and has not severely affected by osteoporosis. The high incidence of subsequent fractures following Balloon Kyphoplasty (BKP) in both the augmented and adjacent vertebrae is quickly becoming a clinically unresolvable complication. The underlying cause of this phenomenon is still unknown and to date medical practitioners are still unable to explain the fundamental cause of this phenomenon. To verify this claim, an image-based finite element analysis was used to investigate the effectiveness of BKP treatment of pre-operative and post-operative osteoporotic spine models. The three-dimensional (3D) non-linear finite element (FE) models of the thoracolumbar spine (T11-L3) were developed from CT-scan images. The biomechanical responses were evaluated based on the models’ load sharing mechanisms, load transfer mechanisms, stiffness recovery, stability, and kyphotic deformity restoration. The margin of safety for each of the models was evaluated under incrementally increased loads (1-10kN). This margin would be determined based on the fracture risk evaluation in accordance to the associated onset fracture load. The results showed that the BKP procedures play a significant role in enhancing the structural integrity of the treated spine by lowering the effect of the bone fracturing and optimizing the biomechanical alterations up to its pre-fracture level. However, the phenomenon of high incidence of vertebral bone failures on the augmented and its neighboring vertebrae indicates that the osteoporosis severity is the most influential factor in determining the sufficiency of the BKP treatment. Cage subsidence, pedicle screw loosening and instability are the most prevalent posterior lumbar interbody fusion (PLIF)-related complications. These may be attributed to interrelated mechanical, biomechanical and environmental factors. Current advancement in medical treatment has paved the way for the implementation of unilateral cages in an oblique position to overcome unintended mechanical and clinical shortcomings. To verify this claim, an imagebased finite element analysis (FEA) was used to evaluate several factors; cage subsidence, screw loosening and PLIF construct stability via stress profiles, fracture risk prediction and range of motion (ROM) evaluations in the different type of cage materials and cage orientations. Obviously, obliquely-placed unilateral fusion cage constructs with PI exhibited the most reliable biomechanical constructs by showing the smallest ROM and producing the minimal distortion stress at the cage-endplate and pedicle screw-bone interfaces. Moreover, these results also showed good agreement with the results obtained using fracture risks assessments by showing the lower numbers of deformation elements at the both contact interfaces in normal and traumatic events. In conclusion, biocompatible cage materials and structural symmetry are the most important criteria in achieving biomechanical advantage in PLIF surgery

    Quantifying Changes in the Spatial Structure of Trabecular Bone

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    We apply recently introduced measures of complexity for the structural quantfication of distal tibial bone. For the first time, we are able to investigate the temporal structural alteration of trabecular bone. Based on four patients, we show how bone may alter due to temporal immobilisation

    Age-related changes in trabecular bone microstructures: global and local morphometry

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    Introduction: A recently developed method allows investigating trabecular bone on an elemental (rod/plate) level. With this method, it is possible to measure local morphometric parameters such as thickness or orientation directly on the extracted rods and plates. Age-related changes of trabecular microarchitecture can thus be investigated on an elemental level, which may help to improve the understanding of age-related bone failure mechanism as well as the effect of pharmaceutical intervention in the prevention of such fractures. Methods: Autopsies from femoral heads (FH) and lumbar spine (LS) were analyzed by global morphometry. Additionally, the trabecular structures were decomposed into rods and plates for the analysis with local morphometry. These morphometric indices were related to age using an analysis of covariance to test for gender differences and linearity with age. Results: In this study, age-related changes showed no gender but site differences. In LS, rods were thinned in aging and finally vanish from the structure, causing a transformation of the trabecular bone structure to longer and, on average, thicker rods. In FH, changes were expressed by a simultaneous thinning and loss of interconnecting trabeculae and perforation of plates leading to new plates and rods. Results were mostly in agreement with earlier findings using descriptive analysis of the aging process. Conclusion: Here we present for the first time preliminary quantitative evidence of changes in the local microstructure, i.e., individual rods and plates. Nevertheless, the number of samples was too small to make for ready conclusions. We conclude that the combination of local and global morphometry is a useful method for a detailed and quantitative description of age-related changes in bone microstructur

    Imaging of metabolic bone disease

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    Osteoporosis is the most important metabolic bone disease, with a wide distribution among the elderly. It is characterized by low bone mass and micro architectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk. Identify bone weakening with an appropriate and accurate use of diagnostic imaging is of critical importance in the diagnosis and follow-up of osteoporotic patients. The aim of this review is to evaluate the detection rates of the different imaging modalities in the evaluation of bone strength, in the assessment of fracture risk and in the management of fragility fractures

    Mechanical and morphometric characterization of cancellous bone

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    [EN] Bone fracture is a social health problem of increasing magnitude because of its prevalence in aged population due to osteoporosis. Bone quality is often characterized by bone mineral density (BMD) measured at cancellous bone regions using dual-energy X-ray absorptiometry (DXA). However, BMD alone cannot predict several cases because not only density is important, but also microstructure plays an important role in cancellous bone strength. The mechanical properties can be used as indicators of bone integrity as a function of age, disease or treatment. Therefore, cancellous bone fracture characterization and its relationship to microstructure has not been completely solved in the literature and is relevant to improve fracture prediction. In this thesis, we aim at characterizing cancellous bone morphometry and mechanical behavior. Morphometry is estimated through the analysis of micro-computed tomography (micro-CT) images of vertebral cancellous bone specimens. With regards to the mechanical behavior, we calculate elastic, yield and failure properties at the apparent and tissue levels. To determine them, we followed different approaches: compression tests, finite element models and micro-CT phantoms. We have developed finite element models that reproduce the elastic and failure response of cancellous bone under compression conditions. We modeled failure as a combination of continuum damage mechanics and the element deletion technique. The numerical models permitted to estimate elastic and failure properties. Failure properties were consistent with results reported in the literature. Specifically, our results revealed that yield strain is relatively constant (0.7 %) over a range of apparent densities, while failure strain presents a wider range of variation. A single strain parameter (equivalent strain) was found as an accurate descriptor of cancellous bone compression failure. Image-based numerical models usually need for the action of a technician to segment the images. Therefore, we studied the sensitivity to variations of the segmentation threshold on the morphometry and the elastic properties of vertebral cancellous bone specimens of different bone volume fractions. The apparent modulus is highly sensitive to the segmentation threshold. We report variations between 45 and 120 % for a ± 15 % threshold variation. Other parameters, such as BS/BV, BS/TV, Tb.Sp, Tb.N, Conn.D and fractal dimension were influenced significantly. Digital image correlation (DIC) was applied to images taken during compression testing to analyze displacement fields at failure and characterize them. Some variables were explored to describe failure and a study is done about how DIC parameters influence the strain field obtained. Facet and step sizes have a relevant effect on the failure strain estimation, and an increment of both parameters reduces the strain estimation up to 40 %. Besides, several parameters combination led to correct failure pattern detection, so values reported in the literature should be referred to the parameters used. Furthermore, we explored if cancellous bone microstructure acts (non-speckle/texture approach) as a proper pattern to calculate displacements using DIC technique. As regards relationships between microstructure and mechanics, single and multiple parameter analysis were performed to assess the morphometric variables that control the explanation of mechanical properties variation. Bone volume fraction (BV/TV), bone surface to volume ratio (BS/BV), mean trabecular thickness (Tb.Th) and fractal dimension (D) presented the best linear correlations to the elastic properties, while both the yield and failure strains did not show correlation to any morphometric parameter. The regressions obtained permit to estimate those mechanical properties that describe the state of a specimen.[ES] Las fracturas óseas constituyen un problema social de salud con magnitud creciente por su prevalencia en la población de edad avanzada debido a la osteoporosis. La calidad del hueso suele caracterizarse mediante la estimación de la densidad mineral ósea (DMO) en regiones de hueso trabecular, utilizando absorciometría de rayos X de energía dual (DXA). No obstante, la DMO por si sola no es capaz de predecir numerosos casos de fractura porque no solo importa la pérdida de densidad, sino que la microestructura también tiene un papel principal en la resistencia del hueso. Las propiedades mecánicas del hueso pueden usarse como indicadores de su integridad en función de la edad, enfermedad o tratamiento. Por lo tanto, la caracterización de la fractura de hueso trabecular y su relación con la microestructura no se ha resuelto de forma completa en la literatura y es relevante para mejorar las predicciones de fractura. En esta tesis, nuestro principal objetivo es caracterizar la morfometría y el comportamiento mecánico del hueso trabecular. Estimamos la morfometría a través del análisis de imágenes obtenidas por micro tomografía computerizada (micro-CT) de muestras de hueso trabecular vertebral de cerdo. Respecto al comportamiento mecánico, calculamos propiedades elásticas, de plasticidad y fractura a escala aparente y de tejido. Para determinar esas propiedades, hemos seguido diferentes procedimientos: ensayos a compresión, modelos de elementos finitos y fantomas de calibración micro-CT. Los modelos de elementos finitos desarrollados reproducen la respuesta elástica y de fallo bajo condiciones de compresión en hueso trabecular, modelando el fallo como combinación de mecánica del daño contínuo y la técnica de eliminación de elementos. Los modelos numéricos desarrollados han permitido estimar propiedades elásticas y de fallo. En concreto, las deformaciones de inicio de fallo estimadas son relativamente constantes para las muestras analizadas (0.7 %), mientras que las deformaciones últimas de fallo presentan un rango de variación mayor. Por otro lado, encontramos que la deformación equivalente es el descriptor más preciso del fallo a compresión del hueso trabecular. Normalmente, los modelos numéricos basados en imágenes suelen necesitar la acción de un técnico para segmentar las imágenes. En este sentido, estudiamos la sensibilidad de la morfometría y la estimación de propiedades elásticas ante variaciones en el umbral de segmentación en muestras con distinta fracción en volumen. Hemos obtenido que la rigidez aparente es muy sensible a cambios en el umbral de segmentación, con variaciones entre 45 y 120 % para una variación de ± 15 % del umbral de segmentación. Otros parámetros, como BS/BV, BS/TV, Tb.Sp, Tb.N, Conn.D y la dimensión fractal se ven afectados significativamente. Por otro lado, hemos aplicado la técnica correlación digital por imagen (DIC) para caracterizar campos de desplazamientos en el fallo a compresión del hueso trabecular, a partir del análisis de imágenes tomadas durante el ensayo de las muestras. Además, estudiamos la influencia de algunos parámetros de la técnica DIC en el campo de deformaciones obtenido. También, hemos explorado la aplicación DIC sin el uso de moteado, utilizando como patrón de reconocimiento la propia microestructura trabecular. En relación al estudio de la influencia de la microestructura en la respuesta mecánica, hemos calculado correlaciones de uno y varios parámetros para analizar qué variables morfométricas explican la variación de las propiedades mecánicas. La fracción en volumen de hueso (BV/TV), la relación entre el área y el volumen de hueso (BS/BV), el espesor trabecular medio (Tb.Th) y la dimensión fractal (D) presentan las mejores correlaciones lineales respecto a las propiedades elásticas, mientras que las deformaciones de inicio de plasticidad y fractura no mostraron correlación con ningún parámetro morfométrico.[CA] Les fractures òssies constitueixen un problema social de salut amb magnitud creixent per la seua prevalença en la població d'edat avançada a causa de l'osteoporosi. La qualitat de l'os sol caracteritzar-se mitjançant l'estimació de la densitat mineral òssia (DMO) en regions d'os trabecular, utilitzant absorciometria de raigs X d'energia dual (DXA). No obstant això, la DMO per si sola no és capaç de predir nombrosos casos de fractura perquè no sols importa la pèrdua de densitat, sinó que la microestructura també té un paper principal en la resistència de l'os. Les propietats mecàniques de l'os poden usar-se com a indicadors de la seua integritat en funció de l'edat, malaltia o tractament. Per tant, la caracterització de la fractura d'os trabecular i la seua relació amb la microestructura no s'ha resolt de manera completa en la literatura i és rellevant per a millorar les prediccions de fractura. En aquesta tesi, el nostre principal objectiu és caracteritzar la morfometria i el comportament mecànic de l'os trabecular. Estimem la morfometria a través de l'anàlisi d'imatges obtingudes per micro tomografia automatitzada (micro-CT) de mostres d'os trabecular vertebral de porc. Respecte al comportament mecànic, calculem propietats elàstiques, de plasticitat i fractura a escala aparent i de teixit. Per a determinar aqueixes propietats, hem seguit diferents procediments: assajos a compressió, models d'elements finits i fantomas de calibratge micro-CT. Hem desenvolupat models d'elements finits que reprodueixen la resposta elàstica i de fallada sota condicions de compressió en os trabecular, modelant la fallada com a combinació de mecànica del dany continu i la tècnica d'eliminació d'elements. Els models numèrics desenvolupats han permés estimar propietats elàstiques i de fallada. Les nostres estimacions respecte a propietats de fallada són consistents amb valors reportats en la literatura. En concret, les deformacions d'inici de fallada estimades són relativament constants per a les mostres analitzades (0.7 %), mentre que les deformacions últimes de fallada presenten un rang de variació major. D'altra banda, trobem que la deformació equivalent és el descriptor més precís de la fallada a compressió de l'os trabecular. Els models numèrics basats en imatges solen necessitar l'acció d'un tècnic per a segmentar les imatges. En aquest sentit, estudiem la sensibilitat de la morfometria i l'estimació de propietats elàstiques davant variacions en el llindar de segmentació en mostres amb diferent fracció en volum. Hem obtingut que la rigidesa aparent és molt sensible a canvis en el llindar de segmentació, amb variacions entre 45 i 120 % per a una variació de ± 15 % del llindar de segmentació. Altres paràmetres, com BS/BV, BS/TV, Tb.Sp, Tb.N, Conn.D i la dimensió fractal es veuen afectats significativament. D'altra banda, hem aplicat la tècnica correlació digital per imatge (DIC) per a caracteritzar camps de desplaçaments en la fallada a compressió de l'os trabecular, a partir de l'anàlisi d'imatges preses durant l'assaig de les mostres. A més, estudiem la influència d'alguns paràmetres de la tècnica DIC en el camp de deformacions obtingut. També, hem explorat l'aplicació DIC sense l'ús de clapejat, utilitzant com a patró de reconeixement la pròpia microestructura trabecular. En relació a l'estudi de la influència de la microestructura en la resposta mecànica, hem calculat correlacions d'un i diversos paràmetres per a analitzar quines variables morfomètriques expliquen la variació de les propietats mecàniques. La fracció en volum d'os (BV/TV), la relació entre l'àrea i el volum d'os (BS/BV), la espessor trabecular mitjà (Tb.th) i la dimensió fractal (D) presenten les millors correlacions lineals respecte a les propietats elàstiques, mentre que les deformacions d'inici de plasticitat i fractura no van mostrar correlació amb cap paràmetre morfomètric.Belda González, R. (2020). Mechanical and morphometric characterization of cancellous bone [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149376TESI
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