Advances in the evaluation of bone health in kidney transplant patients. / Avances en la valoración de la salud ósea en el trasplantado renal.

Bone disease related to chronic kidney disease and, particularly, to kidney transplant patients is a common cause or morbidity and mortality, especially due to a higher risk of osteoporotic fractures. Despite the fact that this has been known for decades, to date, an appropriate diagnostic strategy has yet to be established. Apart from bone biopsy, which is invasive and scarcely used, no other technique is available to accurately establish the risk of fracture in kidney patients. Techniques applied to the general population, such as bone densitometry, have not been subjected to sufficient external validation and their use is not systematic. This means that the identification of patients at risk of fracture and therefore those who are candidates for preventive strategies is an unmet need. Bone strength, defined as the ability of the bone to resist fracture, is determined by bone mineral density (measured by bone densitometry), trabecular architecture and bone tissue quality. The trabecular bone score estimates bone microarchitecture, and low values have been described as an independent predictor of increased fracture risk. Bone microindentation is a minimally invasive technique that measures resistance of the bone to micro-cracks (microscopic separation of mineralised collagen fibres), and therefore bone tissue biomechanical properties. The superiority over bone densitometry of the correlation between the parameters measured by trabecular bone score and microindentation with the risk of fracture in diverse populations led us to test its feasibility in chronic kidney disease and kidney transplant patients.

Bone characteristics of pigs fed different sources of phosphorus / Características óseas de cerdos alimentados con diferentes fuentes de fósforo / Características ósseas de suínos alimentados com diferentes fontes de fósforo

Summary Background: phosphorus supplementation should help to keep bone integrity and prevent fractures during the development and slaughter of animals. Objective: to evaluate the effect of different phosphorus sources on one characteristics of pigs. Methods: one-hundred and twelve piglets (28.65 ± 2.82 Kg body weight) were distributed into an 8×2 factorial arrangement (eight sources of phosphorus × two sexes) in blocks in a completely randomized design. The diets were formulated on a total-phosphorus basis, with 0.32 and 0.31% of P for the control diet and 0.56 and 0.42% of P for the other treatments in the growth and finishing phases, respectively. Phosphorus was supplemented as dicalcium phosphate (DCP); mono-dicalcium phosphate (MDCP); triple superphosphate (TSP); single superphosphate (SSP); Catalão-rock phosphate (ROCK); a mixture of sources (MIX); phosphoric acid (PPA); and the control diet (CTR). Results: there was no interaction between phosphorus sources and sex in any of the parameters. Thickness of the compact tissue was the lowest in the CTR, differing from the diets containing DCP, MDCP, and PPA, followed by diets SSP, TSP, and ROCK, with the greatest value for MDCP. Porosity of the compact tissue was higher for the CTR and SSP diets. Conclusion: the use of less elaborate sources of phosphorus, such as rock phosphate and single superphosphate, was less effective than the other sources to improve bone integrity of pigs.

Resumen Antecedentes: la suplementación dietaria con fósforo ayuda a mantener la integridad del hueso y prevenir fracturas durante el desarrollo y sacrificio de los animales. Objetivo: evaluar el efecto de diferentes fuentes de fósforo sobre las características óseas de los cerdos. Métodos: ciento doce lechones (peso corporal: 28,65 ± 2,82 Kg) se distribuyeron en un arreglo factorial 8×2 (ocho fuentes de fósforo × dos sexos) en bloques al azar. Las dietas se formularon con base en fósforo total, con 0,32 y 0,31% de P para la dieta control y 0,56 y 0,42% de P para los otros tratamientos en las fases de crecimiento y finalización, respectivamente. El fósforo se suplementó como fosfato dicálcico (DCP), monofosfato dicálcico (MDCP), superfosfato triple (TSP), superfosfato simple (SSP), fosfato de roca Catalão (ROCK), mezcla de fuentes (MIX), ácido fosfórico (PPA) y dieta control (CTR). Resultados: no se observó interacción entre las fuentes de fósforo y el sexo en ninguno de los parámetros estudiados. El espesor del tejido compacto fue más bajo en el CTR, y diferente a las dietas que contenían DCP, MDCP y PPA, seguido por las dietas SSP, TSP y ROCK; con el mayor valor para MDCP. La porosidad del tejido compacto fue mayor para las dietas CTR y SSP. Conclusión: el uso de fuentes menos elaboradas de fósforo, tales como el fosfato de roca y superfosfato simple, fue menos efectivo que las otras fuentes en mejorar la integridad ósea de los cerdos.

Resumo Antecedentes: a suplementação de fósforo deve manter a integridade do tecido ósseo e prevenir fraturas durante o desenvolvimento e abate dos animais. Objetivo: avaliar o efeito de diferentes fontes de fósforo sobre as características ósseas dos suínos. Métodos: cento e doze leitões com peso médio inicial de 28,65 ± 2,82 Kg foram distribuídos em esquema fatorial 8×2 (oito fontes de fósforo × dois sexos) em blocos casualizados. As dietas foram formuladas baseadas em fósforo total com 0,32 e 0,31% de P para a dieta controle e com 0,56 e 0,42% de P para os outros tratamentos nas fases de crescimento e terminação, respectivamente. O fósforo nas dietas foi suplementado com fosfato bicálcico (DCP); mono-fosfato bicálcico (MDCP); superfosfato triplo (TSP); superfosfato simples (SSP); fosfato de rocha Catalão (ROCK); uma mistura de fontes (MIX); ácido fosfórico (PPA); e a dieta controle (CTR). Resultados: não houve interação entre as fontes de fósforo e sexo dos animais para qualquer um dos parâmetros estudados. A espessura do tecido compacto é menor na CTR, diferenciando-se das dietas DCP, MDCP e PPA, seguido pelas dietas SSP, TSP e ROCK, sendo que o maior valor foi observado na dieta com MDCP. A porosidade do tecido compacto foi maior com as dietas CTR e SSP. Conclusão: o uso de fontes menos elaboradas de fósforo como superfosfato simples e fosfato de rocha foram menos eficientes do que os outros tratamentos para melhorar a integridade óssea de suínos.

Biomecánica de las fracturas por stress / Biomechanical features of stress fractures

Se define como estrés (stress) tanto la fuerza que una carga externa ejerce sobre un cuerpo sólido como la fuerza reactiva que acompaña a la primera (Ley de Newton), por unidad de área imaginaria transversal a su dirección. Las cargas internas reactivas inducen deformaciones proporcionales del cuerpo. La resistencia del cuerpo a deformarse se llama rigidez. La deformación puede resquebrajar el cuerpo y, eventualmente, producir una fractura por confluencia de trazos. La resistencia del cuerpo a separarse en fragmentos por esa causa se llama tenacidad. La resistencia del cuerpo a la fractura es proporcional al stress que puede soportar sin separarse en fragmentos por deformación (no hay fractura sin deformación y sin stress previo). El stress máximo que un cuerpo puede soportar sin fracturarse resulta de una combinación de ambas propiedades: rigidez y tenacidad, cada una con distintos determinantes biológicos. Una o varias deformaciones del cuerpo pueden provocarle resquebrajaduras sin fracturarlo. La acumulación de resquebrajaduras determina la "fatiga" del material constitutivo del cuerpo, que reduce su rigidez, tenacidad y resistencia a la fractura para la próxima ocasión ("fragilidad por fatiga"). En el caso de los huesos, en general, los términos stress y fatiga tienen las connotaciones amplias referidas, respecto de todas las fracturas posibles. La fatiga predispone a fracturas a cargas bajas, que se denominan (correctamente) "fracturas por fatiga" y también (incorrectamente) "fracturas por stress", para distinguirlas de las que ocurren corrientemente, sin resquebrajaduras previas al trauma, que se denominan (incorrectamente) "fracturas por fragilidad, o por insuficiencia". En realidad, todas las fracturas se producen por stress y por fragilidad o insuficiencia (en conjunto); pero la distinción grosera entre fracturas "por fatiga, o por stress", por un lado, y "por fragilidad" o "por insuficiencia", por otro, aceptando las amplias connotaciones referidas antes, tiene valor en la práctica clínica. Este artículo intenta explicar esas particularidades biomecánicas y describir las distintas condiciones que predisponen a las fracturas "por fatiga o por stress" en la clínica, distinguiéndolas de las fracturas "por fragilidad o por insuficiencia" (manteniendo estas denominaciones) y detallando las características de interés directo para su diagnóstico y tratamiento. (AU)

The term "stress" expresses the force exerted by an external load on a solid body and the accompanying, opposed force (Newton's Law), expressed per unit of an imaginary area perpendicular to the loading direction. The internal loads generated this way deform (strain) proportionally the body's structure. The resistance of the body to strain expresses its stiffness. Critical strain magnitudes may induce micro-fractures (microdamage), the confluence of which may fracture the body. The body's resistance to separation into fragments determines its toughness. Hence, the body's resistance to fracture is proportional to the stress the body can support (or give back) while it is not fractured by the loadinduced strain (no stress, no strain -> no fracture). Therefore, the maximal stress the body can stand prior to fracture is determined by a combination of both, its stiffness and its toughness; and each of those properties is differently determined biologically. One or more deformations of the body may induce some microdamage but not a fracture. Microdamage accumulation determines the fatigue of the material constitutive of the body and reduces body's toughness, leading to a "fatigue-induced fragility". In case of bones, in general, both stress and fatigue have the referred, wide connotations, regarding any kind of fractures. In particular, bone fatigue predisposes to low-stress fractures, which are named (correctly) "fatigue fractures" and also misnamed "stress fractures", to distinguish them from the current fractures that occur without any excess of microdamage, that are named (wrongly) "fragility" or "insufficiency" fractures. In fact, all fractures result from all stress and fragility or insufficiency as a whole; however, the gross distinction between "fatigue or stress fractures", on one side, and "fragility or insufficiency fractures", on the other, accepting the wide connotations of the corresponding terminology, is relevant to clinical practice. This article aims to explain the above biomechanical features and describe the different instances that predispose to "fatigue or stress fractures" in clinical practice, as a different entity from "insufficiency or fragility fractures" (maintaining this nomenclature), and describe their relevant features to their diagnosis and therapy. (AU)

Relación entre los esfuerzos de compresión simple y cantidad de flúor en el tejido óseo / Relationship between simple compressive stresses and fluoride in bone tissue

Se investigó la relación que existe entre la cantidad de flúor en hueso y la resistencia a la compresión simple del mismo. Se analizaron 12 muestras de la quinta costilla humana extraidos de cadáveres frescos de no más de 24 horas de fallecidos en el Instituto de Medicina Legal de Medellin. Los cadáveres seleccionados debian tener datos completos de: edad, sexo, lugar de residencia, y una historia médica referida por sus familiares, en la que no presentara antecedentes de enfermedades sistémicas; posteriormente se investigó si en los respectivos sitios de residencia se utilizaba la fluorízación del agua. Los valores de flúor se determinaron con el método descrito por Alhava en 1980, y la resistencia a la comprensión simple se determino mediante el método descrito por Franke (1976). En los resultados finales no se obtuvieron diferencias estadísticamente significativas entre el contenido de flúor de las muestras óseas y la resistencia a la compresión de las mismas.

The relationship between the amount of fluoride in bone and its resistance to simple compression was investigated. 12 samples were analized from the 5th ribofhuman beings taken from fresh corpse with no more than 24 hours after death, in the Legal Medicine Institute of Medellín. The chosen corpses should have complete data concerning: age, sex, place of residence (address) and aclinical history refered by its relatives, and it couldn't present any previous sistemic illness; subsequently a research in their diferent places of residence was done, to investigate if the water used contained fluoride. The importance of fluoride was determined with the method described by Alhavain 1980, and the resistance to simple compression was determinated throughout the method described by Franke (1976). In the final results no statisticaly significant differences were obtained between the amount of fluoride in the bone sample and its resistance to compression.