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Article Chronic arthritis directly induces quantitative and qualitative bone disturbances leading to compromised biomechanical properties. 2009
Caetano-Lopes J, Henriques R, Canhão H, Duarte J, Amaral PM, Vale M, Moura RA, Pereira PA, Weinmann P, Abdulghani S, Souto-Carneiro M, Rego P, Monteiro J, Sakagushi S, Queiroz MV, Konttinen YT, Graça L, Vaz MF, Fonseca JE. · Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal. · Clin Exp Rheumatol. · Pubmed #19604441 No free full text.
Abstract: OBJECTIVES:Rheumatoid arthritis (RA) is associated with an increased risk of fragility fractures. In RA patients, the direct effect of inflammation on bone is difficult to study because their skeleton is also affected by medication with corticosteroids and other drugs as well as aging and menopause, which contribute to bone fragility. This study used an animal model of chronic arthritis to evaluate the direct impact of chronic inflammation on biomechanical properties and structure of bone.METHODS:In the SKG mouse chronic arthritis model three point bending tests were performed on femoral bones and compression tests on vertebral bodies. Collagen structure was analysed using second-harmonic generation (SHG) imaging with a two-photon microscope, ultramorphology by scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS) and bone density using water pycnometer.RESULTS:Arthritic bones had poor biomechanical quality compared to control bones. SHG, SEM and pycnometry disclosed variable signs of impaired collagen organization, poor trabecular architecture and low bone density.CONCLUSION:Present data demonstrate for the first time that chronic inflammation per se, without confounding influence of drugs and aging, leads to impairment of bone biomechanics in terms of stiffness, ductility and ultimate strength (fracture).
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Article Biomechanical effects of inflammatory diseases on bone-rheumatoid arthritis as a paradigm. 2009
Abdulghani S, Caetano-Lopes J, Canhão H, Fonseca JE. · Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal. · Autoimmun Rev. · Pubmed #19223022 No free full text.
Abstract: Inflammatory diseases, such as rheumatoid arthritis (RA), influence the bone remodelling process and increase the risk of fracture. Bone can be viewed as a composite material comprising of two phases: the organic phase, constituted predominantly by collagen type I, and the mineral phase, composed primarily by calcium phosphate, in the form of mineral crystals. The mineral component confers bone with strength and stiffness while the organic phase is responsible for bone toughness and ductility and acts as a scaffold for the mineralisation process. The efficacy of bone as a structural material depends on the balance between these different bone components and their biomechanical properties. The main determinants of mechanical properties of bone are the amount of mineral, the collagen content, the orientation of the collagen fibers and minerals and the accumulation of microcracks in the bone matrix. In a mice model of arthritis mechanical testing has shown that arthritic femurs have a significantly lower Young's modulus, yield stress and work until ultimate stress. This evidence suggests that one of the major explanations for the increased fracture risk in RA is related to the changes on bone components induced by inflammation that result in compromised biomechanical properties.
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