Annals of The Rheumatic Diseases - ANN RHEUM DIS. 01/2010; 69(2).
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ABSTRACT: Fracture risk assessment tools are useful to calculate the long term probability of osteoporotic fracture. However, how it reflects bone quality is unknown. The aim of this study was to correlate the WHO clinical fracture risk assessment tool, FRAX, with bone mechanical properties.
Six patients submitted to hip replacement surgery, either due to osteoporotic fractures or to osteoarthritis, were evaluated. Bone samples were collected and the mechanical properties assessed by compression tests. Patients' data regarding the presence of clinical risk factors for fracture were registered. Laboratorial assessment of bone metabolic parameters and a dual X-ray absorptiometry(DXA) were done.
Analysis of the load-displacement curves showed that patients with fragility fractures (n=4) had low values of elastic modulus, yield load and energy absorbed until yield point. Osteoarthritis patients tend to have a better biomechanical performance.Femoral neck DXA scan was also performed in 3 patients. Fragility fracture patients had a lower bone mineral density than the patients with osteoarthritis. FRAX algorithm was applied and a positive relation was found between FRAX results and biomechanical parameters. Blood bone metabolic markers were within the normal range for all the subjects.
The worse mechanical properties observed in the fragility fracture patients were related to high probability of fracture given by FRAX. These observations, in a very small sample, need further confirmation. However, they suggest that the fracture risk assessment tool, FRAX, may reflect the current mechanical bone behavior of the patient.
Acta reumatologica portuguesa 34(3):504-10. · 0.70 Impact Factor
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ABSTRACT: 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.
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.
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.
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).
Clinical and experimental rheumatology 27(3):475-82. · 2.66 Impact Factor