The chronic inflammation of rheumatoid arthritis (RA) leads to impairment of bone biomechanics in terms of stiffness, ductility, and ultimate strength (fracture), according to researchers at the Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, in Portugal. The direct effect of inflammation on bone is difficult to study in patients with RA, they noted, because the skeleton also is affected by corticosteroids and other drugs, as well as aging and menopause, which contribute to bone fragility.
Caetano-Lopes and associates1 used an animal model of chronic arthritis to evaluate the direct effect of chronic inflammation on the biomechanical properties and structure of bone. Three-point bending tests were performed on femoral bones and compression tests on vertebral bodies. Second-harmonic generation (SHG) imaging with a 2-photon microscope was used to analyze collagen(Drug information on collagen) structure, scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy to evaluate ultramorphology, and water pycnometer to assess bone density.
Arthritic bones had poor biomechanical quality compared with control bones. SHG imaging, SEM, and pycnometry disclosed variable signs of impaired collagen organization, poor trabecular architecture, and low bone density, respectively. The authors noted that their data are the first to demonstrate that chronic inflammation leads to impairment of bone biomechanics without the confounding influence of drugs and aging.
