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Zimmermann et al. How osteoporosis/BP treatment impacts mechanical bone properties
DOI:10.1038/bonekey.2016.73
Zimmermann et al. used several techniques to explore the properties of the samples taken from the femoral cortex of three groups: a) young healthy individuals with no evidence of bone disease; b) patients who were diagnosed with osteoporosis but who were treatment naïve at the time of the study and c) patients with osteoporosis who had been receiving alendronate for six years.
Three-point bending was used to measure tissue strength and small-angle X-ray scattering was used to determine the extent of deformation at high and low strain rates, which provided information on how the bone would behave under conditions of high-energy traumatic fractures and low-energy fragility fractures.
As expected, the bones of patients with osteoporosis exhibited a lower mineral content, lower strength, less resistance to plasticity and a significantly higher porosity compared to the bones of young healthy subjects. Patients also showed reduced fibrillar deformation under low-strain conditions, suggesting this may be why osteoporotic fragility fractures are common. Encouragingly, analysis of bone samples from patients receiving alendronate revealed improved resistance to plasticity, although this was a trend rather than significant difference.
Editor’s comment: Although not strongly powered (n=3×5) this careful, extensive and convincing study confirms the key role of porosity on osteonal bone bending stiffness and strength. In the absence of differences in advanced glycation end-products, the presence of nanoscale damage uncoupling collagen bundles could explain the reduced average collagen fibril strain observed at yield in the osteoporotic tissue.
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