Biomechanical impact of aluminum accumulation in rat cortical bone

GUSTAVO ROBERTO COINTRY; RICARDO FRANCISCO CAPOZZA; ARMANDO LUIS NEGRI; JOSÉ LUIS FERRETTI

JOURNAL OF BONE AND MINERAL METABOLISM.

Springer Verlag

Lugar: Tokio; Año: 2005 vol. 23 p. 15 - 23

0914-8779

In order to analyze the effects on whole-bone behavior of aluminum accumulation, 14 rats aged 90 days received ip doses of 27 mg/d of elemental Al as Al(OH)3 during 26 weeks while 14 rats remained as controls. Their femur diaphyses were studied tomographically (pQCT) and mechanically tested in bending. The load/deformation curves obtained allowed distinction between effects observed during the linearly elastic (Hookean) and nonlinear (non-Hookean) behaviors of bones before and after the yield point, respectively. Treatment reduced the cortical bone mineralization (volumetric BMD, p<0.01) with a negative impact on the bending stiffness of cortical bone (calculated Young’s elastic modulus, p<0.05). However, the whole-bone stiffness (load/deformation ratio) was maintained while the strength (ultimate load) was reduced (p<0.05). Despite the absence of any cortical mass increase (cross-sectional area), improved spatial distribution of cortical tissue (cross-sectional moment of inertia, p<0.05) occurred through a modulation of modeling drifts. This presumably adaptive response should have resulted adequate for maintaining a normal diaphyseal stiffness according to the bone “mechanostat” theory, but not so to provide a complete neutralization of the impaired diaphyseal strength. An Al-induced impairment of the bone ability to resist loads beyond the yield point (p<0.01) should have caused the unusual disruption observed between effects on bone stiffness and strength. In addition to describe an unusual finding, these results suggest that little-studied microstructural factors affecting the post-yield behavior of cortical bone in these and other conditions ought to be further investigated in specifically designed studies as a novel, promising resource in skeletal research.