Interrelationships between pQCT indicators of cortical bone volumetric density and cross-sectional geometry (distribution / quality curves) in radii and tibiae of normal adults

GUSTAVO ROBERTO COINTRY; RICARDO FRANCISCO CAPOZZA; SARA FELDMAN; NÉSTOR MATÍAS FRACALOSSI; SEBASTIÁN EDUARDO FERRETTI; PAOLA REINA; MARÍA VICTORIA FERRETTI; MARÍA CAROLINA FERULLO; GABRIELA MARCHETTI; JOSÉ LUIS FERRETTI

Ginebra (Suiza)

Congreso; II Joint Meeting, European Calcified Tissue Society and International Bone & Mineral Society; 2005

International Bone & Mineral Society

To analyze the biomechanical interrelationships between pQCT indicators of cortical bone mass (BMC, area -CSA-), mineralization (volumetric cortical BMD, vBMD), cross-sectional design (bending and torsional moments of inertia, xCSMI, pCSMI) or strength (bending and torsional Bone Strength Indices, xBSI or pBSI = xCSMI or pCSMI . vBMD) and muscle strength (muscle CSA -MCSA-) in radial and tibial scans taken at sites 66% of the forearm or leg length proximal to the wrist and ankle joints of healthy men and pre-MP and post-women (n = 40, 60, 100).Results. Indicators of bone mass, diaphyseal design and strength (y) correlated positively with MCSA (x) following always single, nonlinear saturation functions for grouped men and pre-MP women data. Post-MP women showed less significant relationships, with lower slopes than those shown by the other groups, and no relationships between the CSMIs and MCSA. Suitably Z-scored, reference graphs of these relationships allowed to show a lower-right shift of post-MP women data, less evident for the CSMIs than for the other indicators. Calculated Z-scores of those relationships for the post-MP women decreased significantly with time since MP, excepting for the correlations between CSMIs and MCSA. No relationship was observed between cortical vBMD and MCSA.Interpretation. Results reflect the significant impact of regional muscle strength on cortical bone mass, architectural design and strength in normal adults. This impact tend to vanish after MP, more dramatically concerning bone mass and strength than diaphyseal design. The bone mechanostat system (a mechanism adapting cortical bone density and distribution to the history of strains derived from mechanical usage of the skeleton) would optimize the modeling-dependent cortical design in post-MP women, but not enough as to compensate for the negative impact of the remodeling-dependent decrease in vBMD. The Z-scored versions of the curves for men and pre-MP women provide reference charts for a non-invasive evaluation of muscle influences on bone mass, design and strength and the functional status of bone mechanostat specifically for men, pre-MP and post-MP women, regardless of age and anthropometric traits, beyond the DEXA scope.