Poster Presentation 33rd ASM of the Australian & New Zealand Bone & Mineral Society 2023

Bone Fragility is the Result of Bone Loss from Frugally Assembled Larger Bones (#225)

Ali Ghasem-Zadeh 1 , Minh Bui 2 , Esther Briganti 3 , Ego Seeman 1
  1. Departments of Endocrinology and Medicine, Austin Health, The University of Melbourne, Melbourne, Vic, Australia
  2. Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VICTORIA, Australia
  3. School of Public Health and Preventive Medicine Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Vic, Australia

Introduction   Bone modelling and remodelling achieve paradoxical properties of bone strength yet lightness by assembling larger bones with relatively less material (thinner, porous cortices), and smaller bones with relatively more material (thicker, less porous cortices); features that accommodate loading and mobility during young adulthood.  However, longevity is accompanied by remodelling imbalance.  We therefore hypothesised that bone loss will deteriorate bone microarchitecture, compromising the already frugally assembled structure of larger bones.

 Methods         In 324 twin pairs aged 26-76 years, (364 premenopausal, pre-MP), 255 postmenopausal, post-MP) we used HRpQCT to measure distal radial cross-sectional area (CSA) and deterioration in microarchitecture (cortical porosity and trabecular density) captured by the Structural Fragility Score (SFS) and finite element analysis to estimate compressive strength.  Associations are presented as correlation coefficients (SEM).

 Results            As shown in numbered rows (table): univariate associations (1) estimated strength increased in pre-MW but decreased in post-MW across age.  (2) SFS was unchanged in pre-MW but increased in post-MW across age, (3) SFS was higher in pre-MW and post-MW with a larger CSA, but (4) larger CSA was associated with greater strength in pre-MW, not in post-MW despite (5) lower strength with higher SFS.  

 In a multivariate associations (6) larger CSA was now associated with greater strength in both pre-MW and post-MW independent of SFS and age, (7) higher SFS was associated lower strength independent of CSA and age and (8) age remained a predictor of strength independent of SFS and CSA in pre-MW, but not post-MW. 

 Conclusion     Bone fragility is likely to be accounted for by microstructural deterioration due to loss of minimised mass assembled during growth and compromise of the biomechanical advantage of larger bone size.  Bone microarchitecture deterioration is a pivotal determinant of bone fragility, is quantifiable noninvasively and can be prevented or reversed if detected early.

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