Theoretical effects of fully ductile versus fully brittle behaviors of bone tissue on the strength of the human proximal femur and vertebral body

• Published in: Journal of biomechanics 2015-05, Vol.48 (7), p.1264-1269
• Main Authors: Nawathe, Shashank, Yang, Haisheng, Fields, Aaron J, Bouxsein, Mary L, Keaveny, Tony M
• Format: Article
• Language: English
• Subjects: Accidental Falls; Aged; Aged, 80 and over; Behavior; Biomechanical Phenomena; Biomechanics; Bone and Bones - anatomy & histology; Bone and Bones - pathology; Bones; Boundary conditions; Brittleness; Computer Simulation; Ductile brittle transition; Ductility; Elastic Modulus; Female; Femur; Femur - anatomy & histology; Femur - pathology; Finite Element Analysis; Fracture; Human behavior; Humans; Influence; Male; Mathematical models; Microstructure; Middle Aged; Nonlinear Dynamics; Osteoporosis; Physical Medicine and Rehabilitation; Spine - anatomy & histology; Spine - pathology; Strength; Studies; Tensile Strength; Tissue-level ductility; Vertebrae; Whole bone
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2015.02.066

Abstract The influence of the ductility of bone tissue on whole-bone strength represents a fundamental issue of multi-scale biomechanics. To gain insight, we performed a computational study of 16 human proximal femurs and 12 T9 vertebral bodies, comparing the whole-bone strength for the two hypothetical bounding cases of fully brittle versus fully ductile tissue-level failure behaviors, all other factors, including tissue-level elastic modulus and yield stress, held fixed. For each bone, a finite element model was generated (60–82 μm element size; up to 120 million elements) and was virtually loaded in habitual (stance for femur, compression for vertebra) and non-habitual (sideways fall, only for femur) loading modes. Using a geometrically and materially non-linear model, the tissue was assumed to be either fully brittle or fully ductile. We found that, under habitual loading, changing the tissue behavior from fully ductile to fully brittle reduced whole-bone strength by 38.3±2.4% (mean±SD) and 39.4±1.9% for the femur and vertebra, respectively ( p =0.39 for site difference). These reductions were remarkably uniform across bones, but (for the femur) were greater for non-habitual (57.1±4.7%) than habitual loading ( p