title: Multi-scale modeling of the human vertebral body: comparison of micro-CT based high-resolution and continuum-level models.
abstract: The overall goal of this study was to assess the mechanistic fidelity of continuum-level finite element models of the vertebral body, which represent a promising tool for understanding and predicting clinical fracture risk. Two finite element (FE) models were generated from micro-CT scans of each of 13 T9 vertebral bodies--a micro-FE model at 60-micron resolution and a coarsened, continuum-level model at 0.96-mm resolution. Two previously-reported continuum-level modulus-density relationships for human vertebral bone were parametrically varied to investigate their effects on model fidelity using the micro-CT models as a gold standard. We found that the modulus-density relation, particularly that assigned to the peripheral bone, substantially altered the regression coefficients, but not the degree of correlation between continuum and micro-FE predictions of whole-vertebral stiffness. The major load paths through the vertebrae compared well between the continuum-level and micro-FE models (von-Mises distribution), but the distributions of minimum principal strain were notably different. We conclude that continuum-level models provide robust measures of whole-vertebral behavior, describe well the load transfer paths through the vertebra, but provide strain distributions that are markedly different than the volume-averaged micro-scale strains. Appreciation of these multi-scale differences should improve interpretation of results from these sorts of continuum models and may improve their clinical utility.
authors.affiliation: Orthopaedic Biomechanics Laboratory, Department of Mechanical Engineering, University of California, Berkeley, CA 94720, USA.
authors.forename: Senthil K
authors.initials: SK
authors.lastname: Eswaran
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Fields
authors.forename: Prem
authors.initials: P
authors.lastname: Nagarathnam
authors.forename: Tony M
authors.initials: TM
authors.lastname: Keaveny
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001699:Biometry; D015519:Bone Density; D003198:Computer Simulation; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008953:Models, Anatomic; D012307:Risk Factors; D016103:Spinal Fractures / Q000209:etiology; D013131:Spine / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000502:physiology; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data