title: A reconciliation of local and global models for bone remodeling through optimization theory.
abstract: Remodeling rules with either a global or a local mathematical form have been proposed for load-bearing bones in the literature. In the local models, the bone architecture (shape, density) is related to the strains/energies sensed at any point in the bone, while in the global models, a criterion believed to be applicable to the whole bone is used. In the present paper, a local remodeling rule with a strain "error" form is derived as the necessary condition for the optimum of a global remodeling criterion, suggesting that many of the local error-driven remodeling rules may have corresponding global optimization-based criteria. The global criterion proposed in the present study is a trade-off between the cost of metabolic growth and use, mathematically represented by the mass, and the cost of failure, mathematically represented by the total strain energy. The proposed global criterion is shown to be related to the optimality criteria methods of structural optimization by the equivalence of the model solution and the fully stressed solution for statically determinate structures. In related work, the global criterion is applied to simulate the strength recovery in bones with screw holes left behind after removal of fracture fixation plates. The results predicted by the model are shown to be in good agreement with experimental results, leading to the conclusion that load-bearing bones are structures with optimal shape and property for their function.
authors.affiliation: Department of Mechanical Engineering, University of Colorado, Boulder 80309-0427, USA. ganesh@colorado.edu
authors.forename: G
authors.initials: G
authors.lastname: Subbarayan
authors.forename: D L
authors.initials: DL
authors.lastname: Bartel
mesh_terms: D015982:Bias; D015519:Bone Density / Q000502:physiology; D001846:Bone Development / Q000502:physiology*; D001860:Bone Plates; D016723:Bone Remodeling / Q000502:physiology*; D001863:Bone Screws / Q000009:adverse effects; D004734:Energy Metabolism / Q000502:physiology; D008954:Models, Biological; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013718:Tensile Strength; D016474:Weight-Bearing