Trabecular bone adaptation with an orthotropic material model

Zev Miller, Moshe B. Fuchs, Mircea Arcan

Research output: Contribution to journalArticlepeer-review

Abstract

Most bone adaptation algorithms, that attempt to explain the connection between bone morphology and loads, assume that bone is effectively isotropic. An isotropic material model can explain the bone density distribution, but not the structure and pattern of trabecular bone, which clearly has a mechanical significance. In this paper, an orthotropic material model is utilized to predict the proximal femur trabecular structure. Two hypotheses are combined to determine the local orientation and material properties of each element in the model. First, it is suggested that trabecular directions, which correspond to the orthotropic material axes, are determined locally by the maximal principal stress directions due to the multiple load cases (MLC) the femur is subject to. The second hypothesis is that material properties in each material direction can be determined using directional stimuli, thus extending existing adaptation algorithms to include directionality. An algorithm is utilized, where each iteration comprises of two stages. First, material axes are rotated to the direction of the largest principal stress that occurs from a multiple load scheme applied to the proximal femur. Next, material properties are modified in each material direction, according to a directional stimulus. Results show that local material directions correspond with known trabecular patterns, reproducing all main groups of trabeculae very well. The local directional stiffnesses, degree of anisotropy and density distribution are shown to conform to real femur morphology.

Original languageEnglish
Pages (from-to)247-256
Number of pages10
JournalJournal of Biomechanics
Volume35
Issue number2
DOIs
StatePublished - 2002

Keywords

  • Adaptation
  • Mechanical properties
  • Orthotropy
  • Proximal femur
  • Trabecular bone

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