Prediction of apparent trabecular bone stiffness through fourth-order fabric tensors.
The apparent stiffness tensor is an important mechanical parameter for characterizing trabecular bone. Previous studies have modeled this parameter as a function of mechanical properties of the tissue, bone density, and a second-order fabric tensor, which encodes both anisotropy and orientation of trabecular bone. Although these models yield strong correlations between observed and predicted stiffness tensors, there is still space for reducing accuracy errors. In this paper, we propose a model that uses fourth-order instead of second-order fabric tensors. First, the totally symmetric part of the stiffness tensor is assumed proportional to the fourth-order fabric tensor in the logarithmic scale. Second, the asymmetric part of the stiffness tensor is derived from relationships among components of the harmonic tensor decomposition of the stiffness tensor. The mean intercept length (MIL), generalized MIL (GMIL), and fourth-order global structure tensor were computed from images acquired through microcomputed tomography of 264 specimens of the femur. The predicted tensors were compared to the stiffness tensors computed by using the micro-finite element method ([Formula: see text]FE), which was considered as the gold standard, yielding strong correlations ([Formula: see text] above 0.962). The GMIL tensor yielded the best results among the tested fabric tensors. The Frobenius error, geodesic error, and the error of the norm were reduced by applying the proposed model by 3.75, 0.07, and 3.16 %, respectively, compared to the model by Zysset and Curnier (Mech Mater 21(4):243-250, 1995) with the second-order MIL tensor. From the results, fourth-order fabric tensors are a good alternative to the more expensive [Formula: see text]FE stiffness predictions.
School of Technology and Health, KTH Royal Institute of Technology, Huddinge, Stockholm, Sweden. rodrigo.moreno@sth.kth.se.
Rodrigo
0000-0001-5765-2964
R
Moreno
School of Technology and Health, KTH Royal Institute of Technology, Huddinge, Stockholm, Sweden.
Örjan
0000-0002-7750-1917
Ö
Smedby
Institute for Lightweight Design and Structural Biomechanics, Technical University of Vienna, Vienna, Austria.
Dieter H
DH
Pahr
D000465:Algorithms; D001696:Biomechanical Phenomena; D000071556:Cancellous Bone / Q000502:physiology*; D005269:Femur / Q000502:physiology*; D006801:Humans
Fabric tensors; Mean intercept length; Mechanical properties; Stiffness tensor; Trabecular bone