Concept and development of an orthotropic FE model of the proximal femur

Wirtz, Dieter Christian; Pandorf, Thomas; Portheine, Frank; Radermacher, Klaus; Schiffers, Norbert; Prescher, Andreas; Weichert, Dieter; Niethard, Fritz Uwe

Affiliations

¹Department of Orthopaedic Surgery, Technical University of Aachen, Paulwelsstr 30, Aachen 52074, Germany

²Institute of Mechanics, Technical University of Aachen, Aachen, Germany

³Helmholtz-Institute of Biomedical Engineering, Technical University of Aachen, Aachen, Germany

⁴Institute of Anatomy, Technical University of Aachen, Aachen, Germany

Abstract and keywords

Purpose: In contrast to many isotropic finite-element (FE) models of the femur in literature, it was the object of our study to develop an orthotropic FE “model femur” to realistically simulate three-dimensional bone remodelling.

Methods: The three-dimensional geometry of the proximal femur was reconstructed by CT scans of a pair of cadaveric femurs at equal distances of 2 mm. These three-dimensional CT models were implemented into an FE simulation tool. Well-known “density-determined” bony material properties (Young's modulus; Poisson's ratio; ultimate strength in pressure, tension and torsion; shear modulus) were assigned to each FE of the same “CT-density-characterized” volumetric group.

In order to fix the principal directions of stiffness in FE areas with the same “density characterization”, the cadaveric femurs were cut in 2 mm slices in frontal (left femur) and sagittal plane (right femur). Each femoral slice was scanned into a computer-based image processing system. On these images, the principal directions of stiffness of cancellous and cortical bone were determined manually using the orientation of the trabecular structures and the Haversian system. Finally, these geometric data were matched with the “CT-density characterized” three-dimensional femur model. In addition, the time and density-dependent adaptive behaviour of bone remodelling was taken into account by implementation of Carter's criterion.

Results: In the constructed “model femur”, each FE is characterized by the principal directions of the stiffness and the “CT-density-determined” material properties of cortical and cancellous bone. Thus, on the basis of anatomic data a three-dimensional FE simulation reference model of the proximal femur was realized considering orthotropic conditions of bone behaviour.

Conclusions: With the orthotropic “model femur”, the fundamental basis has been formed to realize realistic simulations of the dynamical processes of bone remodelling under different loading conditions or operative procedures (osteotomies, total hip replacements, etc).

Keywords: Finite-element model; Orthotropy; Bone remodelling; Femur

Links

DOI: 10.1016/S0021-9290(02)00309-3

PubMed: 12547369

WoS: 000181003500018

History

Accepted: 2002-08-22

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Cited By (10)

Year	Entry
2009	Schonning A, Oommen B, Ionescu I, Conway T. Hexahedral mesh development of free-formed geometry: the human femur exemplified. Comput Aided Des. 2009;41(8):566-572.
2010	Santos L, Romeu JC, Canhão H, Fonseca JE, Fernandes PR. A quantitative comparison of a bone remodeling model with dual-energy X-ray absorptiometry and analysis of the inter-individual biological variability of femoral neck T-score. J Biomech. December 1, 2010;43(16):3150-3155.
2011	Rudy DJ, Deuerling JM, Espinoza Orías AA, Roeder RK. Anatomic variation in the elastic inhomogeneity and anisotropy of human femoral cortical bone tissue is consistent across multiple donors. J Biomech. June 3, 2011;44(9):1817-1820.
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2006	Whitty M. Development of a Physiological Three Dimensional Finite Element Model of a Human Tibia [Master's thesis]. Kingston, ON: Royal Military College of Canada; May 2006.
2013	Poundarik A. The Role of Non-Collagenous Proteins, in Particular, Osteocalcin and Osteopontin, in the Determination of Bone Matrix Quality [PhD thesis]. Troy, NY: Rensselaer Polytechnic Institute; May 2013.
2013	Enns-Bray WS. Mapping Anisotropy of the Proximal Femur for Improved Image-Based Finite Element Analysis [Master's thesis]. Calgary, AB: University of Calgary; August 2013.
2003	Fox JC. Biomechanics of the Proximal Femur: Role of Bone Distribution and Architecture [PhD thesis]. Berkeley, CA: Berkeley, University of California; 2003.