An improved method for the automatic mapping of computed tomography numbers onto finite element models.

The assignment of bone tissue material properties is a fundamental step in the generation of subject-specific finite element models from computed tomography data. Aim of the present work is to investigate the influence of the material mapping algorithm on the results predicted by the finite element analysis. Two models, a coarse and a refined one, of a human ileum, femur and tibia, were generated from CT data and used for the tests. In addition a convergence analysis was carried out for the femur model, using six refinement levels, to verify whether the inclusion of the material properties would significantly alter the convergence behaviour of the mesh. The results showed that the choice of the mapping algorithm influences the material distribution. However, this did not always propagate into the finite element results. The difference between the maximum Von Mises stress remained always lower than 10%, apart one case when it reached the 13%. However, the global behaviour of the meshes showed more marked differences between the two algorithms: in the finer meshes of the two long bones 20-30% of the bone volume showed differences in the predicted Von Mises stresses greater than 10%. The convergence behaviour of the model was not worsened by the introduction of inhomogeneous material properties. The software was made available in the public domain.

[1]  S A Marom,et al.  Computer aided stress analysis of long bones utilizing computed tomography. , 1990, Journal of biomechanics.

[2]  M Viceconti,et al.  A new method for the automatic mesh generation of bone segments from CT data. , 1999, Journal of medical engineering & technology.

[3]  P Rüegsegger,et al.  Automated finite element analysis of excised human femora based on precision -QCT. , 1996, Journal of biomechanical engineering.

[4]  J P Morucci,et al.  Development of a three-dimensional finite element model of a human tibia using experimental modal analysis. , 1991, Journal of biomechanics.

[5]  W. Hayes,et al.  The compressive behavior of bone as a two-phase porous structure. , 1977, The Journal of bone and joint surgery. American volume.

[6]  R. Taghavi.  Automatic, parallel and fault tolerant mesh generation from CAD , 2005, Engineering with Computers.

[7]  J H Keyak,et al.  Three-dimensional finite element modeling of a cervical vertebra: an investigation of burst fracture mechanism. , 1994, Journal of spinal disorders.

[8]  T. Keller.  Predicting the compressive mechanical behavior of bone. , 1994, Journal of biomechanics.

[9]  M Viceconti,et al.  Material properties assignment to finite element models of bone structures: a new method. , 1999, Medical engineering & physics.

[10]  S. Cowin,et al.  On the dependence of the elasticity and strength of cancellous bone on apparent density. , 1988, Journal of biomechanics.

[11]  R. Huiskes,et al.  Development and validation of a three-dimensional finite element model of the pelvic bone. , 1995, Journal of biomechanical engineering.

[12]  D. Cody,et al.  Femoral structure and stiffness in patients with femoral neck fracture , 2000, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[13]  P M Cattaneo,et al.  A three-dimensional finite element model from computed tomography data: A semi-automated method , 2001, Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine.

[14]  J H Kuiper,et al.  The prediction of stress fractures using a ‘stressed volume’ concept , 2001, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[15]  R. B. Ashman,et al.  Relations of mechanical properties to density and CT numbers in human bone. , 1995, Medical engineering & physics.

[16]  W. Hayes,et al.  Prediction of vertebral body compressive fracture using quantitative computed tomography. , 1985, The Journal of bone and joint surgery. American volume.

[17]  S. Goldstein,et al.  Evaluation of orthogonal mechanical properties and density of human trabecular bone from the major metaphyseal regions with materials testing and computed tomography , 1991, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[18]  R. Huiskes,et al.  Hip-joint and abductor-muscle forces adequately represent in vivo loading of a cemented total hip reconstruction. , 2001, Journal of biomechanics.

[19]  Marco Viceconti,et al.  Border-tracing algorithm implementation for the femoral geometry reconstruction , 2001, Comput. Methods Programs Biomed..

[20]  W. Hayes,et al.  Fracture prediction for the proximal femur using finite element models: Part I--Linear analysis. , 1991, Journal of biomechanical engineering.

[21]  J H Keyak,et al.  Prediction of femoral fracture load using finite element models: an examination of stress- and strain-based failure theories. , 2000, Journal of biomechanics.

[22]  Jean-Daniel Boissonnat,et al.  Three-dimensional reconstruction of complex shapes based on the Delaunay triangulation , 1993, Electronic Imaging.