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MINERVA ORTOPEDICA E TRAUMATOLOGICA
A Journal on Orthopedics and Traumatology
Minerva Ortopedica e Traumatologica 2008 August;59(4):213-20
Mechanical behaviour of physiological and prosthesized human femurs during stair climbing: a comparative analysis via 3D numerical simulation
Andreaus U. 1, Colloca M. 2, Toscano A. 3
1 Department of Structural and Geotecnical Engineering La Sapienza University, Rome, Italy
2 Theoretical and Applied Mechanics La Sapienza University, Rome, Italy
3 Biomedical Engineering La Sapienza University, Rome, Italy
Aim. The aim of this study was to perform finite element investigation of the mechanical behaviour of a prosthesized human femur during stair climbing. In order to numerically analyze the stress shielding phenomenon in a femoral bone with an artificial hip replacement, the strain and stress distributions both in the femur and in the stem were evaluated by using the finite element method.
Methods. From a set of computed tomography (CT) images the geometry of the femur was recovered and meshed. An operation of virtual surgery allowed to insert the metal stem (constructed by a CAD code) in the medullary canal.
Results. Numerical simulation showed evidence that stresses and strain energy density increase in the distal zone of the stem-bone interface of the prosthesized femur; and hence a load transfer is determined from proximal zones to distal ones. As expected, lateral and medial zones are subjected to, respectively, tensile and compressive normal stresses in z-direction, absolute maxima being attained at the distal part of the diaphysis.
Conclusion. The development of a computational model allowed to deal with the complexity of the biomechanical problem and to describe quantitatively the mechanical behaviour of bone tissue in contact with the metal stem. The calculated results motivate the performed analyses because they are sufficient to activate the mechanisms of deposition and resorption in the bone tissue at contact with the artificial biomaterial. Thus, stair climbing confirms to be a critical task for primary stability of the prosthesized femur.