INTER-PROSTHETIC DISTANCE EFFECT IN HUMAN FEMUR FRACTURE AFTER HIP AND KNEE TOTAL REPLACEMENT A.Abdelkader (1), D. Elizondo (1), J.P.M Correia (1), N. Bahlouli (1), C. Cluzel (2), S. Facca (1,3) (1) ICUBE Laboratory, University of Strasbourg - CNRS, 2 Rue Boussingault, 67000 Strasbourg, France. (2) LMT, ENS-Cachan, Université Paris Saclay - CNRS, 94235 Cachan, France, & IUT-d’Evry Val d’Essonne, Dep. SGM, 91025 Evry. (3) Hand Surgery Department, Strasbourg University Hospital, Fédération de Médecine Translationnelle (FMTS), 1 Place de l'Hôpital, BP 426, 67091 Strasbourg Cedex, France.
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Introduction Patients with hip and knee joint replacements in the same leg are at risk of inter-prosthetic (IP) fractures. A FE numerical Study was performed for the mechanical response of a bi-prosthetic femur with different gap distances between the two implants tips under combined compression and bending loading with offset boundary conditions. In this first estimation of the capability of the test procedure, firstly the femur bone was modelled as a uniform cylinder to capture the global structural tendency. Several stem lengths were used in the simulations, then a real bone geometry was modelled to capture the effect of the real geometry in the results.
Material and Methods The base of the assembly is to go through loading transfer boxes. The bending moment values and thus the compressive stress values can be managed along the femur bone by choosing different arm lengths in a symmetric or non-symmetric way.
The mechanical behavior of the bone was assumed to be elastic transversely isotropic. The elastic constant values were taken from Peng et al. The contact between the stems and the femur bone was modeled with a rough-type interaction.
• Different values gap between the two stems were considered : 120, 110, 100, 80, 70, 50, 35 and 20 mm. • Simple cylinder and real bone geometry is being used.
• The stems material made in titanium and the boxes in stainless steel. • Elastic transversely isotropic behavior of the bone material
Results Simple geometry Non Symmetric
Symmetric
strains distribution along the cylinder outer surface
Non Symmetric
Different thickness strains distribution
Real Geometry
Results Meshing and FEM Surface strains results at the lateral side of the femur with different gaps
Conclusion & Future work - Strain distribution achieves always a same maximum value with the increase of IP distance. - IP distance don’t have a stress riser effect . - Start experimental tests and evaluate the correlation between numerical and experimental tests. - The effects of non homogenous density distribution along the femur bone will be investigated
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STL FILEs
References • M. Soenen et al. (2013). • L. Weiser et al. (2014). • Peng et al. (2006)
