Topological and Contact Force Analysis of a Knee Tumor Prosthesis

In the present work, a topological analysis of a knee tumor prosthesis using grade 5 biomedical titanium alloy material (Ti6Al4V) and an ultra-high molecular weight polyethylene insert (UHMWPE) was performed. A three-dimensional finite element analysis (FEM) model was used, taking into account the von Mises stress and the contact forces (CPRESS), using the finite element software ABAQUS that analyzes the mechanical contact between two surfaces. The contact pressure due to the contact force and shear stress from friction, especially in the contact areas in the UHMWPE and Ti6Al4V parts, to be considered occur during the following activities: (1) At the critical point of the walking cycle at 15° of femur flexion with respect to the tibia with a load of 3.3 times the body weight (BW), (2) Climbing stairs with a bend angle of 83° and 3.5 BW and (3) Squatting with an angle of 130° and 5.6 pcs (Alsamhan in J King Saud Univ Eng Sci 25:49–54, 2012, [1]; Brassard in Complicaciones de la artoplasia total de rodilla. Insall, México, 2007, [2]; Buehler in J Arthroplasty 15:698–701, 2000, [3]). The Analysis of the knee tumor was performed by scanning the parts, digitizing them in STL format and debugging the images using CAD software. We performed the simulation of these three conditions using finite element analysis software, obtaining a maximum stress of 229,497 MPa in the squat condition and a displacement of 20.14 μm in this same condition. We used the von Mises failure criterion equation (Jhonson in Mecánica de contacto. Cambridge University, México, 1985, [4]). For the analysis of contact forces in the joints we used the results of CPRESS and were validated with an analytical contact Hertz study (Ludema in Friction Wear Lubrication. CRC Press, Michigan, 1996, [5]). The topology indicates that there are material savings of 80%, mainly on the titanium alloy of the knee. As reference, a male Mexican patient with a weight of 70 kg and 1.70 m of height was taken.