Comparison of the contact conditions in the structural analysis of a polycentric knee prosthesis

The aim of this work is to show the results of the stress analyses performed during the structural design of a polycentric knee prosthesis. This was done by means of the finite element method and three different contact conditions between the assembly parts. The analyses were performed under the most critical load condition defined by the standard ISO 10328 for the principal structural test. The first contact condition considered rigid contact between the linkages and the axes, the second one applied contact with no penetration among all the components and the last one submit the parts to mixed contact, to study the possibility of reducing the number of parts by joining some axes to particular linkages. Results show an important difference in the stresses yielded by each of the simulated conditions. Conditions associated to Case 2 returned the best representation to the simulated mechanism. Simplicity pretended with conditions of Case 1 yielded extreme results, divorced of the real conditions, and on the other hand, results from Case 3 were comparable but not better to the ones obtained with Case 2 contact conditions. Finally, taking into account Case 2, prosthesis' parts will be redesigned in order to guarantee security factors over 1.