Contact between the components of a knee prosthesis: numerical and experimental study

The aim of this work is the analysis of the contact area in a knee prosthesis using two differentapproaches. In particular, the interface between the femoral component and the polyethylene insert has beenstudied both numerically and experimentally. The interest in studying the contact area is related to the fact thatthe wear of the polyethylene insert, due to the high contact pressures, represents one of the major causes offailure of the total knee prosthesis. The possibility to evaluate the contact area at different loads and mutualposition between femur and tibia is, therefore, of fundamental importance to study the service life of aprosthesis and to improve its performance. The finite element numerical approach has required the acquisition,through reverse engineering, and CAD modelling of the prosthetic components. Then the FEM simulationshave been developed considering two different load conditions. In order to compare the calculated data, thesame load configurations have been used for experimental tests based on ultrasonic method. In this case, somepreliminary tests were required to calibrate the system depending on the particular characteristics of materials,geometries and surface finish of the prosthesis.The results show a good correlation between the data obtained with the two different approaches and,consequently, a good level of reliability of the procedures developed for the numerical and experimentalevaluation of the contact area. The numerical procedure can be used to determine the area for different anglesand loads, but especially in the design phase. The ultrasonic technique can be used to validate the numericaldata.