¿Cómo afecta la viscoelasticidad de los polímeros a la lubricación de las prótesis de rodilla? Predicciones desde un modelo de prótesis autolubricada

Polyethylene wear of the tibial component is recognized as the main problem limiting the duration of these implants. The difficulty of in vivo measurements of the variables that influence wear, has motivated the numerical study of theoretical models. Previous works focused on studying the lubricant film thickness, the pressure field and friction coefficient in the contact zone of the prosthesis, showing an optimization of the joint lubrication with the presence of a low rigidity elastic material. However, polymeric materials currently used or under investigation are viscoelastic. This feature can modify previous predictions and consequently the design proposals. This paper presents a model of lubrication of a knee prosthesis comprising a metal femoral component and a tibial component containing a linear viscoelastic material on the articular surface. The results obtained by a numerical technique based on finite elements, show that film thicknesses are considerably affected by viscoelasticity when comparing the results of this work with previous elastic models predictions. Then, conclusions are drawn directed to the optimization of lubrication through the material properties of the polymer and a exudation capacity of a hypothetical material adhered to the tibial component.