Cz En

Musculoskeletal system and artificial replacements

Research on tissues and body structures and biomaterials

Simulation of cyclic loading of total knee replacement where an evaluation of cyclic stress state in tibial plateau is ephasized

Project description:

Relation between true stress [MPa] and logarithmic strain [-] during simple tensile test of a flat specimen from UHMWPE

Relation between force [N] and displacement [mm] during standard test of a miniature disk specimen from virgin UHMWPE according to ASTM F 2183-02 (Small Punch Testing)

Tibial plateau is called a replaceable articulative insert made from ultra-high molecular weight polyethylene (UHMWPE), which is a part of tibial component of a total knee replacement. From many experiments and experiences with human knee or hip replacements there is known that the lifespan of bearing component made from UHMWPE is the limiting factor of the whole total joint replacement. We distinguish several modes of failure of UHWMPE components e.g. generation of mechanically induced polymer debris, delamination and pitting. The last two modes of failure, i.e. delamination and pitting are primarly connected to mechanicaly induced fatigue and degradation of contact surfaces. Due to analysis of kinematics, loading conditions and geometry of a human joint replacement we are able to determine a dominant mode of failure, e.g. considering a total hip replacement where abrasive wear of a polyethylene cup is dominant while considering total knee replacement where the kinematic circumstances and geometry are more complex and and where the fatigue modes of failure become more significant. Goal of this project is to simulate dynamic loading of total knee replacement where accurate material response of UHMWPE really matters. Finite element analysis, user implementation of visco-elastic constitutive model of UHMWPE to FEM code (constitutive model created by J.S. Bergström [Bergström JS, Biomaterials. 2003, 25(1),2171-2178]) and group of experimental measurements to gain relation between true stress and logaritmic strain are used as tools.

Ing. Pavel Růžička, Ph.D.


Institute of Macromolecular Chemistry AS CR, v.v.i. (RNDr. Miroslav Šlouf Ph.D.)



  • Bouda T., et al. Simple tensile test of medical grade UHMWPE to rupture with utilization of 3D optical corelation system. In Abstract book – 2nd Workshop Biotribology – Bringing Engineering and Medicine. Braga : Universidade do Minho, 2009. s. 80.
  • Bouda, T. - Růžička, P. - Konvičková, S.: Implementace konstitutivního modelu UHMWPE do prostředí implicitního řešiče Abaqus 6.9 s využitím user subrutiny UMAT. In Výpočty konstrukcí metodou konečných prvků 2010. Praha: ČVUT FS, Ústav mechaniky, Odbor pružnosti a pevnosti, 2010, díl 1, . ISBN 978-80-01-04670-8.