Constitutive Modelling of Bone Resorption at Orthopaedic Implants
Lars Johansson, Ulf Edlund, Anna Fahlgren and Per Aspenberg
The Swedish Research Council
Orthopaedic implants will sometimes loosen due to bone resorption. This is usually attributed to inflamation due to wear particles. We investigate the possibility of fluid flow or fluid pressure being an important mechanicsm.
In this project, constitutive models for mechanically induced turnover of bone tissue will be formulated. We will focus on the resorption, or destruction (osteolysis), of bone that might occur at the interface between bone and implants such as in artificial hip joints or plates used for surgical repair. Such resorption will, if progressing to far, result in loosening of the implant, with serious consequences for the patient. Previous such studies have been based on the stress or strain state of the tissue itself as the driving force. We plan, instead, to develop a constitutive model based on recent studies that point to fluid pressure, or possibly fluid flow velocity, as a major factor in the bone resorption process.
The major parts of the project are: (i) Constitutive modelling of the relation between bone resorption and flow field quantities, based on experiments already performed and in accordance with termodynamic principles. (ii) Computer implementation. (iii) Validation and refinement the constitutive model, possibly using experiments tailored for this purpose. (iv) Comparisons with clinical observations.
The bone model will be formulated using a general thermodynamic framework that is well suited for future generalizations and refinements. It will provide a tool that makes it possible to understand, in mechanical terms, the mechanisms behind bone resorption. It is then possible to study the effects of improvements of implant design.
Our results have been reported in:
L. Johansson, U. Edlund, A. Fahlgren, and P. Aspenberg, A model for bone resorption, Proceedings of ESDA 2006, Torino, Italy, July 4-7, 2006.
L. Johansson, U. Edlund, A. Fahlgren and P. Aspenberg., Bone resorption induced by fluid flow, Journal of Biomechanical Engineering, 131, 094505, 2009.
A. Fahlgren, M. Bostrom, X. Yang, L. Johansson, U. Edlund, F. Agholme and P. Aspenberg, Fluid pressure and flow as a cause of bone resorption, Acta Orthopaedica, 81(4), 508-516, 2010.
L. Johansson, U. Edlund, A. Fahlgren and P. Aspenberg, Fluid-induced osteolysis: modelling and experiments, Computer Methods in Biomechanics & Biomedical Engineering, 14(4), 305-318, 2011.
A. Fahlgren, L. Johansson, U. Edlund and P. Aspenberg, Direct ex vivo measurement of the fluid permeability of loose scar tissue, Acta of Bioengineering and Biomechanics, 14(2), 47-51, 2012.
Page responsible: Lars Johansson
Last updated: 2012-08-16