Electromechanical response of articular cartilage in indentation—considerations on the determination of cartilage properties during arthroscopy

Abstract

A finite element formulation of streaming potentials in articular cartilage was incorporated into a fibril-reinforced model using the commercial software ABAQUS. This model was subsequently used to simulate interactions between an arthroscopic probe and articular cartilage in a knee joint. Fibril reinforcement was found to account for large fluid pressure at considerable strain rates, as has been observed in unconfined compression. Furthermore, specific electromechanical responses were associated with specific changes in tissue properties that occur with cartilage degeneration. For example, the strong strain-rate dependence of the load response was only observed when the collagen network was intact. Therefore, it is possible to use data measured during arthroscopy to evaluate the degree of cartilage degeneration and the source causing changed properties. However, practical problems, such as the difficulty of controlling the speed of the handheld probe, may greatly reduce the reliability of such evaluations. The fibril-reinforced electromechanical model revealed that high-speed transient responses were associated with the collagen network, and equilibrium response was primarily determined by proteoglycan matrix. The results presented here may be useful in the application of arthroscopic tools for evaluating cartilage degeneration, for the proper interpretation of data, and for the optimization of data collection during arthroscopy.

Keywords:

• Articular cartilage mechanics
• Collagen fibril reinforcement
• Finite element modeling
• Indentation testing
• Streaming potentials
• Material properties

Acknowledgements

This study was initiated at Biosyntech Inc., Laval, Quebec, Canada, and supported by the Natural Sciences and Engineering Research Council of Canada, and the Alberta Heritage Foundation for Medical Research, Canada. LePing Li appreciated many discussions with Michael Buschmann, Martin Garon and Anne Légaré at Biosyntech Inc.