Biomechanical properties of articular cartilage as a standard for biologically integrated interfaces

Articular cartilage integration has been described in in-vitro models, which compare mechanical to biochemical behaviour and histological analysis, respectively. The emphasis of these findings is mainly on the biochemical and histological analysis, rather than on the mechanical performance. The complex in vitro loading conditions and high deviations in the mechanical results due to the biological variance, make interpretations difficult. The aim of this study is to analyse and define the mechanical stress and strain distribution in a single lap configuration by means of an optical strain measurement system. Supportive finite element computation is performed to indicate the heterogeneous stress strain distribution in the integration area. The optical failure analysis of the experiment reveals crack propagation through the integration area comparable to plane shear in fracture mode two. Using the optical strain measurement set up a direct estimation of the shear modulus is achievable by analysing the relative displacement within the bonded joint before the onset of delamination in the adhesive layer. This result lead to a better interpretation of the mechanical behaviour of articular cartilage integration in vitro.