Wear characterisation of articular cartilage surfaces at a nano-scale using atomic force microscopy

Wear particle analysis has been successfully used for machine condition monitoring of mechanical systems. Although this technique has the potential to be used as a non-destructive and effective technique for osteoarthritis (OA) assessment, the current analysis technique needs further development for this application. This study was aimed to characterise cartilage surface topography and its changes with wear progression at a nano-scale. Cartilage samples were generated in wear tests. Three dimensional (3D) cartilage surface data was obtained using atomic force microscopy (AFM) and then characterised using 32 numerical parameters defined in ISO25178-2. As a result of statistical and correlation analyses, six parameters have been selected to characterise the changes in the cartilage surface topography. Three typical trends have been observed. The feature parameters were, for the first time, used for the cartilage surface characterisation in 3D, and at the nano-scale. The results, using the functional (feature) parameters, have given a new insight to the wear process which could not be achieved previously. This work may also contribute to the development of effective wear particle analysis techniques for OA assessment and diagnosis.