Investigation of the nano-mechanical properties and surface topographies of wear particles and human knee cartilages

Although wear particles are the by-products of wear processes in knee joints and carry rich information about the processes and wear conditions, wear debris generated in human knee joints has not been well studied. The purpose of this study was to develop methodologies for investigating the nano-mechanical properties and nano-surface topographies of wear particles found in human knee synovial fluid, and their correlation with those of human cartilages in osteoarthritis (OA) progression. To fulfil the purpose, atomic force microscopy (AFM) was used to study wear particles and human knee articular cartilages in a fluid mode and at a nanometer scale. Young's moduli of wear debris and human cartilages were examined and compared. Image processing and numerical analysis techniques were established to quantitatively characterise the surface topographies of wear debris. The preliminary results demonstrated that the mechanical property and quantitative surface features of the wear particles were successfully studied by using the established methods. This study provided evidence that the nano-scaled surface textures and nano-mechanical property of the wear particles alter with increasing OA grade, and that there is the need for further evaluation of correlations between wear particles and human cartilages, and the effectiveness of analysing wear particles for revealing nano-mechanical and structural changes in the knee joint conditions.