Bio-mechanical behaviour of articular cartilage: characterisation of surface damage, friction and replacement

The progression of cartilage damage has the potential to develop into the joint disease of osteoarthritis. Cartilage repair methodologies involve the implementation of biomaterials, for which the bio-mechanical characteristics should closely align with articular cartilage. To date, the frictional torque of articular cartilage has not been assessed, nor has the coefficient of friction of replacement biomaterials inserted within a defect. Additionally, cartilage damage inducing factors have not been considered for a likely dual effect. Consequently, this thesis presents three novel developments to fulfil the lack of knowledge outlined above. The first novel outcome is the assessment of the dual impact of loading frequency and underlying substrate density, as a replication of bone mineral density, on resulting cartilage damage. The second novel development is a technique to determine the frictional torque of articular cartilage, corresponding to an inserted cartilage replacement biomaterial. The third novel development is a technique to assess the coefficient of friction of a cartilage replacement biomaterial, in line with osteochondral graft surgical procedures. Various approaches have been implemented to include three materials testing machines, Hertzian contact stress analysis and chemical hydrogel manufacture. For this thesis, bovine articular cartilage was modelled for human articular cartilage. The results demonstrate significant cartilage off-bone damage with the multi-factorial effect of a loading frequency of 10 Hz, in combination with an increase in substrate density (p < 0.05). The torque range and characteristics have been identified for which a cartilage replacement biomaterial should adopt, followed by the prospect to assess the coefficient of friction of a biomaterial amongst a defect. The work presented in this thesis has implications on the contribution to osteoarthritis and the manufacture of cartilage replacement biomaterial