Mapping the Micro-Abrasion Mechanisms of CoCrMo: Some Thoughts on Varying Ceramic Counterface Diameter on Transition Boundaries In Vitro

Abstract

The micro-abrasion wear mechanisms for CoCrMo against variable size alumina balls, representing typical artificial femoral head sizes, were investigated over a range of applied loads in foetal calf serum solution. SEM analysis of resulting wear scars displayed two-body and mixed-mode abrasion modes of wear. The wear factor, κ, was found to range between 0.86 and 22.87 (10−6 mm3/Nm). Micro-abrasion mechanism and wastage maps were constructed for the parameter range tested. A dominant two- to three-body abrasion regime was observed with an increasing load and ball diameter. The 28-mm ball diameter displayed the lowest wastage, with an increasing load. Proteins may act to reduce the severity of contact between abrasive particles and bearing surfaces. Wear volumes did not necessarily increase linearly with applied load and ball diameter; therefore, there is a need to develop more accurate models for wear prediction during micro-abrasion conditions. Wear mapping for hip replacements could provide a useful aid for pre-clinical hip wear evaluations and long-term performance.