Residual abrasive material from surface grinding of metal-metal hip implants: A source of third-body wear?

The surfaces of fifteen heads of all metal hip implants were investigated using a scanning electron microscope. The heads were manufactured from Co-Cr-Mo alloy either cast, low carbon wrought or high carbon wrought. Six of the surfaces were investigated prior to hip simulator testing, three after 3 million cycles of simulator testing and six after 6 million cycles of testing. Third-body wear type scratches of varying amounts were observed on all fifteen heads. Residual grinding stone material from the manufacturing process was also found at varying amounts on the surfaces of all fifteen heads. There was a correlation between the extent of this residual material and the extent to which the surfaces were scratched.