Wear couple ceramic-on-polyethylene and ceramic-on-ceramic: In-vitro wear versus in-vivo wear

For more than 30 years ceramics are used for heads and acetabular cups of hip joint arthroplasty. The results of wear rates of metal-on-polyethylene, ceramic-on-polyethylene and ceramic-on-ceramic determined from a hip simulator testing were not confirmed when comparing to results of clinical follow ups using either X-rays methods or investigating retrieved implants. There is consensus that the wear couple of metal-on-poly-ethlene is twice or three times larger than the one for ceramic-on-poly-ethylene. Ceramic-on-ceramic offers the option of 5mum/year. When evaluation novel concepts the best is to investigate retrievals because the hip simulator does not mimic all in-vivo effects. Hip simulator testing is not "worse case testing" as it should be. hip simulator testing is "best case testing". The results may be used for screening purposes.