Wear is the main reason for revision operations after joint arthroplasty. While the survival of modern implants is often longer than the expected life span in old patients, young patients (<60 years) have to expect at least one wear induced revision operation. The reason is the throughout all registries consistantly significantly reduced implant survival rates in young patients. In the swedish arthrplasty registry the 15 year survival for patients older than 75 years is 95 % and for those younger than 50 years is 75 %. This corresponds to a 5fold increased revision rate (5 % vs. 25 %) 15 years after implantation. This significant difference cannot be explained by the higher activity of younger patients alone. Patient specific factors, that modulate the biological reaction on wear particles, are therefore highly probable. These could explain the significant age dependency of implant survival.

The main hypothesis of this study is therefore, that the biological reaction on wear particles depends on the patients age.

Inclusion Criteria:

• having received a total hip arthroplasty 4 weeks before blood sample for this study

Exclusion Criteria:

• no informed consent

80 patients having received a total hip arthroplasty 4 weeks before blood sample for this study