The goal of the study is the analysis of metal ion serum concentrations and of the cytokine production in the blood of patients with a conventional cementless total hip replacement. The rationale is that a) the bearing wear releases particles respectively metal ions into the joint and the blood which will differ in quantity and composition; b) the cytokine production of peripheral blood mononuclear cells (PBMC) might be influenced to a varying degree by the metal and the ceramic particles.

The patients from whom the respective samples will be analyzed are randomized in one of the following three groups: metal-on-metal, ceramic-on-ceramic or ceramic-on-metal. A 36mm bearing is used in all patients. In this separate study, follow-up data of the clinical and radiographic examinations of the patients are available.

Inclusion Criteria:

• age over 18 years, necessity of hip replacement, informed consent

Exclusion Criteria:

• acute inflammatory disease, renal disease, other cobalt-chromium implant, ager over 75 years

total of 30 subjects; 10 with metal-on-metal, 10 with ceramic-on-ceramic and 10 with ceramic-on-metal hip replacement;