 -Second group will be studied through the dosage of circulating ions, deriving from the articular surfaces and through the histological classification of vasculitis in periimplant tissues. There is increasing evidence, indeed that locale release of submicron particles worn out from articular surfaces can release metal ions mainly Chromium and Cobalt responsible for lymphocyte local infiltration. In particular CD20 positive B lymphocyte and CD3 positive T lymphocyte and sometimes CD68 positive plasma cells are present. The cells could justify the development of pseudotumors in metal-on metal hip prosthesis. 