The study aims at comparing the effect of hollow or solid centralizer designs on the long time fixation behaviour of hip prosthesis stems that are polished, tapered and collarless. In a prospective, controlled and randomized study comprising two groups of 30 patients/hips each, the patients will be followed up by RadioStereometric Analysis (RSA) for ten years. In completion general health questionnaires as well as hip specific scoring instruments will be used to evaluate patient satisfaction and outcome.The hypothesis of the study is that the different centralizers will result in different migration patterns of the stems, which might affect the risk for late aseptic loosening.