In Norway it is annually performed approximately 600 primary and 100 revisions THA. Osteolysis around the prosthesis is one of the major difficulties while performing revision surgery. C-stem is a triple tapered cemented prosthesis designed to increase the stress and strain of proximal femur and thereby decreasing osteolysis. We are planning til include 70 patients and randomize to C-stem AMT or Exeter prosthesis. Both prosthesis will be combined with previously non documented "Marathon" acetabular prosthesis.