Hypothesis: Migration of C-Stem AMT is equal to the well documented Exeter prosthesis

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.

The result will be followed clinically and with RSA and DXA. Soft endpoint after 2 years

Inclusion Criteria:

• coxarthrosis

Exclusion Criteria:

• age over 80
• major medial condition such as renal failure, chronic obstructive lung disease heart failure etc

70 patients admitted to orthopedic clinic Ringerike hospital for coxarthrosis are planned to be included in stydy. The all should agree in a written form to participate in study. They are randomized to be operated THA with Exeter- or C-stem AMT femur prostesis. Marathon acetabular prosthesis will be used for all patients included.