H1 Hip Resurfacing Arthroplasty

Inclusion Criteria: * Patient requires primary hip arthroplasty due to degenerative joint disease (primary osteoarthritis, posttraumatic osteoarthritis, avascular necrosis, developmental hip dysplasia) * Patient is eligible for hip resurfacing arthroplasty: i.e. has sufficient bone stock at the level of the femoral head (\<1/3 necrosis of the head) and neck (not osteopenic/porotic, see exclusion criteria) * Patient is between 18 and 70 years old * Patient willing to comply with study requirements * Patient is legally entitled and able to consent, agrees to consent to and to follow the study visit schedule (as defined in the study protocol and informed consent form), by signing the informed consent form approved by the Ethics Committee. * Patient plans to be available through ten (10) years postoperative follow-up * Patient is able to understand the native language of the country of the trial centre Exclusion Criteria: * Patient has a BMI greater than 40 * Patient suffers from an active inflammatory joint disorder * Patient has an active infection or sepsis (treated or untreated) * Patient has insufficient bone stock at the hip (\>1/3 necrosis of the femoral head) or in general as in severe osteopenia or osteoporosis (Tscore \< -2.5 as measured with BMD) * At the time of enrolment, patient has one or more of the following arthroplasties that have been * Implanted less than 6 months before the current hip arthroplasty: * Contralateral primary total hip arthroplasty or hip resurfacing arthroplasty * Ipsilateral or contralateral primary total knee or unicondylar knee arthroplasty * Patient takes medications which potentially affect the bone such as corticosteroids and antimitotic medications. * Patient has a condition that may interfere with the hip arthroplasty survival or outcome (i.e. Paget's or Charcot's disease, vascular insufficiency, muscular atrophy, uncontrolled diabetes, moderate to severe renal insufficiency or neuromuscular disease) * Patient has a known alcohol or drug abuse * Patient has an immunosuppressive disorder * Patient has a malignant tumour, metastatic, or neoplastic disease * Patient has severe comorbidities or a limited life expectancy * Patient lacks capacity to consent * Patient has an emotional or neurological condition that would pre-empt his/her ability or willingness to participate in the study * Patient is not willing or able to sign an informed consent form * Patient pregnant or breast feeding * Patient is not able or willing to come to follow-up visits * In addition, the following exclusion criteria are applied to the 20 patients (Cohort 1 and Cohort 1.1) in the safety study in whom metal ion measurements will be performed, since those conditions may be associated with elevated metal ion levels and could complicate the interpretation of the metal ion results: * Patients who already received another joint replacement, hip, knee, shoulder, ankle. * Workers in the paint, diamond, leather or other industries producing Co or Cr dust. * Patients taking medication, vitamins or food supplements containing Co or Cr and not able or willing to discontinue those.