Fixation and Stability of the Trident® II Clusterhole HA Shells

Inclusion Criteria: * Patient is able to understand the meaning of the study and is willing to sign the EC approved, study specific Informed Patient Consent Form. * The subject is a male or non-pregnant female between 40 and 75 years of age. * Patients with a BMI \< 35. * Patients requiring uncemented primary THA, suitable for the use of the uncemented Trident® Hemi HA or Trident® II Clusterhole HA acetabular component in combination with any compatible Stryker femoral stem. * Patients with no clinical relevant disorders undergoing total hip arthroplasty. * Patients with a diagnosis of osteoarthritis (OA), avascular necrosis (AVN) or post-traumatic arthritis (TA). * Patients who are physically and mentally willing and able to comply with postoperative functional evaluation and able to participate in an appropriate rehabilitation schedule. Exclusion Criteria: * Patients who are unwilling to cooperate with the study protocol and follow-up schedule. * Patients who, as judged by the surgeon, are mentally incompetent or are likely to be non-compliant with the prescribed post-operative routine and follow-up evaluation schedule. * Patients with rheumatoid arthritis hip as well as history of acetabular or femoral osteotomy. * Patients who had a THA on the contra-lateral side within last 6 months. * Patients who had or will need lower joint replacement for another joint within 6 month * Female patients that are pregnant or planning a pregnancy during the course of the study * Patients who require revision of a previously implanted THA. * Obese patients where obesity is severe enough to affect subject's ability to perform activities of daily living (body mass index, kg/m2 \> 35) * Patients with active or suspected infection * Patients with active malignancy * Patients with a diagnosed systemic disease that would affect the subject's welfare or overall outcome of the study (severe osteoporosis, Paget's disease, renal osteodystrophy) or is immunologically suppressed, or receiving steroids in excess of physiologic dose. * Patients with a neuromuscular or neurosensory deficit which would limit the ability to assess the performance of the device or the patient has a neurological deficit which