The purpose of this study is to determine if the Silent™ hip, when used as part of an artificial hip joint, is stable and effective in treatment of patients with joint disease requiring a total hip replacement. Patients who enter the study will be evaluated at regular intervals following hip surgery using patient, clinical, standard and special x-rays (RSA) to allow the position of the Silent Hip within the bone to be accurately monitored.

The Primary Objective of this study was to evaluate the short-term stability of the Silent Hip, implanted using a manual or navigated technique, using radiostereometric analysis (RSA). The study was also intended to provide the clinical data necessary to demonstrate conformance with the essential requirements of the Medical Device Directive. Secondary objectives were to determine the efficacy of the Silent™ Hip femoral prosthesis from a clinical and radiological prospective, to assess the safety of the device and to evaluate the impact of the procedure on the Subjects' Quality of Life.

Inclusion Criteria:

1. Male or female subjects, aged between 25 and 65 years inclusive.
2. Subjects who are able to give voluntary, written informed consent to participate in this investigation and from whom consent has been obtained.
3. Subjects who, in the opinion of the Investigator, are able to understand this investigation, co-operate with the investigational procedures and are willing to return to the hospital for all the required post-operative follow-ups.
4. Subjects with non-inflammatory osteoarthritis of the hip who require a primary total hip replacement.

Exclusion Criteria:

1. Subjects who, in the opinion of the Investigator, have an existing condition that would compromise their participation and follow-up in this study.
2. Women who are pregnant.
3. Subjects who are known drug or alcohol abusers or with psychological disorders that could affect follow-up care or treatment outcomes.
4. Subjects who have participated in a clinical study with an investigational product in the last 6 month(s).
5. Subjects who are currently involved in any injury litigation claims.
6. Subjects who have osteonecrosis of the femoral neck
7. Subjects who have an existing contralateral hip, ankle or knee replacement or an ipsilateral knee or ankle replacement or any metal implant in the lower lumber spine (navigated cases only).
8. Subjects who are greater than 90kg in weight.
9. Subject who have a CCD angle of the anatomical femur less than 125˚
10. Subjects with significant bone loss or gross deformity in the region of the neck of the femur as identified on the pre-operative radiographs, where in the Investigator's opinion, there could be considerable migration of the prosthesis or a significant chance of fracture of the femoral shaft and/or the lack of adequate bone to support the prosthesis.
11. Subjects with a Charnley C classification.
12. Subjects with an active local or systemic infection.
13. Subjects with loss of musculature, neuromuscular compromise or vascular deficiency in the affected limb rendering the arthroplasty procedure unjustified.
14. Subjects with Paget's disease
15. Subjects who still plan in the future to have children.