Inclusion Criteria:
All subjects:
* Subject is a suitable candidate for implanting the OR3O™ Dual Mobility System in primary or revision total hip replacement in the Investigator's judgement.
* Subject is skeletally mature in the Investigator's judgement.
* Subject is 18 - 80 years old (inclusive).
* Subject has any of the following conditions:
* Advanced degeneration of the hip joint as a result of degenerative, post-traumatic, or rheumatoid arthritis (RA);
* Fracture or avascular necrosis of the femoral head;
* Failure of previous hip surgery: joint reconstruction, internal fixation, arthrodesis, hemiarthroplasty, surface replacement arthroplasty, or total hip replacement;
* All forms of osteoarthritis (OA);
* Patients with hips at risk of dislocation;
* Femoral neck fracture or proximal hip joint fracture.
* Subject provides written informed consent for study participation using an Independent Ethical Committee (IEC) / Institutional Review Board (IRB) approved consent form before any study procedures are performed, including pre-operative data review and/or collection of data on electronic Case Report Forms (eCRFs).
* Subject is willing and able to participate in required follow-up visits and is able to complete study activities.
* Subject has all required study pre-operative and operative data available in their medical record for collection if consent is given after their THA surgery.
Revision Subjects:
* Subject has a REDAPT™ Modular Shell implanted which does not require revision or will receive a REDAPT™ Modular Shell during revision THA.
* Subject has a S+N compatible stem which does not require revision or will receive a S+N compatible stem during revision THA.
Exclusion Criteria:
All subjects:
* Subject has conditions that would eliminate or tend to eliminate adequate implant support or prevent the use of an appropriately-sized implant, e.g.:
* blood supply limitations;
* insufficient quantity or quality of bone support, e.g., osteoporosis, metabolic disorders which may impair bone formation, radioactive bone disease, tumor around hip joint, and osteomalacia;
* infections or other conditions which may lead to increased bone resorption.
* Subject has dysplasia of hip joint with CROWE Grade III, IV.
* Subject has bodily disease(s) that may interfere with THA survival or outcome.
* Subject has life expectancy of less than 10 years.
* Subject has mental or neurological conditions which impair the subject's ability or willingness to restrict activities that may put the affected limb at risk.
* Subject has physical conditions or activities which tend to place extreme loads on implants, e.g., Charcot joints, muscle deficiencies, multiple joint disabilities.
* Subject has neuromuscular dysfunctions (paralysis, myolysis and abductor muscle weakness) which will cause unstable hip joint or abnormal gait after surgery.
* Subject has an emotional or neurological condition that would pre-empt their ability or willingness to participate in the study.
* Subject has an active infection - systemic or at the site of intended surgery.
* Subject has a Body Mass Index \> 40.0 kg/m².
* Subject has a known allergy to any component of the devices used in the study.
* Subject is pregnant or breast feeding.
* Subject is entered in another investigational drug, biologic, or device study within 30 days of active study participation.
Revision Subjects:
* Subject has inadequate implant support with an increased risk of implant failure if support is not achieved, poor bone quality exists, or smaller sized implants are utilized.
* Subject needs revision of a fractured ceramic head or liner.
* Subject was already enrolled into this study as primary THA case.
