RSA Study of Sirius Stem and Exceed Cup

Inclusion Criteria: 1. Patients who are eligible for cemented total hip arthroplasty 2. Patients diagnosed with primary Osteoarthritis 3. Patients who are fit for elective surgery (ASA I - III) 4. Patients with a BMI between 16 and 40 5. Patients who are skeletally mature 6. Patients aged over 18 at the time of surgery 7. Patients willing to return for follow-up evaluations 8. Patients who have the ability to follow instructions 9. Patients with sufficient bone stock and quality Exclusion Criteria: 1. Female patients who are pregnant or planning pregnancy during the course of the study (no use of adequate birth control) 2. Patients with diagnosed active infection 3. Patients with marked bone loss which could preclude or compromise adequate fixation of the device 4. Patients with Parkinson disease 5. Patients using immunosuppressive drugs 6. Patients with an immunosuppressive disease 7. Patients with BMI \<16 8. Patient with BMI \>40 9. Patients who are unfit for surgery (ASA IV - V) 10. Patients with acetabular or femoral osteotomy 11. Patients who had a THA on the contralateral side within last 6 months 12. Patients belonging to the vulnerable population: children, patients with mental