A Clinical Trial Study of Hip System in Primary Total Hip Arthroplasty in China

Inclusion Criteria: 1. The subject is ≥55, and ≤80 years old 2. The Subject must be of Chinese ethnic descent and be willing to return on three occasions for clinical evaluations. 3. Subject is a suitable candidate for primary total hip replacement using the devices described in this CIP 4. Subject must meet all criteria specified in BOTH SUN hip stem and Summit hip stem instructions for use (IFU) 5. Before surgery, subject is willing and able to sign the informed consent form approved by the Institutional Review Board (IRB), Ethics Committee (EC) or Ethical Review Board (ERB). 6. Subject, in the opinion of the Clinical Investigator, is able to understand this clinical investigation and co-operate with investigational procedures. 7. Subject must be comfortable with speaking, reading, and understanding questions and providing responses in an available translated language for the patient reported outcomes (PROs) in the CIP. 8. Subject is receiving a unilateral hip replacement or, if a contralateral hip replacement is anticipated, the surgery must occur within 6 months of the first study hip. The second hip will not be enrolled in the study. Exclusion Criteria: 1. Subject does not provide written voluntary consent to participate in the clinical study. 2. The Subject is a woman who is pregnant or lactating. 3. Subjects who have undergone THA in contralateral hip within the past 6 months. 4. Contralateral hip has been enrolled in the study. 5. Presence of any previous prosthetic hip replacement device in affected hip. 6. Previous Girdlestone procedure (resection arthroplasty) or surgical fusion of the affected hip 7. Subject has hip dysplasia CROWE classification grade of 3 or 4. 8. Above knee amputation of either contralateral or ipsilateral leg 9. Subject is anticipated to require a contralateral THA between 6 months and 1-year. 10. Subject has an active infection 11. Subject has a malignant disease, severe condition, alcohol or drug addiction and/or mental disorders that the investigator believes will interfere with the study participation. 12. Subjects with severe osteoporosis, metabolic bone disease, radioactive bone disease or tumor in the bone surrounding the hip joint that, in the opinion of the investigator, will negatively impact implant fixation and the outcome of the investigation; 13. Subject has significant neurological or musculoskeletal disorders or disease that may adversely affect gait or weight bearing (e.g. muscular dystrophy, multiple sclerosis, cerebral infarction, hemiplegia, Charcot disease). 14. Subject is not comfortable with speaking, reading, and understanding questions and providing responses in an available translated language for the PROs in the CIP. 15. Subject has a medical condition with less than 2 years of life expectancy due to other medical conditions. 16. The patient has comorbid condition(s) that could limit the patient's ability to participate in the study, compliance with follow-up requirements or impact the scientific integrity of the study. 17. The patient is currently participating in another investigational drug or device study. 18. Subject is a prisoner. 19. Subject has a known allergy to any component of the implant (metal for example).