BC Study of G7 Cup and Compatible Femoral Stems

Inclusion Criteria: * Male and female ≥18 years * Non-inflammatory degenerative joint disease including osteoarthritis and avascular necrosis, suitable for unilateral primary hip replacement; * Rheumatoid arthritis; * Correction of functional deformity; * Voluntary written Informed Consent obtained Exclusion Criteria Pre-operative: * Prospect for recovery to independent mobility compromised by known coexistent medical problems; * Requiring revision hip replacement; * Requiring bilateral hip replacement; * Previous hip replacement (resurfacing or THR) on the contralateral side and whose outcome is achieving an Oxford Hip score \<18 points; * Likely post-operative leg length inequality \>5cm; * Neuromuscular disease affecting hip (Parkinson's, cerebral palsy, other spasticity); * Primary or metastatic tumour involving this hip; * Loss of abductor musculature, poor bone stock, or poor skin coverage around the hip joint; * Previous organ transplant; * Previous arthrodesis or excision arthroplasty * Abnormal acetabulum: * Acetabular deficiency - \>2cm superior loss acetabular dome or \>1.5cm protrusion acetabulae or wall deficiency\> half a wall; * Dysplasia (DDH) with \>2.5cm subluxation or complete dislocation; * Body mass index \> 40kg/m2; * Active or previous or suspected infection in this hip; * Sepsis or osteomyelitis; * Known sensitivity to device materials; * Women judged by the investigator to be of childbearing potential who are pregnant, nursing, or planning to become pregnant, and those who do not agree to remain on an acceptable method of birth control throughout the entire study period; * Unable to provide informed consent (insufficient English, cognitive disorder such as dementia, psychiatric illness); * Unable to complete follow-ups (life expectancy \<5 years, insufficient English, lives overseas, unable to return easily). Intra-operative: * Abnormal abductor mechanism - trochanter escape \> 1.5cm or gluteus medius totally non-functional or trochanter absence; * Unavailability of required size of prosthesis; * Abnormal acetabulum: * Acetabular deficiency - \>2cm superior loss acetabular dome or \>1.5cm protrusion acetabulae or wall deficiency\> half a wall; * Dysplasia (DDH) with \>2.5cm subluxation or complete dislocation.