Omnifit Hydroxylapatite (HA) Hip Outcomes Study

Inclusion Criteria: For use as a universal hip replacement: * Acute femoral neck fracture. * Non-union of femoral head and neck fractures. * Aseptic necrosis of the femoral head. * Osteoarthritis, rheumatoid arthritis, or post-traumatic arthritis of the hip with minimal acetabular involvement or distortion. * Salvage of failed total hip arthroplasty. For use as a total hip replacement: * Severely disabled joints resulting from painful osteoarthritis, rheumatoid arthritis, or post-traumatic arthritis. * Revision of previous unsuccessful femoral head replacement, cup arthroplasty, or other procedure. Exclusion Criteria: * Active infection in or near the hip joint. * Pathological bone conditions which would significantly compromise the ability to carry physiologic stress levels and for which bone grafting would be inappropriate (i.e. severe osteoporosis, Paget's Disease, renal osteodystrophy, etc.). * Neuro-muscular disorders in which the potentially adverse effects on prosthesis function are not outweighed by the benefits to be gained by the patient from usage of the implant. * Mental disorders which would compromise essential patient post-operative care. * Skeletal immaturity. * Extreme obesity. * Significant probability that patient could not return for required follow-up evaluations.