Metal on Metal Versus Metal on Highly Crossed Linked Polyethylene Sytem (MOM)

• Wear and osteolysis [ Time Frame: 5-15 years ] [ Designated as safety issue: No ]
• Harris Hip Score [ Time Frame: immediate post-op, 6 months, 1 year, 2 years, 4 years ] [ Designated as safety issue: No ]
• Dislocation Rate [ Time Frame: 4 years ] [ Designated as safety issue: Yes ]
• Complication Rate [ Time Frame: 4 years ] [ Designated as safety issue: No ]
  All complications
• Gait Analysis [ Time Frame: 6 months and 1 year post-op ] [ Designated as safety issue: No ]
  Using the Walkabout portable gait monitor
• Metal Ions [ Time Frame: 4 years ] [ Designated as safety issue: Yes ]

This trial will evaluate the 36mm or greater metal head on metal hip system and compare it to the 32mm or 28mm metal head on polyethylene (liner) hip system in patients receiving a primary cementless total hip replacement.

• Osteoarthritis
• Avascular Necrosis
• Rheumatoid Arthritis
• Congenital Dysplasia of the Hip
• Ankylosing Spondylitis
• Post-traumatic; Arthrosis
• Injury of Hip and Thigh

• Device: Metal on Metal Hip System
  Total hip arthroplasty with a metal on metal component system
  Other Name: Depuy ASR
• Device: Highly Cross Linked Polyethylene cup System
  Total hip arthroplasty with Highly Cross Linked Polyethylene cup System
  Other Name: Depuy Pinnacle Cup and Marathon liner

• Active Comparator: Metal on Metal
  Metal on Metal articulation system
  Intervention: Device: Metal on Metal Hip System
• Active Comparator: HCLPC
  THA using Highly Cross Linked Polyethylene cup System
  Intervention: Device: Highly Cross Linked Polyethylene cup System

Inclusion Criteria:

• Male and non-pregnant female subjects 65 years of age or older
• Subjects undergoing cementless hip arthroplasty. If a press fit metal articulation acetabulum is not possible; the modular cup system will be utilized with screw fixation and a metal head of the greatest diameter deemed appropriate and safe for the patient will be utilized.(At the discretion of the surgeon). The cup in this situation may have a metal or poly articulation. The patient will be followed as an intent to treat (the patient will be evaluated and included in the group as randomized)
• Subjects with, but not limited to, original diagnoses of osteoarthritis, avascular necrosis, rheumatoid arthritis, congenital dysplasia of the hip, ankylosing spondylitis, posttraumatic arthritis, and traumatic injury to the hip joint.
• Subjects who are able and willing to understand the conditions of informed consent, to participate in the study according to the protocol for the length of the expected term of follow-up, and to follow their physician's directions.

Exclusion Criteria:

• Subjects undergoing hip arthroplasty using a cemented femoral component and/or a bipolar prosthesis.
• Subjects with gross obesity, >45% over ideal body weight for age and height. Refer to Appendix A, Obesity Table.
• Subjects with active infections.
• Subjects with malignancy in the area of the involved hip joint.
• Subjects with a neuromuscular deficit that interferes with the subject's ability to limit weight bearing or places an extreme load on the implant during the healing period.
• Subjects with a diagnosis of Fibromyalgia
• Female subjects who are pregnant or may be pregnant.
• Subjects whom, as judged by the surgeon, are not capable of understanding the informed consent or the requirements of the protocol, or are reasonably unlikely to be compliant with the prescribed postoperative routine and the follow-up evaluation schedule.
• Subjects who have a known sensitivity to device materials.