Inclusion Criteria:  A severely painful and/or disabled joint from osteoarthritis, traumatic arthritis, rheumatoid arthritis or developmental dysplasia of the hip. Avascular necrosis of the femoral head All subjects must be between the age of 18 and 75 at the time of surgery to take part in this study Scheduled for a primary total hip replacement.  Exclusion Criteria:  Active infection Severe Obesity (BMI over 35) Pregnancy Mental illness Grossly distorted anatomy (surgeon's discretion) Sepsis Osteomyelitis Osteomalacia Distant foci of infections Osteoporosis Metabolic disorders which may impair bone formation Muscular atrophy or neuromuscular disease Allergy to implant material Marked bone loss or bone resorption Patients without sufficient quantities of synovial fluid to allow for proper lubrication, such as patients with Sjogren's syndrome Skeletally immature patients and cases where there is a loss of abductor musculature, poor bone stock or poor skin coverage around the hip joint which would make the procedure inappropriate Any case not described in the inclusion criteria Any patient who cannot or will not provide informed consent for participation in the study Those whose prospects for a recovery to independent mobility would be compromised by known coexistent, medical problems.