Inclusion Criteria:

• Degenerative Disc Disease (DDD) in one or two adjacent vertebral levels between L3 and S1. Diagnosis of DDD requires: a)Back and/or leg (radicular) pain; and b)Radiographic confirmation of any 1 of the following by CT, MRI, discography, plain film, myelography and/or flexion/extension films: Instability (greater than or equal to 3mm translation or 5° angulation); Decreased disc height >2mm; Scarring/thickening of annulus fibrosis; Herniated nucleus pulposus; or Vacuum phenomenon.
• Age between 18 and 60 years.
• Failed at least 6 months of conservative treatment.
• Oswestry Low Back Pain Disability Questionnaire score of at least 20/50 (40%)(Interpreted as moderate/severe disability).
• Psychosocially, mentally and physically able to fully comply with this protocol including adhering to follow-up schedule and requirements and filling out forms.
• Signed informed consent.

Exclusion Criteria:

• No more than 2 vertebral levels may have DDD and all diseased levels, either one or two, must be treated.
• Patients with involved vertebral endplates dimensionally smaller than 34.5mm in the medial-lateral and/or 27mm in the anterior-posterior directions.
• Known allergy to titanium, polyethylene, cobalt, chromium, or molybdenum.
• Prior fusion surgery at any vertebral level.
• Clinically compromised vertebral bodies at the affected level(s) due to current or past trauma.
• Radiographic confirmation of facet joint disease or degeneration.
• Lytic spondylolisthesis or spinal stenosis.
• Degenerative spondylolisthesis of grade >1.
• Back or leg pain of unknown etiology.
• Osteopenia or Osteoporosis: A screening questionnaire for osteoporosis, SCORE (Simple Calculated Osteoporosis Risk Estimation), will be used to screen patients to determine if a DEXA scan is required. If DEXA is required, exclusion will be defined as a DEXA bone density measured T score less than
• 1.0. The World Health Organization defines osteoporosis as a DEXA T score less than or equal to -2.5.
• Paget's disease, osteomalacia or any other metabolic bone disease (excluding osteoporosis which is addressed above).
• Morbid obesity defined as a body mass index >40 or a weight more than 100 lbs. over ideal body weight.
• Pregnant or interested in becoming pregnant in the next 3 years.
• Active infection - systemic or local.
• Taking medication or any drug known to potentially interfere with bone/soft tissue healing (e.g., steroids).
• Rheumatoid arthritis or other autoimmune disease.
• Systemic disease including AIDS, HIV, Hepatitis.
• Active malignancy: A patient with a history of any invasive malignancy (except non-melanoma skin cancer), unless he/she has been treated with curative intent and there has been no clinical signs or symptoms of the malignancy for at least 5 years.