Trial Evaluating the Safety and Effectiveness of NUBAC™ Disc Arthroplasty

Inclusion Criteria: * is at least 18 years of age and skeletally mature * must have symptomatic single level degenerative disc disease at L4/5 requiring surgical treatment * must have completed a minimum of six months of unsuccessful conservative, non-operative care * must have discogenic back pain with or without leg pain * must show radiographic confirmation using plain films, MRI, CT, myelogram or discography of one of the following: decreased disc height when compared to the adjacent level, contained herniated nucleus, or vacuum phenomenon (dark disc) * must score at least 40% on the Oswestry Disability Index * must score at least 4 on a 10cm Visual Analog Scale for back pain * is able to comply with the protocol's follow-up schedule * must understand and sign the informed consent document Exclusion Criteria: * symptomatic DDD at more than one level * previous fusion at any lumbar level or laminectomy at the target level (discectomy, Intradiscal Electrothermal Annuloplasty, laminotomy, or nucleolysis performed \> 6 months ago are permitted) * clinically compromised vertebral bodies, at the affected level due to previous trauma, i.e., compression or burst fracture * pars defect * involved vertebral endplate dimensionally smaller than 34.5 mm in the medial-lateral direction and/or 27 mm in the anterior-posterior direction * disc height less than 5 mm at the target level * bony stenosis * lytic spondylolisthesis, spondylolisthesis greater than 3mm * lumbar scoliosis greater than 11 degrees. * osteoporosis, osteopenia, osteomalacia, Paget's disease or metabolic bone disease * Schmorl's nodes, an incomplete annulus, or endplates that are not intact * spinal tumors * symptomatic facet joint disease * free fragment herniation confirmed radiographically * isolated radicular compression syndrome, especially due to a disc herniation * arachnoiditis * active infection or surgical site infection * is using any medication known to interfere with bone/soft tissue healing * rheumatoid arthritis or other autoimmune disease * systemic disease such as AIDS, HIV, hepatitis * morbid obesity defined as body mass index (BMI) \>40 or a weight more than 100 lbs over ideal body weight * psychosocial disorders that would preclude accurate evaluation or has a history of substance abuse * active malignancy except non-melanoma skin cancer; history of any invasive malignancy unless treated and in remission for at least five years * documented allergies to metal or plastic; i.e., cobalt, chromium, molybdenum, polyethylene, titanium or polyetheretherketone * pregnancy, or interested in becoming pregnant within the next two years * prisoner * involvement in an investigational drug or device study within 30 days