Kineflex Artificial Disc System to Treat Degenerative Disc Disease (DDD)

Inclusion Criteria Summary: * Be between 18 and 60 years of age * Have evidence of degenerative disc disease (DDD) * History of back and/or radicular pain which is severe, ongoing and recurrent * Minimum 6 month period of prior conservative care * Moderate Oswestry Disability Index score * Moderate pain score * Be likely to return for all follow-up visits * Be willing and able to provide Informed Consent for study participation. Exclusion Criteria Summary: * Any back or leg pain of unknown origin * Foot drop * Previous trauma to the study treatment level with compression or bursting * Previous retroperitoneal surgery * Other spinal surgery at affected level except IDET, laminotomy * Previous thoracic or lumbar fusion * Documented abnormal abdominal vessel or muscular/fascial pathology or morphology * Degenerative spondylolisthesis * Ischemic (spondylolytic) spondylolisthesis * Spondylitis * Documented significant spinal, foraminal or lateral stenosis * Severely reduced disc space height * Documented presence of free nuclear fragment * Extensive facet arthritis or degeneration of the facets at any level noted on MRI, CT or X-ray * Scoliosis of the lumbar spine * Metabolic bone disease * Active systemic infection * Hepatitis * Active malignancy or history of metastatic malignancy * Any terminal or autoimmune disease * Any other disease, condition or surgery which might impair healing * Recent history of chemical or alcohol dependence * Current or extended use of any drug known to interfere with bone or soft tissue healing * Known metal allergy * Morbid obesity * Transitional vertebrae at level to be treated that has not clearly fused * Currently a prisoner * Currently involved in spinal litigation * Currently experiencing an episode of major mental illness * Pregnancy at time of enrollment, since this would contraindicate abdominal surgery * Participation in another drug, diologic or medical trial within 30 days of study surgery * Lives more than 300 miles from a study center or participation in any other investigational drug, biologic or medical device study.