XL TDR® eXtreme Lateral Total Disc Replacement for the Treatment of Lumbar Degenerative Disc Disease (DDD)

Inclusion Criteria: * 18-70 years of age (inclusive and skeletally mature) at the time of surgery * Diagnosis of image-confirmed symptomatic DDD at one of the following levels: L1/L2, L2/L3, L3/L4, or L4/L5 * DDD diagnosed using patient history and image-confirmation such as (but not limited to), MRI, CT, or CT Myelogram with one or more of the following factors: contained herniated nucleus pulposus, facet joint degeneration/changes, decreased disc height \>2mm, and/or scarring/thickening of ligamentum flavum, annulus fibrosis, or facet joint capsule * Preoperative ODI ≥ 30 points * Unresponsive to conservative treatment for ≥ 6 months Exclusion Criteria: * Symptomatic multilevel lumbar degeneration * Chronic back or leg pain of unknown etiology * Non-contained or extruded herniated nucleus pulpous * Previous or other lumbar surgery at any level except prior discectomy, laminotomy, or nucleolysis at the same level * Involved vertebral endplates dimensionally smaller than 45mm in the medial-lateral and/or 20mm in the anterior/posterior directions * Idiopathic scoliosis * Defect in the pars interarticularis * Radiographic signs of significant instability at operative level * Lytic spondylolisthesis or degenerative spondylolisthesis \> than grade 1 * Bony lumbar spinal stenosis * Radiographic confirmation of significant facet joint disease or degeneration * Another lumbar device implanted * Clinically compromised vertebral bodies at the affected level due to trauma * Presence of metastases or active spinal tumor malignancy * Osteopenia, osteoporosis, or metabolic bone disease * Active local or systemic infection, including AIDS and hepatitis * Rheumatoid arthritis or other autoimmune disease * Taking any medications or supplements which potentially interfere with bone/soft tissue healing * Progressive neuromuscular disease * Allergy to device materials, specifically: cobalt-chromium-molybdenum alloy, titanium, and hydroxyapatite * BMI \>40 * Pregnant, or may become pregnant within follow-up period of study * Enrolled in another investigational study within the last 90 days * Waddell signs of inorganic behavior ≥3 * History of substance abuse * Involved in active spinal litigation * Receiving workman's compensation for spinal condition * Mentally incompetent * Incarcerated * Unwilling or unable to comply with all protocol visits/assessments