Post-Market Surveillance Study of the TM Ardis Interbody Fusion System

Inclusion Criteria: * Age \> or = 18 years * Degenerative disc disease DDD with up to Grade 1 spondylolisthesis or retrolis-thesis at the involved level. DDD is defined as discogenic back pain with degener-ation of the disc confirmed by history and radiographic studies. * ODI 40 out of 100 * Back pain 4 out of 10 * Mono segmental or two level lumbosacral disease * Skeletally mature patients * Six months failed conservative treatment. * Gave written consent to take part in the study by signing the Ethics Committee's approved Patient Informed Consent Form. * Physically and mentally able to comply with the protocol, including ability to read and complete required forms and adhere to the follow-up requirements of the pro-tocol. Exclusion Criteria: * Prior surgical procedure at the index level(s) using the desired operative approach. * Severe degenerative lesions at more than two level of the lumbosacral spine. * Morbid obesity (BMI greater than or equal to 40). * Active local infection in or near the operative region. * Active systemic infection and/or disease. * Severe osteoporosis or insufficient bone density, which in the medical opinion of the physician precludes surgery or contraindicates instrumentation. * Known or suspected sensitivity to the implant materials. * Endocrine or metabolic disorders known to affect osteogenesis (e.g.Paget's disease, renal osteodystrophy, hypothyroidism) * Systemic disease that requires the chronic administration of nonsteroidal anti-inflammatory or steroidal drugs. * Significant mental disorder or condition that could compromise the patient's ability to remember and comply with preoperative and postoperative instructions (e.g. current treatment for a psychiatric/psychosocial disorder, senile dementia, Alzheimer's disease, traumatic head injury) * Neuromuscular disorder that would engender unacceptable risk of instability, implant fixation failure, or complications in postoperative care. * Pregnant. * Unwilling to follow postoperative instructions, in particular with respect to athletic or occupational activities. * Current vertebral metastatic tumors. * Symptomatic cardiac disease. * Severe congenital or acquired vertebral deformities.