Dynesys Spinal System Post Market 522 Study

Inclusion Criteria: 1. Skeletally mature between the ages of 20-80 2. Candidate for posterior lateral fusion between T1-S1 with autograft 3. Degenerative spondylolisthesis with evidence of neurologic impairment or failed previous fusion (pseudoarthrosis) 4. Symptoms of leg and/or back pain 5. Non-responsive to conservative/non-surgical treatment for at least three (3) months 6. Must be willing and able to comply with study requirements; including complete necessary study paperwork and return for required follow-up visits Exclusion Criteria: 1. Active systemic or local infection 2. Obesity 3. Use of interbody device 4. Pregnancy 5. Mental illness 6. Incarceration 7. Alcohol or drug abuse 8. Severe osteoporosis or osteopenia 9. Use in the cervical spine 10. Sensitivities/allergy to metals, polymers, polyethylene, polycarbonate urethane and polyethylene terephthalate 11. Soft tissue deficit not allowing sound closure 12. Any medical or physical condition that would preclude the potential benefit of spinal implant surgery 13. Congenital abnormalities, tumors or other conditions that would prevent secure component fixation that has the potential to decrease the useful life of the device 14. Active malignancy or other significant medical comorbidities 15. Any medical or mental condition which would put the patient at high risk due to the severity of surgery 16. Inadequate pedicles of the thoracic, lumbar and sacral vertebrae 17. Patient unwilling or unable to follow postoperative instructions