Posterior Lateral Fusion (PLF) With Dynesys

Inclusion Criteria: * Spondylolisthesis of less than Grade II at the index level (degenerative with intact pars) * Will receive a decompression for lumbar stenosis * Symptoms of leg and/or back pain * One pathological level * Between the ages of 20 and 80 at the time of surgery * Non-responsive to non-surgical treatment for at least six months Exclusion Criteria: * Osteolytic spondylolisthesis * Planned complete facetectomy * Two or more pathological levels (and as enumerated int he Dynesys Spinal system instructions for use) * Use in the cervical spine * Active systemic or local infection * Extreme obesity as defined by a Body Mass Index (BMI)over 40. BMI calculated using Appendix A, adapted from the National Heart, Lung, and Blood Institute, Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. * Pregnancy * Mental illness * Severe osteoporosis or osteopenia. The World Health Organization defines osteoporosis as BMD\<-2.5t. Professional discretion should be used and if bone quality is in question a DEXA scan is recommended. * Sensitivities/allergy to metals, polymers, polyethylene, polycarbonate urethane and polyethylene terephthalate * Alcohol or drug abuse * Patient unwilling or unable to follow postoperative instructions * Soft tissue deficit not allowing sound closure * Any medical or physical condition that would preclude the potential benefit of spinal surgery * Inadequate pedicles of the lumbar or sacral vertebrae; congenital abnormalities, tumors or other conditions that would prevent secure component fixation that has the potential to decrease the useful life of othe devices; * Any medical or mental condition which would exclude the patient at high risk from surgery of the severity