A Clinical Study of the Dynesys(R) Spinal System

This non-inferiority study will compare the clinical outcomes of subjects implanted with the Dynesys Spinal System versus the clinical outcomes of subjects implanted with an instrumented posterior lateral spinal fusion.

The purpose of this clinical study is to demonstrate the safety and effectiveness of the Dynesys Spinal System for patients requiring one or contiguous two-level posterior spinal stabilization of the lumbar, and/or sacral spine following decompression. The ability for this implant to maintain spinal alignment and non-fusion of spinal segments, while positively affecting clinical outcomes, will be assessed and compared to a posterior lateral spinal fusion (PLF) procedure using autogenous bone with a semi-rigid, polyaxial posterior spinal fixation system.

Eligibility Criteria:
Inclusion Criteria:

* Patients having degenerative spondylolisthesis or retrolisthesis (up to Grade 1) AND/OR Patients having lateral or central spinal stenosis or other stenosing lesion as diagnosed by radiculopathic signs, neurogenic claudication or imaging studies;
* Candidate for single-level or contiguous two-level PLF between L1-S1;
* Patients have a predominate component of leg rather than back symptoms; symptoms include pain, muscle weakness, and/or sensation abnormality as evidenced by patient history and diagnostic studies.
* Patients may require decompression at the levels considered for treatment
* Pre-operative leg pain score greater than or equal to 40 mm on a 100 mm Visual Analog Scale (VAS);
* Leg pain must be unresponsive to conservative (non-surgical) management for minimum of 3 months;
* Pre-operative Oswestry score greater than or equal to 30 indicating at least moderate disability;
* Skeletally mature individual between ages 20 and 80;
* Must be willing and able to comply with study requirements; including willing and able to sign a study-specific, IRB-approved informed consent form, complete necessary study paperwork and return for required follow-up visits.

Exclusion Criteria:

* Primary diagnosis of discogenic back pain at affected levels as evidenced by a larger back than leg pain component. In the event of multi-level pathology a discogram should be considered;
* Patients with leg pain due to etiologies other than those listed above, such as trauma, peripheral vascular disease and neuropathy should be excluded;
* Degenerative scoliosis greater than 10 degrees at the affected motion segment;
* Supplemental interbody column support (e.g., bone graft, spacers or fusion cages) is planned at the affected level(s);
* Greater than Grade I spondylolisthesis or retrolisthesis at the affected level(s);
* Radiculopathic signs from more than two contiguous or two noncontiguous vertebral body segment(s);
* Previous lumbar fusion attempt(s), previous total facetectomy or trauma at the affected level(s);
* Gross obesity defined as exceeding ideal weight by greater than 40% (measurement details are given in Appendix A);
* Active local or systemic infection;
* Advanced osteoporosis as evidenced by plain film radiographs or history of fractures and confirmed by DEXA scan to confirm adequate bone density;
* Receiving immunosuppressive or long-term steroid therapy;
* Active hepatitis (viral or serum) or HIV positive, renal failure, systemic lupus erythematosus, or any other significant medical conditions which would substantially increase the risk of surgery;
* Documented history of titanium alloy, PET or PCU allergy, or intolerance;
* Active malignancy or other significant medical comorbidities;
* Current chemical dependency or significant emotional and/or psychosocial disturbance that may impact treatment outcome or study participation as evidenced by three or more positive Waddell Signs;
* Pregnancy;
* Incarceration;
* Severe muscular, neural or vascular diseases that endanger the spinal column;
* Missing bone structures, due to severely deformed anatomy or congenital anomalies, which make good anchorage of the implant impossible;
* All concomitant diseases that can jeopardize the functioning and success of the patient;
* Vertebral fractures;
* Treatment of the thoracic and cervical spine;
* Severely deformed anatomy due to congenital anomalies;
* Paralysis