Condition of Approval Study (COAST)

Inclusion Criteria:

1. has a baseline score >2.0 in the Physical Function (PF) domain of the Zurich Claudication Questionnaire
2. is 50 years old or older
3. has leg/buttock/groin pain with or without back pain NOTE: Leg/buttock/groin pain must be completely relieved when flexed such as when sitting in a chair. If back pain is also present, it must be partially relieved when flexed.
4. can sit for 50 minutes without pain
5. can walk 50 feet or more
6. has a confirmed diagnosis of neurogenic intermittent claudication secondary to lumbar spinal stenosis, with X-Ray, MRI and/or CT evidence of thickened ligamentum flavum, narrowed lateral recess and/or central canal narrowing
7. has completed at least six months of conservative care therapy which may include but is not limited to physical therapy, bracing, systemic or injected medications
8. has signed a patient informed consent document
9. is physically and mentally willing and able or has a caregiver who can comply with the postoperative and routinely scheduled clinical and radiographic evaluations
10. lives in the immediate area and has no plans to relocate to another geographic area before completion of the study or lives outside the immediate area and will comply with the scheduled postoperative visits with a prearranged and designated physician

Exclusion Criteria:

1. has a baseline score less than or equal to 2.0 in the Physical Function (PF) domain of the Zurich Claudication Questionnaire
2. cannot sit for 50 minutes
3. cannot walk more than 50 feet
4. has unremitting pain in any spinal position
5. has axial back pain only without leg/buttock/groin pain
6. has a fixed motor deficit
7. has cauda equina syndrome defined as neural compression causing neurogenic bowel (rectal incontinence) or bladder (bladder retention or incontinence) dysfunction
8. has severe symptomatic lumbar spinal stenosis at more than two levels
9. has significant instability of the lumbar spine, e.g., isthmic spondylolisthesis or degenerative spondylolisthesis greater than grade 1 (on a scale of 1 to 4)
10. has an ankylosed segment at the affected level(s);
11. has significant scoliosis (Cobb angle is greater than 25 degrees)
12. has an acute fracture of the spinous process or pars interarticularis
13. has sustained pathologic fractures of the vertebrae or multiple fractures of the vertebrae and /or hips
14. has severe osteoporosis of the spine or hip, defined as bone mineral density (BMD) in the spine or hip more than 2.5 SD below the mean of adult normals in the presence of one or more fragility fractures
15. has Paget's disease at the involved segment(s) or metastasis to the vertebrae
16. has had any surgery of the lumbar spine
17. has significant peripheral neuropathy demonstrated by nerve conduction velocity tests
18. has acute denervation secondary to radiculopathy, as shown by EMG
19. has significant peripheral vascular disease characterized by diminished dorsalis pedus or tibial pulses
20. has extreme obesity as defined by a Body Mass Index (BMI) greater than 40 kg/m2
21. has an active systemic infection or infection localized to the site of implantation
22. has an active systemic disease such as AIDS, HIV, hepatitis, etc.
23. has a medical condition that may interfere with postoperative management and follow-up, or may result in patient death prior to study completion (e.g., Alzheimer's disease, unstable cardiac disease, active malignancy)
24. has a recent history of narcotic abuse (i.e., within last 3 years)
25. has a known allergy to titanium,titanium alloy, or polyetheretherketone
26. is immunologically suppressed, or has received or is receiving steroids at any dose daily for more than one month within the last 12 months
27. is currently involved in a study of another investigational product that may affect the outcome of this study
28. is pregnant or planning to become pregnant during the study period
29. cannot undergo MRI or tolerate closed MRI scanning.