Assessing Superion Clinical Endpoints vs. Decompression

Inclusion Criteria: 1. Male or female subjects ≥ 45 years of age. 2. Persistent leg/buttock/groin pain, with or without back pain that is consistently relieved by flexion activities (example: sitting or bending over a shopping cart). 3. Subjects who have been symptomatic and undergoing conservative care treatment for at least 6 months, without relief. 4. Diagnosis of degenerative spinal stenosis of the lumbar spine, defined as the narrowing of the midline sagittal spinal canal (central) and/or narrowing between the facet superior articulating process (SAP), the posterior vertebral margin (lateral access), and the nerve root canal (foraminal). 5. Radiographic confirmation of at least moderate spinal stenosis which narrows the central, lateral, or foraminal spinal canal at one or two contiguous levels from L1-L5. Moderate spinal stenosis is defined as ≤50% reduction in lateral/central foramen. 6. Must present with moderately impaired Physical Function (PF) defined as a score of ≥ 2.0 of the Zurich Claudication Questionnaire (ZCQ). 7. Subjects who are able to give voluntary, written informed consent to participate in this clinical investigation and from whom consent has been obtained. 8. Subjects, who, in the opinion of the Clinical Investigator, are able to understand this clinical investigation, cooperate with the investigational procedures and are willing to return for all the required post-treatment follow-ups. * Note: In Criteria #5, all imaging used to confirm LSS should be completed within 4 weeks prior to enrollment. Radiographic confirmation of LSS may include MRI and/or CT. Exclusion Criteria: 1. Axial back pain only. 2. Fixed motor deficit in lower extremity(ies). 3. Diagnosis of lumbar spinal stenosis which, if the patient were randomized to the Superion arm, would not require any direct neural decompression or surgical intervention other than that required to implant the Superion® device or if randomized to the direct decompression arm, would not require a decompression procedure which would create significant instability requiring spinal fusion, with or without instrumentation. 4. Unremitting pain in any spinal position. 5. Significant peripheral neuropathy or acute denervation secondary to radiculopathy. 6. Lumbar spinal stenosis at more than two levels determined pre-operatively to require surgical intervention. 7. Significant instability of the lumbar spine as defined by ≥ 3mm translation or ≥ 5° angulation through flexion/extension films. 8. Sustained pathologic fractures of the vertebrae or multiple fractures of the vertebrae and/or hips. 9. Spondylolisthesis or degenerative spondylolisthesis greater than grade 1 (on a scale of 1-4). 10. Spondylosis (pars fracture) at the treatment level(s). 11. Degenerative lumbar scoliosis with a Cobb angle of \> 10° at treatment level. 12. Osteoporosis, defined as a DEXA bone density measurement T score ≤ -2.5. 13. Morbid obesity, defined as Body Mass Index (BMI) \>40kg/m2. 14. Significant peripheral vascular disease (diminished dorsalis pedis or tibial pulses). 15. Prior surgery of the lumbar spine at the treatment level(s). 16. Cauda equina syndrome (defined as neural compression causing neurogenic bowel or bladder dysfunction). 17. Active (systemic, or local in disc or spine) infection at time of surgery. 18. Active systemic disease such as AIDS, HIV, hepatitis, etc. 19. Paget's disease at involved segment or metastasis to the vertebrae, osteomalacia, or other metabolic bone disease. 20. Currently undergoing immunosuppressive therapy or long-term steroid use. 21. Known allergy to titanium or titanium alloys. 22. Tumor in the spine or a malignant tumor except for basal cell carcinoma. 23. Known or suspected history of alcohol and/or drug abuse. 24. Prisoner or transient. 25. Life expectancy less than two years. 26. Any significant psychological disturbance, psychotic or neurotic, that could impair the consent process or ability to complete subject self-report questionnaires. 27. Involved in pending litigation of the spine or worker's compensation related to the back. 28. Enrolled in the treatment phase of another drug or device clinical investigation (currently within past 30 days). 29. Congenital defect of the spine. 30. Pregnant or lactating. 31. Any condition that, in the opinion of the Investigator, would affect the patient's welfare or outcome of the clinical trial.