The purpose of this study is to evaluate the clinical performance of the iO-Flex® System in reducing pain and symptom severity in patients with one or two level lumbar spinal stenosis that requires surgery.

Inclusion Criteria

Candidates for this study must meet ALL of the following criteria:

1. Age ≥18 years
2. Leg/buttock pain with or without back pain
3. Failed nonoperative medical management
4. A minimum leg pain score of 4.0 cm on the Visual Analogue Scale (VAS)
5. Clinical/radiographic diagnosis of LSS in the L2-L3 to L5-S1 region
6. Able and willing to give voluntary, written informed consent to participate in this clinical study

Exclusion Criteria

Candidates will be excluded from the evaluation if ANY of the following apply:

1. Back pain only

2. A diagnosis of central stenosis only

3. More than two levels requiring decompression

4. Fixed motor deficit

5. Significant instability of the lumbar spine as defined by ≥ 4mm translation between standing flexion and extension lumbar spine plain film radiographs

6. Sustained pathologic fractures of the vertebrae or multiple fractures of the vertebrae and/or hips

7. Primary disc pathology and/or patients who will undergo a discectomy

8. Prior surgery of the lumbar spine at the level(s) of planned treatment

9. Spondylolisthesis or degenerative spondylolisthesis greater than Grade 1 (on a scale of 1 to 4)

10. Spondylolysis (pars fracture) at any level in the lumbar spine

11. Degenerative lumbar scoliosis with a Cobb angle greater than or equal to 25°

12. Symptomatic vascular claudication in the lower extremities

13. Cauda equina syndrome (neural compression causing neurogenic bowel or bladder dysfunction)

14. Evidence of active (systemic or local) infection at time of surgery

15. Paget's disease at involved segment or metastasis to the vertebra, osteomalacia, or other metabolic bone disease

16. Tumor in the spine or a malignant tumor except for basal cell carcinoma

17. Prisoner or transient

18. Recent history of known narcotic abuse

19. Any significant psychological disturbance past or present, psychotic or neurotic, that could impair the consent process or ability to complete subject self-report questionnaires

20. Involved in pending litigation of the spine or worker's compensation related to the back

21. Inability to communicate clearly in the English language

22. Morbid obesity (BMI > 40)

23. Plans to relocate within the next 2 years

24. Pregnant or planning to become pregnant

25. Irreversible coagulopathy or bleeding disorder

    a. Subjects on Coumadin or other anticoagulants may participate. Investigators should follow routine practices for perioperative discontinuation and reinitiation of anticoagulants.

26. Subject unwilling to undergo blood transfusion, if necessary

Patients at least 18 years of age presenting with failed conservative treatment for one or two level lumbar spinal stenosis