MiDAS I (Mild® Decompression Alternative to Open Surgery): Vertos Mild Patient Evaluation Study

Inclusion Criteria: * Symptomatic Lumbar Spinal Stenosis (LSS) primarily caused by dorsal element hypertrophy. * Prior failure of conservative therapy. * Radiologic evidence of LSS (L3-L5), Ligamentum flavum \> 2.5mm, confirmed by pre-op MRI and/or CT. * Central canal cross sectional area ≤ 100 square mm. * Anterior listhesis ≤ 5.0mm. * Able to walk at least 10 feet unaided before being limited by pain. * Available to complete 12 weeks of follow-up. * Consistent with the intended labeling statement for use. * Able to use all package components to perform the procedure. * A signed Informed Consent Form is obtained from the patient. Exclusion Criteria: * Prior surgery at intended treatment level. * History of recent spinal fractures with concurrent pain symptoms. * Disabling back or leg pain from causes other than LSS (e.g. acute compression fracture, metabolic neuropathy, or vascular claudication symptoms, etc.). * Significant / symptomatic disk protrusion or osteophyte formation. * Excessive / symptomatic facet hypertrophy. * Bleeding disorders and/or current use of anti-coagulants. * Use of acetylsalicylic acid (ASA) and/or non-steroidal anti-inflammatory drug (NSAID) within 5 days of treatment. * Epidural steroids within prior three weeks. * Inability of the patient to lie prone for any reason with anesthesia support (e.g. chronic obstructive pulmonary disease (COPD), obesity, etc.). * Any potential wound healing pathologies that may compromise outcomes, including diabetes, excessive smoking history, cancer, connective tissue diseases, recent spine radiation and severe COPD. * Dementia and/or inability to give informed consent. * Pregnancy. * Intended treatment that is defined by the product labeling contraindications. * On Workman's Compensation or considering litigation associated with back pain.