DIAM™ Spinal Stabilization System vs. Decompression, Formerly vs. Posterolateral Fusion

Inclusion Criteria: * Has a symptom complex consisting of back, buttock, or groin pain (excluding symptomatic coxarthrosis) with leg pain typical of intermittent neurogenic claudication, which is defined as leg(usually calf) discomfort, pain, numbness, paresthesias, weakness, or fatigue aggravated by standing or walking and is only relieved with resting in flexed lumbar spine position * Leg pain score ≥ 8 and back pain score ≥ 6 based on the Preop Back/ Leg Pain CRF. Leg pain score must be ≥ back pain score * Narrowing of the lumbar spinal canal and/or intervertebral foramen at L2-L3, L3-L4, L4-L5 as indicated by MRI, with other MRI findings typical of spinal stenosis, such as trefoil canal shape; hypertrophy, thickening, buckling, or infolding of the ligamentum flavum; hypertrophied facet joints or facet joint capsule; annular bulging; or lateral (subarticular) stenosis. * Must sit for at least 30 min without severe pain * Must walk at least 100 ft unassisted * 35 yrs of age, inclusive * Preoperative Oswestry score ≥ 40 * Child-bearing potential, pt is not pregnant or nursing and agrees not to become pregnant during study period * Treated non-operatively for a pd of at least 6 mos * Willing and able to comply with study plan and able to understand and sign Pt ICF Exclusion Criteria: * Disease state which requires destabilizing decompression * Axial back pain with no pain in leg, buttock, or groin * Baseline strength grade of 0 (total paralysis), 1 (palpable or visible contraction), or 2 (active movement, gravity,eliminated) in any lower extremity motor group as noted on Neuro Status CRF * Segmental kyphosis \>0° at indicated level * Cauda equina syndrome * Compression of nerve roots that causes neurogenic bowel, bladder dysfunction * Prior surgical procedure at involved or adjacent levels * Diagnosed with significant peripheral neuropathy * Significant vascular disease causing vascular claudication * Requires tx of spinal stenosis at more than 1 lumbar level * Significant lumbar instability, defined as \> 3mm translation on flexion/extension radiographs * Has \> 3mm fixed spondylolisthesis at affected level * BMI ≥ 40 * Sustained vertebral or hip fracture within last year * Has the following (if "Yes" to any risk below, a lumbar spine DEXA Scan is required for eligibility) 1. Previous diagnosis of osteoporosis, osteopenia, or osteomalacia 2. Postmenopausal Non-Black female over age of 60 who weighs ≤ 140 lbs 3. Postmenopausal female who has sustained a non traumatic hip, spine or wrist fracture 4. Male over age of 60 who has sustained non-traumatic hip or spine fracture * If level of DEXA T-score is -1.0 or lower pt is excluded from study * Lumbar scoliosis with Cobb angle of \> 15° * Documented allergy to silicone, polyethylene, titanium or latex * Overt or active bacterial infection, local, systemic, and/or potential for bacteremia * Alcohol and/or drug abuser * Received tx with investigational therapy (device and/or pharmaceutical) within 30 days prior to entering study or such tx is planned during the 24 mos following enrollment in study * Suppressed immune system or has taken steroids at any dose daily for more than 1 mon within the last yr * Presence of active malignancy or prior history of malignancy except for basal cell carcinoma of the skin * History of any endocrine or metabolic disorder known to affect osteogenesis * Chronic or acute renal and/or hepatic failure or prior history of renal and/or hepatic parenchymal disease * History of autoimmune disease * Disease which precludes accurate clinical evaluation of safety and effectiveness of txs in this study * Congenital or iatrogenic posterior element insufficiency * Moderate to advance spondylosis or pts who demonstrate advanced degenerative changes. Such advanced degenerative changes are characterized by 1 or combination of the following a Bridging osteophytes; b Reduction or absence of motion; c Collapse of the intervertebral disc space of \> 50% of its normal ht * Mentally incompetent * Waddell Signs of Inorganic Behavior score of ≥ 3 * Prisoner