This is a multi-center, prospective, observational clinical study to compare patient outcomes following treatment with either the mild® procedure or epidural steroid injection in patients with moderate to severe lumbar spinal stenosis exhibiting neurogenic claudication.

The study was initially designed as a randomized trial. Due to difficulty of enrollment, the study was amended and converted to an observational comparative study with study arm being self-selected by the patient.

Inclusion Criteria:

• Lumbar spinal stenosis (LSS) with neurogenic claudication where the Visual Analog Scale (VAS) of back and leg pain average is ≥ 5.
• Prior failure of conservative therapy.
• Oswestry Disability Index (ODI) score of ≥ 31%.
• Radiologic evidence of LSS, with unilateral or bilateral ligamentum flavum ≥ 4.1mm confirmed by pre-op MRI performed within 6-12 months of baseline visit.
• Able to walk ≥ 10 feet before being limited by pain.
• Available to complete 24-months of follow-up.
• Adults ≥ 50 years of age.

Exclusion Criteria:

• Prior surgery at intended treatment level.
• History of spinal fractures with current related pain symptoms.
• Motor deficit or disabling back and/or leg pain from causes other than LSS neurogenic claudication (e.g. acute compression fracture, metabolic neuropathy, vascular claudication symptoms, etc.).
• Significant/symptomatic disc protrusion or osteophyte formation judged by the Investigator as possible confounding factor to study results.
• Excessive facet hypertrophy judged by the Investigator as possible confounding factor to study results.
• Significant symptomatic foraminal stenosis.
• Confirmed anterior or retro-listhesis ≥ 3mm.
• Bleeding disorders and/or current use of anti-coagulants with the inability to withhold anticoagulants for required time prior to procedure.
• Able to walk ≥ 200 yards unaided in erect non-flexed position before being limited by pain.
• Able to stand ≥ 15 minutes in erect, non-flexed position before being limited by pain.
• Use of acetylsalicylic acid (ASA) and/or non-steroidal anti-inflammatory drug (NSAID) within 7 days of treatment.
• Pregnant and/or breastfeeding.
• Body mass index (BMI) ≥ 32 as calculated using the patient's weight multiplied by 703 then divided by height in inches squared.
• Epidural steroid, systemic steroid or any spine interventional procedure within prior six weeks of study procedure.
• Dementia and/or inability to give informed consent and to understand and complete follow-up patient reported outcomes forms.
• Inability of the patient to lie prone for any reason with anesthesia support (e.g. chronic obstructive pulmonary disease (COPD), obesity, etc.).
• On (or pending) Workman's Compensation or known to be considering litigation associated with back pain.
• Unable to tolerate MRI (pacemaker, spinal cord stimulator, etc.).
• Intrathecal pump.
• Any medical condition determined by the Investigator that would not allow subject to fulfill trial requirements or safely tolerate procedures in this study.