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

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.