Study Evaluating the Safety and Effectiveness of the FLEXUS(TM) Interspinous Spacer

Inclusion Criteria:

- Lumbar spinal stenosis as defined by leg, buttock or groin pain, with or without back
pain, that relieves during flexion, with radiographic confirmation of spinal stenosis
by CT or MRI scans at one or two contiguous levels between L1 and S1. If back pain is
also present, it must be partially relieved during flexion

- Narrowing of the spinal canal, nerve root canal or intervertebral foramen at one or
two levels

- Able to sit for 50 minutes without pain

- Able to walk 50 feet or more

- Age 50 years or over

- Has completed at least 6 months of conservative treatment

- Has a Zurich Claudication Questionnaire (ZCQ) score of ≥ 1.5 for Physical Function
(PF) and ≥ 1.5 for Symptom Severity (SS)

- Other as specified in the approved protocol

Exclusion Criteria:

- Cannot sit for 50 minutes without pain

- Cannot walk for more than 50 feet

- Unremitting pain in any spinal position

- Axial back pain only without leg, buttock, or groin pain

- Fixed motor deficit

- Cauda equine syndrome, defined as neural compression causing neurogenic bowel (rectal
incontinence) or bladder (bladder retension or incontinence) dysfunction

- Severe symptomatic lumbar spinal stenosis at more than two levels

- Significant instability of the lumbar spine

- Has had any surgery of the lumbar spine

- Morbid obesity defined as a body mass index >40 or a weight more than 100 lbs over
ideal body weight

- Active systemic disease such as AIDS, HIV, Hepatitis, etc.

- Active systemic or local infection

- Angina, active rheumatoid arthritis, advanced diabetes or any other systemic disease
that would affect the subject's welfare or outcome of the study

- Osteoporosis, defined as DEXA bone density measured T-score < -2.5

- Spinal metastasis to the vertebrae

- Known allergy to device materials titanium, tantalum, or polyetheretherketone (PEEK)
polymer

- Other as specified in approved protocol