The Archus Total Facet Arthroplasty System® (TFAS®) is a non-fusion spinal implant indicated for treatment of patients with moderate to severe spinal stenosis. TFAS® replaces the diseased facets following surgical removal. TFAS® offers the surgeon new options for treating spinal stenosis patients, enabling a more comprehensive decompression via complete removal of the facets. TFAS® also offers an alternative to rigid spinal fusion fixation enabling intervertebral motion. The clinical trial is intended to demonstrate restoration of stability and sagittal balance to the spine. TFAS® also eliminates the need for painful bone graft harvest from the patient's hip which may be required with fusion procedures.

Inclusion Criteria:

• Degenerative spinal stenosis, central or lateral, at spinal levels L3-L4 or L4-L5
• Skeletally mature male or female between the ages of 50 and 85 years of age inclusive
• No greater than Grade I degenerative spondylolisthesis at the index level
• Persistent leg symptoms,including pain, numbness, burning or tingling for a minimum duration of six months
• Operative candidates with no more than three levels of degenerative lumbar spinal stenosis requiring decompression
• Failed to respond to non-operative treatment modalities for a minimum duration of six months

Exclusion Criteria:

• Male or female less than 50 or greater than 85 years old Grade 2 or higher spondylolisthesis or any retrolisthesis at the index level
• More than 3 vertebral levels of degenerative spinal stenosis requiring decompression
• More than 1 vertebral level of degenerative spinal stenosis requiring instrumentation
• Not available for long term follow-up and interval visits
• Prior or concurrently planned lumbar fusion or disc replacement at any level of the lumbar spine
• Two or more previous surgeries to the lumbar spine at the same level to be implanted
• Is being treated with other devices for the same disorder (e.g. pain control devices)
• Active systemic infection or infection at the operating site
• Osteoporosis
• Known sensitivity to device materials
• Has an immunosuppressive disorder
• Has a medical condition that may interfere with clinical evaluations
• Is obese defined by a patient body mass index greater than 40
• Has significant scoliosis (Cobb >25°)
• Is pregnant or planning to become pregnant within the proposed three year investigation