Patients must meet ALL of the following criteria to be eligible for participation in the study:;

Lumbar degenerative spondylolisthesis (Grade I per Meyerding classificationi), at one level from L1 to S1, with radiographic confirmation using X-ray;

Lumbar spinal stenosis requiring decompression at up to two contiguous levels from L1 to S1, inclusive of the level diagnosed with degenerative spondylolisthesis, and confirmed radiographically using CT or MRI;

Neurogenic claudication or radiculopathic symptoms including leg pain, muscle weakness, and/or sensation abnormality, with or without back pain as evidenced by patient history;

Persistent symptoms despite at least 3 months of conservative treatment that may include but is not limited to physical therapy, medications, and/or epidural injections;

A pre-operative Visual Analog Scale (VAS) leg pain score of >/= 50 on a 100 mm scale;

* Leg pain includes hip and/or buttock pain on the same side

A pre-operative Oswestry Disability Index (ODI) score >/= 35 points on a 100-point scale;

Candidate for surgical decompression at a single level or two contiguous levels with stabilization at a single level between L1 and S1;

Posterior element anatomy is appropriate for interspinous fixation including prediction of presence of spinous processes of segment to be instrumented following decompression (investigational AND control groups) and a prediction of >50% of facet joints present following decompression (investigational group only);

Skeletally mature;

Patient has the necessary mental capacity to participate and is willing and able to participate in the study for the duration of the study follow-up and is able to comply with study requirements;

A primary and predominate diagnosis of discogenic or facet-mediated back pain;

Back or non-radicular leg pain of unknown etiology;

Significant peripheral vascular disease causing vascular claudication;

Significant peripheral neuropathy caused by conditions other than spinal stenosis;

History of fixed or permanent neurologic deficit related to spinal cord injury;

History of any previous surgery at the level(s) planned for treatment or at any level in the lumbosacral spine except for a discectomy or decompression (NOT including epidural injections, rhizotomy or nerve ablation);

Isthmic spondylolisthesis or spondylolysis at any level in the lumbar spine;

Clinically significant compromise of vertebrae at L1 to S1 levels due to osteoporotic vertebral compression fracture or any traumatic, neoplastic, metabolic or infectious pathology or congenital abnormality;

Spinous process fracture(s) or other posterior element fracture(s) of the segment to be instrumented;

Degenerative lumbar scoliosis with a Cobb angle >10° at the affected motion segment;

Symptomatic lumbar stenosis that is not amenable to a direct decompression;

Anklyosed motion segment at the target operative level;

Severe osteoporosis, defined as history of fragility fracture and DXA T-score < -2.5 or QCT T-score < 80mg/cubic cm. History of a fragility fracture requires that a DXA scan or QCT scan is completed;

Planned hip or knee replacement surgery, severe osteoarthritis or other musculoskeletal pathology of the hip or leg that could preclude reliable patient self reporting assessment scales and/or that would likely progress to surgery during study period;

Please contact study team for more exclusion criteria.;

• Bone Diseases

• Constriction, Pathologic

• Decompression

• Degenerative Spondylolisthesis

• Fusion

• Fusion Instrumentation

• LSS17001

• Lumbar Spinal Stenosis

• Musculoskeletal Diseases

• Pathological Conditions, Anatomical

• Spinal Diseases

• Spinal Stenosis

• Spondylolisthesis

• Spondylolysis

• Spondylosis

• Surgery (Orthopedic)

• Empirical Spine, Inc.