The purpose of this trial is to assess whether the Total Posterior Spine System (TOPS System) is more effective than transforaminal lumbar interbody fusion (TLIF) when used to stabilize a single lumbar level (L2 - L5) following surgical decompression in patients diagnosed with (1) at least moderate lumbar spinal stenosis, and (2) Grade 1 spondylolisthesis (or retrolisthesis), and (3) thickening of the ligamentum flavum or scarring of the facet joint capsule.

Success will be assessed by means of a composite endpoint that measures improvement in in patient reported outcomes and the absence of any major device related complications.

Degenerative spine disease is a normal part of the aging process and can cause pain and significantly limit normal movement. The most commonly diagnosed condition is Lumbar Spinal Stenosis (LSS) which presents with pain, and often weakness or numbness in the buttocks and/or lower extremities that is worsened with standing and walking. For patients that do not respond to conservative treatment decompressive surgery is indicated. When LSS is accompanied by a diagnosis of degenerative spondylolisthesis, fusion of the affected segment is often added to prevent progression of the instability that may accompany the removal of bony elements as part of the decompression. While decompression and fusion have been shown to significantly improve patient outcomes, when compared to decompression alone, fusion has been associated with several comorbidities such as adjacent level degeneration and pseudoarthrosis.

The TOPS System was designed as an alternative to fusion and is a motion preserving posterior spine implant designed to provide dynamic stabilization to a single lumbar spine segment following decompression surgery.

Patients meeting all of the entry criteria will be randomized (2:1) to receive either the TOPS System or TLIF following decompression surgery. Patients will be followed for 5 years and the composite primary endpoint will be assessed at 2 years following index surgery.

Inclusion Criteria:

• Be between 35 and 80 years of age;

• Must demonstrate at a single level to be treated (L2/3, L3/4 or L4/5) all three of the following;

  1. Degenerative spondylolisthesis or retrolisthesis up to Grade I, as determined by the investigator based on flexion/extension X-rays,
  2. At least moderate lumbar spinal stenosis, defined as at least a 25% reduction in either the central canal, the lateral recess space, and/or the foramen when compared to an adjacent level, as determined by the investigator based on MRI,
  3. Thickening of the ligamentum flavum and/or scarring of the facet joint capsule as identified by the investigator based on MRI.

• Have had at least six (6) months of failed conservative treatment prior to surgery (e.g., physical therapy, use of anti-inflammatory medications at maximum recommended dosage; administration of epidural/facet injections and/or nerve block);

• Have an Oswestry Disability Index (ODI) score of at least 40/100 at baseline;

• Have leg pain with a VAS score of at least 40/100 for at least one leg at baseline ;

• Lower back pain with a VAS score of at least 10 points less than Worst Leg VAS score;

• Neurogenic claudication (as defined by worsening leg pain when walking or standing, which is reduced when sitting or bending forward);

Exclusion Criteria:

• Presence of free fragment disc herniation at the index level or either adjacent level;
• Less than 4mm of disc height at the index level;
• Spondylolisthesis greater than Grade I;
• Back or non-radicular leg pain of unknown etiology;
• Stenosis caused by an extruded spinal disc fragment (e.g., herniation) or where the etiology is considered to be congenital, iatrogenic, post-traumatic, or metabolic;
• Known allergy or sensitivity to PEEK, titanium, cobalt chrome, and/or polyurethane;
• Prior surgery at any lumbar vertebral level with instrumentation;
• Prior surgery at the index or adjacent lumbar vertebral level;
• Clinically compromised vertebral bodies at the affected level;
• Scoliosis greater than ten (10) degrees by major Cobb angle;
• BMI > 40;
• Osteoporosis;
• Paget's disease, gout, osteomalacia, osteogenesis imperfecta, thyroid and/or parathyroid gland disorder and/or other metabolic bone disease;
• Active infection - systemic or local;
• Active hepatitis;
• AIDS, HIV, Rheumatoid arthritis or other autoimmune disease;
• Tuberculosis - active or in the past 3 years;
• Active malignancy;
• Any medical condition requiring treatment with any drug known to potentially interfere with bone/soft tissue healing or receiving radiation therapy that is expected to continue for the duration of the study;
• Cauda equina syndrome or neurogenic bowel/bladder dysfunction;
• Vascular claudication due to severe arterial insufficiency of the legs;
• Sustained pathologic lumbar fractures of the vertebra or multiple lumbar fractures of the vertebra or hip;
• Significant peripheral neuropathy causing decreased sensation in a stocking-like or non-radicular and non-dermatomal distribution in the lower extremities;
• Insulin-dependent diabetes mellitus;
• Immunologically suppressed, receiving steroids > 1 month out of the past year;
• Current chemical/alcohol dependency;
• Current smoker or user of tobacco products;
• Pregnant or interested in becoming pregnant;
• Currently involved in active spinal litigation;
• Currently having a workman's compensation claim;
• Currently incarcerated;