A Pivotal Study of the Premia Spine TOPS™ System

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 ofthe following;

1. Degenerative spondylolisthesis or retrolisthesis up to Grade I, as determinedby the investigator based on flexion/extension X-rays,

2. At least moderate lumbar spinal stenosis, defined as at least a 25% reductionin either the central canal, the lateral recess space, and/or the foramen whencompared 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 capsuleas 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 recommendeddosage; 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 VASscore;

• 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 adjacentlevel;

• 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 theetiology 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/orparathyroid 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 potentiallyinterfere with bone/soft tissue healing or receiving radiation therapy that isexpected 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 fracturesof the vertebra or hip;

• Significant peripheral neuropathy causing decreased sensation in a stocking-like ornon-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;