Safety and Effectiveness Study of the TOPS System, a Total Posterior Arthroplasty Implant Designed to Alleviate Pain Resulting From Moderate to Severe Lumbar Stenosis

This study is being conducted to evaluate a new surgical implant (TOPS™ System, Impliant). The TOPS™ System is an alternative to spinal fusion that is designed to stabilize but not fuse the affected vertebral level following decompression surgery to alleviate pain stemming from moderate/severe lumbar spinal stenosis while maintaining range of motion.

When non-surgical treatment is ineffective, decompression (including laminectomy and medial facetectomy) and fusion of the spinal segments with moderate/severe lumbar spinal stenosis has been used to stabilize the motion segment and to alleviate the patient's clinical symptoms. Spinal fusion surgery using metal instrumentation is designed to stop motion at a painful, unstable spinal segment by permanently fusing the segment. While fusion may decrease pain generated at the treated segment, the procedure also eliminate motion at the implanted level and transfers and thus increases loads on the adjacent segments.

The TOPS System is intended to provide stabilization following decompression in patients with disease at one level from L3 to L5. The ideal goal of stabilization is to preserve mobility but eliminate abnormal motion and prevent deformity. By using the TOPS System, it may be possible to preserve load-bearing dynamics and spinal biomechanics, and thereby maintaining motion at the treated segment.

The TOPS surgical technique, utilizing a standard top loading pedicle screw-based system, is the same as a standard posterior spinal fusion with the exception of the placement of the TOPS motion segment. Therefore, the surgeon will be executing the steps of surgical exposure, decompression, insertion of pedicle screws (with attention to proper placement/alignment) and closure in the same manner as he/she would in a standard posterior spinal fusion.

The objective of the clinical investigation is to compare the safety and effectiveness of the TOPS System to a control group of patients undergoing posterior spinal fusion with pedicle screws and local autograft bone in the treatment of back and leg pain that results from moderate/severe lumbar spinal stenosis at a single vertebral level between L3 to L5.

Prior to entering the study, patients will be evaluated by the investigator according to the inclusion/exclusion criteria. Patients recruited to the study will be randomized in a 1:1 ratio to undergo implantation of the TOPS System or the control spinal fusion procedure. Patient follow-up will be evaluated immediately post-operatively and at discharge, 6 weeks, 3 months, 6 months, 12 months, and 24 months.

Inclusion criteria

• Moderate to Severe lumbar spinal stenosis at a single level* between L3 - L5, with radiographic confirmation of any one of the following on CT, MRI, plain x-ray or myelography:

• Evidence of thecal sac and/or cauda equina compression
• Evidence of nerve root impingement by either osseous or non-osseous elements;
• Evidence of hypertrophic facets with canal encroachment Moderate/severe spinal stenosis is further defined radiographically as;
• moderate canal stenosis is a 25-49% reduction in the A/P dimension of the central and/or lateral foramen when compared to adjacent (cephlad) level
• Severe canal stenosis is defined as 50% or greater reduction in the A/P dimension of the central and/or lateral foramen when compared to the adjacent (cephlad) level **Patients which require minimal decompressive surgery at an adjacent level, may have a laminonotmy or soft tissue resection as long as the decompression does not compromise the stability of the adjacent segment.
• At least six (6) months of failed, conservative treatment prior to surgery, including physical therapy, use of anti-inflammatory medications at maximum specified dosage; administration of epidural/facet injections.
• Age 40-75 years old (male or female).
• Up to one prior surgery without instrumentation implanted at any lumbar vertebral level limited to the following:

• IDET,
• laminotomy,
• laminectomy,
• foraminotomy
• Discectomy (that occurred at least three years ago without any reoccurrence of herniation)
• Lower back pain and/or sciatica with or without spinal claudication.
• VAS leg pain of at least 40/100 at baseline.
• Oswestry Questionnaire score of at least 40/100 at baseline.

Exclusion criteria

• Back or non-radicular leg pain of unknown etiology
• Spondylolisthesis Grade II or higher
• Stenosis caused by an extruded spinal disc fragment
• Lytic spondylolisthesis
• More than one (1) motion segment involved in the degenerative pathology to the extent that justifies its inclusion in the surgical procedure, unless a decompression alone can be done at that level without compromising stability.
• Known allergy to titanium and/or polyurethane
• Prior fusion surgery at any lumbar vertebral level with or without instrumentation
• Supplemental interbody support required (e.g., bone graft, spacers, VBRs, or fusion cages)
• Clinically compromised vertebral bodies at the affected level(s) due to any traumatic, neoplastic, metabolic or infectious pathology.
• Scoliosis of greater than ten (10) degrees (both angular and rotational)
• Morbid obesity defined as a body mass index > 40 or a weight more than 100 lbs. over ideal body weight.

Note: Additional inclusion/exclusion criteria are applied. Please contact Impliant for further details.