This study is a Post Market Follow Up Study to compare the fusion rates between the NanoFUSE® Bioactive Matrix (75%) w/autograft (25%) and autogenous bone in posterolateral gutter spinal fusion.

NanoFUSE® is indicated to be placed into bony voids or gaps of the skeletal system that are not intrinsic to the stability of the bony structure (i.e. the posterolateral spine and pelvis.) These defects may be surgically created osseous defects created from traumatic injury to the bone. NanoFUSE® must be used with autograft as a bone graft extender in the posterolateral spine. This product provides a bone graft substitute that remodels into the recipient's skeletal system. Radiographic success will be the primary judgement of success. All patient's achieving fused or probably fused status will be judged as a success.

Inclusion Criteria:

• Grade I or II (less than 50% slip f the cephalic vertebra compared to the caudal vertebra) degenerative spondylolisthesis at one or two contiguous levels between L1 and L5
• Lumbar spinal stenosis at the same levels of the degenerative spondylolisthesis producing radiculopathy or neurogenic claudication unresponsive to a minimum of 3 months of nonsurgical treatment, or such patients with worsening neurological condition
• Patients who are medically suitable for surgical management and the use of NanoFUSE® Bioactive Matrix is consistent with product labeling
• Patients who have consented for surgical treatment
• Patients able to provide informed consent for the study and complete the questionnaires

Exclusion Criteria:

• Lytic spondylolisthesis
• Non degenerative stenosis (example: tumor, trauma, epidural, lipomatosis)
• Segmental kyphosis at the level of the spondylolisthesis
• Rheumatoid arthritis
• Active infection
• On long term disability or workers compensation claim