Evaluation Of Spinelink® Fixation In The Treatment Of Degenerative Spondylolisthesis And Spinal Instability

Inclusion Criteria: 1. The patient has demonstrated Grade I or Grade II degenerative spondylolisthesis exhibited by maximum slippage on flexion and extension radiographs with symptoms that include back pain and/or leg pain with spinal fusion indicated, or spinal instability as evidenced by greater than 3 mm of translational motion or greater than 10 degrees of angular motion between the involved vertebrae as evidenced by flexion-extension radiographs. 2. This surgery will be the primary fusion attempt with no more than three (3) vertebrae or 2 disc spaces involved. 3. The patient must be available for yearly follow-up in the study until completion of the 24 month evaluation. 4. The patient must be skeletally mature (epiphyses closed). 5. Bone grafting material must be limited to autograft and/or bone-bank allograft. 6. The patient must be willing to comply with the treatment regimen, follow-up requirements, and have the legal ability to give informed consent. Exclusion Criteria: 1. Patients with supplemental spinal internal fixation devices previously implanted at any other level and/or a previous fusion attempt at the involved level(s) (no interbody fusions, salvage procedures, or prior hardware). 2. Patients with other pathology at the involved spinal level, e.g., osteomyelitis, Paget's disease, pathologic fracture, etc. 3. Patients with a disease entity or condition that totally precludes the possibility of bony fusion such as known active cancer, etc. 4. Patients who have significant metabolic diseases including insulin dependent diabetes, renal dysfunction, etc. 5. Patients involved in personal injury litigation. 6. Pregnant or nursing females. 7. Patient in whom unapproved biologicals (e.g. BMP-2) or bone substitute materials (e.g. Grafton) would be used at the fusion site. 8. Patients who are unable to understand and sign an informed consent or who, in the opinion of the investigator, would be psychologically unwilling or unable to understand or complete the protocol, especially those unwilling or unable to participate in the follow-up.