 Prior to entering the study, patients will be evaluated by the investigator according to the inclusionexclusion 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. 