This study will determine whether instrumented lumbar fusion will provide superior clinical outcomes in comparison to non-instrumented fusion in patients with "STATIC" degenerative spondylolisthesis. At the time of scheduling surgery, patients who meet the inclusion/exclusion criteria will be asked to participate. Patients who agree, will be randomized to either non-instrumented or instrumented arthrodesis group. Intra-operative, peri-operative, and post-operative data will be collected and compared. The investigators predict to get very similar clinical outcomes between the two groups, with possibly less complications from the non-instrumented group and definitely a reduction in cost compared to the instrumented group.