The subject population will include adult (skeletally mature) men and women with spinal conditions for which instrumented posterolateral fusion (PLF) has been indicated as a course of treatment. Such spinal conditions may include symptomatic degenerative disc disease, spondylolisthesis (Grade I or II), or lumbar stenosis. The study is limited to those patients requiring instrumented PLF at one or two levels only. Subjects who are undergoing other spinal procedures during the same surgery (such as interbody fusions) are also eligible.