A controlled, open- label, blinded radiographic assessment, randomized, prospective, multicenter, multinational pivotal study in which patients with single level (L3-S1) degenerative lumbar spondylolisthesis (Grade 1 or 2) with spinal stenosis underwent decompression and spinal fusion and received OP-1 Putty or autograft. This study was a one-sided, non- inferiority trial comparing the overall success between the OP-1 Putty group and the control autograft group.