The trial was designed to demonstrate the comparability of the overall success rate in the OP-1 Putty treatment group to the autograft treatment group.

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.

Inclusion Criteria:

1. The subject has a diagnosis of Degenerative Lumbar Spondylolisthesis of Grade I or II with Spinal Stenosis demonstrated by medical history, physical examination a n d radiographic imaging.
2. The subject is a candidate for decompression and spinal fusion with the use of autograft from the iliac crest.
3. The subject requires one level lumbar fusion (L-3 to S-1).
4. The subject has a preoperative Oswestry Disability Index of 30-100.

Exclusion Criteria:

1. The subject has active spinal and/or systemic infection.
2. The subject is morbidly obese.
3. The subject has a known sensitivity to any component of the OP-1 Putty.
4. The subject has spinal instability measured on flexion / extension radiographs of greater than 50% translation of the vertebrae and greater than or equal to 20 degrees of angular motion.
5. The subject uses tobacco or nicotine or is prescribed steroids such as cortisone.