OP-1 Putty for Posterolateral Fusions

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.