Tushar Ch. Patel, MD, Hopkinton, MA, USA; Alexander R. Vaccaro, MD, Philadelphia, PA, USA; Eeric Truumees, MD, Royal Oak, MI, USA; Jeffrey S. Fischgrund, MD, Southfield, MI, USA; Alan S. Hilibrand, MD, Philadelphia, PA, USA; Harry N. Herkowitz, MD, Southfield, MI, USAIntroduction: Posterolateral intertransverse lumbar fusion is a commonly performed procedure for stabilization of the degenerated lumbar spine. A typical clinical scenario for which such fusions are used is the stabilization of a degenerative spondylolisthesis after decompression. In a recent large series reported in the literature, this type of fusion was noted to have a pseudarthrosis rate of up to 45% [1]. Measures to augment autograft fusions would thus be desirable.Materials and methods: Included are 2-year follow-up data to the study presented at the North American Spine Society (NASS) 2000 meeting. A pilot study was designed to evaluate the safety and efficacy of osteoinductive protein-1 (OP-1, also known as recombinant human bone morphogenetic protein [BMP-7]) in lumbar fusion. Twenty-two patients with the diagnosis of symptomatic spinal stenosis and single-level degenerative spondylolisthesis in the lower lumbar spine (L3–S1) were enrolled (NASS 2000). The patients were randomized to either an OP-1 group or a control group. The OP-1 group received 3.5 mg of OP-1 in a putty carrier per side and iliac crest autograft. The control group received iliac crest autograft alone. Outcomes were measured clinically using the Oswestry score and dynamic radiographs evaluated independently by two blinded radiologists using digital calipers.Results: Two-year results indicate the preservation of fusion in OP-1–treated patients. No acute or long-term adverse effects related to the use of OP-1 were noted in the treatment group.Discussion: Despite the small number of patients enrolled in this pilot study, OP-1 appears to be a safe and effective adjunct to iliac crest autograft in human posterolateral lumbar fusion. Two-year results indicate preservation of fusion in OP-1–treated patients, and the lack of acute and long-term adverse effects speak to the safety of OP-1 in posterolateral fusions. At 2 years, the OP-1 group had a higher radiographic fusion rate than the autograft group. This correlated well with the greater clinical success experienced by the OP-1 group, as measured by improvement in the Oswestry score. None of the previously reported device-related complications related to the use of BMPs in animal studies, such as exuberant bone growth with subsequent neural impingement, ectopic ossification or spinal stenosis, were seen in the treatment group.Conclusion: OP-1 appears to be a safe and effective adjunct to iliac crest autograft in human posterolateral lumbar fusion. The dose, 3.5 mg per side, and the carrier, biodegradable putty, appear to provide a safe and effective means of delivering the bone morphogenetic protein OP-1 to the human lumbar spine.