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The Safety and Efficacy of OP-1 (rhBMP-7) as a Replacement for Iliac Crest Autograft in Posterolateral Lumbar Arthrodesis: A Long-term (>4 Years) Pivotal Study

Study Design. Randomized controlled trial comparing OP-1 (rhBMP-7) with iliac crest autograft in patients with symptomatic degenerative spondylolisthesis and spinal stenosis treated with decompression and uninstrumented posterolateral arthrodesis. Objective. To determine the safety and the clinical and radiographic efficacy of OP-1 (rhBMP-7) Putty as compared with an iliac crest bone autograft control in uninstrumented, single-level posterolateral spinal arthrodesis. Summary of Background Data. Preclinical and preliminary clinical data have demonstrated successful fusion and clinical outcomes with the use of OP-1 Putty in posterolateral spinal arthrodesis. No prior randomized controlled trial with adequate study power has been performed. Methods. A total of 335 patients were randomized in 2:1 fashion to receive either OP-1 Putty or autograft in the setting of an uninstrumented posterolateral arthrodesis performed for degenerative spondylolisthesis and symptomatic spinal stenosis. Patients were observed serially with radiographs, clinical examinations, and appropriate clinical indicators, including ODI, Short-Form 36, and visual analog scale scores. Serum samples were examined at regular intervals to assess the presence of antibodies to OP-1. The primary end point, Overall Success, was analyzed at 24 months. The study was extended to include additional imaging data and long-term clinical follow-up at 36+ months. At the 36+ month time point, CT scans were obtained in addition to plain radiographs to evaluate the presence and location of new bone formation. Modified Overall Success, including improvements in ODI, absence of retreatment, neurologic success, absence of device-related serious adverse events, angulation and translation success, and new bone formation by CT scan (at 36+ months), was then calculated using the 24-month primary clinical endpoints, updated retreatment data, and CT imaging and radiographic end points. Results. OP-1 Putty was demonstrated to be statistically equivalent to autograft with respect to the primary end point of modified overall success. The use of OP-1 Putty when compared to autograft was associated with statistically lower intraoperative blood loss and shorter operative times. Although patients in the OP-1 Putty group demonstrated an early propensity for formation of anti-OP-1 antibodies, this resolved completely in all patients with no clinical sequelae. Conclusion. OP-1 Putty is a safe and effective alternative to autograft in the setting of uninstrumented posterolateral spinal arthrodesis performed for degenerative spondylolisthesis and symptomatic spinal stenosis.