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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

Vaccaro, Alexander R., MD, PhD*; Lawrence, James P., MD, MBA*; Patel, Tushar, MD; Katz, Lee D., MD; Anderson, D Greg, MD*; Fischgrund, Jeffrey S., MD§; Krop, Julie, MD; Fehlings, Michael G., MD; Wong, David, MD**

doi: 10.1097/BRS.0b013e31818a314d
Randomized Trial
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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.

In this randomized controlled trial comparing bone graft alternatives in uninstrumented posterolateral spinal arthrodesis performed for patients with degenerative spondylolisthesis and spinal stenosis, OP-1 Putty demonstrated statistical equivalency to autograft with respect to the composite primary endpoint, relevant clinical and radiographic end points. The OP-1 Putty group also experienced statistically lower operative blood loss and shorter operative times.

From the *Department of Orthopaedic Surgery, Thomas Jefferson University and The Rothman Institute, Philadelphia, PA; †Commonwealth Orthopaedics and Rehabilitation, Fairfax, VA; ‡Department of Radiology and Orthopedic Surgery, Yale University, New Haven, CT; §Department of Orthopaedic Surgery, William Beaumont Hospital, Royal Oak, MI; ¶Stryker Biotech, Hopkinton, MA; ‖Toronto Western Hospital, Toronto, Ontario; and **Denver Spine Center, Denver, CO.

Acknowledgment date: April 9, 2008. First revision date: June 5, 2008. Second revision date: July 23, 2008. Acceptance date: July 28, 2008.

The device(s)/drug(s) that is/are the subject of this manuscript is/are being evaluated as part of an ongoing FDA-approved investigational protocol (IDE) or corresponding national protocol.

Corporate/Industry funds were not received in support of this work. One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: e.g., honoraria, gifts, consultancies.

Address correspondence and reprint requests to Alexander R. Vaccaro, MD, Department of Orthopaedic Surgery and The Rothman Institute, 925 Chestnut Street, 5th Floor, Philadelphia, PA 19107; E-mail: alexvaccaro3@aol.com

© 2008 Lippincott Williams & Wilkins, Inc.