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2008 Annual Meeting Abstracts

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Outcomes Study: Recombinant Human Bone Morphogenic Protein-2 (rhBMP-2) Augmentation in 179 Facial Cleft Repairs and 24 Craniofacial Reconstructions
Michael H. Carstens, M.D., Michael A. Fallucco, MD.
Saint Louis University Health Sciences Center, Saint Louis, MO, USA.

PURPOSE: Reconstruction of craniofacial osseous abnormalities has traditionally relied on transplantation of autogenous bone. Traditional bone grafts act as a scaffold into which native cells integrate, replace and remodel the graft in a process called osteoconduction. Shortcomings of autogenous bone grafting include increased donor site morbidity, critical size limitations, increased length of hospital stay, and longer operative times. We propose an alternative method for reconstruction. Through osteoinduction, the cytokine-mediated conversion of undifferentiated mesenchymal stem cells (MSCs) into osteoblasts facilitates osteosynthesis. rhBMP-2 (Infuse®, Medtronic Sofamor-Danek, Memphis, Tennessee) provides the osteoinductive stimulus for the MSCs/local cellular environment to synthesize bone.
METHODS: 161 patients were treated with rhBMP-2 in conjunction with an absorbable collagen sponge (ACS) carrier to repair various craniofacial defects. The operative technique, in-situ osteogenesis (ISO), involves creating a soft tissue pocket surrounding the recipient osseous defect and its included MSCs/local cellular environment into which rhBMP-2/ACS is placed.
RESULTS: 179 cleft repairs using rhBMP-2/ACS were performed. 61 unilateral left alveolar clefts (4 months to 19 years); 31 unilateral right alveolar clefts (4 months to 18 years); 42 bilateral alveolar clefts (6 months to 16 years); 3 secondary palate clefts (6 months to 13 years). 65% of total cleft repairs used a tricalcium phosphate (TCP) bulking agent. 24 patients underwent craniofacial remodeling/reconstructive procedures utilizing rhBMP-2/ACS; 96% requiring TCP.
Excessive bone production with narrowing of the piriform aperture occurred in 4 of the 179 clefts. This problem was exclusively seen where TCP was used as a bulking agent. 4 patients had insufficient bony fill of the native defect. In the early experience 3 of these failures involved extrusion of the collagen sponge through the sublabial closure site. 2 of the 3 patients attributable to suture line technique. The third patient had suture line disruption due to trauma from a fall. One patient unexplainably failed to form bone despite an anatomically normal recipient site. 4 of the 24 craniofacial reconstruction patients required additional rhBMP-2/ACS due to inadequate bony fill; 1 of the 24 patients had a local wound complication requiring drainage.
CONCLUSION: Osteoinduction using rhBMP-2/ACS represents a paradigm shift in craniofacial surgery. RhBMP-2 is the most extensively studied cytokine in existence with 5000 references extent in the literature by 2003. These studies demonstrate via animal models and human experience the ability of ISO to generate bone in unlimited quantities without donor site morbidity. Furthermore they address the biology of rhBMP-2 in key areas such as pharmacokinetics, while refuting antibody production or carcinogenicity.
Additional benefits of rhBMP-2/ACS demonstrate that in secondary alveolar clefts the bone formed by ISO is histologically identical to native bone and mechanically superior to that from osteoconductive grafting. Future craniofacial studies can emphasize reduction in OR time and how ISO at primary repair in trauma cases can eliminate a secondary reconstructive procedure. Finally, the cleft repair algorithm may change as dental arch stability is achieved in infancy.


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