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BMP-2–Regenerated Calvarial Bone: A Biomechanical Appraisal in a Large Animal Model

Cray, James Jr PhD*; Henderson, Sarah E. BS†‡; Smith, Darren M. MD§; Kinsella, Christopher R. Jr MD; Bykowski, Michael MD§; Cooper, Gregory M. PhD†§¶; Almarza, Alejandro J. PhD†‡¶; Losee, Joseph E. MD§

doi: 10.1097/SAP.0b013e31827f4c82
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Recombinant human bone morphogenetic protein-2 (rhBMP-2) is gaining popularity in craniofacial applications. Calvarial defects are, under normal circumstances, subjected to only minimal levels of the biomechanical stresses known to play an important role in osteogenesis, yet regenerated calvarial bone must be capable of withstanding traumatic forces such that the underlying neurocapsule is protected. The aim of this study is to, for the first time, assess the biomechanical properties of calvarial bone regenerated with derivations of a commercially available rhBMP-2–based system. Standardized calvarial defects were created in 23 adult male canines. These defects were treated with rhBMP-2 on one of several carriers. After 24 weeks, the biomechanical properties of the rhBMP-2–generated bone were compared to those of controls with a modified punch-out test (Bluehill 2; Instron, Norwood, Mass) and compared using a paired nonparametric analyses (SPSS, 17.0, Chicago, Ill). In a previously published report, defects across all the rhBMP-2 therapy groups were observed to have a mean rate of 99.5% radio-opacity at 24 weeks indicating nearly full bony coverage of the calvarial defect (compared to 32.7% in surgical controls). For ultimate load, ultimate energy, and first peak energy, there were significant differences (P < 0.05) with the control native bone having more robust biomechanical properties than the rhBMP-2–generated bone. We conclude from these findings that rhBMP-2–generated calvarial bone is significantly less protective against trauma than native bone at 6 months. Further investigation is required to assess the efficacy of rhBMP-2 in healing calvarial defects in the longer term.

From the *Departments of Oral Biology, Surgery/Plastic Surgery, Orthopaedic Surgery and Orthodontics, Georgia Regents University, Augusta, GA; †Department of Bioengineering, University of Pittsburgh; ‡Center for Craniofacial Regeneration, University of Pittsburgh School of Dental Medicine; §Department of Plastic Surgery and Craniofacial Biology Laboratory, Children’s Hospital of Pittsburgh and University of Pittsburgh, Pittsburgh, PA; ∥Department of Surgery, Saint Louis University Hospital, St Louis, MO; and ¶Department of Oral Biology, University of Pittsburgh, Pittsburgh, PA.

Received May 21, 2012, and accepted for publication, after revision, November 19, 2012.

Presented at the International Society of Craniofacial Surgery, 2011.

Conflicts of interest and sources of funding: This study was funded by a grant of financial support and materials from Medtronic, Inc, the makers of INFUSE (rhBMP-2/Absorbable Collagen Sponge). None of the authors have any financial relationships to disclose.

Reprints: Joseph E. Losee, MD, Division of Pediatric Plastic Surgery, Children’s Hospital of Pittsburgh, 4401 Penn Ave, Floor 3, Pittsburgh, PA 15224. E-mail: Joseph.Losee@chp.edu.

© 2014 by Lippincott Williams & Wilkins