THE EFFECTS OF BMP-2 ON SUTURAL PATENCY IN CRANIOFACIAL DEFECT REPAIR
Darren M. Smith, MD, Ahmned M. Afifi, MD, Gregory M. Cooper, PhD, Mark P. Mooney, PhD, Gary DeCesare, MD, Joseph E. Losee, MD.
University of Pittsburgh, Pittsburgh, PA, USA.
Pediatric craniofacial surgery is complicated by a shortage of autologous bone for the repair of osseous defects. These reconstructions are especially challenging in patients between 2 and 10 years of age, as the dura has lost its osteogenic potential and split calvarial grafts are often unavailable due to the underdeveloped diploic space in this age group. Bone Morphogenetic Protein-2 (BMP-2) is an attractive solution to this problem, however the effects of this potent morphogen on the patent sutures serving as critical growth sites in the developing craniofacial skeleton has yet to be examined.
15 x 15 mm craniectomy defects were created in skeletally mature New Zealand White rabbits. These defects were treated with BMP-2-impregnated acellular collagen sponges (ACS). A total of 6 sutures in 2 rabbits (4 squamosal and 2 interfrontal sutures) in proximity to or directly abutting the BMP-2 sponges were evaluated. Patency of these sutures was assessed by 2D and 3D standard CT and micro-CT 6 weeks postoperatively.
Micro CT analysis revealed that BMP-2-treated ACS sponge ossified as intended. Sutures within 1.5mm of BMP-2-treated ACS sponge (e.g. the squamosal sutures) remained patent. In instances in which BMP-2-treated ACS sponge directly overlaid or abutted a patent suture (e.g. the interfrontal sutures), the suture did not fuse; in one case, a clear shelf of calcified material corresponding to the ossified sponge spanned the patent suture. Finally, areas of the defect that contained sutures prior to craniectomy demonstrated osseous healing without suture regeneration. In summary, of the 6 sutures evaluated, none fused after exposure to BMP-2.
While we have previously demonstrated that BMP-2-treated ACS sponges can effectively reossify calvarial defects in a rabbit model, the effect of these constructs on proximate sutures has not previously been addressed. It is encouraging that BMP-2-treated ACS sponges did not induce sutural fusion in this model, as sutural fusion would likely interfere with craniofacial growth, rendering these constructs impractical for use in children. Further analysis is required to assess the effects of these constructs on sutural patency in skeletally immature animals. Additionally, craniofacial growth patterns in immature animals treated with BMP-2-impregnated ACS sponges must be compared to normative data.