Repair of the Immature Craniofacial Skeleton With a Calcium Phosphate Cement: Quantitative Assessment of Craniofacial Growth

The potential for growth restriction has limited the use of alloplastic materials for reconstruction of the growing craniofacial skeleton. A calcium phosphate cement that has been introduced recently for craniofacial reconstruction crystallizes in situ into a substance that resembles more closely the mineral phase of bone, thereby offering the potential for enhanced bioresorption and osteoconductivity. The purpose of these experiments was to assess quantitatively craniofacial growth after reconstruction of frontal craniectomy defects in skeletally immature animals with this calcium phosphate bone mineral substitute. To simulate the calvarial defects that result from unilateral fronto-orbital advancement procedures, unilateral frontal bone flaps were removed in 3-week-old female Yorkshire piglets. The bone flaps were trimmed medially and posteriorly, and were then reattached to the supraorbital ridge. The resulting 5-mm gap between the frontal bone flap and the native bone was either filled with Norian CRS bone cement (N = 3) or left empty (N = 3). After 90 days, the animals were killed and the skulls were harvested and cleared. Direct craniometric measurements were performed on the prepared dry skulls to assess craniofacial growth in all dimensions. Extensive remodeling was observed within defects treated with the calcium phosphate cement, with complete or near-complete replacement of the cement by host bone, resulting in a solid bony union. Direct craniometric measurements revealed no differences in craniofacial growth in any dimension between the operated and unoperated sides of the cranium in either group. These studies demonstrate that craniofacial growth is not restricted after reconstruction of frontal craniectomy defects with carbonated calcium phosphate cement in skeletally immature animals. The remodeling capacity of this material offers promise for its safe use in reconstruction of the growing calvarium.