PURPOSE: Cranial defects are common sequelae of pediatric craniofacial surgery. The growing cranial skeleton has a unique regenerative capacity to heal small defects; however, when this regenerative capacity is exceeded, the defect is classed as one of critical size and requires surgical treatment to restore protection to the underlying brain. Although it is known what constitutes a critical cranial defect in animal models, it is unclear what can heal in the pediatric human skull. The purpose of this study was to quantify healing of pediatric coronal ring cranial defects over a two year period following fronto-orbital advancement for craniosynostosis.

METHODS: CT scans were performed postoperation (PO) and two years later (2Y) on all patients undergoing fronto-orbital advancement. Digital reformats were created to display the entire coronal ring as flattened images similar to a panorex. This allowed visual comparison between the two time points. The coronal ring was divided into three paired zones: sagittal, parasagittal and temporal. The surface area (SA) of each zonal defect was calculated. Intra-individual comparisons were made between the two time points. Percentage fractional healing was defined as 1-(SA 2Y / SA PO). Percentage fractional healing was then correlated with age and diagnosis.

RESULTS:18 patients (avg age 26 mo) have completed protocols to date (5 unicoronal, 2 bicoronal , 1 sagittal, 5 metopic, 3 multiple, 2 frontosphenoidal). The average PO defect size for each zone was 4.2cm2, which decreased to 1.5cm2 at 2Y. Overall fractional healing was: 75% for the sagittal zone, 51% for parasagittal, and 75% for temporal. Frontosphenoidal defects had the highest fractional healing average at 89%, unicoronal and metopic at 75%, multiple at at 32% and bicoronal at 16%. Correlation of fractional healing with age and diagnosis is underway.

CONCLUSION: This is the first quantitative analysis of fractional healing of pediatric cranial defects with time. Overall 64% of cranial defect size healed spontaneously over a two year period. Sagittal and temporal defects healed better that the intervening parasagittal zone. As this database grows, it will provide invaluable insight into characterization of critical cranial defect size in the pediatric population.