Coronal Suture Morphology and Synostotic Progression in Rabbits With Delayed-Onset Craniosynostosis

Objectives: Delayed-onset (post gestational) craniosynostosis has been reported in the human literature and may represent part of the expanded phenotype of craniosynostosis. Delayed-onset synostosis (DOS) is also an integral part of the phenotypic spectrum in an inbred rabbit strain of craniosynostosis. DOS rabbits show plateauing of the coronal suture growth and synostosis by 42 days of age. However, the morphological events leading up to delayed-onset, coronal suture synostosis are not well understood. The purpose of the present study was to describe the coronal sutures of rabbits with DOS compared to age matched, wild-type control rabbits.
Methods: Coronal sutures from 80 rabbits (39 normal wild-type controls and 41 rabbits with DOS) were collected for gross morphological and histological examination. Ages ranged from term through 150 days of age. The sutures were harvested, fixed, paraffin embedded, and stained with alizarin red for microscopic analysis. Qualitatively the synostotic foci, extent of bony bridging, and suture morphology was assessed in these samples. Histomorphometry of suture length and area will be performed. Regression analysis will be used to statistically analyze the data between groups by age.
Results: Preliminary qualitative results showed that by 25 days of age there was already a dramatic thickening of the sutural ligament, an increase in bone in the osteogenic fronts, and an increase in the frequency of bony bridges between the frontal and parietal bones in rabbits with DOS compared to age matched, controls. Quantitative data will be presented.
Conclusions: Preliminary results suggest that bony bridging and sutural ligament thickening occurs much earlier than coronal suture growth cessation in DOS rabbits and these factors may limit subsequent sutural growth in an additive effect. These data also suggest that examination of the morphology of sutures from unaffected siblings of children born with craniosynostosis may be important for understanding and diagnosing the expanded phenotype of craniosynostosis.