Positional changes of the frontoparietal ossification centers in perinatalcraniosynostotic rabbits

It has been suggested that craniosynostosis is caused by abnormally located ossification centers (i.e., bony tubers) in the developing skull prior to suture formation [Mathijssen et al., 1996, 1997]. The present study was des igned to test this hypothesis in a rabbit model of human familial, nonsyndr omic coronal suture (CS) synostosis. Calvariae were taken from 99 New Zeala nd White rabbit perinates (55 normal controls, 15 with delayed-onset CS syn ostosis, and 29 with bilateral or unilateral CS synostosis), ranging in age from 23 to 34 days postconception (synostosis occurs at approximately 13 d ays in this model). Frontoparietal, interfrontal, and interparietal ossific ation center distances were obtained using a Wild microscope with camera lu cida attachment and a 2-D computer digitization technique. Linear regressio n analysis was used to compare age-related changes in the perinatal ossific ation centers among groups. Results revealed that frontoparietal ossificati on center regression line slopes had similar stare points (24-day intercept s) with significantly (P < 0.05) diverging slopes over lime. Normal and del ayed-onset ossification center distance increased more rapidly than in syno stosed perinates. No significant (P > 0.05) differences were noted in regre ssion line slopes among groups for interparietal or interfrontal ossificati on center distances. Results demonstrated that, in synostosed perinates, fr ontoparietal ossification center location was similar to normals around the time of synostosis and became displaced later. These findings suggest that ossification center (i.e.,bony tuber) displacement seen in infants with cr aniosynostosis is probably a secondary and compensatory, postsynostotic cha nge and not a primary causal factor of synostosis in this rabbit model.