Unicoronal Suture Immobilization in the Fetal Rabbit

Pre-clinical evaluation of surgical procedures aimed to correct craniosynostosis is ideally performed in species of small animals characterized by perinatal brain development, early skeletal maturation, and genuine synostosis in all newborns. It would be nearly impossible to breed such a colony to homozygosity, so most researchers have resorted to artificial postnatal suture immobilization. Our aim was to test the hypothesis that artificial immobilization of a unicoronal suture in the fetal rabbit (25 days of gestation) would result in neurocranial growth alterations similar to those seen in the 9-day postnatally immobilized or congenital synostotic rabbit models. The advantages of prenatal immobilization are that rabbits can undergo the tested corrective procedure at postnatal day 9. This age corresponds to a human age of 6 months and allows the deformity and the effects of its correction to be more readily detected. The heads of 25-day-old fetuses of five time-dated pregnant New Zealand white rabbits were exposed by hysterotomy. The left unicoronal suture of 4 fetuses in each litter was immobilized with a polyglactin suture piercing the frontal and parietal bone plates. The remaining two fetuses were sham-operated. Nine days after spontaneous delivery, all rabbits were marked with four titanium screws close to the sagittal and coronal sutures. Growth was recorded with dorsoventral cephalograms at 9 and 90 days. The group with the immobilized suture showed a small increase in growth across the sagittal sutures. However, the decreases in growth at the unicoronal suture in both the immobilized (5.41-mm difference with sham-treated group) and nonimmobilized (1.17-mm difference with sham-treated group) were significant. Fetal immobilization results in growth alterations similar to those observed after postnatal immobilization.