The effects of long-term fetal constraint in vitro on the cranial base and other skeletal components

Recently it was suggested that some cases of premature closure of the sagittal suture in humans may be due to fetal head constraint. Using various modifications of the procedure for long-term shell-less cultivation of chick embryos, we sought to test the hypothesis that fetal head constraint may result in abnormalities of the cranial base and other skeletal structures of the head. Our experiments with various sized containers demonstrate that fetal constraint is associated with both deformation and malformation of the craniofacial skeleton, including the cranial base, squamosal, columella (stapes), and mandible. The severity of both deformation and malformation appears to be a function of the degree of fetal constraint. If, as some suggest, abnormality of the cranial base is the primary anomaly in craniosynostosis, then our results tend to support the fetal constraint hypothesis as one explanation of simple craniostenosis.