Segmentation Defects of the Human Axial Skeleton Without Dysostoses or Skeletal Dysplasias

The incidence and associations of axial segmentation defects were examined in a series of perinatal autopsies. Variations in vertebral morphology (whether changes in overall numbers or homeotic transformations from one morphological type to another) and of number of well-formed ribs were common, and both were associated with extraskeletal malformations. Rudimentary cervical ribs were present in almost half of all cases and were not specifically associated with extraskeletal abnormalities. Radiographs of all fetuses and infants at autopsy are recommended as they may uncover axial skeletal abnormalities.