Prenatal Development of the Normal Human Vertebral Corpora in Different Segments of the Spine

STUDY DESIGN: Vertebral columns from 13 normal human fetuses (10-24 weeks of gestation) that had aborted spontaneously were investigated as part of the legal autopsy procedure. The investigation included spinal cord analysis. OBJECTIVES: To analyze the formation of the normal human vertebral corpora along the spine, including the early location and disappearance of the notochord. SUMMARY OF BACKGROUND DATA: Reference material on the development of the normal human vertebral corpora is needed for interpretation of published observations on prenatal malformations in the spine, which include observations of various types of malformation (anencephaly, spina bifida) and various genotypes (trisomy 18, 21 and 13, as well as triploidy). METHODS: The vertebral columns were studied by using radiography (Faxitron X-ray apparatus, Faxitron Model 43,855, Hewlett Packard) in lateral, frontal, and axial views and histology (decalcification, followed by toluidine blue and alcian blue staining) in and axial view. Immunohistochemical marking with Keratin Wide Spectrum also was done. RESULTS: Notochordal tissue (positive on marking with Keratin Wide Spectrum [DAKO, Denmark]) was located anterior to the cartilaginous body center in the youngest fetuses. The process of disintegration of the notochord and the morphology of the osseous vertebral corpora in the lumbosacral, thoracic, and cervical segments are described. Marked differences appeared in axial views, which were verified on horizontal histologic sections. Also, the increase in size was different in the different segments, being most pronounced in the thoracic and upper lumbar bodies. The lower thoracic bodies were the first to ossify. The morphologic changes observed by radiography were verified histologically. CONCLUSIONS: In this study, normal prenatal standards were established for the early development of the vertebral column. These standards can be used in the future--for evaluation of pathologic deviations in the human vertebral column in the second trimester.