Embryogenesis and prenatal development of congenital vertebral anomalies and their classification.

Vertebral anomalies were studied in 144 patients. The specific anatomic defects were defined by serial roentgenograms: anterior approaches were used in 42 operations and posterior approaches in 74 operations. Growth features of the spine were examined histologically in 15 embryos and fetuses ranging in length from 6 to 120 mm. After an extensive review of the literature on normal human spine embryology and fetal development, and after defining the specific vertebral anatomic defects and their pathogenesis, some new concepts of congenital vertebral anomalies formation are proposed. Old concepts are found to be inadequate in light of our current knowledge of embryogenesis. The authors' new and all-inclusive classification of congenital vertebral anomalies is based on specific defects, pathogenesis, and time for origin in embryonic or fetal development.