DEVELOPMENT OF THE LUMBAR AND SACRAL VERTEBRAL CANAL IN-UTERO

Study Design. This study analyzed the development of the lumbosacral v ertebral canal and dural sac in human fetus. A collection of fetuses a nd embryos was used to assess the development of different parameters of the spinal canal. Objectives. The data were analyzed for the dynami cs of development and also compared with mean adult spinal parameters. Summary of Background Data. Transversely sec tioned specimens and non sectioned specimens free of abnormalities were selected from the Boyd Collection of human embryos and fetuses. Methods. The sections were ph otographed alongside a micrometric scale, and the nonsectioned specime ns were scanned by magnetic resonance imaging. The films were computer analyzed for spinal and dural parameters. The error of the measuremen ts was assessed. Results. The most rapid growth period of the spinal c anal parameters is between 18-36 weeks' gestation. After 30 weeks of i ntrauterine life, the upper lumbar canal grows faster than the lower l umbar region. The distal end of the dural sac begins to rise from S5 a fter 14 weeks. Conclusions. At the end of intrauterine growth, the int erpedicular diameter of the spinal canal from L1 to L4 is 70% of the a dult size, however, at L5, the canal is only 50% mature at birth. Ther efore, if there is growth impairment in early infancy, the upper lumba r region is partially protected in contrast with the L5 level.