Development of the lumbar and sacral vertebral canal in utero.

STUDY DESIGN

This study analyzed the development of the lumosacral vertebral canal and dural sac in human fetus. A collection of fetuses and embryos was used to assess the development of different parameters of the spinal canal.

OBJECTIVES

The data were analyzed for the dynamics of the development and also compared with mean adult spinal parameters.

SUMMARY OF BACKGROUND DATA

Transversely sectioned specimens and nonsectioned specimens free of abnormalities were selected from the Boyd Collection of human embryos and fetuses.

METHODS

The sections were photographed alongside a micrometric scale, and the nonsectioned specimens were scanned by magnetic resonance imaging. The films were computer analyzed for spinal and dural parameters. The error of the measurements was assessed.

RESULTS

The most rapid growth period of the spinal canal parameters is between 18-36 weeks' gestation. After 30 weeks of intrauterine life, the upper lumbar canal grows faster than the lower lumbar region. The distal end of the dural sac begins to rise from S5 after 14 weeks.

CONCLUSIONS

At the end of intrauterine growth, the interpedicular diameter of the spinal canal from L1 to L4 is 70% of the adult size, however, at L5, the canal is only 50% mature at birth. Therefore, if there is growth impairment in early infancy, the upper lumbar region is partially protected in contrast with the L5 level.