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The size and position of the sacral hiatus in man.

The position and size of the sacral hiatus were examined in sixteen human vertebral specimens. The cranial margin of the sacral hiatus was located caudal to the level of the fourth sacral vertebra in 75% of sacra examined; thus this level is considered to be the representative border for the formation of the vertebral arch. The developmental significance of the sacral hiatus was discussed.