Sacrum with five pairs of sacral foramina

Author(s): Rajani Singh*

Sacrum is wedged between two iliac bones at sacroiliac joint forming posterior wall of pelvis. Normally, there are five sacral vertebrae between cranially, fifth lumbar vertebra and caudally, first coccygeal vertebra forming four pairs of sacral foramina. But during osteology demonstration class of undergraduate MBBS students a sacrum with five pairs of sacral foramina was detected. This is a new anatomical variant.
The fifth pair of sacral foramina is generated either due to fusion of first coccygeal vertebra to apex of sacrum or fifth lumbar vertebra with first sacral vertebra. However, in the sacrum under study, the fifth pair of sacral foramina was developed due to sacralization of first coccyx with the fifth sacral vertebra. This pair of foramina gives passage to fifth pair of sacral nerve and coccygeal nerve. The variant is of paramount importance to surgeons and obstetricians dealing with these nerves.

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