TMSS Medical College Journal

Sacral hiatus is the gap on the lower part of dorsal surface of sacrum. It is formed due to fail to fuse of the lamina of the 5th sacral vertebrae. During research work regarding sacral morphometry, in the department of Anatomy, Sylhet MAG Osmani Medical College, Sylhet, Bangladesh, it was observed that a dry adult human sacrum with abnormal extension of sacral hiatus where apex of sacral hiatus was present at the level of second sacral vertebra. As far abnormal extension up-to second sacral vertebra has not been described in Bangladesh. Such type of variation has paramount importance in clinical field to avoid complication related to caudal epidural block or other spinal surgeries and for some important diagnosis such as low back pain, sciatica etc.

The sacral canal is a continuation of the vertebral canal that terminates as the sacral hiatus’. The sacral canal contains the anterior and posterior roots of the lumbar, sacral and coccygeal spinal nerves, the filum terminale and fibrofatty material. It also contains the lower part of the subarachnoid space down as far as the lower border of the second sacral vertebra. The lower sacral spinal roots and filum terminale pierce the arachnoid and dura mater at that level. The laminae of the fifth sacral vertebra and sometimes those of the fourth fail to meet in the midline forming the sacral hiatus’. Standard textbooks mentions the sacral hiatus is arch shaped and somewhat triangular outline when seen from the dorsal aspect’. On either side of the sacral hiatus are bony projections called the sacral cornua’. These can easily be palpated by the finger immediately above the natal cleft’. The filum terminale with its meningeal coverings emerges below the sacral hiatus and passes downwards across the dorsal surface of the fifth sacral vertebra. The fifth sacral spinal nerves also emerge through the hiatus medial to the sacral comua and lateral aspects of the fifth sacral vertebra’. Considerable variability in the anatomy of sacral hiatus exists between individuals, races and stature. The sacral hiatus may be closed, asymmetrically open or widely open. As age advances the overlying ligaments and the cornua thicken. Consequently the identification the hiatal margins become challenging’. Injection of a drug into the epidural space through the sacral hiatus is involved in caudal epidural blockfor providing anaesthesia and analgesia in various clinical settings. So knowing the anatomical relations of the sacral hiatus will facilitate the procedure’. There is no known study regarding abnormal extension of sacral hiatus is found in Bangladesh. In this case apex of sacral hiatus situated at the level of second sacral vertebra.