Study of dorsal wall of sacrum

Rashmi Benaganahalli Nagendrappa, Jayanthi KS


Background: Sacrum is a large triangular bone formed by fusion of five sacral vertebrae. The opening present at the caudal end of sacral canal is known as sacral hiatus and is formed due to the failure of fusion of lamina of fifth sacral vertebra. Objective of current study was to study the anatomical variations of dorsal wall of sacrum in order to clarify the structural variations of sacral hiatus and surrounding structures for improving the reliability of caudal epidural block

Methods: The present study was done on 50 male and 50 female dry human sacra after calculating the sacral indices and sexing of sacra. The dorsal wall of sacrum was studied with respect to composition of sacrum, level of sacral hiatus, deficiencies and apertures in the bony dorsal wall and also for the presence and absence of sacral cornua.

Results:The level of apex of sacral hiatus can vary from upper part of S2 to lower part of S5. The most common position was at S4 (64%). Elongated sacral hiatus at the level of S2 was present in 4% of cases. Sacrum had normal 5 segments in 70% of cases, 4 segmented sacra were observed in 4% of cases, sacralization of 5th lumbar vertebra in 7%, coccygeal ankylosis in 19% of cases. Less extensive apertures in the bony dorsal wall of sacral canal were observed in 29% of sacra.

Conclusion:The dorsal wall of sacrum has anatomical variations. Understanding these variations may improve the reliability and success of caudal epidural anesthesia.



Sacrum, Sacral hiatus, Caudal epidural anesthesia

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Standring S. Sacrum. In: Standring S, eds. Grays Anatomy. 39th ed. London: Elsevier Churchill Livingstone; 2005: 749-754.

Trotter M, Letterman GS. Variations of female sacrum: Their significance in continuous caudal anesthesia. Surg Gynecol Obstet. 1944;78(4):419-24.

Nagar SK. A study of sacral hiatus in dry human sacra. J Anatomic Soc India. 2004;53(2):18-21.

Trotter M, Letterman GS. Variations of male sacrum: Their significance in continuous caudal anesthesia. Surg Gynecol Obstet. 1944;78(4):419-24.

Senoglu N, Senoglu H, Oksuz H, Gumusalan Y, Yuksel KZ, Zencirci B, et al. Landmarks for the sacral hiatus for caudal epidural block: an anatomical study. Br J Anesth. 2005;95:692-5.

Vinod Kumar, Pandey SN, Bajpai RN, Jain PN, Longia GS. Morphometrical study of sacral hiatus. J Anatomic Soc India. 1992;41(1):7-13.

Trotter M. Variations of sacral canal: their significance in the administration of caudal analgesia. Anesh Analg. 1947;26(5):551-5.

Seikiguchi M, Yabuki S, Kikuchi S. An anatomical study of sacral hiatus: a basis for successful caudal epidural block. Clin J Pain. 2004;20(1):51-4.

Mishra SR, Singh PJ, Agrawal AK, Gupta RN. Identification of sex of sacrum of Agra region. J Anatomic Soc India. 2003;52(2):132-6.

Trotter M, Lanier PF. Hiatus canalis sacralis in American whites ad. Negros. Hum Biol. 1945;17:368-81.

Black MG. Anatomic reasons for caudal anesthesia failure. Anesth Analg (Cleve). 1949;28:33-9.