figure 1.jpg
figure 2.jpg
figure 3.jpg
table 1.jpg

Morphology of the Sacral Hiatus in an African Population – Implications for Caudal Epidural Injections

Authors: Njihia B.N. 1 Bsc, Awori K.O.1 MBChB, MMed, Dip Orth (SICOT), Gikenye G1 MMed, MBChB. Affiliations: 1

Department of Human Anatomy, University of Nairobi, Nairobi, Kenya.*Correspondence to: B. N. Njihia, Department of Human

Anatomy , The University of Nairobi, Riverside Drive off Waiyaki Way, Nairobi, Kenya; Email:



The sacral hiatus exhibits variations in morphology which differ among populations. These variations may influence the success of caudal epidural injections for anaesthesia. This study describes the morphological and morphometric characteristics of the sacral hiatus in an adult Kenyan population.


Study design

A descriptive cross-sectional study.


Materials and methods

Eighty eight dry human sacra obtained from the Department of Oste-ology, National Museums of Kenya, Nairobi were used. The shape of the sacral hiatus was described as inverted-V, dumb-bell, inverted-u or irregular. The distance of the hiatal apex from the lower limit of S2 vertebra, the inter-cornual distance and the apical antero-posterior diameter were measured and tabulated.



The inverted -V was the most common (32.1%) shape. The apex of the sacral hiatus was at the level of 4th sacral vertebra in 62% of cases. Mean distance of the hiatal apex from the S2 level was 43.1 + 12.9 whereas antero-posterior diameter of the sacral hiatus at the apex was 6.4 + 3.1 mm. The sacral hiatus was absent in 1.2% of cases.


The level of the sacral hiatus in the African population implies mini-mal risk of dural puncture during caudal epidural injections.


The standard description of the sacral hiatus is an arched defect in the posterior wall of the sacral canal formed by the failure in fusion of the laminae of the fifth (and sometimes fourth) sacral vertebra dorsally. The rem-nants of the inferior articular processes of the fifth sacral vertebra elongate downward on both sides of the hia-tus, extending from its apex as the sacral cornua (1). The contents of the sacral canal include the cauda equina, filum terminale and the dural sac that terminates at the level of the second sacral vertebra (1). The sacral hia-tus and the cornua are palpable landmarks employed in caudal epidural injections (CEIs) (2, 3).


Variations in the morphology of the sacral hiatus based on its shape (4, 5) and presence of the hiatus and cor-nua (6) have been described. These morphological types may influence various morphometric parameters such as the hiatal antero-posterior diameter at the apex, the inter-cornual distance and the distance of the apex from the level of the second sacral vertebra and could influ-ence the success of CEIs (7). Incorrect needle placement has been reported to occur in up to 36% of cases, even with experienced operators (8).


Data on the pattern of morphological variations and the morphometric parameters of the sacral hiatus in an Af-rican population are not available. The aim of this study therefore was