Zahra H Bokhari, Ameen Sheikh, Mohammad Yasoob, Nadia Tazeen, Attiya Khalid.
An anatomic study of the sacral hiatus and the landmarks for its location in caudal epidural anaesthesia.
Pak Postgrad Med J Jan ;18(1):27-31.

Background: Caudal epidural block (CEB) has been widely used to provide analgesia and anesthesia in various clinical settings with the success rate of 70-80% without fluoroscopy. The cause of failure of CEB may have an anatomical basis i.e. the sacral hiatus and the measurement of sacral apex. Objectives: To determine the anatomical variations of the sacral hiatus and to identify additional landmarks where sacral cornu could not be located. This would help to improve the needle placement and hence the reliability of CEB. Materials and Methods: A total of 80 dry Sacral bones were studied. Anatomical measurements were made using a Vernier caliper accurate to 0.1mm. Location of the sacral hiatus, sacral cornu, diameter of sacral canal at apex of hiatus, distance between superolateral sacral crest and distance between sacral apex and right and left superolateral sacral crest were measured. Results: One sacral hone had complete posterior closure and so was discarded. Agenesis of sacral hiatus was found in two Sacra. As the posterior superior iliac spine impose on the superolateral sacral crests, the latter were accepted as forming the base of a triangle, the apex of which lies on the apex of sacral hiatus. The distance between two superolateral sacral crests was on an average 62.54 (SD5.81) mm and distance between right and left superolateral sacral crest and hiatal apex was 63.72 (SD7.07) mm and 64.01 (SD8.43) mm respectively. Conclusions: The triangle formed between the two superolateral sacral crests and apex of sacral hiatus had the features of equilateral triangle. The location of apex of sacral hiatus is variable. This equilateral triangle will be helpful in ascertaining the location of sacral hiatus and will contribute to the success of CEB.

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