Anatomical variations in the formation of the human oesophageal hiatus.

The formation of the oesophageal hiatus was studied in 50 human diaphragms in which crura and the median arcuata ligaments were carefully dissected and their fibres were carefully traced to the central tendon. In 98% of the cases the right crus was divided into a medial, a middle and a lateral bundle. In 90% the left crus was divided into a medial and a lateral bundle. The medial bundle of the right crus was a constant component in bounding the hiatus. The undivided crura did not contribute to the borders of the hiatus. 5 variations in the formation of the hiatus were observed. In 62% the hiatus was bounded by the 2 crura mainly the right; the left crus shared only in the formation of the posterior border. In 10% the 2 crura contributed equally to the formation of the hiatus; the hiatus was formed by the medial bands. In 10% the hiatus was formed exclusively by the right crus. In 2% the hiatus was formed exclusively by the left crus. In 16% crura had no direct relation to the hiatus except posteriorly and the hiatus was bounded by a V-shaped band from the median arcuate ligament, this finding has not been previously reported. The functional significance of these variations was discussed.