Stratification of the flexor retinaculum and the course and distribution of the ulnar, median, and palmar digital nerves: an anatomical study.

A gross anatomic study of 169 hands from 94 human adult cadavers was carried out to define the morphology of the flexor retinaculum and the relationship of the flexor retinaculum to the course of the median and ulnar nerves and branching of the palmar digital nerves. The following results were obtained. Three parts of the flexor retinaculum were arranged like overlapping tiles on a roof, and in all cases, the median nerve passed deep to the flexor retinaculum, whereas the ulnar nerve passed through various parts of the flexor retinaculum in 19% of cases irrespective of its proximal form and branching of the palmar digital nerves.