Morphological Characteristics of the Ulnar Nerve at the Wrist in a Vietnamese Population: A Descriptive Cadaveric Dissection Study.

PURPOSE: The ulnar nerve at the wrist is vulnerable to injury at Guyon's canal, yet its branching pattern, bifurcation location, and the positional relationship between its motor and sensory branches have not been characterized in any Vietnamese or Southeast Asian cadaveric cohort. This study aimed to describe these morphological parameters and determine whether forearm length predicts key landmark distances.

METHODS: Thirty fresh forearm-wrist specimens from 15 cadavers (mean age, 75.5 years; 53.3% men) were dissected (February-August 2022). Bifurcation location relative to Guyon's canal, terminal branching pattern, motor-to-sensory positional relationship (ulnar vs radial), and ulnar-median communicating branches were documented. Distances from the bifurcation point to the pisiform bone, medial epicondyle, and dorsal cutaneous branch origin were measured. Unpaired t tests, paired t tests, Pearson's correlation, and Bonferroni correction were applied.

RESULTS: Bifurcation occurred proximal to Guyon's canal in 86.7% of specimens; terminal bifurcation predominated (93.3%). No ulnar-median communicating branches were identified. The deep (motor) branch was consistently ulnar to the superficial (sensory) branch in all 30 specimens (100%). Mean bifurcation-to-pisiform distance was 2.03 cm; bifurcation-to-medial epicondyle, 25.96 cm; and bifurcation-to-dorsal cutaneous branch, 8.38 cm. The latter correlated with forearm length and was greater in men. No measurements differed between limb sides.

CONCLUSIONS: The ulnar nerve at the wrist follows consistent morphological patterns in this Vietnamese cadaveric cohort. The motor branch was ulnar to the sensory branch in all 30 specimens examined. The bifurcation-to-pisiform and bifurcation-to-medial epicondyle distances are stable across sex and side; the distance to the dorsal cutaneous branch scales with forearm length, which may assist patient-specific preoperative planning.

CLINICAL RELEVANCE: The consistent ulnar position of the motor branch in all 30 specimens examined provides a reliable landmark for Guyon's canal surgery, ulnar nerve repair, and nerve transfer at the wrist. Preoperative forearm length measurement may assist patient-specific estimation of the dorsal cutaneous branch origin.