Purpose
The motor branch of the ulnar nerve contains fascicles that innervate the intrinsic
musculature of the hand. This cadaveric study aimed to describe the organization and
consistency of the internal topography of the motor branch of the ulnar nerve.
Methods
Five fresh-frozen cadaveric specimens with an average age of 74 years (range, 65–88
years) were dissected. The ulnar nerve was exposed and transfixed to the underlying
tissues to maintain its orientation throughout the dissection. The dorsal cutaneous
branch (DCB) and the volar sensory branch were identified and reflected to expose
the motor branch. The fascicles to the first dorsal interosseus (FDI), flexor pollicis
brevis, and abductor digiti minimi (ADM) were identified. Internal neurolysis was
performed distal to proximal to identify the interfascicular arrangement of these
fascicles within the motor branch. The organization of these fascicles was noted,
and the branch points of the DCB, FDI, and ADM were measured relative to the pisiform
using a handheld electronic caliper.
Results
The internal topography of the motor branch was consistent among all specimens. Proximal
to the pisiform, the arrangement from radial to ulnar was as follows: volar sensory
branch, flexor pollicis brevis, FDI/intrinsic muscles, ADM, and DCB. The position
of these branches remained consistent as the deep motor branch curved radially within
the palm and traveled to the terminal musculature. The locations of the average branch
points of the FDI, ADM, and DCB with respect to the pisiform were as follows: FDI,
4.6 cm distal (range, 4.1–4.9 cm), 4.5 cm radial (range, 4.1–4.9 cm); ADM, 0.65 cm
distal (range, 0.3–1.1 cm), 0.7 cm radial (range, 0.3–1.1 cm), DCB, 7.7 cm proximal
(range, 4.2–10.1 cm), and 0.4 cm ulnar (range, 0.3–0.8 cm).
Conclusions
The internal topography of the ulnar nerve motor branch was consistent among the specimens
studied. The topography of the motor branches was maintained as the motor branch turns
radially within the palm.
Clinical relevance
This study provides further understanding of the internal topography of the ulnar
nerve motor branch at the wrist level.
Key words
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Article info
Publication history
Published online: December 20, 2021
Accepted:
October 6,
2021
Received:
December 10,
2020
Footnotes
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Identification
Copyright
© 2023 by the American Society for Surgery of the Hand. All rights reserved.
