gms | German Medical Science

Objectives/Interrogation: Many surgeons lack clarity on the branches that innervate the lumbricals and interossei. Their surface anatomical knowledge is essential for designing surgical approach for nerve transfers and predicting lesions. We aimed to

1.

determine the surface locations of the nerve fascicles (NFs) that innervate the lumbricals and interossei,

2.

re-examine the branching pattern of the deep branch of the ulnar nerve (dUN), and

3.

provide detailed information about their origin, entrance, and course.

Methods: Eleven fresh-frozen Chinese adult cadaver hands were investigated. We systematically recorded the origin, entrance, and course of every branch. NFs that innervate the lumbricals, interossei, and surface landmarks including the distal wrist crease and 2-5 proximal finger creases were marked by radio opaque fibers and subjected to X-ray. The images were uploaded and analyzed; we set a quadrant-linked hand surface. Subsequently, we measured the lengths of both axes and the coordinates of the locations of NFs in the quadrant.

Results and Conclusions: The branches that innervated the lumbricals and interossei were located from 29.81 ± 4.10% to 75.89 ± 3.33% and 19.39 ± 4.26% to 67.58 ± 4.13% of the X-axis and from 29.67 ± 2.81% to 60.58 ± 5.11% and 29.67 ± 2.81% to 44.41 ± 1.73% of the Y-axis, respectively. The branches of dUN exhibited a 4-group distribution pattern and two variants of innervation. In 4/11 hands, we found dual innervation of the third lumbrical (innervated by dUN and median nerve).

Novel methods for quantitatively locating the surface anatomy of the NFs that innervate the lumbricals and interossei; systematic description of the origin, entrance, and course of these branches; and the demonstration of a 4-group branching pattern of UN's deep branch were established.