Anatomic study of the ulnar nerve and related vascular anatomy at Guyon's canal: a practical classification system

Thirty-one fresh adult upper extremities were microdissected in order to delineate the regional anatomy of the ulnar nerve and artery at the wrist. Two patterns of division of the ulnar nerve trunk were identified: A and B. Three patterns of hypothenar muscle innervation-type 1, 2, and 3- and two patterns of vascular supply to the hypothenar musculature-type 1 and 2-were also identified. Pattern A occurred in 25 of the specimens where the ulnar nerve bifurcated into a main sensory trunk and a motor branch. Pattern B occurred in 6 of the specimens where the ulnar nerve trifurcated into two common digital sensory branches and a motor branch. The hypothenar innervation patterns were categorized as follows: type 1, 10 cases, single branch; type 2, 14 cases, two branches; and type 3, 7 cases, three or more branches. The patterns of hypothenar vascular supply were categorized as follows: type 1, 17 cases, major vascular arcade passing from the ulnar artery to the hypothenar musculature palmar to the entire ulnar nerve; type 2, 6 cases, arcade passing palmar to the motor portion of the nerve only; and type 3, 8 cases, no axial arterial supply identified. In no specimen did we identify a deep branch of the ulnar artery coursing with the deep motor branch of the ulnar nerve and contributing to a deep palmar arterial arcade. This classic description of a deep palmar arterial arch, we believe, is not valid, due to the mistaken identity of hypothenar arterial branches.