Alternative approaches for regional ulnar nerve blockade: A cadaveric study

Wrist blockade is a safe and effective alternative to general anesthesia in surgery of hand injuries. With regard to the ulnar nerve, the volar approach is used, where the needle passes through or medial to the flexor carpi ulnaris tendon; however, the ulnar artery is at risk because the needle may accidentally penetrate it, causing profuse bleeding. Alternatively, the wrist may be approached medially, the ulnar approach, and the needle tip placed posterior to the flexor carpi ulnaris tendon. To determine which of these methods may be preferable for avoiding ulnar artery injury, needles were inserted into the wrist area of cadaver hands (n = 57) using the volar and ulnar approaches; detailed dissection of the region around the inserted needles was subsequently carried out. The position of the ulnar nerve relative to the ulnar artery and injury to the artery was documented. Damage to the ulnar artery using the volar approach was 36.8% (21/57 cases) compared to no (0%) injury observed using the ulnar approach. At the level of the wrist crease just proximal to the pisiform bone, the ulnar nerve was medial to the artery in 92.9% (53/57) of cases, medial and posterior in 5.3% (3/57), and anterior to the artery in 1.8% (1/57) of cases. This study suggests that in cases where ulnar artery pulsation is not reliable, the ulnar approach may be preferable for ulnar nerve blockade due to an increased incidence of ulnar artery penetration with the volar approach.