The retrograde neurocutaneous island flap of the dorsal branch of the ulnar nerve: anatomical basis and clinical application

It is well known that a cutaneous artery is constantly located near a cutaneous peripheral nerve, forming a vascular plexus around it. This vascular axis can be either a true artery or an interlacing network, ensuring the vascularization of the nerve and giving off several neurocutaneous perforators to the skin. The anatomy of the accompanying arteries of the dorsal branch of the ulnar nerve (DBUN) and their relationships with the dorsal branch of the ulnar artery (DBUA) were investigated in 22 fresh upper limbs injected with colored neoprene latex. A constant perineural vascularization of the terminal branch of the DBUN was observed in the fourth web space, connected distally with the corresponding dorsal metacarpal or palmar digital arteries. Our findings therefore provide anatomical bases for a new neurocutaneous island flap. Moreover, they allow us to describe a precise surgical technique in order to raise this flap over the larger branch of the DBUN, in the fourth intermetacarpal space. The flap is harvested on the medial aspect of the dorsum of the hand, and its point of rotation is located in the fourth web space, 1 cm proximal to the metacarpophalangeal joint. It is supplied by a reversed flow originating from distal anastomoses of the perineural vessel with the dorsal metacarpal and digital palmar arteries in the fourth web space. This flap does not involve in its pedicle the distal course of the DBUA. It represents a pure neurocutaneous flap.