U-I flap.

This article describes the principle, vascular basis, and applications of a new flap derived from the dorsal hand skin. The principle is a pedicle-lengthening procedure that is to revert a "U"-shaped vascular structure into an "I"-shaped vascular structure. By using this principle, a dorsal metacarpal flap, comprising the second dorsal metacarpal artery, the dorsal carpal arch, the dorsal branch of the radial artery, and the first dorsal metacarpal artery, was developed. In this flap, the skin territory was placed over the first dorsal metacarpal artery. The flap was rotated around a web space-connecting vessel between the second dorsal metacarpal artery and the palmar arterial system. We used this flap for resurfacing large defects beyond the proximal interphalangeal joint and degloved fingers in six cases. In two cases, the flap was used as an innervated flap. In one case, the flap was used as a tenocutaneous flap with a segment of the extensor indicis proprius tendon. We found this flap to be useful in selected circumstances.