The anatomic basis of the fourth dorsal metacarpal flap: a cadaveric dissection.

Purpose: To study the vascularization of the fourth dorsal intermetacarpal space and to determine the contribution of the dorsal metacarpal artery and the interosseous muscle fascia to flap viability. The fourth dorsal intermetacarpal space is considered to be less reliable as a donor site because of previously reported vascular variations.

Methods: We performed 15 cadaver dissections. The vascular tree was injected with black latex through the radial and ulnar arteries at the forearm. The skin paddle was designed within the fourth intermetacarpal space. The proximal border was placed at the wrist joint line. The distal border was located 1 cm proximal to the head of the fourth and fifth metacarpal. The width of the skin paddle was based on whether the donor site could be closed directly. A zigzag incision was performed from the distal end of the skin paddle to the volar edge of the interdigital web. The borders of the skin paddle were outlined down to the fascia of the dorsal interosseous muscle. Once the fourth dorsal metacarpal artery was identified each vascular connection was dissected and recorded.

Results: The fourth dorsal metacarpal artery was identified in all specimens under the dorsal interosseous muscle fascia. The distal recurrent branch consistently entered the base of the flap superficial to the extensor digitorum communis tendon of the small finger and the dorsal interosseous muscle fascia. Cutaneous perforators branching off the dorsal metacarpal artery were not found consistently.

Conclusions: Reliable flaps can be raised from the fourth dorsal intermetacarpal space based solely on the distal recurrent branch, excluding the dorsal metacarpal artery and interosseous muscle fascia.