Review Question - QID 214007

The first dorsal metacarpal artery (Kite) flap is an axial pattern flap used to cover defects of the dorsal thumb as well as the thumb pulp and delivers antegrade arterial flow.

The first dorsal metacarpal artery (FDMA) arises from the radial artery at the anatomical snuff box. In contrast to a random pattern flap, it is an axial pattern flap based on a known artery that supplies a specific territory – in this case, the dorsoproximal index finger. Although variations exist, the arterial supply to the donor site is relatively consistent. The second dorsal metacarpal artery can be included in the flap for large defects.

Rehim et al. reviewed local flaps of the hand and note the FDMA flap is also known as the “kite flap” because of the resemblance of a kite when being raised with the pedicle. The flap is nourished by the radial artery with sensation supplied by the superficial branch of the radial nerve (SBRN). In addition to providing coverage for dorsal thumb defects, it can be used to restore sensibility to the volar thumb. Disadvantages include the large donor site defect, typically requiring full-thickness skin grafting, and less aesthetically pleasing results due to the presence of hair follicles.

Couceiro et al. reviewed the family of first dorsal metacarpal artery flaps. The authors note the versatility of these flaps, which can incorporate the second dorsal metacarpal artery to create a bilobed flap if needed. Most FDMA flaps are based on the ulnar branch (FDMAu), which terminates as a vascular plexus over the dorsal fascia of the index finger. It is important to persevere the one or two veins that typically accompany the FDMAu. Innervation is provided by the terminal branches of the SBRN, which is present at the dorsum of the proximal phalanx of the index finger. In addition, the dorsal branch of digital nerve can be sacrificed to add innervation to the flap if necessary.

Figure A is a postoperative photo demonstrating a first dorsal metacarpal flap used to cover a wound affecting the dorsal thumb with full-thickness skin grafting of the donor site. Illustration A demonstrates harvest and placement of the FDMA flap. Illustration B demonstrates placement of a posterior interosseous fasciocutaneous flap for a first web space defect. Illustration C is an example of a heterodigital neurovascular island flap.

Incorrect Answers
Answer 1: The ulnar and radial dorsocollateral arteries arise from the radial artery at the first metacarpal head to supply the skin over the dorsal thumb. Reverse flow through either of these arteries can be used to supply a flap covering distal thumb defects.
Answer 3: The second dorsal metacarpal artery can be incorporated into the FDMA flap to cover large defects, using antegrade flow.
Answer 4: The posterior interosseous fasciocutaneous flap can be used to cover a variety of defects including the first web space, dorsal hand, and elbow. Blood is supplied either antegrade or retrograde depending on the area needing coverage.
Answer 5: Examples of flaps using either the ulnar or radial digital arteries are the homodigital island flap, which can cover defects involving the same digit, and the heterodigital neurovascular island flap, used to cover volar pulp and fingertip defects of another digit. These flaps can be harvested on a proximal (antegrade flow) or distal (reverse flow) pedicle.