44: Dorsal Metacarpal Artery Perforator Flap

Published on 20/04/2015 by admin

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Procedure 44 Dorsal Metacarpal Artery Perforator Flap

Sandeep J. Sebastin, Kevin C. Chung

See Video 36: Dorsal Metacarpal Artery Perforator Flap

Indications

Dorsal and lateral finger soft tissue defect proximal to the distal interphalangeal (DIP) joint (Fig. 44-1)

Palmar finger soft tissue defect proximal to the DIP joint in patients with injuries to multiple fingers that make it difficult to use local flaps from adjacent digits

Palmar or dorsal soft tissue defects proximal to the DIP joint in more than one finger

FIGURE 44-1

Examination/Imaging

Clinical Examination

Defect: The flap should be used for defects that are free of infection. This is determined by looking at the wound bed and the surrounding skin for edema and erythema. This is a low-flow flap that is easily compromised by any residual infection.

Perforator: There should be no injury in the vicinity of the selected perforator. Injuries that may disturb the perforator include metacarpal neck fractures, lacerations extending into the web space, contusion on the dorsum of the hand, and previous injection of local anesthetic agent. The perforator artery may be intact, but the tenuous venae comitantes are easily injured and can result in flap failure owing to venous congestion.

Morbidity: This flap requires division of some dorsal sensory branches during flap elevation. This will result in loss of sensation in the territory of the nerve and, rarely, a painful neuroma. Closure of the flap donor site will result in a visible scar on the dorsum of the hand. Patients should be informed about these problems preoperatively.

Imaging

A radiograph of the hand is useful in patients with a posttraumatic defect to rule out any associated metacarpal neck fractures.

A preoperative Doppler assessment of the perforator is not required. It is difficult to separate the Doppler signals of the perforator from the dorsal metacarpal artery (DMA). In our experience, the perforator is always present, and, if the DMA is absent, the perforator should arise directly from one of the branches of the deep palmar arch.

Surgical Anatomy

Vascular basis: The flap is based on the distal cutaneous perforator of the DMA that arises at the level of the metacarpal neck in the second to fourth intermetacarpal spaces. In addition to the DMA, this flap is also nourished by the palmar arterial system through a dorsopalmar anastomosis. This anastomosis is formed by the dorsal perforating branch of the palmar metacarpal artery (arising from the deep palmar arch) and the DMA at the neck of the metacarpal (Fig. 44-2).

Limits of the flap: We limit our flaps between the distal edge of the extensor retinaculum, the metacarpophalangeal (MCP) joint, and the outer borders of the adjoining metacarpals (Fig. 44-3A and B).

FIGURE 44-2

FIGURE 44-3

Positioning

The procedure is performed under tourniquet control.

The patient is positioned supine with the affected extremity on a hand table.

Exposures

Flap design: The DMA perforator closest to the defect is marked at the level of the metacarpal neck in the intermetacarpal space. The location of the perforator represents the pivot point of the flap. The distance between the perforator and the proximal edge of the defect represents the bridge segment of the flap. Based on the size of the soft tissue defect, a flap is designed proximal to the perforator at a distance that equals the bridge segment.

The flap may be designed as wholly cutaneous, cutaneous with a dermoadiposal bridge segment, or wholly adiposal.

Flaps with a dermoadiposal bridge segment can reach the defect by passing the bridge under a skin tunnel or by laying open the intervening skin segment (Fig. 44-4).

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