44: Dorsal Metacarpal Artery Perforator Flap

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Procedure 44 Dorsal Metacarpal Artery Perforator Flap

Sandeep J. Sebastin, Kevin C. Chung

imageSee Video 36: Dorsal Metacarpal Artery Perforator Flap

Indications

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

image 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

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

image

FIGURE 44-1

Examination/Imaging

Clinical Examination

image 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.

image 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.

image 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

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

image 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

image 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).

image 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).

image

FIGURE 44-2

image

FIGURE 44-3

Positioning

image The procedure is performed under tourniquet control.

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

Exposures

image 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.

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

image 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).

image

FIGURE 44-4

Pearls

We design the skin island in an oblique fashion when a wider flap is required to accommodate a defect that involves two surfaces (palmar + lateral or dorsal + lateral).

If the flap design extends proximal to the distal edge of the extensor retinaculum, we design the flap as a curved ellipse instead of a straight ellipse. Once the flap is raised, the curved ellipse is straightened out and inset as a straight ellipse. This results in an additional 8 to 10 mm while maintaining the design within the previously mentioned limits (Fig. 44-5).

image

FIGURE 44-5

Procedure

Step 1

image The skin and subcutaneous tissue on one lateral border of the flap are incised until the underlying extensor tendon is seen (Fig. 44-6).

image

FIGURE 44-6

Step 1 Pearls

The aim of the lateral incision is to identify the correct plane of flap elevation. The flap is elevated in the loose areolar plane superficial to the extensor tendon paratenon. It is difficult to identify this plane, if we make the proximal incision first.

Step 1 Pitfalls

Try to preserve the extensor tendon paratenon because this will maintain the gliding of the extensor tendon postoperatively and prevent any adhesions to the overlying tissue.

Step 2

image The proximal border of the flap is incised using the previously identified plane of elevation.

Step 2 Pearls

Large veins at the lateral borders of the flap are avoided because these veins only add to stasis within the flap. Veins and dorsal sensory nerve branches that pass though the midsubstance of the flap cannot be avoided, are divided, and are included with the flap.

Step 3

image The remaining lateral border of the flap is incised, and the flap is elevated from proximal to distal (Fig. 44-7).

image

FIGURE 44-7

Step 3 Pearls

If the flap is designed with a dermoadiposal bridge segment, it is created by raising thick epidermal skin flaps and keeping the bridge segment as wide as the widest portion of the cutaneous flap.

Step 3 Pitfalls

The flap can be elevated rapidly in the proximal two thirds; however, once the extensor tendon juncturae are visualized, elevation should proceed slowly as the perforator arises immediately distal to the juncturae tendineae.

Step 4

image The DMA perforator is identified, and the flap is incised into an island distal to the perforator (Fig. 44-8).

image

FIGURE 44-8

Step 4 Pearls

Large veins that pass through the flap should be carefully divided distal to the flap. This will make pivoting the flap easier and reduce venous congestion in the flap (Fig. 44-9).

image

FIGURE 44-9

Step 4 Pitfalls

The perforator should not be skeletonized because the connective tissue surrounding the artery contains the draining veins.

Step 5

image Any intervening normal skin between the flap and defect can be laid open, or a wide tunnel can be made under it to enable the flap to reach the defect (see Fig. 44-7).

Step 5 Pearls

We prefer a tunnel for dorsal defects because the lax dorsal skin permits creation of large tunnels. In addition, this preserves the pliable skin over the dorsum of the MCP joint. For palmar defects, we prefer to lay the tunnel open or use a cutaneous bridge segment because making a tunnel in the palmar skin is difficult, and the constrictive fibrous septae can compromise flap vascularity.

Step 6

image The tourniquet is released with the flap in its native position, and the flap is allowed to perfuse for 10 to 15 minutes. This time is used to achieve excellent hemostasis.

Step 6 Pearls

This flap is now dependent only on the perforating vessel for blood supply. Allowing it to perfuse for 10 to 15 minutes gives it time to get accustomed to the new vascular flow pattern.

The pedicle of the flap has to be twisted to allow the flap to reach the defect. This should be done after tourniquet release because an empty vessel is more likely to get kinked than a vessel with flow.

Step 7

image The flap is then rotated into the defect and loosely anchored to the edges of the defect using 5-0 nylon sutures (Fig. 44-10).

image

FIGURE 44-10

Step 7 Pearls

Keeping the proximal interphalangeal (PIP) and MCP joints in extension will decrease the stretch on the pedicle.

When the flap is used to cover lateral or palmar defects, a folded gauze placed between the fingers that is incorporated into the final dressing keeps the web open and prevents compression of the bridge segment.

Step 7 Pitfalls

Flaps wider than 3 cm will require a skin graft for wound closure.

Step 8

image The flap donor site is closed in layers using 4-0 Vicryl and 4-0 nylon.

Step 8 Pearls

A dermal suture closure will prevent suture hatch marks on the dorsum of the hand and improve the aesthetic appearance.

Primary closure is aided by extension of the wrist.

Step 8 Pitfalls

Flaps wider than 3 cm will need a skin graft for wound closure.

Postoperative Care and Expected Outcomes

image A volar splint is used for 1 week to keep the fingers and the wrist in extension. Patients are discharged on the first postoperative day and advised to keep the limb elevated. They are started on range-of-motion exercises at 1 week, the sutures are removed at 2 weeks, and patients are then allowed to resume normal activities (Fig. 44-11).

image The DMA perforator flap is easy to raise and has minimal donor site morbidity. It is the ideal flap for resurfacing dorsal soft tissue defects because it provides single-stage “like-for-like” reconstruction (color match, skin thickness, and texture). It provides excellent coverage of defects in the web space and the lateral aspect of the fingers, although the color match is not ideal. It has a valuable role in resurfacing palmar defects, especially in cases when multiple fingers are injured, and it is risky to harvest homodigital/heterodigital vascular island flaps or a cross-finger flap. In addition, more than one flap can be raised at the same time, permitting coverage of multiple fingers simultaneously.

image

FIGURE 44-11

Evidence

Quaba AA, Davison PM. The distally-based dorsal hand flap. Br J Plast Surg. 1990;43:28-39.

This is the first description of this flap. The authors carried out dissections in 18 cadavers and noticed the consistent presence of the cutaneous perforator of the dorsal metacarpal artery distal to the juncturae. They used the flap in 21 clinical cases and were able to resurface dorsal defects up to the DIPJ. They reported partial loss of one flap and total loss of one flap. (Level IV evidence)

Sebastin SJ, Mendoza RT, Chong AK, et al. Application of the dorsal metacarpal artery perforator flap for resurfacing soft-tissue defects proximal to the fingertip. Plast Reconstr Surg. 2011;128:166-178.

The authors used 56 DMA perforator flaps to resurface 58 finger soft tissue defects in 54 patients. The average flap size was 4.6 × 2.3 cm; 34 flaps were based on the second DMA perforator, 14 were based on the third DMA perforator, and 8 were based on the fourth DMA perforator. Twenty flaps were used to resurface defects distal to the PIP joint, and 36 flaps were used to resurface defects over the PIP joint and proximal to it. Skin graft was needed to close the donor defect in 7 patients. Complications included venous congestion in 6 flaps, arterial insufficiency in 3 flaps with total loss of 2 flaps, and infection in 1 case. The authors felt that this flap could reliably cover soft tissue defects up to the proximal half of the middle phalanx and could be extended to reach the DIP joint by designing it as a curved ellipse or by dividing the DMA proximal to the origin of the perforator. (Level IV evidence)

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