Dorsal Metacarpal Artery Flaps and Dorsal Metacarpal Flaps
The first description of dorsal metacarpal artery (DMCA) flaps was by Early and Milner1 as early as 1980. Their work was based on anatomical dissections performed by Manchot,2 Salmon,3 and Spalteholz,4 who described the vascular architecture of the hand, and was focused on the interconnections between the palmar arterial system and its perforating vessels into the vascular network of the dorsum of the hand. Distally based DMCA flaps have become well established procedures in reconstructive hand surgery. The DMCA flaps provide one-stage coverage of excellent quality with independent vascularization and permit primary closure of the recipient site without sacrificing relevant arteries (e.g., proper digital artery) ( Fig. 38.1a,b ).
The following are the most frequent indications for these flaps:
Restoration of sensibility in the thumb
Defects of the dorsum of the proximal phalanx
Defects over the proximal interphalangeal (PIP) joint
Dorsal defects over the total length of the finger
Palmar defects over the entire length of the finger
Defects of the interdigital web space
Defects over the dorsum of the hand
The flaps can be used in primary and secondary reconstruction, as well as following skin-grafting of burned hands.
DMCA flaps cannot be used in the following cases:
Severe crush injury to the first web or the relevant dorsal metacarpal arteries
Deep lacerations to the dorsum of the hand
Injuries to the web space damaging the palmar-dorsal perforators
The course of the dorsal metacarpal vessels should be identified preoperatively by Doppler and marked on the skin, especially in burned and grafted hands.
The intended pivot point should also be marked on the skin.
The dorsal carpal branch of the radial artery usually originates at the level of the trapezium and runs in an ulnar direction, forming the dorsal carpal rete after penetrating the radiocarpal ligaments deep to the extensor carpi radialis muscles.
With the exception of the first dorsal metacarpal artery (FDMA), the dorsal metacarpal branches normally arise from the dorsal carpal rete.
The dorsal metacarpal arteries run axially and distally between the metacarpal bones in a fascial pocket of the dorsal interosseus muscles.5,6 They usually give off six to eight cutaneous perforators.7
In 97% of cases, the second dorsal metacarpal artery runs distally as an axial vessel in the fascia between the two heads of the second dorsal interosseus muscle.8,9 The third metacarpal artery arises in 93% from a perforating branch of the palmar branches.
The dorsal metacarpal branches usually form distal anastomoses with the branches of palmar arterial systems, such as the common palmar digital arteries, the proper digital arteries, and the palmar metacarpal arteries, which are located at the level of the deep transverse metacarpal ligament.6,10
The fifth dorsal metacarpal artery can be found as an axially running vessel in only 33% of cases and is absent in 17–30% of cases. In 66% of cases, palmar branches provide the vascular supply to the distal skin area.7,11
The dorsal metacarpal arteries bifurcate at the level of the second, third and fourth web space into the dorsal digital branches supplying adjacent dorsal sides of the index, middle, ring, and little fingers.
The dorso-palmar anastomoses form the basis for modifications of the dorsal metacarpal artery flaps.
The dorsal metacarpal branches are accompanied by venae comitantes, which permit venous drainage of the dorsal metacarpal artery flaps.13
Kite Flap (Foucher Flap)
The flap is based on the first dorsal metacarpal artery and usually includes the sensory branch of the radial nerve. It is suitable for all dorsal defects and is frequently used for restoration of sensibility in case of the loss of the pulp. Using the kite flap provides immedaiate sensibility and is therefore especially indicated in older patients ( Fig. 38.2a–d ).
Flap dimensions are marked on the proximal phalanx. The skin island can be up to 4 × 2.5 cm. A proximal cutaneous extension, or tail, is added to facilitate the flap insetting and to avoid tunneling.
Harvest of the kite flap usually starts with a curvilinear incision above the second metacarpal, where one of the large dorsal veins is identified.
The fascia of the first dorsal interosseus muscle is then “peeled off” the muscle fibers thereby preserving the vascular bundle, which runs deep in a fascial pocket. All the fascia and the connective tissue surrounding one of the veins should be included in the pedicle. It is not desirable to dissect the FDMA at this level, since it may lead to a disconnection of the vascular pedicle and the flap.
After the pedicle has been dissected, the flap is incised distally and dissection starts in the plane above the paratenon. It is of utmost importance to preserve the paratenon to secure healing of the full-thickness skin graft for donor defect closure.
An important step follows at the distal border of the flap at the level of the extensor hood. A strip of the sagittal bands should be included to secure the delicate tissue bridge from the pedicle to the skin island. This makes the pedicle more robust against shear forces and allows flap inset without the risk of jeopardizing the vascular supply.8,17
A full-thickness graft is used to reconstruct the donor site. The sagittal bands are repaired with 4.0 resorbable sutures.
Distally Based DMCA Flap (“Classic” DMCA Flap)
Quaba and Davison12 (1990) did not include the dorsal metacarpal arteries in their flap but based it on the main palmardorsal perforator in the web space. Based on the studies of Early and Milner,1 the distally based DMCA island flap was described by Maryuamain in 199013 and Dautel and Merle in 1991.11
Their modifications of this technique involved the constant anastomoses between the DMCA and the palmar arterial system, thus providing the vascular basis for the flap by securing a sufficient retrograde blood flow.6,18–22
The DMCA flaps were usually based on the largest palmar perforators, penetrating the interdigital web space to connect to the dorsal arterial system. Thus, the flaps could be rotated 180 degrees to reach the web spaces, the palmar and dorsal aspects of the proximal phalanges, and also the PIP joint9 ( Fig. 38.3a–g ).
Extended Distally Based DMCA Flap
This flap was introduced by Pelissier19 and colleagues in 1999.
This flap cannot be used if the area of the palmardorsal perforator and/or the web space has suffered severe trauma.
Perforating vessels can be identified and marked with Doppler.
Mark the pivot point.