Sir,
We congratulate Balan et al., for their work describing the reverse dorsal metacarpal artery flap for cover of
finger defects. They have exemplified its utility in a wide spectrum of dorsal finger
defects, providing a simple single stage cover with like tissue without any donor
site morbidity.[[1]]
However, the authors describe this flap being based on retrograde flow through the
dorsal metacarpal artery (DMA) through communicating perforators, while in the surgical
procedure described, they have not mentioned that they have raised the flap with the
DMA. That implies that the flap is based on a perforator. With this in mind, we beg
to differ in understanding the dynamics of blood flow to the flap- antegrade vis-a-vis
retrograde. To clarify the same, we would like to highlight a few anatomical features
of dorsal hand circulation [[Figure 1]] and exemplify with description of two flaps based on DMA- reverse dorsal metacarpal
artery (RDMA) flap and dorsal metacarpal artery perforator (DMAP) flap [[Figure 2]].
Figure 1: Illustration of vascular anatomy of a ray forming the vascular basis of volar and
dorsal flaps
Figure 2: Cadaveric dissection showing the dorsal metacarpal artery based flaps (A) reverse
dorsal metacarpal artery flap shows the dorsal metacarpal artery in the flap marked
as ‘a’ and the branch communicating with the palmar metacarpal artery at the level
of head of metacarpal marked as ‘b’. (B) Dorsal metacarpal artery perforator (DMAP)
flap shows DMA in situ as ‘c’ with its dominant cutaneous perforator at the level of web space marked as
‘d’. There are small communicating branches passing volarly from this cutaneous perforator
Distally, the DMA ramifies at the level of the metacarpal heads and its branches can
be identified distal to the metacarpophalangeal joint travelling to the dorsal proximal
phalangeal skin of the fingers where they anastomose with the dorsal branches of the
palmar digital arteries.[[2]] Quaba and Davison, in 18 cadaveric dissections, described that these branches travelled
proximally (recurred) forming longitudinally oriented plexuses. In each of these vascular
leashes, a small (0.3–0.5 mm) perforator arising directly from the DMA, or when the
latter is absent, a perforator from the volar system was demonstrated.[[3]] Such perforators connecting the palmar and dorsal metacarpal arteries are seen
either proximal to metacarpal head or at the level of the base of proximal phalanx-near
the web.
In RDMA flap, superficial veins are interrupted and the proximal end of the vessels
(veins and DMA) are ligated at the proximal margin of the flap. Blood flows into and
out of the flap through a number of branches and tributaries, contained in a mesentery
or a fascial septum. To reach the general circulation, the blood must reverse its
flow through the veins. The arterial flow is retrograde in the DMA through the communicating
perforators [[Figure 3]]
Figure 3: Patient with a volar surface thumb defect resurfaced with a first reverse dorsal
metacarpal artery flap (A) volar thumb defect (B) dorsal metacarpal artery seen harvested
in the flap marked as ‘a’; perforator seen at neck of second metacarpal marked as
‘b’. (C) Reverse first dorsal metacarpal artery flap inset into the defect with primary
closure of donor site
The DMAP flap is based on a dominant communicating perforator or a direct cutaneous
vessel which enters the flap, anatomically speaking, at its distal end. Although out-flow
through superficial veins may be interrupted, venous return through the deep system
remains undisturbed [[Figure 4]]. This is thus based on antegrade flow through the DMA and/or the palmar metacarpal
artery through the perforator, and it is a perforator-based flap. Flap based on the
proximal perforator at the level of metacarpal head, is called ‘DMAP flap’ while flap
based on the distal perforator at the level of web space, is called ‘extended DMAP
flap’.
Figure 4: Patient with dorsal finger defect resurfaced with dorsal metacarpal artery perforator
flap (A) Dorsum of proximal phalanx defect with exposed bone and loss of extensor
tendon (B) dorsal metacarpal artery perforator flap elevated with dorsal metacarpal
artery seen in the second interosseous space marked as ‘a’ and perforator supplying
the flap seen at the level of head of metacarpal marked as ‘b’. (C) Flap inset completed
with primary closure of donor site
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Nil.
