Adipofascial Flap Finger Coverage
The adipofascial turnover arterial flap has appeared as an excellent alternative for achieving early coverage of cutaneous wounds at the dorsal aspect of the middle and distal phalanges of the long fingers. This flap can be designed as an arterial flap in a predictable and reliable way based on new anatomic data on the vascularization of the dorsum of the finger.
Indications
All defects on the dorsal aspects of the middle and distal phalanges can be covered with this flap, based on the third (the last branch of proximal phalanx) or on the fourth (the first branch of the middle phalanx) cutaneous dorsal branches of the proper palmar digital artery (PDA).
In cases of extensive soft-tissue loss of both the middle and distal phalanges, this flap length can be extended to include the subcutaneous tissue over the metacarpophalangeal (MP) joint and, sometimes, a portion of the dorsal metacarpal surface, based on the anastomosis between the dorsal vascular system of the proximal phalanx and the dorsal metacarpal vessels.
Contraindications
Severe circumferential crush injuries or partial degloving injuries
Defects requiring simultaneous vascularized extensor tendon reconstruction, which can be treated with other flaps
Injuries of the PDA
Extensive burns of the digits
Examination/Imaging
To ensure inclusion of the dorsal digital arteries in the flap pedicle, it is necessary to locate them with the help of a Doppler probe or to design the pedicle large enough to reduce the probability of not harboring an arterial branch. Provided that precise location of the dorsal branches is established, it is possible to preclude the use of Doppler studies to avoid unnecessary length of the flap pedicle and to choose which dorsal artery will be included.
Relevant Anatomy
Yang and Morris1 dissected 16 cadaver hands and established that there were two sources of the cutaneous arterial supply to the dorsum of the digit: the dorsal digital branches of the dorsal metacarpal arteries and the dorsal cutaneous branches of the PDAs. The dorsal cutaneous branches of the paired proper PDAs supply the dorsal surface of the proximal phalanx distally and the dorsum of the middle phalanx. There are a series of small dorsal cutaneous perforators (usually two) at each phalanx from the PDA ( Fig. 36.1a ).
The size of the dorsal cutaneous branches varies between 0.2 and 0.5 mm in external diameter. These branches tend to become smaller from the proximal to the distal end of the finger as the PDA diminishes in caliber. All the dorsal cutaneous branches of the PDA along the finger dorsum longitudinally anastomose with each other. The proximal dorsal cutaneous branches of the palmar digital arteries anastomose with the dorsal digital branches from the dorsal metacarpal arteries2–5 on the dorsum of the proximal phalanx.
The dorsal carpal branch of the ulnar artery runs along the ulnar side of the fifth metacarpal and anastomoses with the dorsal branch of the ulnar PDA of the little finger. In addition, there are a series of reduced-caliber choke anastomoses crossing the mid-line between the radial and ulnar dorsal branches of the palmar digital arteries over each of the phalanges.
Endo et al5 dissected 71 fingers injected with latex and noted there were two to three dorsal branches in the proximal phalanx region and two in the middle phalanx region ( Fig. 36.1b ).
Metacarpal Head and Web Space
The dorsal metacarpal artery bifurcates into two dorsal digital arteries of the adjacent digits at the MP joint and terminates at approximately the middle portion of the proximal phalanx, where it joins the proximal dorsal branch of the proper PDA. These branches of the dorsal metacarpal artery give off some twigs to the skin around the MP joint.
Dorsum of the Proximal Phalanx
The proximal dorsal branch arises from the palmar digital artery at the middle point of the proximal phalanx just distal to the proximal finger crease. This artery penetrates the cribriform part of the Cleland ligament, which originates from the lateral margin of the proximal portion of the proximal phalanx and appears as a septum between the palmar and dorsal aspects of the finger.
The dorsal branch runs close to the lateral wall of the proximal phalanx and then emerges on the dorsal aspect of the finger, giving a small branch to the periosteum of the dorsal surface of the proximal phalanx ( Fig. 36.1a ). This artery passes to the lateral margin of the extensor lateral band and divides into three or four small branches that distribute to the skin of the proximal phalangeal region. Some of these twigs anastomose with the terminal branches of the dorsal metacarpal artery. The size of the proximal dorsal branch at the base is 0.3 to 0.6 mm (average, 0.44 mm).
In some of the fingers there is another proximal dorsal branch that originates from the vincula branch and is found just distal to the MP joint ( Fig. 36.1a ). The size of this artery at the base is 0.3 to 0.5 mm (average, 0.42 mm).
The distal dorsal branch arises from the proximal digital palmar arch, which lies beneath the flexor tendon below the neck of the proximal phalanx. This branch arises from the digital palmar arch just before it penetrates the flexor tendon sheath. It penetrates the proximal portion of the Cleland ligament at the proximal interphalangeal (PIP) joint, runs close to the bone, and emerges on the finger dorsum, where it bifurcates into a branch to the dorsal periosteum of the proximal phalanx and a branch to the skin over the PIP joint. The size of this branch at the base was 0.3–0.6 mm (average, 0.39 mm) ( Fig. 36.1b ).
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