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The radial, ulnar, and interosseous arteries provide the vascular supply of the hand and wrist. The perforators from these vessels form the basis of fasciocutaneous flaps from the forearm that are commonly used in the reconstruction of the hand.
There are four dorsal metacarpal arteries. The first dorsal metacarpal artery originates from the radial artery, whereas the remaining three originate from the dorsal carpal arch. These continue on the dorsal aspect of the proximal phalanges and communicate with branches of the proper digital arteries at the proximal interphalangeal joints.
In the hand, the superficial palmar arch forms as the continuation of the ulnar artery (with contribution from the radial artery) and the deep palmar arch as the continuation of the radial artery (with contribution from the ulnar artery). The common digital arteries arise from the superficial palmar arch to supply the fingers and receive contributions from the deep palmar arch. The numerous palmar and dorsal branches of the digital arteries allow for a variety of flaps for digital reconstruction.
The thumb has two proper digital arteries (radial and ulnar) on the palmar surface that originate from the princeps pollicis artery in most of the population. The dorsal arteries are variable and arise from the first dorsal metacarpal artery. The palmar or the dorsal circulation is sufficient to support the vascularity of the thumb, independent of each other. This allows mobilization of the entire palmar skin as an advancement flap.
Understanding the blood supply, branches, and perforators to the skin at different levels is important for reconstructive surgery of the hand.
The vascular supply of the hand and forearm is a complex network of vessels derived from the radial and ulnar arteries. This typical pattern is observed in 84% of the population. However, there are some variations. There may be a persistent median artery arising from the ulnar artery seen in 8% of the population, or a superficial brachial artery, which is a branch from the brachial artery, present in another 8% of the population.
The radial artery is the smaller of the terminal branches of the brachial artery. It begins in the cubital fossa approximately 2.2 cm inferior to the transverse crease at the level of the neck of the radius.
The artery lies within the lateral intermuscular septum of the forearm. Proximally it lies between the supinator muscle and the origin of the flexor digitorum superficialis muscle. In the middle third of the forearm, it lies anterior to the pronator teres. In the distal third it lies anterior to the flexor pollicis longus muscle and ulnar to the tendon of the flexor carpi radialis tendon. Throughout the proximal two-thirds of its course, it lies posterior to the medial border of the belly of the brachioradialis muscle. The superficial radial nerve runs along with the radial artery in the middle third of the forearm. The radial recurrent artery arises immediately after the origin of the radial artery. It courses proximally superficial to the supinator muscle, and passes anterior to the lateral epicondyle, where it anastomoses with the radial collateral artery, a branch from profunda brachii. Muscle branches supply the muscles on the radial side of the forearm, and septocutaneous branches arise along the entire course of the radial artery. These branches lie within the lateral intermuscular septum. In the proximal two-thirds of the forearm, the lateral intermuscular septum is located between the bellies of the brachioradialis and the flexor carpi radialis. The largest septocutaneous branch is the inferior cubital artery, arising distal to the radial recurrent artery.
Along its course within the lateral intermuscular septum between the brachioradialis and flexor carpi radialis muscles, the radial artery gives rise to multiple periosteal branches to the radius, which allow the harvest of bone segments on the radial artery. Specifically between the insertion of the pronator teres and the brachioradialis muscles on the lateral aspect of the radius, there is no muscle interposed between the radial artery and the radius. At the radiocarpal joint it gives rise to the superficial palmar branch, which joins the superficial branch of the ulnar artery to form the superficial palmar arch. The radial artery then turns around the radiocarpal joint as the dorsal branch, and crosses the anatomic snuff box to the first interosseous space to enter the palm. It then gives rise to the princeps pollicis, the radialis indicis, and terminates as the deep palmar arch.
The ulnar artery is the larger of the two branches of the brachial artery. It passes deep to the heads of the pronator teres and the superficial flexors of the forearm. It then runs in a medial and distal direction anterior to the flexor digitorum profundus muscle. Proximally it is crossed by the median nerve, which passes between the two heads of the pronator teres muscle and courses longitudinally in the midforearm. Immediately after its origin, it gives rise to the anterior and posterior recurrent arteries. Approximately 2 cm from the bifurcation of the brachial artery, it gives rise to a short common interosseous artery that further divides into anterior and posterior interosseous arteries.
In the proximal forearm, the ulnar nerve is lateral to the ulnar artery deep to the muscle belly of the flexor carpi ulnaris muscle. The ulnar artery remains associated to the ulnar nerve throughout the distal two-thirds of the forearm, where it remains on its lateral side.
divided the forearm into 10 zones (10%–100% marked from distal to proximal direction); the highest number of perforators was noted in the distal third of the forearm (labeled 30%) and the next highest concentration was noted in the proximal third in the zone labeled 70%.
The radial artery fasciocutaneous perforators in the distal third of the forearm are the basis for the elevation of the proximally based radial forearm flap. The proximal group of septocutaneous perforators forms the basis of the reverse flow or the distally based radial forearm flap.
The ulnar artery provides vascularity to the skin of the distal two-thirds of the ulnar forearm and the dorsum of the hand. The ulnar artery gives rise to a cutaneous artery 2 to 5 cm before the pisiform. In cadaveric studies by Becker and colleagues
this cutaneous branch had a diameter of 1 to 1.3 mm and passed dorsally from the ulnar artery deep to the flexor carpi ulnaris muscle. This branch supplied the skin and the fascia (9–20 cm long and 1.5–10 cm wide) over the distal two-thirds of the ulnar side of the forearm. This cutaneous artery forms the basis for the ulnar artery perforator flap, or the Becker flap. Similar to the radial artery the fasciocutaneous perforators in the distal and proximal thirds of the forearm are used as the basis for ulnar artery forearm flap; however, this flap is not preferred because it eliminates the major blood supply of the hand.
The interosseous arteries
The interosseous arteries arise either from the common interosseous artery, which is a branch of the ulnar artery, or they may arise directly from the ulnar artery. The posterior interosseous artery forms the axis for the posterior interosseous artery faciocutaneous flap. The posterior interosseous artery enters the deep extensor compartment of the forearm, underneath the supinator at an average distance of 7.9 cm from the lateral epicondyle of the humerus. The interosseous recurrent artery originated at this level in 91% of dissected specimens. The posterior interosseous artery gives rise to a series of fasciocutaneous perforators along its length in the septum between the extensor carpi ulnaris and the extensor digiti minimi.
Clinically the axis of the artery is marked as follows. The elbow is flexed 90° and the forearm placed in full pronation. A line drawn from lateral epicondyle to the distal radioulnar joint indicates the axis of the posterior interosseous artery. The cutaneous perforators are found along this line. The average number of posterior interosseous artery cutaneous perforators in the dorsal forearm is 5 ± 2 and most of them are concentrated in the proximal part of the artery.
Three distinct patterns of septocutaneous perforators have been observed: (1) the septocutaneous branches are distributed in two subgroups, one proximal and the other distal, each containing three or four vessels; (2) in the most predominant pattern, multiple small branches arise at 1- to 2-cm intervals along the total length of the posterior interosseous artery; and (3) in the least common pattern, there is a large proximal perforator in the proximal group sharing the same origin as the interosseous recurrent artery, with a larger diameter than the remaining septocutaneous vessels and fanning out into several branches.
It anastomoses with the posterior branches of the anterior interosseous artery, forming the anastomotic network on the posterior aspect of the wrist. The anastomosis rate of its terminal and dorsal branch of the anterior interosseous artery is 98.6% to 100%.
The anterior interosseous artery courses on the anterior surface of the interosseous membrane. It gives off branches to the radius and ulna and a median branch to the palm. Throughout the forearm, it gives off direct muscle branches and septocutaneous perforators. Usually the proximal septocutaneous perforator is the largest and arises 3 to 4 cm distal to the common interosseous branch. Distally, at the proximal border of the pronator quadratus muscle, the anterior interosseous artery goes to the dorsal side of the interosseous membrane and gives rise to the dorsal septocutaneous branch, which reaches the skin between extensor pollicis longus and brevis, and also gives small branches to extensor muscles and distal radius.
At the level of the carpus the arteries of the forearm communicate to form three dorsal and three palmar arches.
The dorsal radiocarpal arch (Fig. 1) lies deep to extensor tendons at the level of the radiocarpal joint. It is present in 80% of the population and receives contributions from the radial artery, the ulnar artery, and a dorsal branch of the anterior interosseous artery in 67% of the population. The dorsal intercarpal arch is consistently seen in all dissections, and lies at the level of the midcarpal joint. It receives contributions from the radial, ulnar, and the anterior interosseous arteries in 60% of the specimens; however, contributions from the radial artery is absent in 20% of specimens and from the ulnar artery in another 20%. The dorsal proximal metacarpal arch is present at the level of the carpometacarpal joints. A complete arch is seen in 27% of the population. It is supplied by communicating branches of the deep palmar arch.
This arch gives rise to the second, third, and fourth dorsal metacarpal arteries that supply the dorsal skin of the hand.
Palmar Carpal Arches
There are three palmar carpal arches; the most proximal or the radiocarpal arch is consistently present in 100% of the population. It receives branches from the radial, ulnar, and the anterior interosseous arteries. The palmar intercarpal arch is seen in 53% of the population. Similar to the radiocarpal arch it receives contribution from the three arteries. The distal palmar arch (also known as the distal arterial convergence zone) lies superficial to the bases of the fourth and fifth metacarpals and receives recurrent arteries that are small branches from the radial and ulnar arteries.
The vascular supply of the hand is derived from the superficial and the deep palmar arches on the palmar aspect and from the dorsal metacarpal arteries that arise from the dorsal metacarpal arch on the dorsal aspect.
The superficial palmar arch
The ulnar artery passes through Guyon canal and after giving off a deep palmar branch, which anastomoses with the deep palmar arch (formed predominantly by the radial artery), it continues as the superficial palmar arch that lies superficial to the flexor tendons. At its termination on the radial side of the hand it anastomoses with the superficial palmar branch of the radial artery.
The superficial palmar arch crosses the palm 1 to 2 cm distal to the distal edge of the transverse carpal ligament. The surface anatomy, however, has been a cause of confusion from Kaplan’s original drawing where it was depicted at the level of the distal palmar creases. The actual location lies distal to the transverse carpal ligament (Fig. 2).
It gives rise to the three common digital arteries that divide to form the proper digital arteries of the fingers. The superficial palmar arch is subject to several variations. A complete arch is seen in 42% of cases and is classified as (1) radioulnar (normal), (2) medioulnar (composed of median and ulnar arteries), or (3) radiomedioulnar. The nomenclature is based on the contributing vessels, ulnar artery, median artery, and radial artery.
An incomplete arch is seen in 58% of all cases where the common digital arteries arise from ulnar, median, or radial components. Incomplete palmar arches put digits at risk in situations of arterial injuries and when the radial or ulnar arteries have been harvested as parts of a radial forearm or the ulnar forearm flaps.
The deep palmar arch is the continuation of the dorsal branch of the radial artery. The radial artery enters the palm through the first interosseous space and crosses the palm as the deep palmar arch, lying deep to the flexor tendons. It gives rise to the princeps pollicis artery that supplies the thumb, and branches that communicate with the common digital arteries.
The Dorsal Metacarpal Arteries
The dorsal branch of the radial artery passes between the two heads of the first dorsal interosseous muscle to enter the palm. Before passing through this muscle, it gives rise to the first dorsal metacarpal artery and a transverse branch, which forms the dorsal arch of the carpus (the dorsal proximal metacarpal arch). This dorsal metacarpal arch gives rise to the second, third, and fourth dorsal metacarpal arteries that lie in the respective interosseous regions (Fig. 3). The dorsal metacarpal arteries continue on the dorsal aspect of the proximal phalanges and communicate with the branches of palmar arteries at the level of the proximal interphalangeal joints.
The first dorsal metacarpal artery, which arises directly from the deep branch of the radial artery, is consistent and is the pedicle for the so-called “kite flap.” The other dorsal metacarpal arteries connect with the deep palmar network at the level of the metacarpal neck. These interosseous communications form the basis of the distally based dorsal hand flap or the Quaba flap.
The ulnar digital artery is larger in the index and middle fingers and the radial vessel is almost always larger in the ring and small fingers. The common digital vessel to the third web space divides into branches that are large on both sides of the web space.
The proper digital arteries communicate with each other through three major palmar arches that connect the digital arteries: the proximal, middle, and distal transverse arches. The middle transverse and distal arches are 1.5 times larger than the proximal. Their location is constant: the proximal arch is located in association with the C1 pulley and the middle arch in association with the C3 pulley. These arches lie deep to the flexor tendon. These transverse communications between the digital arteries are the basis for distally based vascular island flaps. The distal arch is formed when both digital arteries turn centrally to join each other, just distal to the insertion of the flexor digitorum profundus tendon.
These branches travel in the subcutaneous plane and arborize with corresponding branches from the contralateral digital artery. Three types of anatomic branching patterns were observed: (1) I-shaped, consisting of a single vessel (64%); (2) V-shaped, with a bifurcation immediately after the beginning of the vessel (23%); and (3) Y-shaped, branching off beyond the origin of the vessel (13%). It was also noted that these small arterial branches were lateral to the digital nerve in most (82%) cases.
These rich connections between the digital arteries and the soft tissue allow for mobilization of islands of palmar skin along with the vessel, such as neurovascular island flaps, or without mobilization of the arteries, such as the homodigital subcutaneous flap.
described four vessels: (1) a condylar vessel supplying the condylar area of the metacarpal and proximal phalanx, respectively; (2) a metaphyseal vessel supplying the metaphysis of the proximal and middle phalanx, respectively; (3) dorsal skin vessels; and (4) transverse palmar arch vessels (palmar branches), supplying the proximal and middle palmar arches, respectively. These dorsal branches arising from both proper digital arteries supply the skin over the dorsum of the finger. The dorsal branching vessels originating from the proper digital artery in the middle phalanx of finger are constant. These vessels pass distally and dorsally over the middle phalanx and travel distally and obliquely over the distal interphalangeal joint to anastomose with corresponding vessels from the contralateral side of the finger, forming a superficial arcade. A large vascular network across the midline of the finger is normally present.
A similar pattern was also noted for the distal phalanx but with some crucial differences. The dorsal skin vessel, arising just before the distal transverse palmar arch, joins with its counterpart from the other side to form the proximal matrix arch. Thereafter, both digital vessels join with each other forming the distal transverse palmar arch.
Extending from the distal transverse palmar arch are three large vessels that travel to the tip of the pulp and turn dorsally to communicate with the distal matrix arch. There are three dorsal arches that supply the dorsum of the distal phalanx and nail complex, known as the proximal, middle, and distal matrix arches. The two longitudinal lateral vessels on either side of the pulp give off a dorsal branch, which divides into two. Anastomoses from these two divisions form the middle and distal matrix arches, respectively. This branch going dorsally to become the middle and distal matrix arches travels through a defect in the fibrous tissue from the lateral tendon expansion at a point distal to its insertion.
A network of longitudinal, parallel vessels arising from the distal matrix arch traveling distally gives rise to a superficial capillary network supplying the hyponychium, nail folds, and nail bed. Hasegawa and coworkers
observed that within the sterile matrix, there are numerous capillary loops, with the loops becoming longer and more inclined to the nail bed distally. At the level of the germinal matrix, there were no capillary loops. Instead, there was a single layered rectangular plexus of capillaries in the plane of the nail matrix.
Venous drainage of the digits
There are two networks of veins: dorsal and palmar. The dorsal system is larger and more constant than the palmar one. Each of these systems resembles a ladder and are interconnected by lateral anastomotic and commissural veins. In a series of dissections, Lucas
found a constant vein that terminated over the dorsal midline of the distal phalanx to arborize over the surface of the nail matrix. The veins running longitudinally along the nail margins were also constant. The longitudinal palmar veins do not travel with the arteries. They are situated more superficially and have a more random pattern, traveling in and out of Cleland and Grayson ligaments. In some, there are deep longitudinal veins on the palmar side along the tendon sheath receiving branches from the vincular system.
The thumb has two arterial systems, the palmar and the dorsal systems (Fig. 6), either of which is sufficient to support the vascularity of the distal thumb independent of the other.
Palmar arteries of the thumb
There are two proper digital arteries on the palmar surface: the ulnar digital artery and the radial digital artery. In 90% of individuals, the radial digital artery originates from the princeps pollicis artery and travels radial to the flexor pollicis longus. In 10% of all cases, it is seen to originate directly from the superficial palmar branch of the radial artery.
The ulnar digital artery is larger in diameter and its origin is variable. In 50% to 70% of cases, it originates from the princeps pollicis artery and passes superficial to the insertion of the adductor pollicis. In the other 50% of the population, it may arise from the superficial palmar arch, the superficial branch of the radial artery, or the first dorsal metacarpal artery.
Typically they arise from the first dorsal metacarpal artery, which itself is a branch of the dorsal branch of the radial artery before it enters the palm. The dorsal radial artery arises at the anatomic snuffbox, courses along the abductor pollicis brevis, and terminates as the dorsal arcade at the nail matrix. The dorsal ulnar artery originates either from the first dorsal metacarpal artery or as direct branches from the dorsal branch of the radial artery. Rarely they may originate from the princeps pollicis artery. These arteries are absent in 30% of the population. The robust dorsal vasculature of the thumb allows for mobilization of the entire volar skin on the palmar vasculature as in the Moberg flap without compromising the vascularity of the dorsal skin.
Likewise the dorsal radial artery of the thumb has been used to design a distally based flap known as the Moschella flap.
The understanding of the vascular anatomy of the hand and particular awareness of the common variations is crucial for the surgeon performing reconstructive surgery of the hand. Of particular importance are the variations in the communication between the radial and the ulnar systems in the palm. The possibility of incomplete arches must be kept in mind when sacrificing a major vessel for reconstruction. Clinical or Doppler confirmation must be performed before such procedures. Similar caution must be extended to flaps based on digital arteries and possible insufficiency of one of the vessels may compromise the viability of the digit. Besides congenital variations, prior use or shunting of vessels for arteriovenous fistulas for procedures, such as dialysis, must be checked. In other cases, the presence of vasculopathies, such as in diabetes, may compromise the soft tissue circulation and the vessels may be insufficient to support the digit or the flap.