Surgical Approaches from an Angiosomal Perspective

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CHAPTER 9 Surgical Approaches from an Angiosomal Perspective

Michael K. Matthew, MD, Michael R. Hausman, MD

The concept of the angiosome was initially described in the cutaneous blood supply,¹ but has subsequently been shown to pertain to the underlying viscera and skeleton.² Devascularization of these deeper structures is less obvious than skin necrosis, but is known to occur, resulting in problems such as nonunion of fractures and avascular necrosis of bones. We seek to organize such information, using the angiosome concept, to present a cogent, comprehensible surgical approach to the three-dimensional vascular anatomy of the forearm and wrist.

Functional Microvascular Anatomy

The distal forearm, including the radius, ulna, carpal bones, and overlying soft tissues, is supplied by a network of longitudinal vessels: the radial artery, ulnar artery, anterior interosseous artery (AIA), and posterior interosseous artery (PIA). They are interconnected by dorsal and volar transverse arches (Figs. 9-1 and 9-2). The overlying skin is supplied by direct or septocutaneous perforators arising from these longitudinal vessels (Fig. 9-3), which are small arteries and veins that course along the fibrous septa that separate the muscles in the forearm.

FIGURE 9-1 Palmar Vascularity.

(From Cooney WP, Linscheid RL, Dobyns JH: The Wrist: Diagnosis and Operative Treatment. St Louis: Mosby, 1998, p 108.)

FIGURE 9-2 Dorsal Vascularity. 1, dorsal supraretinacular arch; 2, dorsal intercarpal arch; 3, fifth intercompartmental artery; 4, fourth intercompartmental artery; 5, 2,3 intercompartmental artery; 6, 1,2 intercompartmental artery; U, ulnar artery; AIA, anterior interosseous artery; PIA, posterior interosseous artery; ODA, oblique dorsal artery.

(From Cooney WP, Linscheid RL, Dobyns JH: The Wrist: Diagnosis and Operative Treatment. St Louis: Mosby, 1998, p 107.)

FIGURE 9-3 Perforators of the Forearm, Wrist, and Hand. ADM, abductor digiti minimi; ANC, anconeus muscle; APB, abductor pollicis brevis; APL, abductor pollicis longus; BR, brachioradialis; ECRB, extensor carpi radialis brevis; ECRL, extensor carpi radialis longus; ECU, extensor carpi ulnaris; ED, extensor digitorum; EDM, extensor digiti minimi; EPB, extensor pollicis brevis; EPL, extensor pollicis longus; FCR, flexor carpi radialis; FCU, flexor carpi ulnaris; FDM, flexor digiti minimi; FDS, flexor digitorum sublimus; FPB, flexor pollicis brevis; PL, palmaris longus; PT, pronator teres.

Rights were not granted to include this figure in electronic media. Please refer to the printed book.

(From Inoue Y, Taylor GI: The angiosomes of the forearm: anatomic study and clinical implications. Plast Reconstr Surg 1996; 98:198.)

Most of the distal radius and proximal carpal row are supplied via the radial and anterior interosseous arteries, which have a rich collateral circulation. The single exception is the pisiform, which is supplied by the ulnar artery. In contrast, the ulna is primarily supplied by the posterior interosseous and ulnar arteries. The distal carpal row is supplied from the dorsal intercarpal arch and deep palmar arch and has contributions from the radial, ulnar, and anterior interosseous arteries. The skin of the distal forearm is supplied on the radial/palmar side by the radial artery; on the ulnar/palmar side by the ulnar artery; and dorsally by the AIA, PIA, and dorsal ulnar artery. These skin territories overlap significantly secondary to the connections afforded by the subdermal and subfascial plexus.

An angiosome is a section of tissue that can remain viable based on a single feeding vessel. These angiosomes do not have absolute boundaries, or necrosis from skin incisions would be very common. There is some “built-in” redundancy from the fact that each angiosome connects with the adjacent one via small arteriole branches termed “choke vessels.”¹ These vessels respond to ischemic insults within an adjacent angiosome by increasing their diameter to increase blood flow to provide adequate, collateral circulation to the adjacent, compromised angiosome.³ This phenomenon explains the physiology behind the delay procedure commonly used to extend the margins of a flap to be transposed. This process takes 3 days in animal models. In most human clinical applications, the flaps are delayed 1 to 2 weeks before flap transposition. One angiosome may be expanded to include an adjacent angiosome, but it may not cover a more distant angiosome. Adjacent angiosomes tend to interconnect within tissue rather than between intercompartmental fascia separations as might seem intuitive.² In a traumatic incident or in a surgical dissection if a specific angiosome is rendered ischemic along with its neighboring angiosomes, that angiosome becomes devitalized, predisposing to nonunion or infection.

Radial Artery Angiosome

The radial artery (Fig. 9-4) directly supplies bone (radius, scaphoid, and trapezium), muscle (pronator teres, extensor carpi radialis longus and brevis, brachioradialis, flexor carpi radialis [FCR], flexor digitorum sublimus [FDS], and flexor pollicis longus), and overlying volar radial skin of the forearm, including the mobile extensor wad (see Fig. 9-9).² The radial forearm flap based on this angiosome has been used as a pedicled septocutaneous flap for coverage of the antecubital fossa; as a pedicled reverse flow septocutaneous flap for hand coverage; and as a free flap to provide skin, muscle, and bone to distant sites.^4,⁵ The radial artery travels between the brachioradialis and FCR, and gives off numerous perforators along the lateral intermuscular septum that either ascend to the overlying skin or dive down to supply the underlying radius and flexor pollicis longus. The versatility of this pedicle and its associated composite flaps is well documented.⁵^–⁹

FIGURE 9-4 Radial Artery Angiosome. DICA, dorsal intercarpal arch; DRCA, dorsal radiocarpal arch; DSRA, dorsal supraretinacular arch; PMA, palmar metaphyseal arch; PRCA, palmar radiocarpal arch; 1,2 SRA, 1,2 supraretinacular artery.

The radial artery not only supplies the voloradial aspect of the distal radius, as might seem intuitively obvious, but also the dorsal aspect of the bone via the 1,2 supraretinacular artery (1,2 SRA), and the dorsal radiocarpal arch (DRCA). The 1,2 intercompartmental artery (ICA) originates from the radial artery approximately 5 cm proximal to the radiocarpal joint. It traverses superficial to the extensor retinaculum over the 1,2 intercompartmental septum sending branches down to the cortical and rarely cancellous bone. Sheetz and colleagues ¹⁰ described a branch from the 1,2 SRA to the second compartment floor, which penetrates into cancellous bone. This artery connects variably to the radial artery, DRCA, or dorsal intercarpal arch (DICA). The 1,2 SRA also gives off the dorsal supraretinacular arch (DSRA), which connects variably to the 2,3 supraretinacular artery (2,3 SRA), fourth intercarpal artery, fifth intercarpal artery, or ulnar artery. The DRCA, which arises from a direct branch off the radial artery, gives several small feeding vessels to the ridge of the radius at the radiocarpal joint, which descend to the cancellous bone of the metaphysis.¹⁰

The radial artery supplies the volar distal radius in a retrograde fashion via the palmar metaphyseal arch (PMA) and palmar radiocarpal arch (PRCA). The PMA originates from the palmar AIA within the pronator quadratus and courses through the muscle to connect with the radial artery giving off scattered perforating branches to the underlying, largely cortical bone. Sheetz and colleagues ¹⁰ pointed out that the more proximal perforating branches are more likely to penetrate into cancellous bone. This observation was consistent for all of the penetrating vessels of the distal radius in their observations. The PMA pedicle has been used for vascularized bone grafts to the scaphoid. Some authors consider the results of this vascularized bone graft to be inconsistent, which is likely due to the variable penetrating vessels. A larger bone graft rather than a smaller one based on this pedicle is advisable to capture as many perforators as possible. Also, the more proximally the bone graft is harvested to obtain a larger arc of rotation, the more likely it is to have a perforator that penetrates into cancellous bone.

The PRCA is located just proximal to the radiocarpal joint, travels within the palmar wrist capsule, and connects with the palmar AIA and ulnar artery. The PRCA is subdivided into a radial and ulnar component by the palmar AIA forming the T-anastomosis described by Haerle and associates (see Fig. 9-1).¹¹ The radial PRCA gives off multiple branches to the distal radius periosteum supplying cortical and cancellous bone.¹⁰

The radial artery supplies the carpus from proximal to distal through (1) branches off the DRCA, (2) branches to the scaphoid tubercle and dorsal ridge, (3) a branch to the DICA, (4) a branch to the trapezium, and (5) branches off the deep palmar arch (Fig. 9-5; see Figs. 9-4 and 9-14). The DRCA arises at the level of the radiocarpal joint and supplies the distal radius, lunate, and triquetrum. It continues to connect to the ulnar artery and possibly the AIA. The branches to the scaphoid arise at the level of the scaphotrapezial joint to enter the distal scaphoid. The volar scaphoid branch frequently connects to the superficial palmar arch (Fig. 9-6), and the dorsal branch connects to the DICA (Fig. 9-7). These arches serve as collateral circulation if the radial artery should become occluded proximally. The DICA originates just distal to the dorsal scaphoid branch and supplies the distal carpal row. Similar to the DRCA, the DICA traverses the wrist to connect with the AIA and ulnar arteries. The branch to the trapezium is the last branch to the carpus before continuing as the dominant vessel to the deep palmar arch. The vascular anatomy of the arches is discussed in further detail later.

FIGURE 9-5 Schematic of Radial Artery Angiosome.

(From Cooney WP, Linscheid RL, Dobyns JH: The Wrist: Diagnosis and Operative Treatment. St Louis: Mosby, 1998, p 109.)

FIGURE 9-6 Injection of Radial Artery Angiosome. RS, Radial styloid; S, scaphoid; T, trapezium; R, radial artery; 1, superficial palmar branch of radial artery; 3, dorsal radiocarpal arch; 4, branch to the tubercle of the scaphoid and trapezium; 5, artery to dorsal ridge of scaphoid; 6, dorsal intercarpal arch; 7, branch of the lateral trapezium and thumb metacarpal; 8, medial branch of radial artery (seen in 22% of the specimens) penetrating the base of the index-long web space. (Note, in this view, 2 the palmar radiocarpal arch, cannot be seen.

(From Cooney WP, Linscheid RL, Dobyns JH: The Wrist: Diagnosis and Operative Treatment. St Louis: Mosby, 1998, p 109.)

FIGURE 9-7 Injection of Scaphoid Vascularity. Close-up view of the dorsoradial aspect of the wrist, demonstrating nutrient vessels entering the dorsal ridge of the scaphoid. RS, Radial styloid; S, scaphoid; R, radial artery; 2, dorsal radiocarpal arch; 3, branch to the dorsal ridge of the scaphoid; 4, dorsal intercarpal arch. *, communication between DICA and dorsal branch to scaphoid.

(From Gelberman RH, Panagis JS, Taleisnik J, et al: The arterial anatomy of the human carpus, part I: the extraosseous vascularity. J Hand Surg 1983; 8A:371.)