Vascular territories

Angiosome

The angiosome (from the Greek angeion , meaning vessel, and somite , meaning segment or sector of the body derived from soma , body) is defined as a composite block of tissue supplied by a main source artery. The source arteries (segmental or distributing arteries) that supply these blocks of tissue are responsible for the supply of the skin and the underlying deep structures. When pieced together like a jigsaw puzzle, they constitute the three-dimensional vascular territories of the body. In this section we present the basis of the anatomical studies which are the foundation of the angiosome concept.

The angiographic studies produced by Salmon using lead oxide, gelatin, and water were exceptional; however, modifications of the technique have further improved results. In particular, reducing the concentration of lead oxide has improved computed tomographic (CT) angiographic anatomic studies. A review of vascular injection techniques reveals the wide array of techniques available for investigation.

Initially, cadaver injection studies to study the vascular anatomy of the human integument and other structures utilized intra-arterial injections of radiopaque substances such as barium sulfate or lead oxide or visible substances such as latex and ink. Depending on the specific study, the area of tissue of interest was then dissected and radiographed. As the radiographic film quality improved, the quality of the image of the small blood vessels improved. However, studies using simple radiographs have largely been replaced by CT techniques. These investigations were conducted in fresh cadavers. In the majority of studies, the anatomical question was problem-oriented in a desire to provide a surgical solution to the individual patient's needs. We have performed a large number of fresh cadaver studies, investigating various regions, tissues, and combinations of tissues. This has included an investigation of the entire integument and underlying deep structures in a series of total body studies of the arteries, which led to the angiosome concept, discussed in detail in a later section. This was followed by studies of the veins and the neurovascular territories of the body and detailed studies of the angiosomes of the forearm, the leg, and the head and neck, as well as a comparative study of a series of mammals. As well, we have performed detailed analyses of numerous muscle flaps, including sartorius, rectus femoris, gracilis, pectoralis major, and skin flaps, including the reversed sural artery flap, thoracodorsal artery perforator flap, profunda femoris artery perforator flap, and the superior and inferior gluteal artery perforator flaps.

The investigations initially involved an analysis of various regions of the body to define possible donor sites for free skin flap transfer. The studies subsequently focused on other tissues and included the anatomic basis for the transfer of bone, nerve, and certain muscles. Encouraged by the success of some of the resulting clinical procedures, the authors expanded the research to investigate composite units of tissue, supplied by a single vascular system. Units of skin and tendon, muscle with nerve, and skin, muscle, and bone were analyzed. It was from this work that the angiosome concept germinated. Various regions, including the anterior abdominal wall, the anterior thorax, the lower limb, and the upper limb, were studied. The results added strength to the angiosome concept of the blood supply and revealed the interconnections that exist at all levels between adjacent vascular territories, a relationship that is evident throughout the body.

In cadaver vascular research, various techniques can be used to identify and study the area of interest. In the past, the integument (skin and subcutaneous tissue) was removed, and the sites of emergence of the dominant cutaneous perforators (0.5 mm diameter or more) were identified on the surface of the deep fascia with lead beads. Currently, individual perforators are easily identified on CT angiography (CTA). Approximately 400 cutaneous perforators on average were identified per body. The three-dimensional branching pattern of main source vessels can be identified. Previous workers, including Salmon, had made topographic boundary incisions to remove areas of skin, particularly in the lines of the groins, axillae, neck, and limb joints ( Fig. 23.5 ). These junctional regions are of great clinical importance, and for this reason the incisions were designed to retain their continuity wherever possible. In our current techniques, using CTA, the incisions utilized for dissection are not as crucial since the pathway and branches of individual vessels are clearly documented prior to dissection.

In the original studies of the vascular supply of tissues of the body, the integument was radiographed, and a montage of the entire cutaneous circulation was constructed in “plan view” ( Fig. 23.6 , Fig. 23.7 ). Although Manchot and Salmon described the origin and course of the cutaneous arteries, and Salmon made a separate study of the individual muscles, neither worker illustrated the course of the arteries between the deep tissues and the skin. Therefore, the skin and subcutaneous tissues were cut into parallel strips and placed on their side, and radiographs were taken to provide “elevation views” of the vessels in different regions of the body ( Fig. 23.8 ). Current CTA techniques allow a far more detailed three-dimensional appraisal of the vascular anatomy of tissues ( Fig. 23.9 ).

All cutaneous perforators of diameter greater than 0.5 mm were traced to their underlying source arteries. The results were averaged from each cadaveric study and plotted on a diagram of the body ( Fig. 23.10 ). Subsequently, investigations were expanded to map out the venous territories (venosomes) of the body along with the neurovascular territories of the skin and muscle. These results have led to an overall picture of the vascular territories of the entire body. The remainder of this section gives a brief overview of the arterial, venous, and nervous territories of the body.

Arterial territories

The arterial network of the body forms a continuous interlocking arcade of vessels throughout each tissue and throughout the body, linked by reduced caliber choke anastomotic vessels or true anastomoses. The course of the cutaneous perforators depends on the proximity of the source artery to the undersurface of the deep fascia. As Michel Salmon noted in 1936, arteries supply branches to each tissue that they pass, including the intermuscular septae, fascia, nerves, and tendons. Arteries generally fall into two groups, direct and indirect ( Fig. 23.11 ). In our anatomical dissections, it is clear that there is great variability in the exact course and size of individual perforators; however, the main source vessels are relatively consistent. The direct cutaneous vessels pass between the deep tissues before piercing the outer layer of the deep fascia. They are usually the primary cutaneous vessels and their main destination is the skin. They tend to supply the skin with larger-diameter vessels, which have a large vascular territory (e.g., circumflex scapular artery). The direct branches include direct cutaneous vessels (sometimes called axial vessels) and septocutaneous vessels. The indirect vessels can be considered the secondary cutaneous supply. They emerge from the deep fascia as terminal branches of arteries which supply the muscles and other deep tissues. The majority of indirect branches are musculocutaneous perforators which emerge to supply the skin. In fact, there is usually significant variability in the distribution of direct and indirect vessels and their vascular territory from individual to individual. There is a vast interconnected network of direct and indirect arteries which supply the skin. The vascular territories of individual perforators vary and tend to be reciprocal with adjacent arterial vascular territories according to the so-called law of equilibrium, described by Salmon and supported by our work.

The direct cutaneous vessels arise from: (1) source arteries just beneath the deep fascia (e.g., the superficial inferior epigastric artery); (2) direct continuation of the source artery (e.g., the cutaneous branches of the external carotid artery); (3) deeply situated source artery or one of its branches to a muscle; they follow the intermuscular septa to the surface (e.g., septocutaneous branches of the lateral circumflex femoral artery). Indirect cutaneous vessels generally emerge from the main source artery as it courses on the undersurface of a muscle and penetrate through the muscle; e.g., musculocutaneous perforators of the deep inferior epigastric arteries (DIEA). In the human body, there are approximately 400 perforators, about 40% of vessels are direct and 60% indirect perforators.

The direct cutaneous perforators pierce the deep fascia near where it is anchored to bone or the intermuscular and intramuscular septa (see Fig. 23.10 ). These lines and zones of fixation also correspond to the fixed skin areas of the body. From these points, the vessels flow toward the convexities of the body surface, branching within the integument. In general, the wider the distance between the cavities and the higher the summit, the longer the vessel (see Fig. 23.8 ). The size and density of the direct perforators also vary in different regions. For example, in the head, neck, torso, arm, and thigh, the vessels are larger, longer, and less numerous. In the forearm, leg, and dorsum of the hands and feet, the vessels tend to be smaller, shorter, and more numerous. In the palms of the hands and the soles of the feet, where the skin is fixed, there is a high density of smaller perforators. Hence, the primary supply of each cutaneous territory varies between source arteries. Each of these territories also has indirect perforators.

The course of the cutaneous perforators between the deep fascia and the skin also varies in different regions. Regardless of their site, however, they follow the connective tissue framework of the superficial fascia, interconnecting at all levels. They ramify on the undersurface of the subcutaneous fat adjacent to the deep fascia and then branch and course toward the subdermal plexus, working their way between the fat lobules. The smaller vessels tend to course vertically toward the skin, whereas the larger vessels branch in all directions in a stellate pattern or course in a particular axis, branching as they pass parallel to the skin surface.

In the scalp and limbs, where the skin is relatively fixed to the deep fascia, the larger vessels hug that surface. They course on the deep fascia for a considerable distance in the loose areolar layer that separates them from the subcutaneous fat (see Fig. 23.8 ). This is especially true when a perforator accompanies a cutaneous nerve.

In the loose skin areas of the body, the direct cutaneous vessels course for a variable distance parallel to the deep fascia. They are more intimately related to the undersurface of the subcutaneous fat, however, being plastered to it by a thin fascial sheet that separates them on their deep surface from a plexus of smaller vessels. This plexus lies in loose areolar tissue on the surface of the deep fascia. It is formed by branches that arise from the direct perforators as they pierce the deep fascia and the connections these branches make with smaller indirect perforators. The large direct perforators then pierce the subcutaneous layer. They ascend within the superficial fascia (subcutaneous fat) to reach the rich subdermal plexus, where they travel for considerable distances (see Fig. 23.8 ).

Within the deep tissue, whether muscle, tendon, nerve, or bone, a pattern similar to that in the integument exists, with a three-dimensional network of vessels interlinking between vascular territories, the perimeters of which are linked by choke arteries. Within the muscles, these choke vessels often exhibit a characteristic corkscrew appearance on angiography.

Venous drainage

The cutaneous veins also form a three-dimensional plexus of interconnecting channels throughout the body ( Fig. 23.12 ). There are valved segments in which valves direct flow in a particular direction, and there are avalvular segments where no valves are present. The avalvular or oscillating veins allow bidirectional flow between adjacent venous territories. They connect veins whose valves may be oriented in opposite directions, thus providing for the equilibration of flow and pressure. Indeed, there are many veins whose valves direct flow initially in a distal direction, away from the heart, before joining veins whose flow is proximal. An example of this is the superficial inferior epigastric vein that drains the lower abdominal wall integument toward the groin. In some regions, valved channels direct flow radially away from a plexus of avalvular veins, for example, in the venous drainage of the nipple–areola complex. In other areas, valved channels direct flow toward a central focus, as seen in the stellate branches of the cutaneous perforating veins of the limbs.

In general, venous anatomy parallels arterial anatomy ( Fig. 23.13 ). From dermal and subdermal venous plexuses, the veins collect either into horizontal large-caliber veins, where they often relate to cutaneous nerves and a longitudinal system of chain-linked arteries, or alternatively in centrifugal or stellate fashion into a common channel that passes vertically down in company with the cutaneous arteries to pierce the deep fascia. Thereafter, the veins travel with the direct and indirect cutaneous arteries, draining ultimately into the venae comitantes of the source arteries in the deep tissue.

In general, the origin, course, and distribution of the deep veins (vena comitantes) are a mirror image of the deep source arteries, but they are larger and more plentiful. Although the anatomy of the veins is subject to considerable variation between sides in the same individual as well as between other individuals, the pattern of venous arcades is evident throughout. These arcades generally become smaller and more numerous as the periphery of the region or the tissue is reached. The superficial veins, however, are independent of the deep arteries (e.g., greater saphenous vein, cephalic vein) and may have a different area of drainage. For example, in the forearm there are paired vena comitantes to the radial and ulnar arteries but a separate system of large-caliber subcutaneous veins, including cephalic, basilic, and antebrachial veins.

The site and density of the valves within the deep venous network are variable. The deep veins follow the bony skeleton of the body or the intermuscular septa with their associated arteries. In some regions, these veins are single; in others, they are duplicated as venae comitantes. In the limbs, the veins commence distally in the hands and feet as single channels linked by venous arcades. These arcades become progressively larger as they approach the wrist and ankle. The veins are duplicated in the forearm and leg, and each pair of veins is linked by a rich stepladder of venous channels that are usually free of valves. These venae comitantes then reunite to form single channels. In the lower limb, this occurs in the popliteal fossa, but in the upper limb, the union is most commonly in the proximal arm or even as high as the axilla.

In the torso, the pattern of arcades is conspicuous (see Fig. 23.13 ); the parent veins are oriented as longitudinal and transverse arcades that match the pattern of the source artery. Distinct territories are evident. Where choke arteries define the arterial territories, they are matched by oscillating veins in the venous network. The existence of venae comitantes is variable.

Within the muscle, the intramuscular venous network mirrors that of the arterial side. Where arterial territories are linked by choke arteries or true anastomotic arteries without changing caliber, the venous territories of the muscles, which drain in opposite directions, are linked by avalvular oscillating veins. Broadly, the muscles can be classified into three types on the basis of their venous architecture. Type I muscles have a single venous territory that drains in one direction. Type II muscles have two territories that drain from the oscillating vein in opposite directions. Type III muscles consist of three or more venous territories that drain in multiple directions ( Fig. 23.14 ).

The extramuscular veins are of two types. The first group consists of the efferent veins. They contain valves and drain the muscles to their parent veins. The other group consists of the afferent veins. They are derived from the overlying integument as musculocutaneous perforators or from adjacent muscles (see Fig. 23.14 ).

Neurovascular territories

In our anatomical studies of neurovascular territories, fresh human cadavers were injected with a radiopaque lead oxide mixture, and the nerves were dissected and labeled with fine computer wire. The nerves and vessels were then segregated by subtraction angiography.

The most obvious feature seen throughout the skin and muscle is the linear arrangement of the nerves and their branches, compared with the looping arcades of the interconnecting vessel network, with the nerves taking the shortest route between two points. In general, the orientation of cutaneous nerves is longitudinal in the limbs, transverse or oblique in the torso, and radiating from loci in the head and neck. Of particular note is that the cutaneous nerves, like the arteries, pierce the deep fascia at fixed skin sites.

Each cutaneous nerve is accompanied by an artery, but the relationship is variable. Some of the arrangements seen in the integument are shown in Fig. 23.15 . In each case, either a long artery or a chain-linked system of arteries “hitchhikes” with the nerve.

When the cutaneous nerve and artery appear at the deep fascia together, their relationship is often established early (e.g., the lateral intercostal neurovascular perforators on the torso or the saphenous system in the lower limb). However, the nerve sometimes pierces the deep fascia at a point remote from the emergence of its associated artery (e.g., the lateral cutaneous nerve of the thigh and the superficial circumflex iliac artery below the inguinal ligament; Fig. 23.16 ). Alternatively, the nerve leaves one vascular system with which it is traveling in parallel to cross the path of another (e.g., the lateral intercostal nerve, which courses initially with its artery and then leaves it to meet the superficial inferior epigastric vessel). In many of these cases, secondary or tertiary branches of the artery often peel off to accompany the nerve (see Fig. 23.16 ). Sunderland noted that each peripheral nerve is abundantly vascularized by a “vascular net” of a series of nutrient arteries entering the nerve at different levels.

The vascular architecture of the intramuscular veins and arteries is almost identical for each muscle. Therefore, to simplify the description of the nervous supply to the muscles, only the arterial relations of the nerves are discussed and illustrated. The intramuscular branches of the nerves were dissected to, but not within, the individual muscle bundles. The following observations were made:

• 1.

  The nerves follow the connective tissue framework. Dissection showed the motor nerves coursing in the connective tissue sheath from its origin at the nerve trunk to the neurovascular hilum of the muscle. Thereafter, the nerve and its branches follow the intramuscular connective tissue to reach the muscle bundles.

• 2.

  The nerves are economical. As in the integument, the direct course of the motor nerves is in stark contrast to the wandering pattern of the vessels. The nerves take the shortest extramuscular and intramuscular routes compatible with the function of each muscle.

• 3.

  Neurovascular relations vary with the muscle, the extramuscular course, and the intramuscular branching of the nerves and the vessels. Some muscles have a single nerve supply; others receive multiple motor branches. All receive multiple arterial pedicles. However, despite the variables, certain observations can be made:

  • Each motor nerve is accompanied by a vascular pedicle, but the reverse does not apply.

  • The motor nerve is usually accompanied by the dominant vascular pedicle. There are exceptions to this, however. For example, the nerve supply to sternocleidomastoid is usually accompanied by a minor vascular pedicle.

  • The nerve may enter the muscle before branching.

  • Once within the muscle, the nerve divides early, and its branches sweep rapidly into position, parallel to the muscle fibers. The vessels, however, branch and form primary and secondary arcades, often crossing the muscle bundles and nerves before tertiary and quaternary branches are provided to the muscle fibers.

Ultimately, the terminal branches of the vessels and nerves come into close contact and course together in the connective tissue framework parallel to the muscle bundles.

Neurovascular anatomy of muscles of the body

Several methods have been used to classify muscles on the basis of morphology, function, blood supply, or nerve supply ( Table 23.1 ). We have classified muscles of the body according to their most common pattern of innervation ( Fig. 23.17 ). The pattern of neurovascular anatomy of the muscles influences the way a whole muscle or segment of muscle can be harvested as a functioning muscle microvascular transfer. It is possible to subdivide certain muscles, based on the neurovascular anatomy, into separate neurovascular units if each segment has an individual vascular pedicle. Clinically, serratus anterior, latissimus dorsi, gracilis, and rectus femoris are often used in this way, taking a portion of the muscle with their motor nerve and blood supply.

• Type I. The muscle is supplied by a single motor nerve that divides after entering the muscle ( Fig. 23.18 ). Multiple vascular pedicles supply each muscle and form a continuous network throughout the tissue. It is possible in each case to remove a vascularized segment of muscle with its nerve supply and yet leave viable muscle in situ .

  

• Type II. A single motor nerve supplies each of the muscles in this group, but the nerve divides before entering the muscle. Muscles in this group include the deltoid (see Fig. 23.18 ), gluteus maximus, trapezius, vastus lateralis, serratus anterior, and flexor carpi ulnaris.

• Type III. Multiple motor nerve branches derive from the same nerve trunk (see Fig. 23.18 ). Once again, it is possible to subdivide each muscle into separate functional units because of the multiple vascular pedicles as well as the several nerve branches. Gastrocnemius is often split in this way, taking one head for reconstruction, leaving behind the other functional unit with its neurovascular supply attached.

• Type IV. Multiple motor nerves are derived from different nerve trunks (see Fig. 23.18 ). It is apparent that each muscle can be subdivided anatomically into several functional units because of the multiple, often segmental neurovascular pedicles. Indeed, several of these muscles are formed developmentally by the fusion of adjacent somites (e.g., rectus abdominis and internal oblique).

The angiosome concept

Following a review of the works by Manchot and Salmon, along with the results of our total body studies of blood supply to the skin and the underlying deep tissues, it has been possible to divide the body anatomically into three-dimensional vascular territories named angiosomes. Each of these three-dimensional angiosomes is supplied by a source (segmental or distributing) artery and its accompanying vein or veins ( Figs. 23.22–23.24 ). Each angiosome can be subdivided into matching arteriosomes (arterial territories) and venosomes (venous territories) or into further subunits based on individual perforators to the skin. Forty of these territories were initially described, but subsequent investigation has led to many of these territories being subdivided further into smaller composite units and revealed some that do not reach the skin surface. In a later study, 61 vascular territories were identified. Recent work has illustrated no fewer than 13 angiosomes of the head and neck, originally mapped as eight supplied by branches of the external carotid, internal carotid, and subclavian arteries. The angiosome concept indicates that the three-dimensional block of tissue is supplied by a major source artery and its accompanying vein(s), but it is important to note that the angiosome itself may be divisible depending on the branching pattern of the source vessel.

These composite blocks of skin, bone, muscle, and other soft tissues fit together like the pieces of a jigsaw puzzle, to make up the vascular supply of the body. In some of the angiosomes, there is a large overlying cutaneous area and a relatively small deep tissue region; in others, the reverse pattern exists. Each angiosome is linked to its neighbor at every tissue level, either by a true (simple) anastomotic arterial connection without change in caliber of the vessel or by a reduced-caliber choke anastomosis. A similar pattern with avalvular (bidirectional or oscillating) veins on the venous side links adjacent venosomes (see Fig. 23.24 ).

The angiosome concept has several important clinical implications:

• 1.

  Each angiosome defines the safe anatomic boundary of tissue in each layer that can be transferred separately or combined on the underlying source vessels as a composite flap (e.g., skin and muscle, muscle and bone, etc.). Also, the anatomic territory of each tissue in the adjacent angiosome can usually be captured with safety when it is included in the flap design based on one of the source vessels.

• 2.

  Because the junctional zone between adjacent angiosomes usually occurs within muscles of the deep tissue, rather than between them, these muscles provide an important anastomotic detour (bypass shunt) if the main source artery or vein is obstructed.

• 3.

  Because most muscles span two or more angiosomes and are supplied from each territory, one is able to capture the skin island from one angiosome by muscle supplied in the adjacent territory. As we shall see later, this fact provides the basis for the design of many musculocutaneous flaps.

Comparative anatomy

In the course of parallel investigations to describe animal models for vascular studies, it was noted that there are close similarities in vascular anatomy between animal species. However, there are also important differences of which investigators should be aware. The purpose of this section is to provide a more complete picture of the vascular territories. As we shall see, the angiosome concept can be applied equally to other members of the animal kingdom as well as to humans.

In plastic surgical research, selection of various animals for the study of flap physiology is based on cost, convenience, availability, and/or ethical considerations rather than on a profound knowledge of their vasculature. The pig, for example, is a fixed-skin animal, and because human integument is also fixed in many areas, it has been assumed that this animal is therefore most ideally suited for experiments on skin flaps. It is important to understand the vascular basis of the experimental animal model since results may not be generalizable to humans.

Study of these animals also leads us to gain further insight into the development and arrangement of the vascular system. It may aid in identification of the ideal animal for other experiments, such as investigation of the delay phenomenon, use of tissue expansion, programming of vessels, and prefabrication of flaps – whether they are skin, other tissues, or combinations of tissues.

When the radiographs of four animals are reviewed ( Fig. 23.19 ), it is obvious there is a marked dissimilarity in the vasculature of the integument between them and that of the human (see Fig. 23.7 ). Surprisingly, however, this is in marked contrast to the dramatic similarity of the radiographs of deep tissue of the mammalian torsos ( Fig. 23.20 ).

The pattern of the cutaneous vasculature of the integument ranges from the fixed skin of the pig (supplied by a large number of small vessels over most of the hemitorso) to the mobile skin of the rabbit, in which four large vessels supply the majority of this area. The duck, not surprisingly, shows considerable diversity in the vasculature of its integument. Nevertheless, basic patterns are evident, having been modified by the growth and functional demands of the species.

The similarity in vasculature of the deep tissue is not confined to the anterior torso. Certain muscles between species have a remarkably similar vascularity, as can be seen in Fig. 23.21 .

It appears that the vascular blueprint of the deep tissues of the torso of mammals remains relatively constant. It is simply enlarged from the fetus to the adult and from small to large mammals. The reason for this may be that the functional requirements of the torso are the same in each mammal, that is, respiration, protection of the viscera, and aid in removal of the contents. Beyond the deep tissues of the torso, it appears that the vasculature of the overlying integument, the head and the neck, and the limbs has been modified to meet the functional demands of each species, as Hunter predicted more than 200 years ago.

Similarities are also seen in comparing the torso studies of mammals with those of other species, for example, the bird. In each case, vascular arcades arise from three basic sites: cranially from the subclavian and axillary vessels (aortic arch), laterally from the aorta (descending part), and caudally from the iliac and femoral vessels (terminal aorta). These three arcades form the basic vascular loops in the body that are common throughout the animal kingdom, including the human.

An underlying theme of the vascular architecture is that of vascular loops and arcades. Comparison of the vascular architecture in the human with that of other animals and other species reveals a similar arrangement. In loose-skinned animals, the arcades in the integument are stretched over long distances (see Fig. 23.18 ). In the wings of insects and in the leaves of plants, the “veins” assume a pattern of interconnecting arcades similar to those of the intestinal mesentery.

The anatomical and clinical territory of a cutaneous perforator

The angiosome concept provides a framework to understand the vascular anatomy of the human body. Plastic surgeons tend to focus on the vascular anatomy of skin but the angiosome concept applies equally to all tissues. The main vascular trunks that supply each angiosome are relatively consistent in size and position, however the individual cutaneous perforators are highly variable in size and position. Each individual cutaneous perforator territory fits together with its neighboring territories like a giant jigsaw puzzle ( Fig. 23.25 ). The arterial connection between adjacent cutaneous perforators may be through reduced caliber choke anastomotic vessels or through vessels that are not reduced in caliber (true anastomoses). True anastomoses occur variably throughout the body, most commonly along cutaneous nerves or in areas where the skin is mobile.

The importance of true anastomoses relates to the clinical territory of an individual cutaneous perforator. Generally, it has been found in experimental work on a series of animals including pig, dog, guinea pig and rabbit that the limit of viability of a skin flap is related to the anatomy of the pedicle of the flap and the surrounding perforator angiosomes. Based on the flap perforator, it is possible to reliably capture an adjacent cutaneous territory in any direction. In about 80% of the animal studies, the limit of flap survival was at the junction between second and third territory.

However, if there are true anastomoses between vascular territories, the third territory potentially could be captured based on an individual perforator. This would be analogous to a delay procedure (see Fig. 23.53 ) in which the choke anastomotic vessels dilate between vascular territories, increasing flap survival. Thus, it is the vascular anatomy of individual perforators and the vascular connections between perforators which govern the survival of flaps based on the perforator. A novel technique using dynamic thermography to preoperatively map cutaneous perforators and their interconnections has been reported which is non-invasive and non-irradiating and shows promise as a tool to predict flap survival.

Vascular territories of the body

The angiosome concept has led to the segregation of the body anatomically into three-dimensional vascular territories. Further work has led to the investigation and detailing of angiosomes in certain parts of the body. Some of these regions are highlighted to expand and to clarify the concept. The description of vascular territories is important to the design of flaps throughout the body.