Angiosome concept

FROM Neligan

1. Angiosome C oncept By:Dr.Amit KumarChoudhary

2. 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.

3. The angiosome theory has become well accepted in the field of plastic and reconstructive surgery and allows the conceptualization of the vascular supply to all tissues of the human body . An angiosome is a composite block of tissue supplied by a main source vessel. The adjacent angiosomes are linked either by reduced caliber choke anastomotic vessels or vessels without reduction in caliber – the true anastomoses on the arterial side.

4. The vascular architecture of the body is arranged anatomically as a continuous series of vascular loops, like that increase in number while their size and caliber decrease as they approach the capillary bed . The reverse situation occurs on the venous side . The “keystones ” of these arcades are represented usually by reduced-caliber (choke anastomotic ) arteries and arterioles , matched on the venous side by avalvular (oscillating ) veins that permit bidirectional flow. Choke arteries and avalvular veins have an essential role in controlling this pressure gradient across the capillary bed.

5. Historical perspective In 1889 , Manchot performed the first examination of the vascular supply of the human integument . His treatise, Die Hautarterien des menschlichen Körpers [The Cutaneous Arteries of the Human Body ], was initially published in German and later translated to English . Manchot identified the cutaneous perforators , assigned them to their underlying source vessels , and charted the cutaneous vascular territories of the body .

6. In 1893 , Spalteholz published an important paper on the origin, course, and distribution of the cutaneous perforators in adult and neonatal cadavers. He performed arterial injections of gelatin and various pigments. Spalteholz’s main study concentrated on the detailed circulation of the skin . He made an important distinction between direct cutaneous vessels, which supply the skin, and indirect cutaneous vessels, which are terminal branches of vessels supplying the deeper organs, especially the muscles.

7. Salmon a French anatomist and surgeon [1930]. Manchot had defined approximately 40 cutaneous territories that excluded the head, neck, hands, and feet. Salmon work Aided by radiography, he was able to delineate the smaller vessels of the cutaneous circulation and charted more than 80 territories encompassing the entire body Salmon noted the interconnections that exist between perforators, and his observation of the density and size of the vessels in different regions of the body led him to define what he called the hypervascular and hypovascular zones

8. In 1975, Schafer , published an important study on the arterial and venous anatomy of the lower extremity In 1937, Webster again cited the work of Manchot when he described a long, bipedicled thoracoepigastric flap based on named arteries that extended from the groin to the axilla . The 1970s “ anatomic revolution .” McGregor and Morgan differentiated between large flaps based on a known axial blood supply and those based on random vessels. Daniel and Williams reappraised the work of Manchot and others and classified the cutaneous arteries into direct cutaneous and musculocutaneous vessels . Studies on the free flap by Taylor and Daniel were published in 1973, and a few years later the musculocutaneous flap was revived by McCraw and Mathes and Nahai

9. Overview of the arterial, venous, and nervous territories

10. Arterial territories The arterial network of the body forms a continuous interlocking arcade of vessels throughout each tissue and throughout the body, linked together as loops of vessels , often of reduced caliber . The course of the cutaneous perforators depends on the proximity of the source artery to the undersurface of the deep fascia Arteries generally fall into two groups, direct and indirect

11. 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 , their main destination being 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 perforating branches which emerge to supply the skin

12. 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., septal cutaneous branches of the lateral circumflex femoral artery ).

13. The direct cutaneous perforators pierce the deep fascia near where it is anchored to bone or the intermuscular and intramuscular septa . 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. The wider the distance between the cavities and the higher the summit, the longer the vessel.

14. 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.

15. The course of the cutaneous perforators between the deep fascia and the skin also varies in different regions . 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.

16. 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. The large direct perforators then pierce the subcutaneous layer. They ascend within the superficial fascia (subcutaneous fat) to reach the rich subdermal plexus.

17. Venous drainage The cutaneous veins also form a three-dimensional plexus of interconnecting channels throughout the body . 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.

18. 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.

19. In general, venous anatomy parallels arterial anatomy From dermal and subdermal venous plexuses , the veins collect either into horizontal large caliber veins , 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 .

20. 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

21. 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.

22. Neurovascular territories 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. 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.

23. Each cutaneous nerve is accompanied by an artery, but the relationship is variable. In each case, either a long artery or a chain-linked system of arteries “hitchhikes” with the nerve.

24. When the cutaneous nerve and artery appear at the deep fascia together, their relationship is often established early . 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.

25. 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 segregate the body anatomically into three-dimensional vascular territories named angiosomes . Each angiosome can be subdivided into matching arteriosomes (arterial territories) and venosomes (venous territories). Each angiosome is linked to its neighbor at every tissue level, either by a true (simple) anastomotic arterial connection or by a reduced-caliber choke anastomosis . A similar pattern with avalvular (bidirectional or oscillating) veins on the venous side defines the boundaries of the venosome

26. Vascular territories of the body Vascular territories of the forearm

27. Vascular territories of the lower leg

28. Vascular territories of the head and neck The muscles usually have vessels of two or more angiosomes supplying them. Head and neck skin and superficial musculoaponeurotic system The blood supply to the skin of the face, scalp, and neck follows the connective tissue framework. The main skin perforators pierce the deep fascia from fixed skin sites, especially around the base of the skull, around the orbits , around the nostrils, over the parotid gland, along the skin crease lines of the face, and beside the muscles in the neck.

29. Anatomic concepts related to flap design

30. Vessels follow the connective tissue framework of the body This concept is fundamental to the design of flaps in general and to fasciocutaneous and septocutaneous flaps in particular. The connective tissue framework of the body is a continuous syncytium , like the walls of a honeycomb. The vessels follow this framework down to the microscopic level. In general, if the connective tissue is rigid, such as intermuscular septa, periosteum , or deep fascia, the vessels travel beside or on it. If the connective tissue is loose, they travel within it. The vessels occasionally travel in a fibrous sheath or a bony canal, but this tunnel always contains loose areolar tissue, physiologically, to allow the veins to dilate and the arteries to pulsate.

31. Arteries radiate from fixed to mobile areas and veins converge from mobile to fixed areas The cutaneous vessels pierce and emerge from the outer layer of the deep fascia near where it is anchored, either to its deep septa or to bone. The veins course parallel to the plane of mobility, often for long distances, and cross where the tissues are anchored to fascia or bone. This is seen at the same site as the arteries.

32. Vessels “hitchhike” with nerves There is an intimate relationship between nerves and blood vessels throughout the deep tissues and the skin and subcutaneous tissues of the body, especially where a cutaneous nerve courses on the surface of the deep fascia. An artery may accompany the nerve for a considerable distance, often connecting with its neighbor in chain-link fashion to provide the basis for an axially oriented neurovascular flap. The cutaneous vessels and the nerve are occasionally in juxtaposition; in other situations, they course parallel to each other but at a distance. When the cutaneous nerve crosses a fixed skin site, it frequently “picks up” its next vascular companion.

33. Vessel growth and orientation are products of tissue growth and differentiation There are numerous examples to support this hypothesis. The sternomastoid and trapezius muscles split from the same somite . The trapezius “drags” its supplying transverse cervical artery (and nerve) across the root of the neck to the back, together with a large band of skin that it nourishes.

34. Vessels interconnect to form a continuous three-dimensional network of vascular arcades

35. Vessels obey the law of equilibrium There are numerous venous channels, large and small, that are free of valves and allow flow within their lumens in either direction.

36. Vessels have a relatively constant destination but may have a variable origin This is typical of the vessels that emanate from the groin to supply the skin of the lower abdomen and upper thigh. The superficial inferior epigastric and the superficial circumflex iliac arteries, for example, may arise either separately from the common femoral artery or as a combined trunk from that vessel or from one of its branches. Whatever the case, their destination is constant to supply the integument of the lower abdomen and the hip .

37. Venous networks consist of linked valvular and avalvular channels that allow equilibrium of flow and pressure Directional veins- Directional veins are valved veins which exist either as longitudinal channels, well developed in the subcutaneous and deep tissues of the limbs, or as a stellate pattern of collecting veins, which converge on a pedicle. Oscillating avalvular veins- Oscillating avalvular veins are avalvular vessels which are numerous and may reach large dimensions. They connect and allow free flow between the valved channels of adjacent venous territories, territories whose valves are oriented in the opposite direction.

38. Applications of angiosome concept

39. 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. Also , the anatomic territory of each tissue in the adjacent angiosome can usually be captured with safety when it is combined in the flap design . 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 .

40. The Doppler Probe and Mapping of Perforators The Doppler probe allows surgeons to locate cutaneous perforators with precision in individual cases. By use of the knowledge that most cutaneous arteries emerge from fixed skin sites a their expected origin can be anticipated and located rapidly.

41. Flap design It has been determined clinically and experimentally that flaps can be safely designed by identifying a cutaneous perforator and an adjacent perforator; a line drawn between the two perforators should represent the axis of a viable flap.

42. Axes of skin flaps The cutaneous arteries of the skin have provided the basis of “axial” flaps used extensively in plastic and reconstructive surgery. The origin, course, size, density, and interconnections of the cutaneous perforators. It therefore provides for the logical planning of the base and axis of a skin flap.

43. Skin flap dimensions The survival length of a skin flap must depend on: (1) the caliber and length of the dominant vessels on which the flap is based; (2) the caliber and span of the adjacent captured artery or arteries, vein or veins; (3) the caliber and length of the connecting choke vessels; and (4) an anatomically favorable or unfavorable venous return.

44. The Delay Phenomenon

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