Angiosomes and perforators — Designing the flap around the vessel
Taylor and Palmer’s vascular map, the choke vessels that explain the delay phenomenon, and how to locate the perforator with Doppler to design the flap outward from the vessel.
Content intended for healthcare professionals. It does not replace clinical assessment and is not written as patient information.
Key points
- The body is organised into some 40 angiosomes: three-dimensional blocks of skin and deep tissue supplied by a source artery. Skin is not supplied in isolation.
- Between neighbouring angiosomes lie choke vessels. They are what allow a flap to survive one territory beyond its own, and what explain the delay phenomenon.
- The conceptual shift: one no longer picks a flap and hunts its pedicle, but locates the perforator and designs the flap around it.
- The handheld 8 MHz Doppler costs little and changes the design. Mark before infiltrating: infiltration displaces the vessel and masks the signal.
- In the face this matters doubly: territories are small, richly anastomotic, and a well-designed local flap avoids having to bring tissue from afar.
What an angiosome is
In 1987 Taylor and Palmer reported the result of injecting and radiographing whole cadavers, and what they found reorganised reconstructive surgery. The body divides into some 40 vascular territories, each supplied by a source artery with its accompanying vein. The decisive contribution was not that territories exist — that was known — but that each territory is a three-dimensional block: the artery supplies skin and the underlying tissue, muscle or bone included, forming a composite unit. Hence the name: angiosome.
Choke vessels: the key to everything
Neighbouring angiosomes are not isolated: they connect through two vessel types. True anastomoses, of calibre equal to the vessels they join, and choke vessels, of smaller calibre. That distinction explains three things at once. Why a flap can safely extend one angiosome beyond its own and not two. Why the delay phenomenon works: partially dividing the pedicles dilates the choke vessels and widens the captured territory. And why distal necrosis occurs exactly where it does: at the choke zone of the next angiosome, not at random.
Facial angiosomes and the flap each yields
| Source artery | Territory | Flaps it supports |
|---|---|---|
| Facial | Upper and lower lip, medial cheek, nasolabial fold, nasal ala | Nasolabial, Abbé-Estlander, Karapandzic, facial artery perforator flaps |
| Superficial temporal | Temple, lateral scalp, preauricular region | Temporoparietal fascia, auricular island flaps, axial bilobed, Fricke |
| Ophthalmic | Medial forehead, glabella, nasal dorsum, eyelids, medial canthus | Paramedian forehead on the supratrochlear, glabellar, dorsal nasal |
| Infraorbital | Medial cheek and lower eyelid | Cheek advancement, contribution to the Mustardé rotation flap |
| Occipital and posterior auricular | Posterior scalp and retroauricular region | Retroauricular island flap, full-thickness skin grafts from the area |
Two types of perforator, two behaviours
The perforator is the vessel crossing from the deep plane to the skin, and it can do so in two ways. Direct or septocutaneous perforators run through an intermuscular septum and reach the skin without crossing muscle: they are easier to dissect and give longer pedicles. Indirect or musculocutaneous ones traverse the muscle belly, demanding meticulous intramuscular dissection but allowing the flap to be raised without sacrificing the muscle. The face is dominated by the former, with short courses, which makes dissection quicker but leaves less margin for error: a divided facial perforator has fewer substitutes than one in the thigh.
The shift: from flap to vessel, or from vessel to flap
For decades the reasoning was: I choose a described flap and go looking for its pedicle where the book says it is. The concept of the free-style flap, formulated by Wei and Mardini in 2004, inverts the order: the perforator is located first, and the flap designed around it. The consequence is liberating: any area with an identifiable perforator can be a donor site, and the design adapts to the defect rather than the reverse. Applied to the face, this is what has turned local flaps into something more precise than a repertoire of geometric figures.
Locating the perforator with Doppler: how it is done
- 1. WhenBefore infiltrating and with the patient in the operative position. Infiltration displaces the vessel and the vasoconstrictor mutes the signal
- 2. ProbeHandheld 8 MHz Doppler for superficial vessels. Plenty of gel and minimal pressure: pressing collapses the perforator and makes it vanish
- 3. SweepSweep the donor area in two perpendicular directions and mark each signal with a dot, not a large cross
- 4. DiscriminateDistinguish the perforator from the deep axial vessel running underneath: the perforator gives a brief, punctate signal; the axial vessel, a continuous one along a course
- 5. DesignPlace the perforator at the pivot point, not at the centre of the flap, and check the arc of rotation reaches the defect without tension or kinking
- 6. Plan BMark more than one perforator before starting. If the chosen one fails on exposure, the design changes without having lost the donor site
What the handheld Doppler does not tell you
Its limits are worth knowing so as not to over-trust it. The handheld Doppler detects flow, not calibre: a strong signal does not guarantee a usefully sized perforator, and it gives false positives from deep axial vessels running underneath. Nor does it report flow direction or intramuscular course. Colour duplex does provide calibre, velocity and course, and CT angiography a complete map, but for most local facial flaps the handheld device suffices if its limitations are understood. The practical rule: Doppler guides the design, dissection confirms it, which is why an alternative is always marked.
What changes in the local facial flap
Applied to the face, perforator reasoning changes three concrete things. First, the pivot point stops being chosen by geometry and starts being chosen by vascularity: a rotation flap whose pivot coincides with an identified perforator tolerates arcs that would otherwise be reckless. Second, it permits propeller flaps on a single perforator, rotating up to 180° and closing defects with skin of identical colour and thickness without needing two stages. And third, it justifies thinning: if inflow enters at a known point, the rest of the flap can be trimmed to fit an eyelid or a nasal ala without compromising viability.
Rules that follow from the vascular map
- One angiosome further, not two. Extending a flap into one adjacent territory is reasonably safe; two is where distal necrosis appears.
- Crossing a choke line has a price. If the design forces it, consider a prior surgical delay.
- Delay is not an antique: it is deliberate manipulation of the choke vessels, and remains the most reliable way to extend a territory in compromised tissue.
- In the smoker and the irradiated patient the map does not hold equally. Microvasculopathy reduces choke vessel dilating capacity, and the real territory is smaller than the anatomical one.
- Reconstruct the subunit, not the defect, remains the aesthetic principle; the vascular map says from where it can be done without risking the flap.
References
- 1.Taylor GI, Palmer JH. The vascular territories (angiosomes) of the body: experimental study and clinical applications. Br J Plast Surg. 1987;40(2):113-141.
- 2.Houseman ND, Taylor GI, Pan WR. The angiosomes of the head and neck: anatomic study and clinical applications. Plast Reconstr Surg. 2000;105(7):2287-2313.
- 3.Wei FC, Mardini S. Free-style free flaps. Plast Reconstr Surg. 2004;114(4):910-916.
- 4.Hallock GG. Doppler sonography and color duplex imaging for planning a perforator flap. Clin Plast Surg. 2003;30(3):347-357.
- 5.Papel ID, ed. Facial Plastic and Reconstructive Surgery. 4th ed. New York: Thieme; 2016.
Related specialty: Complex Facial Reconstruction