A flap is only as good as its blood supply. This is why flaps are classified not only by their tissue or location, but also by how blood flows into and out of them. This knowledge determines how large a flap may be and where it can be raised.
The angiosome concept
In 1987, the Australian anatomists and surgeons G. Ian Taylor and J. H. Palmer described the body as a mosaic of three-dimensional tissue blocks, each supplied by a particular source artery – the angiosomes. Neighbouring angiosomes are linked by fine connecting vessels (choke vessels). A flap can therefore safely include its own angiosome and usually also the adjacent one; the further it extends beyond this, the greater the risk of insufficient perfusion at its tip.
Random-pattern flaps
These flaps have no defined main artery. They are supplied by the fine vascular network of the skin, which enters via the base of the flap. This is why the length-to-width ratio is limited – on the trunk and limbs, about 2:1 to 3:1 is a rule of thumb, while longer flaps are possible in the well-vascularised face. Many local flaps, such as advancement or rotation flaps, belong to this group.
Axial flaps
Axial flaps contain a named artery with an accompanying vein running lengthwise through the flap. This allows them to be considerably longer than random-pattern flaps. A classic example is the groin flap, which is supplied by the superficial circumflex iliac artery.
A special form are reverse-flow flaps, in which the vascular pedicle lies at the distal end and blood flows in against the normal direction – for example in the reverse radial forearm flap.
Fasciocutaneous flaps
Here the fascia, i.e. the connective tissue sheath of the muscles, is raised as well. It carries a fine vascular plexus that reliably supplies the overlying skin. Common classifications are those of Cormack and Lamberty (1984) and of Mathes and Nahai; they distinguish whether the supply comes from many small vessels, a single main branch or several segmental branches.
Muscle flaps
Muscles have their own well-defined vascular system. The Mathes and Nahai classification (1981) divides them into five types – depending on whether a muscle is supplied by a single dominant vascular pedicle or by several smaller ones. Muscle flaps are particularly valuable for filling deep cavities or treating poorly vascularised, infected areas.
Perforator flaps
The most modern development is the perforator flap. Here, skin and fat are supplied exclusively by a small vessel that passes through or between muscles to the skin (perforator). The muscle itself is left untouched. Well-known examples are the DIEP flap from the lower abdomen for breast reconstruction and the ALT flap from the thigh. Advantage: less loss of function at the donor site; disadvantage: demanding microsurgical dissection.
Note: This article is for general information only and does not replace medical advice.
Sources and further information
- 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.
- Cormack GC, Lamberty BG: A classification of fascio-cutaneous flaps according to their patterns of vascularisation. Br J Plast Surg 1984; 37(1): 80–87.
- Mathes SJ, Nahai F: Classification of the vascular anatomy of muscles: experimental and clinical correlation. Plast Reconstr Surg 1981; 67(2): 177–187.
- Considerations in Flap Selection for Soft Tissue Coverage of the Hand and Digits (PMC)
