The History of Evolution

Robert J. Allen, MD
C. Heitmann, MD

Abstract
This article reviews the recent evolution of perforator flaps. The tie between perforator flaps and skin flaps as well as perforator flaps and musculocutaneous flaps is explained. The paraumbilical perforator flap, the deep inferior epigastric artery flap (DIEP flap), the gluteal artery perforator Hap (GAP flap) and various perforator flaps and perforator-based flaps are described in combination with the review of the relevant literature. As a prospect into the future, the technique of "supra-microsurgery is presented.

	Fig. 1 Drawing of the donor site of the gluteal artery perforator (GAP) flap with the course of the superior gluteal artery and the gluteus maximus muscle (from Allen and Tucker 19952, with permission).
	Fig. 2 Drawing of the GAP flap harvest in which the perforator vessels are followed through the muscle to the superior gluteal artery to gain pedicle length (from Allen and Tucker 19952, with permission).
	Fig. 3 Drawing after inset of the GAP-flap with microanastomoses to the internal mammary vessels (from Allen and Tucker 19952, with permission).

The History of Evolution
Something new.. is something old that has been forgotten. With this ancient Russian proverb in mind we start this article on the recent evolution of perforator flaps with the work of Stuart Milton in the 1960's (New Orleans, LA and Oxford, England). At that time wound closure relied heavily on skin flaps. An established principle was that the length of the skin flaps was not supposed to be greater than 1.5xthe width. It was Stuart Milton who challenged this concept in his classic investigations on porcine skin flaps. Milton demonstrated that the surviving length of skin flaps is not directly proportional to the flap width,but that long, narrow skin flaps can be raised with safety as long as they are based on a known vessel. Thus, axial pattern skin flaps such as the groin flap and the whole concept of cutaneous vascular territories became popular. In the following years, however, these ideas were no longer pursued because muscle flaps gained momentum in reconstructive Plastic surgery. Rapidly the whole body was screened for possible muscle and musculocutaneous flaps. And with the advent of the operative microscope, the various free muscle or musculocutaneous flap transfers soon offered a solution to practically every reconstructive problem. Later on, surgeons focused on two points: Reducing the donor site morbidity and reducing unnecessary bulk. This led to debulking procedures and to the concept of muscle sparing techniques as represented by the split latissimus and partial rectus abdominis muscle transfer.

A fresh and different approach to address donor-site morbidity and unsightly bulk was initiated by Koshima and Soeda. Koshima utilized the skin territory of the rectus abdommis muscle to reconstruct the floor of the mouth and the groin with free skin flaps. These flaps were based on a single paraumbilical perforator vessel from the deep inferior epigastric artery. Technically, the perforator vessels were followed towards the deep inferior epigastric vessels and dissected from the rectus abdominis muscle to gain pedicle length. The resulting flap was thin, consisted only of skin and the vascular pedicle and left behind an intact rectus abdominis muscle.

Independently, Allen and Treece and Allen and Tucker followed the same principles and transformed the transverse rectus abdominis flap and the superior gluteus maximus flap into the deep inferior epigastric perforator (DIEP) flap and gluteal artery perforator (GAP) flap for breast reconstruction (Figs. 1 to 3). At the same time, Angrigiani et aldeveloped the thoracodorsal artery perforator (TAP) flap and thus the concept of perforator flaps was established. This concept shifts the focus in standard myocutaneous flaps towards the vascular pedicle that leads to a known skin territory. In the TAP flap, DIEP flap, and GAP flap it could be demonstrated that the muscle component was not mandatory for the survival of the dependent skin territories and the attempt was justified to spare the muscle and simply harvest the skin component with the musculocutaneous perforator vessels and the main vascular pedicle. The authors of this article believe that perforator flaps close the circle to Stuart Milton, because with perforator flaps it is again just skin flaps with a known vascular supply.

The work of Allen, Koshima, and Angrigiani was joined by Blondeel, Blondeel, Feller and Galla and Webster. Annual international courses focusing on perforator flaps are held with alternating hosts since 1997 and a vast number of perforator flaps was developed (Table 1). This broad variety of perforator flaps caused confusion in the literature about the correct nomenclature concerning perforator flaps. Weit et al defined a true perforator flap as a skin flap that is nourished by musculocutaneous perforator vessels. Therefore, the radial artery perforator flap and the anterior thigh flap that derive from septocutaneous perforator vessels would be no true perforator flaps. However, both these flapsrepresent skin flaps with a known axial vessel as a pedicle and both flaps are harvested according to the principle that perforator vessels are followed to their main vascular source. Therefore, the authors of this article would like others suggest the term perforator-based flap to address that kind of flap.

The future direction of perforator flaps might be represented by Koshima's supra-microsurgery. Koshima developed the technique, the equipment, and the skills to perform microvascular anastomoses of vessels with a kaliber of 0.5 mm. This allows Koshima to raise for example the paraumbilical flap just to the level of the perforator vessel. A further dissection to the deep inferior epigastric artery is no longer necessary. This would theoretically enable us to raise free skin flaps wherever a perforator vessel can be picked up by the Doppler and create "freestyle free flaps without concern about anatomic variation, resulting in absolute freedom in flap choice.

References

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2. Allen RI, Tucker C: Superior gluteal artery perforator free flap for breast reconstruction. Plast Reconstr Surg 1995; 95: 1207- 1212

3. Angrigiani C, Grilli D, Siebert I: Latissimus dorsi musculocutaneous flap without muscle. Plast Reconstr Surg 1995; 96: 1608 2614

4. Ao M, Mae 0, Namba Y, Asagoe l(: Perforator-based flap for coverage of lumbosacral defects. Plast Reconst Surg 1998; 101: 987 -991

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6. Blondeel PN: The sensate free superior gluteal artery perforator (5- GAP) flap: A valuable alternative in autologous breast reconstruction. BrJ Plast Surg 1999; 52: 185293

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8. Deiler 5, Pfadenhauer A, Widmann J, Stutzle H, l(anz KG, Stock W: Tensor fasciae latae perforator flap for reconstruction of composite Achilles tendon defects with skin and vascularized fascia. Plast Reconstr Surg 2000; 106: 342-349

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