The "Gent" Consensus on Perforator Flap Terminology: Preliminary Definitions

Pbillip N. Blondeel, M.D., Ph.D., Koen H. I. Van Landuyt, M.D., Stan J. M. Monstrey, M.D., Ph.D., Moustapha Hamdi, M.D., Guido E. Matton, M.D., RobertJ. Allen, M.D., Charles Dupin, M.D., Axel-Mario Feller, M.D., Ph.D., Isao Koshlina, M.D., Naci Kostakoglu, M.D., and Fu-Chan Wei, M.D.
Gent, Belgium; New Orleans, La.; Munich, Germany; Okayama, Japan; Ankara, Turkey; and Taipei, Taiwan

In 1989, Koshima and Soeda1 used the terminology "perforator flaps" for the first time in a clinical setting. In two cases, Koshima and Soeda had used a paraumbilical skin and fat island based on a muscular perforator to reconstruct the groin and the tongue. Koshima introduced the concept of perforator flaps to differentiate them from fasciocutaneous flaps, as he was convinced that the fascial vascular plexus did not contribute to the vascularization of the flap. Since the first applications and the popularization of the use of perforator-based lower abdominal wall skin flaps in breast reconstruction,2-4 the principle of perforator flaps has become more and more popular over the last decade. Its growing popularity is mainly related to the important decrease in donor-site morbidity as a consequence of the preservation of muscle innervation, vascularization, and functionality of the donor muscle. In addition, it has been observed that patients in general have less postoperative pain and a swifter rehabilitation. The advantages of harvesting relatively large and thin skin flaps include the absence of postoperative muscle atrophy as seen in myocutaneous flaps, the presence of long vascular pedicles based on well-known source vessels, and the possibility of harvesting sensory nerves with the flap, providing a tool to perform more accurate and precise reconstructions. Given that an ideal reconstruction should replace "like with like," and the knowledge that about 80 percent of free flaps are used for resurfacing purposes and only a minority of patients need a free flap to fill up dead space or deep defects, free flaps consisting of skin and subcutaneous fat tissue are predominantly needed in a daily practice.

In the pioneer phase, the principles of a perforator flap were defined as a free flap consisting of skin and subcutaneous fat only, based on a transmuscular perforator vessel that was dissected by splitting the muscle and not harvesting it. Both vascularization and innervation of that muscle were left intact. A perforator flap was seen as an ultimate upgrade of a myocutaneous flap because it preserved all the intrinsic advantages of its myocutaneous analogue. In the last few years, the plastic surgery journals have been filled with reports of new perforator flaps. Slowly, perforator flaps have become a common denominator for any type of skin flap that is dissected on a single vascular pedicle consisting of one artery and one vein. The origin and the route the perforators followed have become less relevant and confusion has increased. The exact definition of a perforator flap is not clear, and the terminology and the classification of the different perforator flaps have not yet been identified. In this article, we attempt to address these issues.

Fig. 1. Schematic drawing of the different types of direct and indirect perforator vessels with regard to their surgical importance. 1, Direct perforators perforate the deep fascia only; 2, indirect muscle perforators predominantly supply the subcutaneous tissues; 3, indirect muscle perforators predominantly supply the muscle but have secondary branches to the subcutaneous tissues; 4, indirect perimysial perforators travel within the perimysium between muscle fibers before piercing the deep fascia; 5, indirect septal perforators travel through the intermuscular septum before piercing the deep fascia.

Definition of a Perforator Flap

Before we could come up with a clear definition of a perforator flap, it was important to define what a "perforating vessel" is. A perforating vessel, or, in short, a perforator, is a vessel that has its origin in one of the axial vessels of the body and that passes through certain structural elements of the body, besides interstitial connective tissue and fat, before reaching the subcutaneous fat layer. Hallock5 defines a perforator as any vessel that enteis the superficial plane through a defined fenestration in the deep fascia, regardless of origin. Hallock discerns direct and indirect perforators according to the distinct origin of their vascular supply and the structures they traverse before piercing the deep fascia. Perforators that pierce the deep fascia without traversing any other structural tissue are called direct perforators. All other perforators that first run through deeper tissues, mainly muscle, septum, or epimysium, are called indirect perforators. In 1986, Nakajima et al.6 classified the deep fascial perforators into six patterns of vascular supply. Despite the very accurate and precise description of the main target of each vessel and its course through the deeper tissues, we do not believe such a complex classification is necessary. From a surgical point of view (i.e., surgical elevation of the perforator flap), it is important to know which surgical plane to follow during dissection by recognizing the tissues through which the perforators are passing. All perforators will eventually perforate the deep fascia. Therefore, we suggest differentiating among the following five types of perforators (Fig. 1):

It is very important to establish good definitions and a correct terminology of perforator flaps to make it possible for reconstructive surgeons to communicate with each other and to talk about the same thing at the same moment. Equally important is the ability to understand the surgical anatomy of each flap, its preoperative planning, and the necessary surgical approach.7 For this reason, Wei et al.7 defined a perforator flap as a flap supplied by fascial perforators that have required an intramuscular dissection during elevation. With the knowledge and the distinction of the different perforating vessels (Fig. 1), we defined a perforator flap as follows:

Definition 1: A perforator flap is a flap consisting of skin and/or subcutaneous fat. The vessels that supply blood to the flap are isolated perforator(s). These perforators may pass either through or in between the deep tissues (mostly muscle).

This definition of a perforator flap is very general. It is important to note that a perforator flap can consist of skin and fat, but if skin is not included, the flap can consist of Scarpa fascia and subcutaneous fat.
Taking into account the different types of perforators, it would be easy to classify them accordingly. Nevertheless, we believe it is important that the classification of perforator flaps reflect the clinical relevance of the different types of perforator flaps. In analogy to the recommendations of Hallock,5 perforator flaps can be vascularized by direct or indirect perforators. Direct perforators only perforate the deep fascia and are therefore rather easy to dissect. In the subgroup of indirect perforators, two types of perforators need to be distinguished according to the clinical relevance: perforators that traverse muscle (transmuscular perforators, transepimysial perforators) and cutaneous side branches of muscular vessels and perforators that run through intermuscular septa.
During the dissection of a muscular perforator flap, one will only take into account the size, position, and course of the perforator vessel and not whether it runs in between muscle fibers or epimysium. In relation to the surgical importance, we decided to only distinguish between muscle perforators and septal perforators, as follows:

Definition 2: A muscle perforator is a blood vessel that traverses through muscle to supply the overlying skin.

Definition 3: A septal perforator is a blood vessel that traverses only through septum to supply the overlying skin.
It is important to notice the word "only" in definition 3. Some perforators can have a mixed septal and intramuscular course before reaching the skin. A good clinical example is the anterolateral thigh perforator flap, where the perforators from the descending branch of the lateral circumflex femoris artery can partially run in the septum in the proximal part and turn into the vastus lateralis muscle before piercing the deep fascia into the skin in the more distal part. In those cases, we would talk about a muscle perforator and only talk about a septal perforator if the perforator itself would run through the intramuscular septum only. After the previous two definitions, the following two important definitions were established:

Definition 4: A flap that is vascularized by a muscle perforator is called a muscle perforator flap.

Definition 5: A flap vascularized by a septal perforator is called a septal perforator flap.
The purists among us stated that a muscle perforator flap is the only real perforator flap. The principle that additional effort and time need to be spent to dissect the perforator out from between the muscle fibers to reduce the donor morbidity was the main argument for the statement. However, the term "muscle perforator flap" clearly opposes the term "septal perforator flap," and it clearly points out the different surgical approach during elevation. In a further refinement of definition 4, it was also stated that the vessels of a muscle perforator flap can pierce any muscle independent of the donor morbidity created, independent of the muscle fiber direction in relation to the course and direction of the perforator, and also independent of the length of the pedicle. Sometimes the perforator vessel may pierce several muscles of which the muscle fibers run perpendicular to the direction of the axial vessels, before emerging from the outer layer of the deep fascia. In these cases, some muscle fibers may have to be divided to reach the source vessel, as with the deep circumflex iliac perforator flap. This would not preclude the use of the term "perforator flap." Also flaps containing the perforator together with the deeper axial vessels would still be called perforator flaps.

Classification

One of the main problems we face in the literature of the last few years is that every author is coming up with his own names for different perforator flaps. A typical example is the perforator flap from the lower abdomen that is called the paraumbilical perforator flap by some and deep inferior epigastric perforator flap by others. From an anatomical point of view, these flaps are almost identical. Another example is the perforator flap from the latissimus dorsi area, called the thoracodorsal artery perforator flap or the latissimus dorsi perforator flap. Some call it the thoracodorsal perforator based cutaneous island flap or the thin latissimus dorsi perforator based free flap. Again, in each of these flaps, the same vessel is used to vascularize the skin island from the same area. It will be important in the future to use corresponding names (and abbreviations) to define the same flaps. For these reasons, a standard nomenclature is very important. To achieve more standardization, a consensus was reached around the following definition:

Definition 6: A perforator flap should be named after the nutrient artery or vessels and not after the underlying muscle. If there is a potential to harvest multiple perforator flaps from one vessel, the name of each flap should be based on its anatomical region or muscle.
A typical example of this are the lateral circumflex femoris artery and vein that can be 'the origin for the tensor fasciae latae perforator flap or the anterolateral thigh flap. These flaps will be called either by their anatomical region or by the underlying muscle to clarify that the skin is taken from a different location but from the same axial vessel. Table I shows examples of correct terminology for indirect perforator flaps. To avoid further confusion, it was also agreed that terms such as "thin," "perforator based," and "cutaneous island" should no longer be used together with the term "perforator flap." One is obviously free to add the type of transfer, either free or pedicled, to the name of a flap.

Conclusions

With the appearance of many new perforator flaps described in the literature in the last few years and the absence of any kind of standardization in terminology, confusion among reconstructive surgeons increased rapidly. It often occurred that, during a meeting, two surgeons were talking about the same flap but were using different names. The lack of standardized terms has led to a lot of confusion. Standardization of terminology is essential when surgeons are communicating with each other and discussing anatomy, preoperative planning, intraoperative surgical techniques, and postoperative care.

In the human body, different types of perforators can be identified anatomically. If we would take the six definitions provided in this article very literally, any vessel that branches off the aorta and eventually reaches the skin could be called a perforator, because all of the aorta's branches will eventually perforate the deep fascia. It is clearly not our intention to define every flap described until now as a perforator flap. The terminology and the classification into direct and indirect perforator flaps and further into septal and muscle perforator flaps were set up to clearly identify the course of these small terminal branches of axial vessels just before they pierce the deep fascia and the technical implications during the surgical procedure. It is evident that the dissection of a direct perforator flap is much easier than dissection of a muscle perforator flap. In addition, septal perforators are easier to identify and slightly easier to dissect.

It still remains controversial whether skin flaps vascularized by direct perforators should be called perforator flaps. This means that most of the skin and/or fasciocutaneous flaps described before, such as the groin flap (superficial circumflex iliac vessels), the superficial inferior epigastric artery flap, and the scapular and parascapular flap (circumflex scapulae vessels), would certainly have to be called perforator flaps. Even some neurocutaneous flaps, such as the saphenous flap (on a perforator of the descending genicular artery) and the radial forearm flap, dissected as such, could be called perforator flaps. For the moment, we believe it is most logical that only skin flaps with septal or muscle perforators should be called perforator flaps because of the different surgical approach that is needed. This would have the advantage of focusing the attention of the surgeon on the anatomy of the perforator and the source vessel according to the angiosome principle as described by Taylor and Palmer.8 The definitions and terminology proposed in this article are temporary and can be reviewed in a later phase. The International Course on Perforator Flaps will be an annual forum to discuss this important topic in the future.

Phillip N Blondeel, M.D., Ph.D.
Department of Plastic and Reconstructive Surgery University Hospital Gent, 2K12C
De Pintelaan 185
B-9000 Gent, Belgium
phillip.blondeel@rug.ac.be www.gentplasticsurg.com

Received for publication October 3, 2002.
Presented at the Fifth International Course on Perforator Flaps, in Gent, Belgium, September27 to 29, 2001, and at the Inaugural Congress of the World Society for Reconstructive Microsurgery, in Taipei, Taiwan, October 30 to November 3, 2001.

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