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Flap reconstruction in hand surgery: The evolution of presently used methods
THE JOURNAL OF
HAND
SURGERY
Official journal
AMERICAN SOCIETY FOR SURGERY OF THE HAND
ORIGINAL COMMUNICATIONS
Flap reconstruction in hand surgery: The evolution of presently used methods Ian A. McGregor, Ch.M., F.R.C.S., Hon. F.R.A.C.S., Glasgow, Scotland
The problems of distant flaps in hand surgery arise
from the need to preserve function in the hand and at the same time to have a flap which remains viable when it is used in an acute clinical problem. It might be added that the ideal flap also leaves a secondary defect which is acceptable in terms of site, size, and appearance. When these requirements are translated into practical terms, it means that the ideal flap must be capable of being raised and transferred in a single stage; it needs to be long in relation to its breadth and to have a single pedicle. Above all it needs a blood supply and general robustness which is sufficient to ensure its survival in a high percentage of instances. Prior to 1970 it generally was not considered possible to design a flap which met all of these requirements simultaneously. If it had to be raised without preparation, as was necessary in an acute injury, such a flap had to be designed as short as possible in relation to its breadth in order to stay viable. It had also to be planned and executed with considerable care to avoid the disastrous effects of tension and shearing on its circulation. If a long flap was essential, it had to be Founder's Lecture presented at the Thirty-third Annual Meeting of the American Society for Surgery of the Hand, Dallas, Texas, Feb. 21, 1978. From the Plastic and Maxillo-Facial Surgery Service, Canniesburn Hospital, Bearsden, Glasgow, Scotland. Received for publication July 25, 1978. Reprint requests: Ian A. McGregor, Ch.M., F.R.C.S., Hon. F.R.A.C.S., Plastic and Maxillo-Facial Surgery Service, Canniesburn Hospital, Bearsden, Glasgow G61 IQL, Scotland.
prepared carefully in stages in order to enhance its vascular efficiency and to ensure its survival. Two alternative solutions did exist, but neither solved the problem in its entirety. The tube pedicle had a satisfactory length: breadth ratio but required a preliminary period of preparation (Fig. 1); the direct flap could be used primarily, but had a strictly controlled length: breadth ratio (Fig. 2). These statements, of course, ignore the hypogastric flap which Shaw and Payne! described in 1946. This flap did combine many of the desirable qualities of both the tube pedicle and the direct flap. To ignore the flap in this way is not done with the intention of belittling it. It is merely that a survey of the American literature since 1946 leads inescapably to the conclusion that the flap they described succinctly and clearly either was misunderstood or ignored completely. Yet their short paper contained the kernel of much later work on axial flaps. The place of the hypogastric flap in the evolution of flap design has to be given to it retrospectively as a result. Prior to 1970 it generally was accepted that, if the head and neck, which has a rather special vascular anatomy, were excluded, the geometry and design of flaps virtually were controlled by the limiting factor of length: breadth ratio. The freeing of flaps from this restriction was not specifically in relation to hand surgery, and so, if the logic of events is to be followed, it is necessary to consider flap development for the moment in a broader context. The major change in thinking about flaps occurred in 1965 when Bakamjian 2 described the deltopectoral flap
0363-5023/79/010001 + 10$01.00/0 © 1979 American Society for Surgery of the Hand
THE JOURNAL OF HAND SURGERY
1
2
McGregor
The Journal of HAND SURGERY
Fig. 1. Tube pedicle used in hand reconstruction, showing that, although the flap has a good length: breadth ratio, it requires a preliminary period of preparation.
Fig. 2. A direct abdominal flap (A) used to resurface a defect caused by a crush-degloving injury of the forearm (B), showing the breadth of the flap in relation to its length.
Vol. 4, No . I January , 1979
Flap reconstruction
3
Fig. 3. The deltopectoral flap used to resurface the palm of the hand, showing the favorable ratio of length to breadth .
(Fig. 3). This was a single-pedicled, medially based flap running across the front of the chest. With its single medial pedicle , the deltopectoral flap flouted completely the restrictions of length: breadth ratio. It flouted other restrictions too. It appeared to be based on the mid-line, a line generally accepted to be avascular and not one on which normally to base a flap . But despite these heresies the deltopectoral flap was found in practice to be more robust than the flaps then in common use. The fact that the deltopectoral flap was obviously a safe flap in spite of its heretical design required investigation and revision of ingrained beliefs. At this time two papers appeared and certain of their findings, taken together, provided an explanation. The first described investigations into the vascular pressure in tube pedicles. The authors (Muir et aI., 3 1968) found that a striking pressure gradient sometimes was present from one end of the tube to the other, and they concluded that, when this happened, the gradient was due to the fact that an artery accidentally had been incorporated into one of the attachments. This they called the dominant end of the tube. They noted as an incidental finding that in the chest the medial end of the tube was dominant, and they presumed that the presence of an intercostal vessel was responsible. The second paper (Milton,4 1970) described an experimental investigation into flaps of varying width raised on the flank of the pig . The purpose of the paper and its conclusions are not relevant to the present dis-
Fig. 4. The deItopectoral flap with its axial arteries .
cussion, but an unexpected finding was that virtually all of the flaps survived to the same length, regardless of their widths. This finding appeared to be due to the presence in the flank of the pig of a segmental pattern of blood vessels. As a result, each flap contained an artery. The discovery that flaps could be raised in the pig which flouted the restrictions of length: breadth ratio because each contained an arteriovenous system, taken in conjunction with the finding that an intercostal vessel entered the mid-line attachment of a tube pedicle raised on the chest, provided a possible explanation for the survival and success of the deltopectoral flap. In man
4
The Journal of
McGregor
HAND SURGERY
Fig. 5. The vascular anatomy of the groin, showing the "cartwheel" of arteries and veins. there is a system of segmental anterior perforating vessels and also of lateral perforating vessels in the trunk. Comparing the pattern of these vessels in the abdomen and the chest, it is clear that the development of the upper limb has had the effect of pushing the lateral perforating vessels out into the axilla. It seemed possible that the territory of the anterior perforators might be correspondingly increased laterally to compensate (Fig. 4). The increase in lateral extent of the anterior perforating system of vessels in the chest provided a potential explanation (McGregor and Jackson , 5 1970) for the remarkable length of the deltopectoral flap which could be raised successfully. Much of this reasoning admittedly is commonplace today, but in 1970 it was far from self-evident; indeed it was revolutionary enough to be viewed more as a hypothesis than as a fact. The next steps necessary concerned the confirmation of its validity. This was achieved in two ways-first, by establishing that the perforating branches of the internal mammary artery did indeed have a vascular territory which corresponded to the deltopectoral flap; second, by instituting a search for comparable arteriovenous systems elsewhere. It was thought that if a flap with geometry similar to the deltopectoral flap could be raised successfully, using as its basis such a new found arteriovenous system, success could be taken as strong support for the hypothesis. The obvious area to look at was the groin, where
there is a cartwheel of arteries branching from the femoral artery just below the inguinal ligament to supply the skin all around and a corresponding return of veins to the saphenous opening nearby (Fig. 5). This area was examined and it was decided that the superficial circumflex iliac arteriovenous systems constituted the most likely candidate. A single-pedicled, long, narrow flap then was raised which incorporated this arteriovenous system (McGregor and Jackson,6 1972). It was found to have virtually the same characteristics as a deltopectoral flap and now is referred generally to as the groin flap (Fig. 6). It was during the preparation for publication of our experience of the groin flap in clinical practice that the paper of Shaw and Payne (1946) describing the hypogastric flap (Figs. 6 and 7), with its use of the superficial epigastric as its arteriovenous system, was brought to our attention. It was clear immediately that Shaw and Payne already had noted the effect of incorporating an arteriovenous system in a flap. The recognition that these flaps were distinctive made it necessary to devise a nomenclature to distinguish flaps which contain an arteriovenous system from flaps which do not. The terms random pattern flap and axial pattern flap have been adopted generally (McGregor/ 1975). A random pattern flap may be defined as a flap with a vascular pattern which lacks bias in any particular direction and which is subject to relatively strict limi-
Vol. 4, No. I
Flap reconstruction
January, 1979
ri~
5
~
tnC".'on 6n abdomen ~ from ",hic.h f1dP WCI.s .,. 14ken, i~ clo6ed by ... continu0U6 .$Ub, c..1icu\dr .suture
Fig. 6. The outlines of the groin and hypogastric flaps, with the relevant anatomical landmarks marked on the skin . tations of length: breadth ratio. The opinion has been expressed on the basis of flaps raised on the pig that length: breadth ratio is not relevant to random pattern flap survival, but the combined experience over the years of a multitude of plastic surgeons, admittedly built up empirically, indicates that, for the present at any rate, the restriction of length: breadth ratio is still the best guide we have in clinical practice. An axial pattern flap may be defined as one constructed around a preexisting, anatomically recognized arteriovenous system . It is independent of length: breadth ratio; its length is dictated by the territory of its axial artery. The territories of the deltopectoral and groin flaps are the ones investigated most extensively. Investigation has taken three forms and each has played its part in elucidating the facts . The first method has used dissection and injection studies in the cadaver to estimate the probable territory of the axial artery . The second method has been the empirical one of gradually increasing the length of the flap in successive clinical cases, until it became obvious that the safe limit had been reached. The third method has used intraarterial dye injection into the axial artery (McGregor and Morgan,8 1973). A bolus of dye, carried along by the arterial blood, stains the skin which corresponds to the territory. The dye used has been fluorescein. It has the advantages of being safe, unobtrusive, except in ultraviolet light, and quickly excreted. In making dye studies of axial systems, it clearly is not feasible to raise a particular axial flap and to inject
Fig. 7. The hypogastric flap as originally drawn by Shaw and Payne (published by permission of Surgery, Gynecology & Obstetrics. )
its axial artery. The opportunities to establish the groin and hypogastric territories have arisen during groin dissection. The internal mammary artery has been approached by inserting a fine catheter retrograde into the superior epigastric artery while it is exposed during the taking of a carLilage graft from the costal margin. Much of our present knowledge of the vascular physiology of these flaps and its application in clinical practice has come from correlating the information obtained from these separate techniques. At the same time it has been possible to establish factors governing the extent of territories as well as whether and how territories can be modified and, in particular, increased in length. The findings in investigating the arteriovenous system of a particular flap frequently have general relevance and illumine a particular facet of behavior thereby enabling a composite picture to be built up in this way. It has been possible to answer certain questions-some obvious, some more obscure. 1. Do these territories exist? In each instance it is clear that they do-in the deltopectoral, groin, and hypogastric sites-and the striking finding is the clear-cut margin of each territory (Fig. 8).
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McGregor
The Journal of HAND SURGERY
Fig. 8. The vascular territories (A) of the perforating branches of the internal mammary artery on the anterior chest wall, and (B) of the combined territories of the superficial circumflex iliac and superficial epigastric arteries as demonstrated by intra-arterial fluorescein, photographed by ultraviolet light.
Fig. 9. Extension of internal mammary vascular territory into adjoining acromiothoracic territory when the deltoid branch of the acromiothoracic axis is occluded. A. The original territory which fluoresced on injection into the internal mammary artery. B. The additional area fluorescing when further fluorescein was injected after the deltoid branch of the acromiothoracic axis has been occluded by digital pressure for 2 minutes.
2. What factors determine the margin and why is it so clear-cut? Why does it not tail off gradually towards its margin? Is the margin fixed or can it be altered? The clearest answer to these questions has been found by studying the deltopectoral flap. In the chest there is a small skin territory adjoining the deltopectoral axis. Its point of emergence can be pinpointed with extreme accuracy using a Doppler. If this vessel is occluded by finger pressure for as little as 2 minutes and the deltopectoral territory is established again with a fresh bolus of dye, it is found that the territory has extended considerably with a new and equally clear-cut edge (Fig. 9). We conclude from this that it is not structural factors which separate territories but rather relative vascular pressures. One can see the line between two territories as a watershed along which the blood from each side meets in an equal and opposite pressure confrontation. The result is no mixing and a clear-cut line of demarcation. If the pressure in an adjoining territory is reduced for any reason, as by finger pressure in the experimental situation, a new territorial watershed is created where the pressures once again become equal. The obvious clinical counterpart to the experimental creation of a drop in pressure in adjacent territories is the raising of an axial flap. The vascular pressure in skin normally part of an adjacent territory which happens to be incorporated will drop to zero, and extension of the territory of the axial artery of the flap will follow. Exactly how much extension occurs in clinical prac-
Vol. 4, No. I January, 1979
Flap reconstruction
7
Fig. 10. Closure of the secondary defect of a groin flap by direct suture.
tice? It is not possible to say precisely, but the amount occurring within 2 minutes suggests that it is significant in extent. It also is likely to be a significant factor in the answer to the next question. How well does the flap known from experience to be safe correspond to the territory of its axial artery? It has been found that the flap can be raised safely well beyond the territory of its arteriovenous system, even allowing for a reasonable amount of extension of the type we have discussed. The territory of the superficial circumflex iliac artery extends little more than 5 cm beyond the anterior superior iliac spine, yet in practice groin flaps are consistently raised which are considerably longer than this. In the deltopectoral flap there is an equal disparity between territory and flap. It is postulated that, as far as the distal part of these flaps is concerned, we are dealing with a random flap tacked on to the end of an axial flap. It has been found convenient as well as effective in practice to apply the "rules" of length: breadth ratio to this element of the flap. It certainly seems to work on an empirical basis that the random element should only be as long as it is broad. Generally applying these findings discovered in relation to axial flaps to the context of hand surgery, we have three potential flaps which approach the ideal more nearly than any described previously. Even so, each has advantages and disadvantages, good points and bad points. The groin and hypogastric flaps share the theoretical disadvantage of a dependent hand during transfer, but in practice edema has not developed, given adequate exercises of the hand and wrist and other joints. This would indicate that the efficiency of the muscle pump can more than offset gravity.
To the casual observer, the deltopectoral flap might appear to be free of gravitational problems, but in a percentage of patients this may be replaced by other problems which may be just as prone to give rise to edema, especially in acute injuries. Depending on their physical configuration, some patients may find that the arm position demanded by a deltopectoral flap flexes the elbow enough to produce venous obstruction of a degree to give rise to edema in the hand. 9 The regular absence of hair in the distal segment of the groin flap (Fig. 6) and the possibility of direct suture of the donor area in an unobtrusive body site (Fig. 10) are considerations which might influence the selection of the flap used. More important is the safe length of the flap in comparing the groin and hypogastric flaps . Here the experimental evidence would indicate that the safe length of the groin flap is greater than the hypogastric flap, the territory of the superficial epigastric being about two thirds as long as the superficial circumflex iliac. A further factor, whose relevance is not clear-cut, is the dual blood supply of the skin of the hypogastrium. The superficial epigastric artery is strongly reinforced by the perforating branches of the inferior epigastric, and of course these branches are divided when the hypogastric flap is raised. The groin flap has no comparable vessels entering its deep surface. It seems probable that the dual blood supply makes no difference clinically; but, however, one fact may have considerable relevance. In reviewing the photographic records of some of the early groin flaps raised, it seems probable that the line of the flaps was nearer the vertical than the line of the vessel. One cannot resist speculating whether any flap of average size centered on the origin of the vascular
8
McGregor
The Journal of HAND SURGERY
Fig. 11. The shape of the territory of the arterial "cartwheel" of the groin in two patients, showing the outline to be elliptical rather than circular, with the long axis in the line of the groin flap and the short axis in the line of the hypogastric flap. cartwheel, 2 to 3 cm below the inguinal ligament on the line of the femoral artery, might well survive because it has enough of an axial arteriovenous system. If this indeed were so, and clinical experience would suggest that it may be, what would matter would be the length of the territory of that particular spoke of the cartwheel. The intraarterial fluorescein studies of the cartwheel indicate that its outline is not a circle (Fig. II). It is a segment of an ellipse which has its long axis in the line of the groin flap and its short axis along the line of the hypogastric flap. This would suggest, on the basis of length of territory in the particular' 'cartwheel spoke," that the safe length of a groin flap is in considerable excess of that of a hypogastric flap. Other factors which will influence flap selection are the thickness of fat in the flap and the amount of thinning which is safe. An axial flap can be divided into two parts-the proximal part, in which the arteriovenous system is clearly present, and the part distal to the arteriovenous system. The proximal part is usually the bridge segment; the distal part the segment which provides the raison d' etre of the flap, the part ultimately transferred. In the proximal part the presence of the arteriovenous
system clearly is crucial to flap survival, and thinning' the flap over this part of its length would be unwise. But how safe is it to thin the random part of the flap? The thinning of flaps cannot be discussed properly without considering the work of Colson et al. 10 Colson et al. have raised skin flaps at what appears to be the level of the subdermal plexus. Their work is extremely significant, though it has been strangely neglected in the Anglo-American literature. Colson et al. have found that surprisingly large flaps can survive apparently entirely on this plexus with virtually no subcutaneous fat (Fig. 12). Such a flap level with its highly vascular deep surface would "take" almost like a free skin graft, combining the in-built safety of a flap with the characteristics of a graft in terms of rapid vascularization from the bed to which it is applied. This is an extremely difficult area to investigate in a strictly scientific way, but it does provide a basis for the empirical practice of defatting the distal part of a groin flap relatively ruthlessly, even if carefully. The various factors we have discussed do allow us to use these flaps with relative safety, but they are far from being the whole story. Our ignorance of the venous side of such flaps is striking. The pattern of ne-
Vol. 4, No. I January, 1979
Flap reconstruction
9
Fig. 12. Demonstration of the effectiveness of the dermal circulation in flap survival as used by Colson. A, The bridge segment of a tube pedicle after division . B, After removal of virtually all of the subcutaneous fat and its contained arteries and veins. C, The tube reconstituted after fat removal. D, Its virtually total survival. crosis and the sequence of events are virtually a closed book. There still is much to be done if we are to achieve a full understanding of these flaps and if they are to be exploited in hand surgery as well as other clinical situations. This consideration of the evolutionary aspect of flaps in hand surgery is incomplete without mentioning free flaps . In these the axial arteriovenous system is divided and the flap is transferred en masse to its new site, using microvascular anastomotic techniques to reestablish its axial blood vessels . Whether or not this has enough advantage in hand surgery to justify its use in a routine manner is debatable. But even in those other clinical contexts, free flaps are capable of adding to our knowledge of axial flap behavior, for example in e stablishing the importance of the venous side of the flap, and even more in elucidating the sequence of events and the factors involved in axial flap necrosis . The carefully controlled vascular environment of the free flap is capable of providing an excellent physiological experiment. Even the crosssectional area of the arterial input and venous outflow are known in such circumstances .
The site of a thrombus, for example, as well as its clinical effect, will be demonstrable, with much greater precision than is possible at present. A two-pronged approach, experimental and clinical, is likely to provide the best opportunity to glean as many facts as we can from free flaps so that we may better understand the axial flaps we use routinely. The experimental approach in investigating and elucidating these vascular factors is important even in the human situation. Clinical observation and the control it exerts on the experimentalist's flights of fancy is equally important. Both have their parts to play in creating the total picture. REFERENCES I. Shaw DT, Payne RL: One stage tubed abdominal flaps. Surg Gynecol Obstet 83:205, 1946 2. Bakamjian VH: A two stage method for pharyngooesophageal reconstruction with a primary pectoral skin flap . Plast Reconstr Surg 36: 173, 1965 3. Muir IFK , Fox RH , Stranc WE , Stewart FS: The measurement of blood flow by a photoelectric technique and its application to the management of tubed skin pedicles. Br J Plast Surg 21:14 , 1968
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McGregor
4. Milton SH: Pedicled skin flaps. The fallacy of the length:width ratio. Br J Surg 57:502, 1970 5. McGregor lA, Jackson IT: The extended role of the deltopectoral flap. Br J Plast Surg 23: 173, 1970 6. McGregor lA, Jackson IT: The groin flap. Br J Plast Surg 25:3, 1972 7. McGregor IA: Fundamental techniques of plastic surgery, ed 6, Edinburgh, 1975, Churchill-Livingstone, Ltd
The Journal of HAND SURGERY
8. McGregor lA, Morgan RG: Axial and random pattern flaps . Br J Plast Surg 26:202, 1973 9. Lister GO, McGregor lA, Jackson IT: The groin flap in hand injuries. Injury 4:229, 1973 10. Colson P, Houot R, Gangolphe M, de Mourgues A, Laurent J, Biron G, Janvier H: Use of thinned flaps (flapgrafts) in reparative hand surgery. Ann Chir Plast 12:298, 1967
Information for Authors Most of the provisions of the Copyright Act of 1976 became effective on January I, 1978. Therefore, all manuscripts must be accompanied by the following written statement, signed by one author: "The undersigned author transfers all copyright ownership of the manuscript (title of article) to the American Society for Surgery of the Hand in the event the work is published. The undersigned author warrants that the article is original, is not under consideration by another journal, and has not been previously published. I sign for and accept responsibility for releasing this material on behalf of any and all co-authors." Authors will be consulted, when possible, regarding repUblication of their material.
HAND
SURGERY
Official journal
AMERICAN SOCIETY FOR SURGERY OF THE HAND
ORIGINAL COMMUNICATIONS
Flap reconstruction in hand surgery: The evolution of presently used methods Ian A. McGregor, Ch.M., F.R.C.S., Hon. F.R.A.C.S., Glasgow, Scotland
The problems of distant flaps in hand surgery arise
from the need to preserve function in the hand and at the same time to have a flap which remains viable when it is used in an acute clinical problem. It might be added that the ideal flap also leaves a secondary defect which is acceptable in terms of site, size, and appearance. When these requirements are translated into practical terms, it means that the ideal flap must be capable of being raised and transferred in a single stage; it needs to be long in relation to its breadth and to have a single pedicle. Above all it needs a blood supply and general robustness which is sufficient to ensure its survival in a high percentage of instances. Prior to 1970 it generally was not considered possible to design a flap which met all of these requirements simultaneously. If it had to be raised without preparation, as was necessary in an acute injury, such a flap had to be designed as short as possible in relation to its breadth in order to stay viable. It had also to be planned and executed with considerable care to avoid the disastrous effects of tension and shearing on its circulation. If a long flap was essential, it had to be Founder's Lecture presented at the Thirty-third Annual Meeting of the American Society for Surgery of the Hand, Dallas, Texas, Feb. 21, 1978. From the Plastic and Maxillo-Facial Surgery Service, Canniesburn Hospital, Bearsden, Glasgow, Scotland. Received for publication July 25, 1978. Reprint requests: Ian A. McGregor, Ch.M., F.R.C.S., Hon. F.R.A.C.S., Plastic and Maxillo-Facial Surgery Service, Canniesburn Hospital, Bearsden, Glasgow G61 IQL, Scotland.
prepared carefully in stages in order to enhance its vascular efficiency and to ensure its survival. Two alternative solutions did exist, but neither solved the problem in its entirety. The tube pedicle had a satisfactory length: breadth ratio but required a preliminary period of preparation (Fig. 1); the direct flap could be used primarily, but had a strictly controlled length: breadth ratio (Fig. 2). These statements, of course, ignore the hypogastric flap which Shaw and Payne! described in 1946. This flap did combine many of the desirable qualities of both the tube pedicle and the direct flap. To ignore the flap in this way is not done with the intention of belittling it. It is merely that a survey of the American literature since 1946 leads inescapably to the conclusion that the flap they described succinctly and clearly either was misunderstood or ignored completely. Yet their short paper contained the kernel of much later work on axial flaps. The place of the hypogastric flap in the evolution of flap design has to be given to it retrospectively as a result. Prior to 1970 it generally was accepted that, if the head and neck, which has a rather special vascular anatomy, were excluded, the geometry and design of flaps virtually were controlled by the limiting factor of length: breadth ratio. The freeing of flaps from this restriction was not specifically in relation to hand surgery, and so, if the logic of events is to be followed, it is necessary to consider flap development for the moment in a broader context. The major change in thinking about flaps occurred in 1965 when Bakamjian 2 described the deltopectoral flap
0363-5023/79/010001 + 10$01.00/0 © 1979 American Society for Surgery of the Hand
THE JOURNAL OF HAND SURGERY
1
2
McGregor
The Journal of HAND SURGERY
Fig. 1. Tube pedicle used in hand reconstruction, showing that, although the flap has a good length: breadth ratio, it requires a preliminary period of preparation.
Fig. 2. A direct abdominal flap (A) used to resurface a defect caused by a crush-degloving injury of the forearm (B), showing the breadth of the flap in relation to its length.
Vol. 4, No . I January , 1979
Flap reconstruction
3
Fig. 3. The deltopectoral flap used to resurface the palm of the hand, showing the favorable ratio of length to breadth .
(Fig. 3). This was a single-pedicled, medially based flap running across the front of the chest. With its single medial pedicle , the deltopectoral flap flouted completely the restrictions of length: breadth ratio. It flouted other restrictions too. It appeared to be based on the mid-line, a line generally accepted to be avascular and not one on which normally to base a flap . But despite these heresies the deltopectoral flap was found in practice to be more robust than the flaps then in common use. The fact that the deltopectoral flap was obviously a safe flap in spite of its heretical design required investigation and revision of ingrained beliefs. At this time two papers appeared and certain of their findings, taken together, provided an explanation. The first described investigations into the vascular pressure in tube pedicles. The authors (Muir et aI., 3 1968) found that a striking pressure gradient sometimes was present from one end of the tube to the other, and they concluded that, when this happened, the gradient was due to the fact that an artery accidentally had been incorporated into one of the attachments. This they called the dominant end of the tube. They noted as an incidental finding that in the chest the medial end of the tube was dominant, and they presumed that the presence of an intercostal vessel was responsible. The second paper (Milton,4 1970) described an experimental investigation into flaps of varying width raised on the flank of the pig . The purpose of the paper and its conclusions are not relevant to the present dis-
Fig. 4. The deItopectoral flap with its axial arteries .
cussion, but an unexpected finding was that virtually all of the flaps survived to the same length, regardless of their widths. This finding appeared to be due to the presence in the flank of the pig of a segmental pattern of blood vessels. As a result, each flap contained an artery. The discovery that flaps could be raised in the pig which flouted the restrictions of length: breadth ratio because each contained an arteriovenous system, taken in conjunction with the finding that an intercostal vessel entered the mid-line attachment of a tube pedicle raised on the chest, provided a possible explanation for the survival and success of the deltopectoral flap. In man
4
The Journal of
McGregor
HAND SURGERY
Fig. 5. The vascular anatomy of the groin, showing the "cartwheel" of arteries and veins. there is a system of segmental anterior perforating vessels and also of lateral perforating vessels in the trunk. Comparing the pattern of these vessels in the abdomen and the chest, it is clear that the development of the upper limb has had the effect of pushing the lateral perforating vessels out into the axilla. It seemed possible that the territory of the anterior perforators might be correspondingly increased laterally to compensate (Fig. 4). The increase in lateral extent of the anterior perforating system of vessels in the chest provided a potential explanation (McGregor and Jackson , 5 1970) for the remarkable length of the deltopectoral flap which could be raised successfully. Much of this reasoning admittedly is commonplace today, but in 1970 it was far from self-evident; indeed it was revolutionary enough to be viewed more as a hypothesis than as a fact. The next steps necessary concerned the confirmation of its validity. This was achieved in two ways-first, by establishing that the perforating branches of the internal mammary artery did indeed have a vascular territory which corresponded to the deltopectoral flap; second, by instituting a search for comparable arteriovenous systems elsewhere. It was thought that if a flap with geometry similar to the deltopectoral flap could be raised successfully, using as its basis such a new found arteriovenous system, success could be taken as strong support for the hypothesis. The obvious area to look at was the groin, where
there is a cartwheel of arteries branching from the femoral artery just below the inguinal ligament to supply the skin all around and a corresponding return of veins to the saphenous opening nearby (Fig. 5). This area was examined and it was decided that the superficial circumflex iliac arteriovenous systems constituted the most likely candidate. A single-pedicled, long, narrow flap then was raised which incorporated this arteriovenous system (McGregor and Jackson,6 1972). It was found to have virtually the same characteristics as a deltopectoral flap and now is referred generally to as the groin flap (Fig. 6). It was during the preparation for publication of our experience of the groin flap in clinical practice that the paper of Shaw and Payne (1946) describing the hypogastric flap (Figs. 6 and 7), with its use of the superficial epigastric as its arteriovenous system, was brought to our attention. It was clear immediately that Shaw and Payne already had noted the effect of incorporating an arteriovenous system in a flap. The recognition that these flaps were distinctive made it necessary to devise a nomenclature to distinguish flaps which contain an arteriovenous system from flaps which do not. The terms random pattern flap and axial pattern flap have been adopted generally (McGregor/ 1975). A random pattern flap may be defined as a flap with a vascular pattern which lacks bias in any particular direction and which is subject to relatively strict limi-
Vol. 4, No. I
Flap reconstruction
January, 1979
ri~
5
~
tnC".'on 6n abdomen ~ from ",hic.h f1dP WCI.s .,. 14ken, i~ clo6ed by ... continu0U6 .$Ub, c..1icu\dr .suture
Fig. 6. The outlines of the groin and hypogastric flaps, with the relevant anatomical landmarks marked on the skin . tations of length: breadth ratio. The opinion has been expressed on the basis of flaps raised on the pig that length: breadth ratio is not relevant to random pattern flap survival, but the combined experience over the years of a multitude of plastic surgeons, admittedly built up empirically, indicates that, for the present at any rate, the restriction of length: breadth ratio is still the best guide we have in clinical practice. An axial pattern flap may be defined as one constructed around a preexisting, anatomically recognized arteriovenous system . It is independent of length: breadth ratio; its length is dictated by the territory of its axial artery. The territories of the deltopectoral and groin flaps are the ones investigated most extensively. Investigation has taken three forms and each has played its part in elucidating the facts . The first method has used dissection and injection studies in the cadaver to estimate the probable territory of the axial artery . The second method has been the empirical one of gradually increasing the length of the flap in successive clinical cases, until it became obvious that the safe limit had been reached. The third method has used intraarterial dye injection into the axial artery (McGregor and Morgan,8 1973). A bolus of dye, carried along by the arterial blood, stains the skin which corresponds to the territory. The dye used has been fluorescein. It has the advantages of being safe, unobtrusive, except in ultraviolet light, and quickly excreted. In making dye studies of axial systems, it clearly is not feasible to raise a particular axial flap and to inject
Fig. 7. The hypogastric flap as originally drawn by Shaw and Payne (published by permission of Surgery, Gynecology & Obstetrics. )
its axial artery. The opportunities to establish the groin and hypogastric territories have arisen during groin dissection. The internal mammary artery has been approached by inserting a fine catheter retrograde into the superior epigastric artery while it is exposed during the taking of a carLilage graft from the costal margin. Much of our present knowledge of the vascular physiology of these flaps and its application in clinical practice has come from correlating the information obtained from these separate techniques. At the same time it has been possible to establish factors governing the extent of territories as well as whether and how territories can be modified and, in particular, increased in length. The findings in investigating the arteriovenous system of a particular flap frequently have general relevance and illumine a particular facet of behavior thereby enabling a composite picture to be built up in this way. It has been possible to answer certain questions-some obvious, some more obscure. 1. Do these territories exist? In each instance it is clear that they do-in the deltopectoral, groin, and hypogastric sites-and the striking finding is the clear-cut margin of each territory (Fig. 8).
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The Journal of HAND SURGERY
Fig. 8. The vascular territories (A) of the perforating branches of the internal mammary artery on the anterior chest wall, and (B) of the combined territories of the superficial circumflex iliac and superficial epigastric arteries as demonstrated by intra-arterial fluorescein, photographed by ultraviolet light.
Fig. 9. Extension of internal mammary vascular territory into adjoining acromiothoracic territory when the deltoid branch of the acromiothoracic axis is occluded. A. The original territory which fluoresced on injection into the internal mammary artery. B. The additional area fluorescing when further fluorescein was injected after the deltoid branch of the acromiothoracic axis has been occluded by digital pressure for 2 minutes.
2. What factors determine the margin and why is it so clear-cut? Why does it not tail off gradually towards its margin? Is the margin fixed or can it be altered? The clearest answer to these questions has been found by studying the deltopectoral flap. In the chest there is a small skin territory adjoining the deltopectoral axis. Its point of emergence can be pinpointed with extreme accuracy using a Doppler. If this vessel is occluded by finger pressure for as little as 2 minutes and the deltopectoral territory is established again with a fresh bolus of dye, it is found that the territory has extended considerably with a new and equally clear-cut edge (Fig. 9). We conclude from this that it is not structural factors which separate territories but rather relative vascular pressures. One can see the line between two territories as a watershed along which the blood from each side meets in an equal and opposite pressure confrontation. The result is no mixing and a clear-cut line of demarcation. If the pressure in an adjoining territory is reduced for any reason, as by finger pressure in the experimental situation, a new territorial watershed is created where the pressures once again become equal. The obvious clinical counterpart to the experimental creation of a drop in pressure in adjacent territories is the raising of an axial flap. The vascular pressure in skin normally part of an adjacent territory which happens to be incorporated will drop to zero, and extension of the territory of the axial artery of the flap will follow. Exactly how much extension occurs in clinical prac-
Vol. 4, No. I January, 1979
Flap reconstruction
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Fig. 10. Closure of the secondary defect of a groin flap by direct suture.
tice? It is not possible to say precisely, but the amount occurring within 2 minutes suggests that it is significant in extent. It also is likely to be a significant factor in the answer to the next question. How well does the flap known from experience to be safe correspond to the territory of its axial artery? It has been found that the flap can be raised safely well beyond the territory of its arteriovenous system, even allowing for a reasonable amount of extension of the type we have discussed. The territory of the superficial circumflex iliac artery extends little more than 5 cm beyond the anterior superior iliac spine, yet in practice groin flaps are consistently raised which are considerably longer than this. In the deltopectoral flap there is an equal disparity between territory and flap. It is postulated that, as far as the distal part of these flaps is concerned, we are dealing with a random flap tacked on to the end of an axial flap. It has been found convenient as well as effective in practice to apply the "rules" of length: breadth ratio to this element of the flap. It certainly seems to work on an empirical basis that the random element should only be as long as it is broad. Generally applying these findings discovered in relation to axial flaps to the context of hand surgery, we have three potential flaps which approach the ideal more nearly than any described previously. Even so, each has advantages and disadvantages, good points and bad points. The groin and hypogastric flaps share the theoretical disadvantage of a dependent hand during transfer, but in practice edema has not developed, given adequate exercises of the hand and wrist and other joints. This would indicate that the efficiency of the muscle pump can more than offset gravity.
To the casual observer, the deltopectoral flap might appear to be free of gravitational problems, but in a percentage of patients this may be replaced by other problems which may be just as prone to give rise to edema, especially in acute injuries. Depending on their physical configuration, some patients may find that the arm position demanded by a deltopectoral flap flexes the elbow enough to produce venous obstruction of a degree to give rise to edema in the hand. 9 The regular absence of hair in the distal segment of the groin flap (Fig. 6) and the possibility of direct suture of the donor area in an unobtrusive body site (Fig. 10) are considerations which might influence the selection of the flap used. More important is the safe length of the flap in comparing the groin and hypogastric flaps . Here the experimental evidence would indicate that the safe length of the groin flap is greater than the hypogastric flap, the territory of the superficial epigastric being about two thirds as long as the superficial circumflex iliac. A further factor, whose relevance is not clear-cut, is the dual blood supply of the skin of the hypogastrium. The superficial epigastric artery is strongly reinforced by the perforating branches of the inferior epigastric, and of course these branches are divided when the hypogastric flap is raised. The groin flap has no comparable vessels entering its deep surface. It seems probable that the dual blood supply makes no difference clinically; but, however, one fact may have considerable relevance. In reviewing the photographic records of some of the early groin flaps raised, it seems probable that the line of the flaps was nearer the vertical than the line of the vessel. One cannot resist speculating whether any flap of average size centered on the origin of the vascular
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The Journal of HAND SURGERY
Fig. 11. The shape of the territory of the arterial "cartwheel" of the groin in two patients, showing the outline to be elliptical rather than circular, with the long axis in the line of the groin flap and the short axis in the line of the hypogastric flap. cartwheel, 2 to 3 cm below the inguinal ligament on the line of the femoral artery, might well survive because it has enough of an axial arteriovenous system. If this indeed were so, and clinical experience would suggest that it may be, what would matter would be the length of the territory of that particular spoke of the cartwheel. The intraarterial fluorescein studies of the cartwheel indicate that its outline is not a circle (Fig. II). It is a segment of an ellipse which has its long axis in the line of the groin flap and its short axis along the line of the hypogastric flap. This would suggest, on the basis of length of territory in the particular' 'cartwheel spoke," that the safe length of a groin flap is in considerable excess of that of a hypogastric flap. Other factors which will influence flap selection are the thickness of fat in the flap and the amount of thinning which is safe. An axial flap can be divided into two parts-the proximal part, in which the arteriovenous system is clearly present, and the part distal to the arteriovenous system. The proximal part is usually the bridge segment; the distal part the segment which provides the raison d' etre of the flap, the part ultimately transferred. In the proximal part the presence of the arteriovenous
system clearly is crucial to flap survival, and thinning' the flap over this part of its length would be unwise. But how safe is it to thin the random part of the flap? The thinning of flaps cannot be discussed properly without considering the work of Colson et al. 10 Colson et al. have raised skin flaps at what appears to be the level of the subdermal plexus. Their work is extremely significant, though it has been strangely neglected in the Anglo-American literature. Colson et al. have found that surprisingly large flaps can survive apparently entirely on this plexus with virtually no subcutaneous fat (Fig. 12). Such a flap level with its highly vascular deep surface would "take" almost like a free skin graft, combining the in-built safety of a flap with the characteristics of a graft in terms of rapid vascularization from the bed to which it is applied. This is an extremely difficult area to investigate in a strictly scientific way, but it does provide a basis for the empirical practice of defatting the distal part of a groin flap relatively ruthlessly, even if carefully. The various factors we have discussed do allow us to use these flaps with relative safety, but they are far from being the whole story. Our ignorance of the venous side of such flaps is striking. The pattern of ne-
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Fig. 12. Demonstration of the effectiveness of the dermal circulation in flap survival as used by Colson. A, The bridge segment of a tube pedicle after division . B, After removal of virtually all of the subcutaneous fat and its contained arteries and veins. C, The tube reconstituted after fat removal. D, Its virtually total survival. crosis and the sequence of events are virtually a closed book. There still is much to be done if we are to achieve a full understanding of these flaps and if they are to be exploited in hand surgery as well as other clinical situations. This consideration of the evolutionary aspect of flaps in hand surgery is incomplete without mentioning free flaps . In these the axial arteriovenous system is divided and the flap is transferred en masse to its new site, using microvascular anastomotic techniques to reestablish its axial blood vessels . Whether or not this has enough advantage in hand surgery to justify its use in a routine manner is debatable. But even in those other clinical contexts, free flaps are capable of adding to our knowledge of axial flap behavior, for example in e stablishing the importance of the venous side of the flap, and even more in elucidating the sequence of events and the factors involved in axial flap necrosis . The carefully controlled vascular environment of the free flap is capable of providing an excellent physiological experiment. Even the crosssectional area of the arterial input and venous outflow are known in such circumstances .
The site of a thrombus, for example, as well as its clinical effect, will be demonstrable, with much greater precision than is possible at present. A two-pronged approach, experimental and clinical, is likely to provide the best opportunity to glean as many facts as we can from free flaps so that we may better understand the axial flaps we use routinely. The experimental approach in investigating and elucidating these vascular factors is important even in the human situation. Clinical observation and the control it exerts on the experimentalist's flights of fancy is equally important. Both have their parts to play in creating the total picture. REFERENCES I. Shaw DT, Payne RL: One stage tubed abdominal flaps. Surg Gynecol Obstet 83:205, 1946 2. Bakamjian VH: A two stage method for pharyngooesophageal reconstruction with a primary pectoral skin flap . Plast Reconstr Surg 36: 173, 1965 3. Muir IFK , Fox RH , Stranc WE , Stewart FS: The measurement of blood flow by a photoelectric technique and its application to the management of tubed skin pedicles. Br J Plast Surg 21:14 , 1968
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4. Milton SH: Pedicled skin flaps. The fallacy of the length:width ratio. Br J Surg 57:502, 1970 5. McGregor lA, Jackson IT: The extended role of the deltopectoral flap. Br J Plast Surg 23: 173, 1970 6. McGregor lA, Jackson IT: The groin flap. Br J Plast Surg 25:3, 1972 7. McGregor IA: Fundamental techniques of plastic surgery, ed 6, Edinburgh, 1975, Churchill-Livingstone, Ltd
The Journal of HAND SURGERY
8. McGregor lA, Morgan RG: Axial and random pattern flaps . Br J Plast Surg 26:202, 1973 9. Lister GO, McGregor lA, Jackson IT: The groin flap in hand injuries. Injury 4:229, 1973 10. Colson P, Houot R, Gangolphe M, de Mourgues A, Laurent J, Biron G, Janvier H: Use of thinned flaps (flapgrafts) in reparative hand surgery. Ann Chir Plast 12:298, 1967
Information for Authors Most of the provisions of the Copyright Act of 1976 became effective on January I, 1978. Therefore, all manuscripts must be accompanied by the following written statement, signed by one author: "The undersigned author transfers all copyright ownership of the manuscript (title of article) to the American Society for Surgery of the Hand in the event the work is published. The undersigned author warrants that the article is original, is not under consideration by another journal, and has not been previously published. I sign for and accept responsibility for releasing this material on behalf of any and all co-authors." Authors will be consulted, when possible, regarding repUblication of their material.