Annals of the,Royal College of Surgeons of England (1977) vol 59
The viability of skin flaps P M Stell chM FRCS Department of Otolaryngology, ENT Infirmary, Liverpool
Summary The historical development of skin flaps is outlined, and in particular their division into two types: random, which are supplied by small musculocutaneous vessels; and axial flaps, which are supplied by named cutaneous vessels running within the flap. Experiments are described into the viability of random skin flaps, using the pig as an experimental model. These experiments confirm that random flaps should not be designed longer than their base and probably should not exceed I2.5 cm (5 in) in length. Introduction Historical Skin flaps have been in use for repairing visible defects of the face for many hundreds of years and there is recorded evidence that they were used by Susruta, a Hindu surgeon, in 600 Bcl. At that time the punishment for adultery was amputation of the nose; a technique was developed for reconstructing the nose from a flap of skin from the forehead, a method to be known later as the Indian rhinoplasty. After the Renaissance, when syphilis became rife in Europe, the Italian school, notably under Tagliocozzi, perfected the technique of replacing the nose with a flap of skin from the arm, the so-called Italian rhinoplasty'. Unfortunately, Tagliacozzi fell foul not only of the Church, which deprecated any attempt to improve on God's work, but also of his colleagues. Pare" held that the operation was too difficult for the surgeon and too painful for the patient and the Faculty of Medicine in Paris prohibited operative repair of the face as late as I798.4 Plastic surgery was revived only during the I gth century, by the German and French schools. The Germans, notably under Dieffenbach5, made few contributions to plastic surgery and merely revived what had gone before, but the French under Jobert made
great advances. Jobert in I849 published a 2-volume textbook6, in the second part of which he described many operations, some previously described, such as cheiloplasty, the repair of cleft lip, and some previously undescribed, such as the repair of a vesicovaginal fistula. In the first volume of his textbook he laid down the principles of plastic surgery, and his account would not have sounded oldfashioned had it been written ioo years later. He described the temperature changes that take place in a skin flap; he described the reinnervation of flaps; he stated when the pedicle of the flap should be divided; and, of relevance to this lecture, he stated that 'la largeur du pedicule doit etre en rapport avec les dimensions du lambeau'-the size of the pedicle should be in proportion to the size of the flap. In the First World War Sir Harold Gillies founded the specialty of plastic surgery in Britain when he became involved in repairing the terrible deformities caused by the 1914-I8 war. In his textbook, published after that war, he said that in general a flap should not be longer than the width of its base7, and this statement, that the length-to-breadth ratio of a flap should be I: I , has been accepted until recently.
Delayed flaps There are two major problerns of flap surgery: developing a flap which is large enough; and bridging the distance between the donor and recipient site. For the next 40 years most of the clinical and experimental efforts were devoted to the technique of delay-that is, a technique that increases the length of a flap that will survive. A flap of skin derives its blood supply from each side and from beneath. If a flap of length-to-breadth ratio 2: I is marked out and both sides are divided and the flap undermined, leaving it attached by the ends only, in some way not entirely understood the blood supply along the flap increases so that
Hunterian Lecture delivered on 22nd September 1976
The viability of skin
2-3 weeks later it is possible to divide one end of the flap; the length of flap that will then survive is much greater than that which would have done so originally. It is possible in this way to develop a flap that is twice as long as its base. If the flap has to move over intervening tissue it is usual not to return it to its bed when it has been delayed but rather to turn the skin into a tube with the skin surface outwards and to graft the donor site beneath it. This is a tubed pedicled flap. This technique was used for about 40 years to increase the length of flap that could be used in safety, and a great deal of experimental and clinical work went into the development of these tubed pedicled flaps. But in I920 Gillies had added a rider to what he had said about the viability of flaps that in general the length of a flap should be no more than that of the base, but a longer flap could be raised if the flap contained in its base a large vascular pedicle, such as the superficial temporal artery. Gradually this concept began to crystallize, and in about I960 it was realized that skin flaps could be divided into axial flaps and random flaps8. Axial flaps are those that contain a large vascular pedicle in their base and random flaps are those that do not. The great advantage of an axial flap is that it is larger and longer than a random flap of the same size of base. The principle of an axial flap Axial flaps is that in its base there is a large cutaneous artery that runs within the skin, parallel to the skin surface and superficial to the muscles of the trunk. There are few sites where this obtains, so that the number of axial flaps is strictly limited (Table I). Axial flaps are all named, they have a specific vascular pedicle, and they have a specific design that does not depend on length-to-breadth ratios but on the vascular territory of the vessel. The nape flap develops its supply superiorly from the occipital artery. It is not a very useful flap; it is rather thick and its only satisfactory use is to provide cover for the anterior part of the neck. The temporal flap is based on the superficial temporal artery9. Its main use is in replacement within the mouth, the alveolus, or the inner surface of the cheek. The entire forehead or
TABLE i Axial
237
flaps
Name
Deltopectoral flap Temporal flap Nape Groin
flaps
Vascular pedicle Perforating branches of internal mammary Superficial temporal Occipital Circumflex iliac
half the forehead, depending on the circumstances, is lifted, pedicled on the superficial temporal vessels, and passed into the mouth through a tunnel in the cheek and sewn into the intraoral defect. This temporal flap is a very reliable and vascular flap but unfortunately leaves a deformity on the forehead. The deltopectoral flap'0 is nourished by the upper 4 perforating branches of the internal mammary artery, its boundaries being the clavicle, the acromion, and a line passing medially through the anterior axillary fold. The area of distribution of the arteries supplying the flap has been worked out by experimental techniques". This is a very versatile flap that can be used for four common indications: (i) replacement of the skin of the neck; (2) closure of salivary fistulae; (3) reconstruction within the mouth; (4) reconstruction of the pharynx. The use of the deltopectoral flap for these indications has been described elsewhere'0' 12, 13, but replacement of the hypopharynx is worth comment. The use of the deltopectoral flap for replacement of the pharynx was first described iI years ago by Bakamjian'0. Replacement of the pharynx after resection of a carcinoma of the hypopharynx is an extremely difficult technical pro-ceduire. This technique has been used for 9 years on ioo patients, with a crude 5-year survival rate of 35%. This figure demonstrates the dramatic effect that the development of axial flaps has had on the treatment of head and neck cancer, because carcinoma of the hypopharynx was previously regarded by virtually all surgeons as a disease that was not amenable to surgery; it was also not usually amenable to radiotherapy, and the 5-year survival in most hands was never better than about 5%. Yet by the development of these techniques using axial flaps-a deltopectoral flap in this case-we are now able to obtain a .5-year crude unadjusted survival rate of I in 3.
238
P M Stell
Nearly all the interest, both clinical and Method and material experimental, over the past I5 years or so has The first series of experiments was designed gone into the axial flaps, and the random flap to see whether Milton's concept of area-tohas been rather neglected. base ratios is true of flaps of different shapes. Random flaps were designed in pairs opposite to each other on the abdominal skin of Random flaps A random flap derives its the pig parallel to the coronal axis, one flap blood supply as follows. The segmental artery being rectangular and one triangular. Four in this case runs deep to the muscles of the different sizes of base (20, 30, 40, and 50 trunk and gives off branches that perforate mm) were used and the position of the flaps the muscle layers and rtin into the skin was randomized. The operation was done perpendicularly, each branch supplying a small under the usual operating conditions, using area of skin. A random flap is thus much pigs of a Large White/Landrace cross weighing smaller than an axial flap. It is possible to approximately 35 kg; the pig was allowed to raise this sort of skin flap on the pig by rais- recover, was reanaesthetized on the day, ing a flap superficial to the panniculus and the surviving length and area5th of the carnosus. flaps measured. A typical experiment is shown Random flaps are of no specific design; in Fignre i. An experiment was then designed to inthey have no specific vascular pedicle, they vestigate the length-to-breadth ratio. In the are un-named, and the principles governing results it will be shown that there is no their viability are not definitely known. statistically significant difference between the Over the past 50 years certain clinical rules surviving lengths of triangular and rectangular of thumb have emerged. It is known that a flaps of the same size of base. The results for randoim flap is more viable on the face than the above four sizes of base could therefore be anvwhere else, and its viability decreases with pooled; they were supplemented by a further its distance from the face. The viability of a 8i rectangular flaps of smaller and larger random flap is reduced by the scarring due bases between 5 and I00 mm. The surviving to previous surgery or radiotherapy and by length was again measured after 5 days. peripheral vascular disease. As regards the actual laws govering the flap's survival, there Analysis of data ratio has been very little experimental work apart The relationship of area to Area-to-base base was tested from a well-known paper by Milton14 in which by comparing the surviving area of rectangular he studied the surviving area of rectangular flaps with that of triangular flaps of the same flapS of different sizes and found that the size of base, using the rank-sum test. This test surviving area of his flaps bore a constant was used since the data for surviving area do ratio to the base of his flaps, so that he deduced that a constant area-to-base ratio was required. Milton then went on to make a simple arithmetical deduction from his results. The area of a rectangle is equal to its length multiplied by its base, so that the area-tobase ratio is equal to the length; thus if the area-to-base ratio is constant the length must be constant. From this Milton deduced that the surviving length of all flaps is constant irrespective of the size of their base, which was in direct conflict with what Gillies had said so years previously and which all plastic surgeons had accepted during that period. The remainder of this paper is devoted to a reinvestigation of this important practical FIG. I Rectangular and triangular flaps point. arranged in pairs.
The viability of skin flaps
239
TABLE II Mean surviving area Rectangular
Triangular flaps
flaps
WVidth of No of Meani area SEM base (mm2) flaps 2o mm 40 mm 50 mm
fliaps
Mean area (mmn2)
SEM
R
P
912.3
56.o
I0
507.3
32.9
55
The viability of skin flaps P M Stell chM FRCS Department of Otolaryngology, ENT Infirmary, Liverpool
Summary The historical development of skin flaps is outlined, and in particular their division into two types: random, which are supplied by small musculocutaneous vessels; and axial flaps, which are supplied by named cutaneous vessels running within the flap. Experiments are described into the viability of random skin flaps, using the pig as an experimental model. These experiments confirm that random flaps should not be designed longer than their base and probably should not exceed I2.5 cm (5 in) in length. Introduction Historical Skin flaps have been in use for repairing visible defects of the face for many hundreds of years and there is recorded evidence that they were used by Susruta, a Hindu surgeon, in 600 Bcl. At that time the punishment for adultery was amputation of the nose; a technique was developed for reconstructing the nose from a flap of skin from the forehead, a method to be known later as the Indian rhinoplasty. After the Renaissance, when syphilis became rife in Europe, the Italian school, notably under Tagliocozzi, perfected the technique of replacing the nose with a flap of skin from the arm, the so-called Italian rhinoplasty'. Unfortunately, Tagliacozzi fell foul not only of the Church, which deprecated any attempt to improve on God's work, but also of his colleagues. Pare" held that the operation was too difficult for the surgeon and too painful for the patient and the Faculty of Medicine in Paris prohibited operative repair of the face as late as I798.4 Plastic surgery was revived only during the I gth century, by the German and French schools. The Germans, notably under Dieffenbach5, made few contributions to plastic surgery and merely revived what had gone before, but the French under Jobert made
great advances. Jobert in I849 published a 2-volume textbook6, in the second part of which he described many operations, some previously described, such as cheiloplasty, the repair of cleft lip, and some previously undescribed, such as the repair of a vesicovaginal fistula. In the first volume of his textbook he laid down the principles of plastic surgery, and his account would not have sounded oldfashioned had it been written ioo years later. He described the temperature changes that take place in a skin flap; he described the reinnervation of flaps; he stated when the pedicle of the flap should be divided; and, of relevance to this lecture, he stated that 'la largeur du pedicule doit etre en rapport avec les dimensions du lambeau'-the size of the pedicle should be in proportion to the size of the flap. In the First World War Sir Harold Gillies founded the specialty of plastic surgery in Britain when he became involved in repairing the terrible deformities caused by the 1914-I8 war. In his textbook, published after that war, he said that in general a flap should not be longer than the width of its base7, and this statement, that the length-to-breadth ratio of a flap should be I: I , has been accepted until recently.
Delayed flaps There are two major problerns of flap surgery: developing a flap which is large enough; and bridging the distance between the donor and recipient site. For the next 40 years most of the clinical and experimental efforts were devoted to the technique of delay-that is, a technique that increases the length of a flap that will survive. A flap of skin derives its blood supply from each side and from beneath. If a flap of length-to-breadth ratio 2: I is marked out and both sides are divided and the flap undermined, leaving it attached by the ends only, in some way not entirely understood the blood supply along the flap increases so that
Hunterian Lecture delivered on 22nd September 1976
The viability of skin
2-3 weeks later it is possible to divide one end of the flap; the length of flap that will then survive is much greater than that which would have done so originally. It is possible in this way to develop a flap that is twice as long as its base. If the flap has to move over intervening tissue it is usual not to return it to its bed when it has been delayed but rather to turn the skin into a tube with the skin surface outwards and to graft the donor site beneath it. This is a tubed pedicled flap. This technique was used for about 40 years to increase the length of flap that could be used in safety, and a great deal of experimental and clinical work went into the development of these tubed pedicled flaps. But in I920 Gillies had added a rider to what he had said about the viability of flaps that in general the length of a flap should be no more than that of the base, but a longer flap could be raised if the flap contained in its base a large vascular pedicle, such as the superficial temporal artery. Gradually this concept began to crystallize, and in about I960 it was realized that skin flaps could be divided into axial flaps and random flaps8. Axial flaps are those that contain a large vascular pedicle in their base and random flaps are those that do not. The great advantage of an axial flap is that it is larger and longer than a random flap of the same size of base. The principle of an axial flap Axial flaps is that in its base there is a large cutaneous artery that runs within the skin, parallel to the skin surface and superficial to the muscles of the trunk. There are few sites where this obtains, so that the number of axial flaps is strictly limited (Table I). Axial flaps are all named, they have a specific vascular pedicle, and they have a specific design that does not depend on length-to-breadth ratios but on the vascular territory of the vessel. The nape flap develops its supply superiorly from the occipital artery. It is not a very useful flap; it is rather thick and its only satisfactory use is to provide cover for the anterior part of the neck. The temporal flap is based on the superficial temporal artery9. Its main use is in replacement within the mouth, the alveolus, or the inner surface of the cheek. The entire forehead or
TABLE i Axial
237
flaps
Name
Deltopectoral flap Temporal flap Nape Groin
flaps
Vascular pedicle Perforating branches of internal mammary Superficial temporal Occipital Circumflex iliac
half the forehead, depending on the circumstances, is lifted, pedicled on the superficial temporal vessels, and passed into the mouth through a tunnel in the cheek and sewn into the intraoral defect. This temporal flap is a very reliable and vascular flap but unfortunately leaves a deformity on the forehead. The deltopectoral flap'0 is nourished by the upper 4 perforating branches of the internal mammary artery, its boundaries being the clavicle, the acromion, and a line passing medially through the anterior axillary fold. The area of distribution of the arteries supplying the flap has been worked out by experimental techniques". This is a very versatile flap that can be used for four common indications: (i) replacement of the skin of the neck; (2) closure of salivary fistulae; (3) reconstruction within the mouth; (4) reconstruction of the pharynx. The use of the deltopectoral flap for these indications has been described elsewhere'0' 12, 13, but replacement of the hypopharynx is worth comment. The use of the deltopectoral flap for replacement of the pharynx was first described iI years ago by Bakamjian'0. Replacement of the pharynx after resection of a carcinoma of the hypopharynx is an extremely difficult technical pro-ceduire. This technique has been used for 9 years on ioo patients, with a crude 5-year survival rate of 35%. This figure demonstrates the dramatic effect that the development of axial flaps has had on the treatment of head and neck cancer, because carcinoma of the hypopharynx was previously regarded by virtually all surgeons as a disease that was not amenable to surgery; it was also not usually amenable to radiotherapy, and the 5-year survival in most hands was never better than about 5%. Yet by the development of these techniques using axial flaps-a deltopectoral flap in this case-we are now able to obtain a .5-year crude unadjusted survival rate of I in 3.
238
P M Stell
Nearly all the interest, both clinical and Method and material experimental, over the past I5 years or so has The first series of experiments was designed gone into the axial flaps, and the random flap to see whether Milton's concept of area-tohas been rather neglected. base ratios is true of flaps of different shapes. Random flaps were designed in pairs opposite to each other on the abdominal skin of Random flaps A random flap derives its the pig parallel to the coronal axis, one flap blood supply as follows. The segmental artery being rectangular and one triangular. Four in this case runs deep to the muscles of the different sizes of base (20, 30, 40, and 50 trunk and gives off branches that perforate mm) were used and the position of the flaps the muscle layers and rtin into the skin was randomized. The operation was done perpendicularly, each branch supplying a small under the usual operating conditions, using area of skin. A random flap is thus much pigs of a Large White/Landrace cross weighing smaller than an axial flap. It is possible to approximately 35 kg; the pig was allowed to raise this sort of skin flap on the pig by rais- recover, was reanaesthetized on the day, ing a flap superficial to the panniculus and the surviving length and area5th of the carnosus. flaps measured. A typical experiment is shown Random flaps are of no specific design; in Fignre i. An experiment was then designed to inthey have no specific vascular pedicle, they vestigate the length-to-breadth ratio. In the are un-named, and the principles governing results it will be shown that there is no their viability are not definitely known. statistically significant difference between the Over the past 50 years certain clinical rules surviving lengths of triangular and rectangular of thumb have emerged. It is known that a flaps of the same size of base. The results for randoim flap is more viable on the face than the above four sizes of base could therefore be anvwhere else, and its viability decreases with pooled; they were supplemented by a further its distance from the face. The viability of a 8i rectangular flaps of smaller and larger random flap is reduced by the scarring due bases between 5 and I00 mm. The surviving to previous surgery or radiotherapy and by length was again measured after 5 days. peripheral vascular disease. As regards the actual laws govering the flap's survival, there Analysis of data ratio has been very little experimental work apart The relationship of area to Area-to-base base was tested from a well-known paper by Milton14 in which by comparing the surviving area of rectangular he studied the surviving area of rectangular flaps with that of triangular flaps of the same flapS of different sizes and found that the size of base, using the rank-sum test. This test surviving area of his flaps bore a constant was used since the data for surviving area do ratio to the base of his flaps, so that he deduced that a constant area-to-base ratio was required. Milton then went on to make a simple arithmetical deduction from his results. The area of a rectangle is equal to its length multiplied by its base, so that the area-tobase ratio is equal to the length; thus if the area-to-base ratio is constant the length must be constant. From this Milton deduced that the surviving length of all flaps is constant irrespective of the size of their base, which was in direct conflict with what Gillies had said so years previously and which all plastic surgeons had accepted during that period. The remainder of this paper is devoted to a reinvestigation of this important practical FIG. I Rectangular and triangular flaps point. arranged in pairs.
The viability of skin flaps
239
TABLE II Mean surviving area Rectangular
Triangular flaps
flaps
WVidth of No of Meani area SEM base (mm2) flaps 2o mm 40 mm 50 mm
fliaps
Mean area (mmn2)
SEM
R
P
912.3
56.o
I0
507.3
32.9
55
