Histologic Findings of Skin

Figures 44.1 and 44.2 depict the major differences between dorsal and palmar hand skin. Common to both is the irregularity of the border between the basal layer of the epidermis and the dermis, at the juncture of which are located the dermal papillae and the epidermal rete ridges. Both also contain intraepidermal nerve endings terminating in Merkel cell/neurite complexes and sweat ducts extending out from glands located in the base of the dermis and subcutaneous fat. A network of blood vessels and sensory and autonomic nerve fibers in the dermis is shared by all skin.

Dorsal hand skin is similar to skin of the rest of the body in that it has hair and sebaceous glands. A, Merkel’s cell/neurite complex. B and B′, Hair follicle and sebaceous apparatus. C, Sweat gland.

Palmar hand skin. There are no pilosebaceous structures present. Meissner and pacinian corpuscles exist almost exclusively here. A, Meikel cell/neurite complex. B, Meissner corpuscle. C, Sweat gland. D, Vater-Pacini corpuscle.

Figure 44.1 depicts dorsal hand skin, which is similar to skin found anywhere else on the body. The basal layer of the epidermis is continuous with the hair sheaths and sebaceous glands. Hair follicles lie at different depths and are surrounded by a network of fine nerve endings.

Figure 44.2 depicts the palmar hand skin. The papillae and ridges are deeper and the keratin layer is considerably thicker than in dorsal hand skin. Most significant, however, are the absence of pilosebaceous structures and the presence of spe­cialized encapsulated nerve endings. Meissner corpuscles are present in dermal papillae, and Vater-Pacini corpuscles are present in the deep dermis. These latter structures are also found along nerve trunks, joints, and other areas but exist in the skin almost exclusively in digits and the genital area.

Substitution by Skin Grafts

Because it is similar to the skin of most other areas, dorsal hand skin can usually be adequately replaced by a skin graft. No matter how thick the graft is, however, palmar skin cannot always be fully substituted by ordinary grafts because the special dermal neural mechanoreceptors will be absent. Only glabrous skin will provide these, and, unfortunately, not much of this type of skin is available for grafting.

When a split-thickness graft is removed, healing of the donor area occurs by epithelialization from hair follicles and very little dermal regeneration occurs. The deeper the graft, the better the quality of the skin, but the less there is left behind at the donor site to aid in healing. Also, a deeper graft increases the chance of reinnervation of Merkel complexes and restoration of sensibility in the recipient site. Thick nonglabrous grafts will transfer hair follicles, however, and result in unwanted hair growth if placed on palmar surfaces. In addition to poor return of sensibility, grafts on palmar areas do not provide the vascularized subcutaneous tissue necessary to cover tendons and nerves. In general, palmar grafts should be considered a compromise and are usually only indicated in release of flexion contractures in areas not requiring critical sensibility.

Response to Injury

Any injury that results in the loss of a full-thickness segment of skin initiates the process of wound contraction. Although beneficial in helping to minimize defects in other parts of the body, this process of gradual shrinking of the wound edges can be disastrous in hand wounds ( Figure 44.3 ). It appears that fibroblasts migrate into the base of the wound and differentiate into so-called myofibroblasts. These cells have the ability to contract, and the network of these cells and collagen fibers that forms in the base of the wound is responsible for pulling the wound edges together. It has been shown that contraction can be temporarily halted by treatment of the wound with smooth muscle relaxants. Once the contraction process has begun, it is not altered to any extent by split-thickness skin grafting.

The end result of scar contracture due to severe burn to the hand.

In a series of experiments by Stone and Madden, wounds in animals were treated with immediate grafting, delayed grafting, and immediate and delayed grafting with splinting. They concluded that immediate grafting with split-thickness skin did not significantly affect wound contraction. However, immediate grafting and splinting with a compressive dressing for 7 days did significantly inhibit wound contraction. On the other hand, delayed grafting had no effect on wound contraction no matter what adjunctive therapy was used. Splinting, although effective with immediate grafting, was ineffective in preventing contraction when used with delayed grafts.

It is generally believed that the condition of the wound is the main determinant in the result of skin grafting. Even full-thickness skin grafts can be found to contract if wound contraction has already begun. Rudolph has found that the application of split-thickness skin does not seem to have as much effect on the differentiation of fibroblasts into myofibroblasts as does a full-thickness graft. He has shown in animal experiments that wounds mature much more rapidly after the application of full-thickness grafts than after split-thickness grafts. The amount of actin and fibronectin found in rat wounds that were allowed to heal secondarily was compared in wounds with split-thickness grafts and those with full-thickness grafts. The thicker the graft, the less matrix protein present, which correlated well with the extent of wound contraction that occurred.

This is important in considering the source of a graft for palmar wounds. The Shriners Burn Institute has compared the results of split-thickness and full-thickness grafts for coverage of deep palmar burns. Normal range of motion was found in over half of the full-thickness group, and only a fourth needed reconstructive procedures. In contrast, normal range of motion was present in only a fourth of the split-thickness group, and two thirds required reconstructive procedures.

Effect of Infection on Wound Healing

A great deal of bacteria is normally present on the skin. It has been estimated that about 1000 organisms per gram of tissue are normally present in hair follicles, crevices, and recesses of the skin. This number of organisms does not seem to have a negative effect on wound healing. However, when contamination of the wound takes place, much higher levels are present. Surface bacteria, which can easily be removed, do not appear to be important in skin grafting if the wound is carefully prepared before surgery. On the other hand, penetration of the bed of the wound is of great significance. It has been established that 10,000 organisms per gram of tissue is a fairly critical level of contamination. Wounds that contain fewer organisms than this do not commonly become infected. In a series of skin grafts applied to contaminated wounds, Krizek and colleagues have shown that no matter what technique was used to prepare the bed of the wound for grafting, a bacterial count of greater than 10,000 organisms resulted in a successful skin graft take of only 19%. If the count was less than 10,000 organisms, however, there was a 94% successful take.

Vascularity of the Wound

After application of a skin graft to the wound, the graft first survives in a precarious fashion, apparently nourished by transudate from the wound. This has been referred to as “plasmatic circulation.” It is imperative that the graft become vascularized for ultimate survival, however, and anything that acts as a barrier to this process will cause loss of the graft. The most potent of all barriers is blood, and hematoma will kill a graft even in the absence of infection.

The actual process of vascularization is not altogether clear, but it is certain that this process must begin within a few days if the graft is to survive. It appears that the most important process is the ingrowth of capillary buds into the skin graft from the edges of the wound and, more importantly, from the bed of the wound. For this process to take place, there must be a vascularized bed containing the necessary fine network of capillaries from which budding will take place. Grafts will not take on denuded bone or tendon, and skin grafts are not satisfactory coverage for vital structures.

Timing of Grafting

From the previous discussion, it is obvious that the ideal time for grafting the wound is as soon as it is clean enough and after the fine network of vessels has been established. In this way, contamination of the wound and establishment of a large milieu of myofibroblasts are avoided. In general, immediate débridement and grafting are often possible, and no more than 2 or 3 days should be allowed to pass for the purpose of establishment of a good bed. The principle of allowing a healthy bed of granulation to develop is no longer considered correct, and it should be replaced with the concept of early grafting. The vacuum-assisted wound closure device may be helpful in promoting granulations in severe wounds and may aid in obtaining granulations over tendons and bone, but its use in the hand should be limited to avoid the marked scarring often caused by the device and increasing stiffness.

Types of Grafts

The two primary types of skin graft are split-thickness and full-thickness grafts. While other differences were discussed earlier, the main clinical difference in these grafts is in the way in which they are harvested. Split-thickness skin grafts are harvested with a knife or dermatome, and only the superficial layer of the skin is taken. The donor site of a split-thickness graft will heal on its own from propagation of epithelial cells from the deeper skin appendages (hair follicles and sweat glands). Full-thickness grafts are harvested with an incision with a knife and involve taking the entire layer of skin down to the subcutaneous fat. These donor sites must be closed as with an incision; otherwise the patient is left with a wound.

The standard thickness for harvesting split-thickness skin grafts is in the range of 0.015-inch thick. Split-thickness skin grafts may be taken as either “thin” grafts (0.008 to 0.010 inch) or “thick” grafts (0.016 to 0.020 inch). Thicker split grafts have the theoretical advantage of potentially less contraction, because they contain more dermis. The downside of these types of grafts is that the donor site may have difficulty healing, and this can lead to worse scarring. One prospective study of the differences between standard and “thick” split grafts in the hand found no advantages in terms of range of motion, appearance, or patient satisfaction.

Although it is true that full-thickness grafts afford better protection, hold up better, establish better sensibility, contain more epidermal appendages, and contract less than split-thickness grafts, thick grafts are not always desirable. There are several disadvantages to thick grafts. Full-thickness grafts do not take as readily as split grafts. A full-thickness graft requires a much better bed on which to be placed, and the graft is more prone to infection.

In addition, the availability of skin must be considered. It is not always possible to sacrifice enough skin to afford the luxury of full-thickness grafting, and split-thickness grafts must often be substituted. In general, full-thickness grafts should be used only in situations in which the quality of the skin and the tendency to less contracture are crucial. As a rule, these conditions are necessary only on palmar skin grafts, and the greater level of return of sensibility is an added bonus under these circumstances. Full-thickness grafts have recently been shown to be superior to split-thickness grafts in coverage of palmar wounds extending onto the digits in a large series of children with burns. Dorsal wounds can generally be treated very adequately with intermediate split-thickness grafts.

Skin Substitutes

There have been many attempts in recent years to develop skin substitutes. Autogenous epithelial cells have been cultured and placed on a variety of collagen matrices and used as skin grafts. These have been of great value in the treatment of massive burns, but the take of the graft is not equal to that of standard autografts and the quality is not predictable. Cultured epithelial autografts remain extremely expensive and afford very poor coverage, particularly in the hand.

Work continues on the goal of providing skin coverage without the need for a donor site, particularly in terms of reconstruction of the dermal layer. Several products now exist that provide a collagen matrix to act as a layer of dermis when placed on a vascularized wound. The primary problem with these dermal substitutes is that they generally have to be applied 1 or 2 weeks before coverage with a split-thickness graft to allow for revascularization of the collagen matrix, thus necessitating two operations. Some authors have noted no statistically significant long-term difference in elasticity, scar contracture, and patient satisfaction in patients treated with dermal substitutes plus split-thickness skin grafts versus split-thickness skin grafts alone in the management of donor sites from radial forearm free flaps. It should be noted that the time necessary for rehabilitation of the hand was significantly longer with the dermal substitutes, as the hand had to be immobilized while the dermal autograft became vascularized.

Recent reports have noted that dermal substitutes have few complications when utilized in the upper extremity and obviate the morbidity of a full-thickness skin graft donor site. One fairly large study found that placement of dermal substitute after contracture release was as effective as full-thickness grafting. Other reports of smaller series of patients have shown the utility of this approach to avoid the need for a full-thickness graft in burns and wounds of the upper extremity. Skin elasticity in patients managed with dermal substitutes and split-thickness skin grafts has been found to be close to normal in objective testing. The issue remains, however, that the application of dermal substitutes in the hand necessitates a period of immobilization while the dermis becomes revascularized, and then a potential second period of immobilization while the split-graft heals. Coupled with the fact that the morbidity of most full-thickness skin graft donor sites is minimal, the utility of these materials in the hand remains in question in my mind.

Skin Thickness

When determining the thickness of a graft to be removed, the skin thickness of the donor area must be considered. Epidermis and dermis vary according to age and sex, as well as location. It is said that the epidermis ranges from 20 to 1400 µm in thickness and the dermis from 400 to 2500 µm. When considering donor sites, however, there is only a practical range of 25 to 80 µm of epidermis and 500 to 1800 µm of dermis. In relation to dermatome settings, these values translate to 0.001 to 0.003 inch of epidermis and 0.020 to 0.070 inch of dermis.

In general, the epidermis is quite thin in infants and reaches a maximum thickness at puberty; it then becomes thinner with age until it is almost as thin in old age as it was during childhood. There is very little difference in epidermal thickness between sexes. The dermis, however, remains relatively thin in youth; it reaches its maximum thickness at about the fourth decade and subsequently becomes thin again in old age. There is a marked difference between sexes, with male dermis being significantly thicker than female dermis.

The skin of the trunk and dorsal and lateral surfaces of the extremities is the thickest. Skin thickness may range from 0.020 to 0.025 inch in a small child to 0.100 inch on the anterior of the abdomen in an adult man. In general, most donor sites cannot be expected to be much thicker than about 0.060 inch in a man and about 0.040 inch in a woman.

Choice of Donor Sites

Removal of a skin graft is a morbid procedure. Although regeneration of the epidermis will occur, it appears that loss of the dermis is irretrievable. The thicker the skin graft, the poorer the quality of the donor site after healing. Therefore, the thickness of the desired graft must, to a certain extent, determine the location of the donor site. The thicker portions of the body, such as the posterolateral aspects of the trunk and thighs, afford the best chance of good healing when a thick graft is desired. The thinner areas, such as the inner aspect of the thigh, are generally unsuitable for donor sites (unless they are absolutely necessary) because of the poor quality of healing of the donor site and the tendency of the skin graft to become hyperpigmented in its new area. So that morbidity and subsequent scarring are prevented, a reasonable guideline for graft thickness is offered in Table 44.1 .

The optimal thickness for split-thickness grafts is 0.015 inch in thickness. Thinner grafts of 0.010 to 0.012 inch may be best for wounds where graft survival is at risk. Split grafts greater than 0.018 inch are seldom indicated because of donor site morbidity. If thicker skin is desired, it is best to use a full-thickness graft.

If possible, a graft should be taken from an area that is easy to care for during the healing process. No one likes to have to lie or sit on a donor site, and donor areas that cross intertriginous areas are very unsuitable because of the constant cracking and subsequent drainage with motion of the area. In women and children, it is desirable to remove the graft from the lateral aspect of the upper thigh or buttocks or perhaps the lower portion of the abdomen. These donor sites can be covered by a bathing suit or some other article of clothing. It is important to remember that the thicker the skin graft, the larger the number of hair follicles that are transferred in the graft; thus whenever possible, a relatively hairless area should be selected as a donor site for the hand.

Harvesting Skin Grafts

A very small piece of skin can be removed with a No. 10 knife blade by dissecting superficially just under the surface of the skin. It is convenient to make a very shallow incision in skin that has been distended with intradermal lidocaine before beginning the tangential dissection. In this way the appropriate depth and width of the graft can be selected. The blade is then placed into the depth of the incision, and with a back-and-forth sawing action, parallel to the skin, the desired size of graft can be removed. It is possible to remove a reasonably uniform piece of skin up to about the size of a dime with this technique, but the procedure is difficult for a surgeon without some experience.

A much more satisfactory method of taking a small skin graft is with the Weck-Goulian knife set. There are a number of depth gauges available that can be fitted over the blade ( Figure 44.4 ). These gauges vary in thickness from 0.004 to 0.030 inch. By placing the gauge next to the skin, the appropriate depth and angle of cut are automatically established. Because this instrument tends to take a rather thick graft, I prefer to use the 0.010 guard, avoiding excessive thickness. A strip of skin 2 cm or so in width can easily be removed, and with practice a long strip can be taken. This instrument has the advantage of removing a strip of skin of relatively uniform thickness.

The Weck-Goulian skin graft knife set before assembly. Depth gauges of many thicknesses make it possible to remove a graft of uniform thickness.

Although it is very convenient to remove a split-thickness skin graft from the upper inner aspect of the forearm because it is in the operative field, this is, in practice, a very poor procedure. The skin of the forearm is relatively thin in this area, and often the scar will become hypertrophic. These scars are very obvious to both patients and casual observers, and often women will complain more of the donor site scar than the recipient area scar. It is preferable to remove these grafts from areas of thicker skin, where the scar will not be so readily apparent.

Dermatomes

Padgett Dermatome.

The Padgett dermatome is a motorized dermatome (via electricity or nitrogen turbine) and uses a disposable blade that cuts with a very rapid back-and-forth motion. There is a depth gauge on the side of this instrument with which the surgeon can set the desired depth of the graft. Variable-sized plates determine the width of the graft taken ( Figure 44.5 ). After determination of the desired width, the blade is fitted on the machine and the appropriate plate placed over the two screws and screwed down tightly. To put the blade on, it is necessary to first slip the base of the blade under the two projecting metal pieces and snap it down so that the hole in the blade fits onto the projection of the drive shaft. The appropriate graft thickness is selected by moving the blade up and down by using the depth gauge on the side of the machine. The depth of the graft taken is also determined by the pressure applied to the device on the skin and the angle of attack of the blade against the skin.

The Padgett gas-turbine driven dermatome. Guards are shown on the lower left with variable openings to control the width of the graft. The blade is seen loaded on the device.

The skin is surgically prepped and cleansed with saline before taking the graft. The skin should be lubricated so that the dermatome will slide easily and not skip. Either mineral oil or a surgical soap solution can be used for this purpose and is placed both on the skin and on the flat surface of the instrument that is in contact with the skin. The dermatome is placed flat on the donor site, and traction is held behind the dermatome. It is not necessary to stretch the skin in the direction in which the dermatome will be advanced. It is easy to remove a piece of skin with this dermatome, and very minimal pressure should be exerted on the donor area. A common mistake is to dig the edges of the dermatome into the skin and press too hard, which creates an improper cutting angle. As the dermatome is advanced, the skin may be lifted up to check the thickness, if desired. This is not necessary, however, and in general, a very uniform piece of skin is removed with the Padgett dermatome. This is probably the best instrument to use to take a skin graft if one is not experienced in this area.

Meshed Grafting

At times the condition of the wound cannot be made optimal for grafting. The risk of infection or hematoma may be so great that the chance of survival of a sheet of autograft would be small. In these instances, it is often wise to use a piece of skin that has been “meshed” so that many perforations are present through which blood or exudate can escape. An instrument has been devised that will automatically make these perforations. The skin can be expanded so that the interstices allow drainage and rapidly become epithelialized ( Figure 44.6 ). This method of grafting has wide application in the treatment of burns and large wounds.

A meshed split-thickness graft placed over an innervated gracilis muscle to the forearm.

It must be remembered, however, that only the portion of the wound that has skin applied to it is being grafted and the interstices of the mesh are left open and allowed to epithelialize. The quality of the graft will not be as good as that of a sheet of skin, and the tendency toward contraction and poor cosmetic results is greater. If meshed grafts of this nature are placed over flexion creases, joint contractures are likely to occur. These factors can be limited somewhat by compression, and it is imperative to treat wounds grafted in this fashion with long-term compression, such as can be obtained by use of a custom-fitted pressure glove.

Although they were not specifically evaluating hand grafts, el Hadidy and colleagues evaluated the results of meshed versus nonmeshed grafts in burns. As expected, the results of either graft in late excision were significantly worse than the results in early excision, but the meshed grafts contracted more in both groups. In addition, there was a difference in the amount of growth that occurred in the two groups. With early excision, nonmeshed grafts grew back to a size of 91% as compared with 78.5% in the meshed group.

Meshed grafts are often placed on a wound without the graft “expanded,” which prevents collection of fluid under the graft but avoids the necessity for skin to grow over the open interstices. Whereas using a meshed graft in this way inevitably leads to more scarring than using a nonmeshed graft, the functional differences are usually minimal. The advantages of meshing a graft usually outweigh the disadvantages. Nonetheless, split-thickness skin grafts are usually reserved for coverage of the dorsum of the hand, whether meshed or not. When the dorsum of the hand is covered with a muscular or fascial flap, it is certainly acceptable to place an expanded meshed split-thickness graft over the flap. It is sometimes convenient to use a mesh graft as a “temporary” biologic dressing, however, until a later resurfacing procedure can be done as part of the reconstruction.

Technique of Obtaining a Full-Thickness Graft

After the appropriate size has been determined, an area for harvest of the full-thickness graft is marked. I prefer to infiltrate underneath this area with plain lidocaine or marcaine, which will elevate the skin somewhat and make harvesting easier (as well as provide some anesthesia in the postoperative period). Local anesthetic with epinephrine should be avoided as this has been reported to cause spasm in the capillary bed of the graft and lead to poor “take” of the graft. An ovoid of skin is excised from the predetermined area with the axis in the direction of minimal tension. The wound is closed in standard fashion. Most donor sites for hand coverage will be small, and primary closure can be performed easily without undermining of the edges. Because there will be a moderate amount of tension on the edges, it is probably best to close the wound with buried subdermal sutures and a subcuticular suture to minimize the cross-hatching that might occur with ordinary cutaneous sutures. The wound can be dressed with sterile skin closure strips only.

It is necessary to remove all fat and subcutaneous tissue from the undersurface of the graft because they will otherwise act as a barrier and prevent vascularization. If desired, this can be done at the time of removal of the graft by very carefully excising only the skin and lifting it off its bed of subcutaneous tissue by dissecting sharply with a scalpel in the subdermal plane. The graft can be rolled over a finger as it is taken, and, with appropriate tension, most of the underlying subcutaneous fat can be removed. Once the graft is excised, the remaining subcutaneous tissue is removed. This is easily done by draping the graft around the surgeon’s nondominant index finger while holding tension with the ends of the graft in the other fingers. The remaining fatty tissue is removed with a small curved pair of scissors. The normal tendency is to remove portions of the dermis as well, which can actually lead to creating a “thick” split-thickness graft and lead to more contracture. The final result in terms of quality of the graft will be better if the subdermal areolar tissue is left with the graft. The fat can also be removed by placing small mosquito hemostats on the very tips at each end of the graft and draping the skin over a finger or the thumb while keeping tension on both hemostats. If some tension is maintained, it is very easy to snip away the fat in this fashion.

Choice of Graft

As previously indicated, a thicker graft contracts less, holds up better, and regains better sensibility than a thinner one. In general, split-thickness grafts should not be used on palmar surfaces of the hand unless there is no other choice or the coverage is considered to be temporary, with secondary resurfacing to be performed at a later date. If split-thickness grafts are to be used, they should be relatively thick and long-term compression with an elastic glove should be used.

Full-thickness grafts are seldom indicated on the dorsal surface of the hand. The need for coverage is not as critical on the dorsum, and split-thickness grafts are generally satisfactory. In addition, the convexity of the dorsum and the subsequent greater tension on the wound edges with motion in the postoperative period appear to allow split grafts to be used with less contraction than would be the case on the concave palmar aspect. The general rule is that a sheet of graft of good-quality skin approximately 0.015 inch thick, if placed on a well-vascularized bed early in the evolution of the wound, will heal so well that it is difficult for a casual observer to know that a graft has been done ( Figure 44.9 ). If the bed is not ideal, it makes no difference what kind of graft is used, because the result will always be less than satisfactory. Large areas of bare tendon, bone denuded of periosteum, and nerves and vessels bowstringing in the wound should never be covered with a graft; in such instances, coverage should be obtained by the use of a flap (see later in this chapter). Very small areas of exposed tendon can sometimes be covered successfully with a full-thickness graft if the surrounding bed is good. This is due to the presence of the capillary bed in a full-thickness graft, which will allow vascularization of small areas of graft that are not over areas with adequate vascularity (assuming that the rest of the graft becomes vascularized).

Hand of a patient who suffered burns of the hands and was treated with excision and primary split-thickness sheet grafting. Note quality of dorsal hand skin after placement of sheet graft.

Random-Pattern Flaps

The manner in which the skin receives its blood supply has been studied by many anatomists. Lamberty and Cormack described angiotomes in the upper limb, these being areas of skin with a known single arterial supply. The constancy of these arteries has been confirmed by Doppler studies in patients and volunteers. Taylor et al studied the venosomes and reported that venous territories correspond closely to recognized areas of arterial supply. The blood supply of a flap may come not from a single arteriovenous pedicle but from the many minute vessels of the subdermal or subcutaneous plexus. Such a flap is termed a random-pattern flap. Although the shape of a random-pattern flap need not be quadrilateral, it is usually conceived as such, and it is raised by incising three of the four sides. The fourth constitutes the pedicle, or base, of the flap. The side opposite the base is called the free margin. Because the adequacy of the subdermal plexus varies from location to location, the area of skin that can be supported by the vessels of the pedicle also varies. As a general rule, a random-pattern flap with a length not exceeding the width of the pedicle—in other words, a rhomboid—is considered to be reliable with respect to blood supply. This is the one-to-one (1 : 1) rule. It does not always apply, however. For example, it is too cautious for the face (and usually the hand) and too bold for the foot. Observation of this rule and the need to protect the pedicle from undue distortion that would impair blood flow through the subdermal plexus clearly limit the range of applications for the random-pattern flap.

The relatively inadequate blood supply of a random-pattern flap may be enhanced by a “delay” procedure and will often allow a flap larger than the 1 : 1 rule to be rotated. In a delay procedure, the margins of the flap are incised, but it is not lifted off the underlying tissue and the incisions are sutured. This causes enhancement of the vascularity via the pedicle by interrupting that blood supply to the skin of the flap through the incised margins. The optimal time of delay has been shown to be around 10 days. During that time, both arteries and veins that were random become enlarged and oriented parallel to the axis of the pedicle. They are therefore better able to support the flap when it is transferred.

Axial-Pattern Flaps

When a flap receives its blood supply from a single, constant vessel, it is termed an axial-pattern flap. Such a single vessel is materially larger than the vessels of the subdermal plexus. For example, the superficial circumflex iliac artery that supplies the groin flap (see following description) has an average diameter of 2 mm, or five times that of the largest subdermal vessel. Although Poiseuille’s law of flow in rigid tubes cannot be applied precisely to blood vessels, it indicates that flow would be approximately 625 times greater through the axial vessel of the groin flap than through a subdermal vessel. The area of skin supplied by such an axial vessel is termed a vascular territory.

The area where the vascular territories of two axial pedicles meet is termed a watershed, and the small arteries that cross it, choke vessels . In these areas, veins have no valves and can be said to allow blood to oscillate between territories. Occlusion of one of the two pedicles results in a shift of the watershed toward the site of occlusion, extending the vascular territory of the other, open pedicle. In raising an axial-pattern flap, it is safe to increase the length of the flap beyond the known vascular territory by the amount that would constitute a random-pattern flap. That is, a safe axial-pattern flap equals the normal vascular territory of the flap with a 1 : 1 extension on the distal portion of the flap.

The vessel of an axial-pattern flap may be purely cutaneous ( Figure 44.12, A ), supplying skin alone and proceeding directly to it. The superficial circumflex iliac artery to the groin flap is such a vessel. In reaching its cutaneous territory, the axial vessel may first supply fascia. In such circumstances, the vessel commonly reaches the fascia by running in an intermuscular septum. Because this is attached to bone, a segment of bone may be taken with skin and be vascularized by the same pedicle. Axial flaps whose vessels first pass through fascia are termed fasciocutaneous vessels (see Figure 44.12, B ). As with the musculocutaneous flap, fascia may be transferred without skin, but not skin without fascia. Such a flap is the lateral arm flap supplied by the posterior radial collateral artery. The axial vessel may first supply muscle (see Figure 44.12, C ). The secondary vessels to the overlying skin are multiple, so the muscle must be taken with the skin to ensure survival of the skin, but the muscle may be transferred without skin. Such flaps have been called musculocutaneous, myocutaneous, and myodermal flaps. An example of this type of flap is the latissimus dorsi flap, supplied by the thoracodorsal artery.

Axial-pattern flaps are either cutaneous (A), fasciocutaneous (B), or musculocutaneous (C), depending on the source of the major portion of their blood supply. Fasciocutaneous vessels commonly run in intermuscular septa and therefore supply the periosteum of underlying bone. The flap can be taken with a segment of that bone where necessary.

(From the Christine Kleinert Institute for Hand and Microsurgery, Inc., with permission.)

Axial-pattern flaps clearly have several advantages over random-pattern flaps. The 1 : 1 ratio can be disregarded in flaps with an axial vessel. Axial-pattern flaps have a blood supply superior to that of random flaps. It has been shown experimentally that axial-pattern flaps resist infection better than do random ones. Because axial flaps can be made longer, they can cover a larger primary defect. In addition, the flap tissue adjacent to the pedicle need not be applied to the defect, permitting much more freedom of movement of the part to which the flap is attached. This bridge segment between the primary and secondary defects may be sutured free edge to free edge, creating a tube that closes off all exposed subcutaneous tissue, or a so-called tubed pedicle flap . A further advantage of the axial-pattern flap is that the pedicle can be made much narrower, even to the point of reducing it to the (neuro)arteriovenous bundle itself, in which event it is called an island pedicle flap . This permits much more movement of the flap than is possible with a wide skin pedicle. Finally, with the advent of reliable microvascular technology, the pedicle can be divided and anastomosed to vessels adjacent to the primary defect, the so-called free flap .

The disadvantage of an axial-pattern flap is that its vascular pedicle must always be preserved at the time of elevation of the flap; at that first stage, it cannot be thinned to the same degree as a random-pattern flap that depends on the subdermal vessels. The vascular advantages of the axial flap are lost if the pedicle is divided in the process of thinning the flap. Indeed, in those instances in which skin from the bridge segment is to be used on an area adjacent to the primary defect, it is prudent to divide the artery in the pedicle 1 week before complete detachment. This constitutes a delay of sorts, as it promotes increased blood flow across the inset wound into the primary defect.

Staging of Flaps

Flaps that come from skin adjacent to the primary defect are called local flaps and require only one operative procedure for their completion. Flaps that come from elsewhere on the limb and commonly require two stages are called regional flaps . Those from other parts of the body are called distant flaps . With the exception of free flaps, all distant flaps require at least two stages for completion. In the first, the flap is raised and applied, attached, or inset. In the second, the pedicle is divided and the free margins inset. In certain instances in which the blood supply is doubtful after division of the pedicle, the final inset may be left until a third stage. This may be necessary if the most distant portion of the divided pedicle has questionable vascularity (as in a pedicled groin flap transfer).

Preparation of the Wound for Flap Transfer

The wound to which a flap is to be applied is called the primary defect , or recipient site . This may be simply the wound created by trauma or a wound created by excision of a lesion. However, the skin margins are rarely perfect in a traumatic injury, and generally the wound margins should be excised back to healthy skin prior to flap transfer. Similarly, it is important to recreate the original defect in secondary reconstruction and all scarred skin should be excised so that the flap will be sutured to healthy margins. A pattern of this final primary defect may be taken for future use. This is easily done by marking the margins with ink and taking an imprint of this with a pliable, nonporous material (e.g., a piece of Esmarch bandage), the surface of which has been moistened with alcohol. The wound from which the flap is taken is termed the secondary defect. The secondary defect may be closed directly, as in a groin flap, or may require application of a skin graft, as in a cross-finger flap. The region from which a skin graft is taken is called the donor site.

Raising a Flap

Between the vascular strata defined earlier—subdermis, subcutaneous tissue, fascia, and muscle—lie relatively avascular planes, the optimal planes of dissection. It is evident that, in order to attain these planes, it is necessary to cut through the vessels of the more superficial strata. Thus, in raising a fascial flap, one must first incise the subdermal and subcutaneous plexus and then the fascia. Only when the surgeon has cut through the peripheral ramifications of the vessels from which the flap obtains its blood supply is he or she in the correct plane. To be one plane too superficial results in division of the vessel, or branches of the vessel, supplying the flap. To be one plane too deep results in a time-consuming, often bloody, and entirely unnecessary struggle.

Applied tension plays a major role in flap dissection. Once the marginal incision has been carried down to the correct plane for dissection, skin hooks or stay sutures are applied to the corners of the flap. Firm upward traction away from the bed displays the plane for dissection. Often this contains only loose areolar tissue that can be stroked away with a knife. Care must be taken not to create a “cave” beneath the flap, that is, a central recess between two marginal pillars of unincised skin, muscle, or fascia. No tension can be applied to the tissues in such a cave, and dissection therein may result in damage to the pedicle. Rather, the marginal pillars are incised progressively in such a way as to avoid caves and permit tension to be applied evenly, thereby protecting the pedicle. Tension on a flap lifts the pedicle off the floor of the secondary defect, on which the knife is dissecting, into the roof formed by the inclined vascular stratum. If dissection proceeds far enough, a point will be reached where the pedicle emerges through the floor to gain the roof. At that point, the surgeon decides whether to proceed. To do so requires dissection of the pedicle. All progress thus far is best made with a scalpel. A scalpel is the instrument of choice both to incise the vascular strata and to dissect the planes, provided that appropriate tension can be applied to the tissues. Cutting with a knife is a result of two opposing forces: the pressure applied to the knife, and the resistance offered by the tissues. The traction applied to a flap produces, and varies, that resistance. It therefore plays a primary role in determining which tissue is cut and which is not. This is why the blade must always be equally sharp, and why the assistant who holds the flap must do so at the same tension first applied by the surgeon. If the assistant cannot do so, the surgeon must apply the necessary tension by grasping and lifting surrounding tissues with dissecting forceps as he or she proceeds.

Scissors provide both the pressure and the resistance required to cut tissue. They are required when the surgeon cannot efficiently control the relationship between tissue tension and knife pressure. When scissors are introduced closed into the tissues and then opened under gentle pressure to clear planes, they can be both precise and innocuous. They create and enter caves, defining structures to be preserved and those to be divided. When scissors are introduced open and then closed to cut, they are less precise than a knife and can do harm in the hands of even the most experienced surgeon. It is therefore important when using scissors that the surgeon sees both surfaces of the tissue to be divided so that he or she is confident what tissues are included between the jaws of the scissors. This often requires that closed-to-open scissor dissection proceed until the instrument can be seen through the tissue to be cut. Such scissor dissection is required as a vascular pedicle is mobilized. Although it has been shown that metal clips are not always secure and that bipolar coagulation may harm the pedicle, both are routinely used in dissecting the pedicle. The clips must be applied with sufficient force to ensure that they will not slip, and the vessel to be clipped should be placed in the middle of the clip, rather than the base (where the clip bends to come together). When dividing small vessels between surgical clips, it is likewise helpful to leave a small amount of tissue surrounding the vessels. This approach gives adequate tissue purchase for the clips so that they do not fall off. The setting on the control box of the coagulator must be of adequate temperature to allow coagulation and sealing of the vessel. The pedicle (i.e., the main vessel) is insulated by holding the branch with a smooth forceps between the pedicle and the point of coagulation.

Transposition Flaps

Random-Pattern Flaps

“Z”-Plasty.

The “Z”-plasty is one of the simplest forms of random flaps commonly used in hand surgery and is considered a “transposition” flap. The sides of a standard “Z”-plasty should always be of equal length, but the angles vary according to the needs of the situation and the local skin topography. The angles of the design may also differ. As the angles increase, so does the lengthening that occurs along the line of the central limb of the design when the flaps are transposed. The commonly used 60-degree “Z”-plasty theoretically results in 75% lengthening along the line of the central limb ( Figure 44.13 ). The skin that is introduced into the line of the central limb is derived from the transverse axis of that line. Said another way, skin must be available lateral to the central limb before a “Z”-plasty can be used. If sufficient skin is not present for one large “Z”-plasty, multiple “Z”-plasties can be used in series, for the longitudinal gain is aggregate, whereas the transverse loss is not. The following are important points in technique:

• 1.
  

  The angles and limbs should be measured with a ruler and a protractor. When this is not done, mistakes are made, the most common being to cut the angles at 45 degrees when believing them to be 60 degrees.

  
  
• 2.
  

  The incisions of the “Z”-plasty should be cut and tested in sequence ( Figure 44.14 ).

  
  

  
  

  
  

  

  
  

  
  

  “ Z”-plasty performed for scar contracture at base of finger. A, Markings for transposition flaps. B, Flaps after incision. C, With extension of finger, flaps automatically rotate into the defects created. With a properly designed “Z”-plasty, this should always happen.

  
  

Standard 60-degree “Z”-plasty. Here all limbs of the “Z”-plasty are of equal length, and the angles between the limbs are 60 degrees. When the flaps are transposed, the lengthening that is achieved along the line of the central limb is 70 to 75% of its original length.

First, the central limb and one side limb are incised. The flap created is raised and carried across the central limb with a skin hook. If the side limb cut on the flap can be brought by at least half its length across the central limb, there is sufficient tissue transversely, and the design has been well chosen. If it goes further, a larger “Z”-plasty will work if more lengthening is required. Such a larger design can be made simply by lengthening both initial cuts and testing again. If this first flap can be carried less than halfway across the central limb, the design is too ambitious and must be modified. Because only two limbs have been cut, this modification can be done relatively easily by shortening both the proposed central limb and the as yet uncut second side limb. The excessively long first side limb is simply shortened with one or two stitches.

Critical Points

“Z”-Plasty

Indications

• •
  

  Scar contracture, especially on volar surface of fingers

  
  
• •
  

  Minimal web space contracture

Preoperative Evaluation

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  Must examine surrounding skin for elasticity and scars

  
  
• •
  

  Generally should not “Z”-plasty grafted skin

Pearls

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  Central limb of “Z” goes along line of scar

  
  
• •
  

  Lateral limbs should be designed in areas with loose skin

  
  
• •
  

  Limbs should be 60 degrees to central limb; the tendency is to make them 45 degrees

  
  
• •
  

  Avoid sewing the flaps back where they came from

Technical Points

• •
  

  Central tight scar should be excised

  
  
• •
  

  Tips of small flaps should not be grasped with forceps

  
  
• •
  

  Base of flap should be thicker than tip when elevating

  
  
• •
  

  Cut only enough skin so that flap will transpose without tension

  
  
• •
  

  Avoid placing sutures in midportion of flap

  
  
• •
  

  Tip suture (half-buried horizontal mattress suture) for tip of flaps

  
  
• •
  

  Only enough sutures to hold flaps in place

Pitfalls

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  Poor design

  
  
• •
  

  Flaps with scar at base

  
  
• •
  

  Undermining base of flap so that it is thinner than tip

  
  
• •
  

  Suturing flaps under too much tension

Postoperative Care

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  If flaps fit easily, immobilization may not be necessary

  
  
• •
  

  Massage and stretching when healed

Advancement Flaps

A simple advancement flap for use in thumb tip amputation was described by Moberg ( Figure 44.23 ), which in fact is a bipedicled flap (based on the two neurovascular bundles of the thumb). This is reserved for amputations through the distal phalanx, because flexion of the interphalangeal joint may be required to assist in closure of the defect. The two parallel incisions to create the flap are made just dorsal to the two neurovascular bundles of the thumb, which are carefully preserved throughout dissection. The flap is elevated from the flexor tendon sheath. Because the bundles are included in the flap, there is theoretically no limit to the length of the flap, but customarily the base is placed at the MP joint skin flexion crease. It is usually best to design the base of the flap with a “V”-shaped incision, which allows the flap to be advanced further and may be closed as a “V-Y” advancement flap ( Figure 44.24 ). Alternatively, a full-thickness graft may be applied to the secondary defect overlying the neurovascular bundles and tendon sheath. This advancement is usually safe in the thumb, for the dorsum is well perfused by dorsal branches from the radial artery. If the base of the flap is too proximal, however, necrosis of a portion of the distal thumb skin can occur. The dorsal neurovascular branches of the digital vessels should be preserved on one or both sides of the flap, which will obviate any vascular problems of the distal dorsal skin. This will decrease the length that the flap can be advanced, however.

Moberg advancement flap. A, Most useful for amputations distal to the thumb interphalangeal joint, the Moberg advancement flap is composed of the entire palmar skin of the thumb, including the neurovascular bundles. B, Flexion of the interphalangeal joint assists in coverage of the defect by the advancement flap.

(Modified from Lister GD: The theory of the transposition flap and its practical application in the hand. Clin Plast Surg 8:115–128, 1981.)

A, Thumb amputation in patient with Moberg advancement flap marked out; note proximal “V” incision for advancement. B, Flap after dissection. Several dorsal branches have been left intact to help avoid necrosis of the dorsal skin. C, Flap healed.

A similar procedure has been reported in the finger, but greater care must be exercised here, or loss of the dorsal skin may result. Macht and Watson reported 69 cases with no skin necrosis in either the palmar or dorsal region, two-point discrimination within 2 mm of normal, and a maximum flexion deficit of 5 degrees. However, they emphasized the importance of maintaining the dorsal branches of the proper digital arteries as noted above. Likewise, the risk of flexion contracture after a volar advancement in the finger is much higher than in the thumb and probably not worth the risk.

“V-Y” Advancement Flap.

Commonly used to repair fingertip amputations, the “V-Y” advancement may be a single midline (Atasoy ) or double lateral (Kutler ) element. Which one is used, and whether the technique is appropriate at all, is determined by examining the primary defect. It should be stated from the outset that the great majority of fingertip amputations are best managed by allowing secondary healing to occur. Even if a small portion of the bone is exposed, it can be trimmed back, and wound contracture will close the wound. Allowing secondary healing and wound contraction pulls normal pulp skin into the defect, and is usually superior to a badly scarred tip resulting from ill-advised local flaps. If more tissue has been lost from the palmar than from the dorsal surface, a local palmar flap is unlikely to provide the necessary cover, and a cross-finger or thenar flap may be required. If the loss is equal, or greater on the dorsal aspect, a “V-Y” flap can be used, provided the skin from which it comes is not also damaged.

Suitability for coverage with local flaps is determined by looking at the angle of amputation. Amputations that are transverse (A) or have more dorsal loss (B) can be treated by local flaps. Where the loss is more palmar (C) , palmar flaps have been described (see text) but regional flaps are more reliable.

(Modified from Lister GD: The theory of the transposition flap and its practical application in the hand. Clin Plast Surg 8:115–128, 1981.)

There are three facts to remember if a “V-Y” flap is to be raised successfully. First, more problems arise through inadequate mobilization than excessive mobilization; the flap should advance easily into position ( Figure 44.26 ). Second, only nerves and vessels need be kept intact. Third, the nerves and vessels in the pulp are slender and elastic and will not resist appreciably the movement of the flap; a corollary of this rule is that any tissue that does offer firm resistance can be divided with impunity. The apex of the “V” in a single midline advancement for most fingertip amputations worthy of reconstruction (i.e., at or distal to the midportion of the nail) should be at the distal digital crease. In the rare case in which length is deemed sufficiently important to justify a “V-Y” advancement in more proximal amputations, the apex can be placed more proximally. The base of the triangle, which lies on the free distal margin, should be as wide as the nail bed but no wider, or the tip will have a flattened appearance. The incisions are made through the skin with a knife, carrying it to bone at either end of the base, where there are periosteal attachments but no vessels. These periosteal attachments should be divided. The deep surface of the flap is freed completely from the underlying tendon sheath as far as its apex. The skin and subcutaneous tissue some 6 or 7 mm on either aspect of the apex are incised down to the sheath. With skin hooks on one lateral margin of the flap distracting the flap away from the digit, the lateral subcutaneous tissues that contain the pedicle of the flap are spread apart with microscissors. Using loupe magnification, any restraining bands are accurately defined and divided, remembering that nerves and vessels will not resist gentle traction.

A, Patient after release of scarred fingertip and nail. “V-Y” (Atasoy) flap marked to correct hook-nail. B, View of neurovascular pedicle. All tissues except the neurovascular bundles are released. C, Flap advanced. D, Flap after advancement and suturing. E, View 3 months following operation.

(An anatomic point should be made here. The veins that accompany the artery of the digital neurovascular bundle are at different levels and of differing, smaller calibers. Therefore, in dissecting a neurovascular bundle for any form of island flap in the digit, no attempt should ever be made to define the artery and nerve independently, for such skeletonization will serve only to damage the veins and thereby seriously impair flap venous drainage.)

The flap should advance easily into place (see Figure 44.26 ). If it does not, and firm resistance is encountered, one of the fibrous septa must still be intact and must be divided. This process is repeated until the flap moves easily. If the distal end of the flap fails to easily reach the nailbed, it is better to place a small split-thickness skin graft over the raw distal edge of the flap rather than close it too tightly. Closure of the flap is begun at the apex, creating the vertical stem of the “Y” and so advancing the flap. The flap can be inset with the tourniquet inflated, and upon completion and after tourniquet release, color usually returns to the flap. If it does not, time and warmth in the form of hot packs should be permitted to play their valuable role for 20 timed minutes. If there is still inadequate flow, the most distal suture(s) in the vertical limb of the “Y” should be released, which usually produces the desired effect.

The lateral or Kutler “V-Y” advancement flap ( Figure 44.27 ) is raised in identical fashion to the midline “V-Y,” with the exception that there is only one neurovascular bundle to be protected in each flap. These flaps tend to lead to a scarred fingertip, however. “V-Y” flaps need not be based on a single known pedicle such as the proper digital artery and nerve. They can be raised on a pedicle of subcutaneous tissue, relying on random vessels contained therein. In such flaps, the pedicle is made as wide as possible. Such “V-Y” flaps have been described for closure of defects and release of contractures. The use of lateral “V-Y” flaps should be limited, however, as they lead to significant scarring of the fingertip and are rarely indicated in clinical practice.

Kutler double lateral “V-Y” advancements. A, The advancement flaps are designed over the neurovascular pedicles and carried right down to bone (B) . The fibrous septa are defined and (C) divided, permitting free mobilization (D) on the neurovascular pedicles alone. The flaps then advance readily to the midline (E) .

(From the Christine Kleinert Institute for Hand and Microsurgery, Inc., with permission.)

Random-Pattern Regional Flaps

The cross-finger and thenar flaps are random-pattern regional flaps. Both are used in the repair of fingertip defects, in particular, those with bone exposed and with more loss of palmar tissue than dorsal tissue. Although the cross-finger flap continues to be used at time, the thenar flap has largely been abandoned in recent years due to problems with flexion contracture of the recipient finger. Fingertip tissue loss is much better managed with secondary healing or a digital artery island flap as described previously.

Cross-Finger Flap.

Although the cross-finger flap has several variants that are outlined later, the basic design is for loss of palmar digital tissue and is fashioned on the dorsal aspect of the middle phalanx of the adjacent finger ( Figure 44.28 ). For pulp loss, the middle finger is used for the index finger, but otherwise, the donor finger is the finger radial to the injured one. Flaps to and from the thumb are discussed later. The cross-finger flap can be tailored to fit a pattern of the primary defect. The margin of the defect that is adjacent to the donor finger is designated “the hinge.” It corresponds closely to the base of the flap, which is also called a hinge. It is similar to the pivot point of transposition flaps, in that it is a fixed reference around which tissues move. It differs in that it is a line rather than a point. A pattern of the primary defect is made and turned through 180 degrees around the hinge and applied to the dorsum of the donor finger. By adjusting the position of the hinge, the necessary flap can be derived entirely from the skin of the dorsum of the middle phalanx. The flap to be raised is outlined to include not only the necessary flap but also all the skin of the dorsum of the middle phalanx, from midlateral line to midlateral line and from the proximal extension crease of the DIP joint to the distal extension crease of the PIP joint. In marking the hinge, one should recall that in all random-pattern flaps, the direction that they face can be altered by extension cuts. Thus, in the cross-finger flap, a proximal transverse incision that extends more palmarly than the distal transverse incision will cause the deep surface of the flap to face proximally; one in which the distal cut extends more palmarly will face distally. The former is more often required, causing the flap to fit well to an amputation stump. The latter is needed only in longer, more palmar defects when considerable flexion of the injured finger is necessary.

Cross-finger flap. The flap is raised from the dorsal middle phalanx of the adjacent finger. In this case, a skin graft is tacked to the side of the defect on the finger first, but this is used to close the donor defect. The flap is then sewn in place.

(From the Christine Kleinert Institute for Hand and Microsurgery, Inc., with permission.)

The flap margins are incised. Immediately beneath the skin, multiple longitudinal veins are encountered. These are coagulated and cut in order to reach the correct plane, which lies immediately superficial to the extensor tendon. Once the veins are divided, the flap is raised with ease, because only loose areolar tissue lies in the plane of dissection. The flap is hinged away from the donor site and applied to the primary defect to check the fit. If the pedicle is kinked to reach the defect, this can often be eliminated by extending either the proximal or distal transverse cut of the flap. When the flap does not fold easily away from the donor finger, the Cleland ligament may be restraining it. The ligament can be incised to permit easier folding of the flap. The vessels to the flap penetrate the more superficial part of the ligament and may be damaged unless care is taken to incise it at its depth, against the skeleton.

Once the flap has been raised satisfactorily, a pattern of the full-thickness graft required for the secondary defect is taken. The tourniquet is released at this juncture, and hemostasis is achieved. During this process, the full-thickness graft to cover the secondary defect is obtained. This is commonly taken from the same limb, usually the inner aspect of the upper forearm or arm. This practice is unacceptable in all except perhaps an older working man in whom scars may be of little consequence. In a young patient and, especially, female patient, the infliction of a wound in any of these sites is to be condemned. Rather, the grafts should be taken from over the iliac crest. Skin taken from the groin crease tends to be much darker than the skin on the hand and should be avoided, but skin over the anterior superior iliac spine is generally hairless and a more acceptable color match.

As in all flaps, it is desirable to close all raw surfaces. When one considers the hinge of the cross-finger design, the only free edge to which the skin graft can be sutured is the hinge margin of the primary defect, which is inaccessible after the flap has been sutured in place, lying as it does between the fingers. To overcome this difficulty, the skin graft is first laid on the primary defect, as if it were intended to use it to cover the primary wound rather than the flap already raised. The graft is sutured to the hinge margin of the primary defect. It will be appreciated that there are now two “flaps,” the cross-finger and the graft, with contiguous hinges. If both are swung 180 degrees around their hinges, the flap will come to lie on the primary defect and the graft on the secondary defect. One last time, the positioning of the flap is checked. If the flap has been well chosen, any kinks can be eliminated by lengthening the extension cut. The flap can now be inset and sutured into position, trimming as necessary. The skin graft is sutured to the secondary defect. The circulation to the flap should be good, although a little blanching around the margins is common and acceptable. If the flap appears very pale and has been designed and raised correctly, it may be that the recipient finger is extending, thereby exerting undue pressure on the flap and its pedicle. This can be overcome by flexing the recipient finger until circulation returns and then maintaining the position by inserting a suture or Kirschner wire between the fingers, usually transfixing the middle phalanx of the injured finger and the proximal phalanx of the donor. This is rarely necessary.

Axial-Pattern Regional Flaps

Regional flaps applicable to the upper extremity that have a known pedicle are the neurovascular island flap, the fillet flap, and those axial cutaneous, fasciocutaneous, and musculocutaneous flaps that may be used in the upper extremity.

Neurovascular Island Flap.

The neurovascular island flap ( Littler flap ) has been used historically for reconstruction of the thumb pulp to provide stable and sensate coverage for loss of a significant portion of the touch surface of the thumb. It is described generally as using the ulnar side of the ring finger transferred as a neurovascular island flap to the thumb ( Figure 44.29 ). One has to be sure that the contralateral digital artery is patent to avoid ischemia of the donor finger ( Figure 44.30 ). Although the neurovascular island pedicle flap should be in every hand surgeon’s armamentarium, it has little application today. Most significant thumb defects can be managed by other local or regional flaps or vascularized toe pulp transfers. These procedures avoid the donor site problems presented in the finger and provide adequate soft tissue reconstruction, with toe transfers offering the “best” reconstruction of the thumb with little in the way of donor site morbidity. Although one may argue that microvascular toe pulp transfer suffers from the need for microsurgical expertise, the successful dissection, rotation, and tunneling of a neurovascular island flap approaches the difficulty of a microsurgical tissue transfer. The reader is referred to previous editions of this chapter if a complete description of the dissection of this flap is desired.

A, Patient with loss of thumb pulp. B, View of neurovascular island flap after dissection of pedicle from ulnar side of ring finger into palm. C, Flap after passage under palmar skin to reconstruct thumb.

Neurovascular island flap: preliminary evaluation. It is necessary to ensure by Doppler studies that flow exists not only in the vessel that will supply the flap and in the vessel that will maintain the donor digit after the flap has been raised (left arrow) but also in the contralateral digital artery of the adjacent finger (right arrow) because the ipsilateral vessel will be divided (bar) in mobilizing the pedicle.

(From the Christine Kleinert Institute for Hand and Microsurgery, Inc., with permission.)

Fillet Flap.

Fillet flaps are developed from a well-vascularized digit that is otherwise worthless due to extensive injury to skeleton, nerves, or tendons and commonly to all three. The technique of filleting a finger requires that the skeleton and tendons be removed, preserving all other soft tissues on one or both vascular pedicles. Because the circumference of a finger at the free edge of the web is equal to the distance from the web to a point just proximal to the nail fold, a fillet flap as described here is roughly a square. The difficulties in planning to use such a flap are, first, determining whether or not it can reach the presenting primary defect, and second, incising it to ensure that it does. Measuring the distance from the web of the digit to be sacrificed to the nearest point of defect provides only a rough guide, particularly in the secondary situation in which scar in the soft tissues of the digit reduces their elasticity significantly.

In preparing to fillet a finger, the patency or occlusion of the two proper digital vessels is determined. With this knowledge, the surgeon then plans the longitudinal incision in the digit by visualizing how the flap will first open in a lateral direction and then fold over proximally into the defect. For example, if the middle finger is to be filleted for a defect on the dorsum of the hand, the incision in the finger should be on its radial aspect if that defect is predominantly to the ulnar side of the third metacarpal, on the ulnar aspect if the defect is on the radial side. A further consideration when middle or ring fingers are to be sacrificed is whether the adjacent ray (index or small finger, respectively) is to be transposed into the defect left by the ray ablation. If it is, then the fillet flap is best reduced to an island flap by appropriate excision of palmar skin. Although technically more demanding, this gives a more mobile flap and a more pleasing final result. Once these decisions have been made, the appropriate longitudinal incision is made down to the skeleton ( Figure 44.31 ). At its distal end, a circumferential incision is made around the finger at a point 5 mm proximal to the nail fold. This means discarding the pulp tissue, because its bulk makes it a rather unsatisfactory cover for its new location. At the proximal end of the longitudinal incision, its continuation depends on whether the metacarpal of the digit is to be resected and an adjacent digit transposed. If the metacarpal is not to be resected, a transverse incision is made over the dorsum of the finger so as to create a hinge along the side of the finger opposite the incision. All dorsal veins are ligated with the exception of the end of the proximal venous arcade that corresponds to the hinge. This single vein alone gives excellent venous drainage. If there is intention to transpose a digit, thereby making the fillet an island flap, the incision is again circumferential at the level of the proximal digital crease, that is, at the free margin of the web. A further incision is made in a zigzag manner proximally into the palm, through which the necessary neurovascular bundle is dissected. This is always done before the skeleton is removed, as dissection of supported tissues is easier. To remove the digital skeleton, skin hooks are applied to the margins of the longitudinal incision distally, and the soft tissues are peeled off the underlying extensor tendon, bone, and flexor tendon sheath. The deep branches and tributaries of the vessels are ligated as this is done. The flap can now be opened and folded onto the primary defect. The necessary movement of the flap is more readily obtained if the injury to the donor digit is fresh and if the fillet has been raised as an island. Now, for the first time, the surgeon can really judge whether the flap will fit the primary defect. If it is too small, other solutions must be added. If it is too large, but the defect is deep, the excess should not be discarded; rather, it should be deepithelialized and turned in to fill the depths of the wound. If the hole in the depths of the wound is caused by a segmental bony defect, a portion of phalanx can be taken as a vascularized bone graft with the fillet flap.

A, View of patient’s hand 1 year after gunshot wound through hand with loss of metacarpal length and soft tissue deficit. B, Palmar view; note first web space contracture. C, Middle finger being dissected for use as fillet flap for first web space release; skin has been dissected off of tendons and bones. D, View of skin with bone retracted out of the way. E, Thumb after release and rotation of fillet flap through the palm as an island flap. F, Donor site after resection of metacarpal and closure.

Axial Cutaneous Flap

The scapular flap, commonly used as a free flap, can reach the upper extremity as an island and can be used after the release of burn contractures of the axilla. This flap has some utility in reconstruction of the scarred axilla, but it suffers from the potential to be bulky when placed in this position. This can be obviated by making sure the fascia of the flap is tacked deep into the axilla and can also be improved by later thinning of the flap. The scapular flap will cover the superior shoulder as well if taken as a long “parascapular” flap. It has little value as a pedicle flap in coverage of the elbow and lower arm because the pedicle is not lengthy and the flap will not reach these areas. For a description of this flap, see Chapter 45 on free tissue transfer.

Fasciocutaneous Flap

Regional fasciocutaneous flaps have been described from the forearm to the periolecranon region and from the medial arm for release of axillary and elbow burn contractures. However, the major fasciocutaneous flaps of the upper extremity are the lateral arm flap; the radial artery forearm, or “Chinese,” flap; the ulnar artery flap; and the posterior interosseous artery flap. The lateral arm flap is primarily used as a free flap for hand coverage, but a small area of the elbow can be covered by a distally based flap ( Figure 44.32 ). This procedure may leave an unsightly scar and also lead to numbness in the proximal forearm. By contrast, the reversed radial artery flap, with its potential area of much of the forearm skin and a pedicle located at the anatomic snuffbox, is capable of covering almost any defect in the hand.

A, View of recurrent elbow wound in patient after radial forearm flap for coverage. B, Lateral arm flap dissected on distal vessels (radial recurrent). C, Flap after transposition from lateral arm to medial elbow. D, Flap healed at 6 months.

Radial Artery Forearm Flap

The radial forearm flap represents one of the best flaps for coverage of hand defects. Based on its distal pedicle, it can cover nearly any wound of the hand and can import a variety of tissues, including skin, fascia, tendon, and bone. It has been called a “reconstructive chameleon” because of its versatility. It can also be based proximally and used for elbow coverage. The two primary disadvantages of this flap are the necessity for harvesting the radial artery and the poor cosmesis of the donor site, particularly in younger patients. One study noted that the radial artery was the dominant vessel to the hand in 12%, and acute ischemia and cold intolerance have been reported. The absolute need for reconstruction of the radial artery after harvest is not known, although some have suggested that this may decrease the incidence of cold intolerance. In personal experience with several hundred radial forearm flaps (both pedicled and free), I have seen only two patients who required vein grafting of the radial artery who had a normal Allen test preoperatively. This experience is borne out by several studies, with one group noting that while flow to the hand was initially decreased, this improved over time to normal levels via the remaining circulation of the ulnar artery. Although functional problems are minimal, the cosmesis of the donor site remains problematic. The donor site usually requires skin grafting, and it remains ugly, particularly in younger patients. Proposals to improve cosmesis include suturing the superficialis muscle over the flexor carpi radialis tendon to improve skin graft “take” and various local flaps to avoid the need of a skin graft. In many instances, the cosmetic defect can be minimized by taking a fasciosubcutaneous flap only. This modification will be discussed below.

The radial artery ( Figure 44.33 ) pursues a relatively superficial course in the forearm from its source at the division of the brachial artery to the point where it passes deep to the tendon of the abductor pollicis longus to reach the anatomic snuffbox. In the proximal forearm, it lies on the superficial surface of the pronator teres, just beneath the anterior margin of the muscle belly of the brachioradialis. Leaving the pronator teres, it comes to lie in turn on the radial head of the flexor digitorum superficialis and the flexor pollicis longus, here being palpable through the skin. Throughout its course, the artery gives branches to a plexus of vessels in the overlying deep fascia, and this plexus supplies the skin of the anterior and radiodorsal surfaces of the forearm. By means of similar fascial branches it also supplies the periosteum of the distal half of the radius between the insertions of pronator teres and brachioradialis. This allows construction of osteocutaneous flaps if so desired. The artery is accompanied by two or more venae comitantes. The multiple anastomoses between these veins permit reversal of flow in the venae comitantes without valvular obstruction. Thus the artery and veins can be divided proximally, and no venous engorgement will result (valvulotomy has been described to enhance flow ). The minimal precaution that should be taken before raising a forearm flap is a timed Allen test to ensure that flow is present and adequate through both vessels. Conversely, a “dynamic” Doppler examination can be done with the arch identified with the Doppler pencil and flow through the ulnar artery confirmed by digital pressure on the radial artery at the wrist.

The course of the radial artery is superficial throughout much of the forearm, lying just beneath the margin of the brachioradialis on the pronator teres and the flexor digitorum superficialis. The cutaneous branches supply the overlying skin and nutrient branches of the radius.

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