Local Flaps § §
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A flap is a piece of tissue with a blood supply that can be used to cover a wound. A flap can be created from skin with its underlying subcutaneous tissue, fascia, or muscle, either individually or in some combination. Depending on the reconstructive requirements, even bone can be included in a flap. A local flap implies that the tissue is adjacent to the open wound in need of coverage, whereas in a distant flap, the tissue is brought from an area away from the open wound. Local flap coverage of a wound is the next higher rung up the reconstructive ladder after a skin graft. Examples of wounds that require flap coverage include wounds with exposed bone, tendon, or other vital structure and large wounds over a flexion crease, for which a split thickness skin graft or secondary closure would result in tight scarring. Donor site: where the flap originates. Recipient site: the open wound/soft tissue defect in need of coverage. Pedicle: the blood supply of the flap (i.e., its arterial inflow and venous outflow). The pedicle varies from a wide bridge of tissue (skin, subcutaneous tissue, muscle, or some combination) to an isolated artery and vein. Most local flaps can be classified as either (1) skin flaps, which are skin and subcutaneous tissue with or without the underlying fascia, or (2) muscle flaps, which are created from a muscle with or without the attached overlying skin.
Skin Flaps § A portion of skin and subcutaneous tissue and, when possible, the underlying fascia (the thin layer of connective tissue overlying muscle that has an excellent vascular supply) is moved to fill the defect. This movement of tissue results in a new defect at the donor site. Often the donor site can be closed primarily, but sometimes a skin graft is needed. Classification: Skin flaps are classified as either axial or random, based on the blood supply. Axial Flaps § The circulation of an axial flap is supplied by specific, identifiable blood vessels. Careful anatomic study has identified several donor sites with a single artery and vein responsible for circulation to a particular area of skin. Examples include the volar forearm skin supplied by the radial artery and skin on the back supplied by the circumflex scapular artery. § Circulation based on specific vessels results in a highly reliable blood supply and a reliable flap. You can be confident that unless there is an injury to the vessels, the majority of the flap tissue should survive in its new position. § An axial flap can be completely detached from all surrounding tissue as long as it remains connected to its supplying blood vessels. These vessels serve as the pedicle. The thin pedicle allows axial flaps to be easily positioned to fill the wound defect (unlike the random flap). § The difficulty with an axial flap is locating the blood vessels. You must be very careful not to injure the vessels when creating the flap. The necessary technical expertise is beyond the realm of most providers without reconstructive surgical training. Random Flaps § Circulation to a random flap is provided in a diffuse fashion through tiny vascular connections from the pedicle into the flap. The pedicle must be bulky to increase the number of vascular connections. The more vascular connections, the better the circulation to the flap. The better the circulation to the flap, the better its survival. § In general, a random flap does not have as reliable a blood supply as an axial flap. Nonetheless, the relative ease of creating random flaps makes them useful almost anywhere on the body.
Delay Procedure § The circulation and thus the reliability of the flap can be increased by “delaying” the flap before final transfer. § Before the flap is created, the tissue gets its blood supply via all of the surrounding skin and underlying tissue attachments. When the flap is created, the circulation to the flap comes only from the pedicle. § The purpose of the delay procedure is to enable the pedicle to assume its role as the main source of circulation before the flap is moved to its new position. This goal is obtained by making some of the incisions needed to create the flap but not separating the flap from the underlying tissues. The flap is not moved to its new position; instead, the skin edges are sutured together loosely. § The total blood supplied to the flap initially decreases when the incisions are made. This decrease promotes opening of new vascular channels between the pedicle and flap. Thus, more blood will flow into the flap through the pedicle than if the delay procedure had not been done. § Delaying the flap before final transfer allows more confidence in the viability of the flap. Wait about 7–10 days after the delay procedure before moving the flap to the recipient site. Local Flaps § Local flaps are an ideal solution in reconstruction because they have similar skin color and texture to the defect, the secondary defect can be closed primarily, and so local flaps often present less contracture with better functional and aesthetic result § Planning the flap is an important principle. The flap should be designed slightly longer than needed, as some length will be lost in the rotation process and slight redundancy may avoid kinking of the flap blood supply. The process is repeated, being certain each time the base is held in a fixed position and not allowed to shift with the flap. Measure twice, cut once. It is easier to trim a flap that is slightly long than to add to one that is too small. Skin Biomechanics § § §
Creep is time dependent plastic deformation of any material or tissue in response to constant stress. Stress relaxation occurs over a period of time when skin is stretched to a given constant length, and the force required to maintain it is gradually decreased. When a constant mechanical stress is applied to skin over time, two phenomena occur: mechanical creep and biological creep.
Mechanical creep is based on morphologic changes that occur on a cellular level in response to the applied stress—the cell is stretched. Biologic creep results from disruption of gap junctions and increased tissue surface area that initiates cell proliferation. Growth of the tissue by cell proliferation restores resting tension of the stretched tissue to baseline. The epidermis gets thicker with concurrent thinning of the dermis and alignment of collagen fibrils. These effects are maximized at 6 to 12 weeks post expansion.
Skin Blood Supply: Direct Cutaneous Vessels: § Contribute to the primary (dominant) cutaneous supply to the area and are particularly well developed in the limbs. They arise from the underlying source artery or from one of its muscle branches before they enter the muscle. They pass between the muscles and other deep structures in the intermuscular septa and rapidly reach and perforate the outer layer of the deep fascia, where their main destination is the skin. They are usually large and spaced well apart in the torso, head, neck, arms, and thighs, especially where the skin is mobile. § Direct cutaneous vessels follow the connective tissue framework of the deep tissue to the skin. They pass between the muscles and tendons, sometimes closely related to true intermuscular septa, as septocutaneous vessels.
Indirect Cutaneous Vessels: § Arise from the source arteries and penetrate the deep tissues, usually muscle, vertically or obliquely before piercing the outer layer of the deep fascia They can be quite large, contribute to the primary dominant) blood supply to the skin § Alternatively, they may emerge as small, “spent” terminal branches to provide the secondary (supplementary) supply to the skin. § These are small vessels, often quite numerous, which emerge as terminal twigs of vessels whose predominant supply is to the various deep tissues, especially the muscles.
Technique of Flap Transfer §
Local skin flaps are of two types: flaps that rotate about a pivot point (rotation, transposition, and interpolation flaps) and advancement flaps (single-pedicle advancement, V-Y advancement, Y-V advancement, and bipedicle advancement flaps).
Rotation flap: is a semicircular flap of skin and subcutaneous tissue that rotates about a pivot point into the defect to be closed. The donor site can be closed by a skin graft or by direct suture of the wound. §
A flap that is too tight along its radius can be released by making a short back-cut from the pivot point along the base of the flap. Because this back-cut decreases the blood supply to the flap, its use requires some degree of caution. With some flaps it is possible to back-cut only the tissue responsible for the tension, without reducing the blood supply to the flap.
Transposition flap: is a rectangle or square of skin and subcutaneous tissue that also is rotated about a pivot point into an immediately adjacent defect. This necessitates that the end of the flap adjacent to the defect be designated to extend beyond it. As the flap is rotated, with the line of greatest tension as the radius of the rotation arc, the advancing tip of the flap will be sufficiently long. The flap donor site is closed by skin grafting, direct suture of the wound, or a secondary flap from the most lax skin at right angles to the primary flap Rhomboid flap (1200; 600 )
Bilobed: Double transposition flaps § 90 degree arcs § Final 180 degree arc
Z plasty : Two triangular flaps (600; 600; 600;) § Reorients scar; Breaks up scar; Lengthens scar
Advancement flap: is slid directly forward into a defect simply by stretching the skin, without any rotation or lateral movement. The simplest example of this type of movement is direct wound closure. Variations are the single- and double pedicle advancement, V-Y advancement, and its opposite, the Y-V advancement flap. Unipedicle (utilizing Burowʼs triangles)
A-T (bilateral advancement for triangular defect)
Suggested Reading: Thorne, C. (2007) Techniques and principles in Plastic Surgery. In: Thorne C, et al: Grabb and Smithʼs Plastic Surgery, 6th ed (pp. 3-14). Philadelphia: Lippincott Williams & Wilkins. Park G. Local Cutaneous Flaps. Facial Plastic Surgery Clinics of North America. (2005) Baker S. Local Flaps in Facial Reconstruction 2nd ed. Mosby. (2007)