The dermatologic surgeon is regularly faced with the challenge of repairing a tissue defect caused by the surgical removal of a lesion. Less frequently, such defects may be encountered following local trauma or tissue necrosis. The range of options for repairing such defects may be reduced conceptually to a few choices: natural healing by secondary intention; direct side to side closure; placement of a skin graft; or mobilization and movement of adjacent tissue. This article will focus on the mobilization and movement of adjacent tissue, namely the planning and creation of local skin flaps.

A flap has been defined as “a tongue or lip of tissue, cut away from the underlying parts but attached at one end; used …for filling a defect in a neighboring region …”<sup>15 Stedman's Medical Dictionary  Baltimore: Williams & Wilkins (1961).  590

Cliccare qui per andare alla sezione Riferimenti</sup> The critical element in differentiating a flap from a skin graft is that the flap retains its connection with its blood supply (nutrition and oxygenation) as it is moved. A graft has its blood supply severed, and to achieve long-term viability it must establish a new secondary vascularization.

Certain large flaps are carefully constructed along a major defined arterial vessel, so that their viability will be guaranteed. These are referred to as axial flaps and may be created in one anatomic region and transferred relatively great distances to defects in other regions. Likewise, free flaps may be harvested from one region and moved to another without maintaining the original blood supply; they differ from grafts in that the surgeon reestablishes a vascular connection at the new site at the time of surgery. Both of these flap types are normally outside the scope of dermatologic surgery.

Local flaps, which have become such a major part of the dermatologic surgeon's practice, are not based upon large named vessels. They are composed of immediately adjacent tissue, which carries with it a random blood supply via arterioles, capillaries, and venules. Such flaps usually have the advantage of providing coverage of the defect with tissue that very closely resembles the missing skin in color, texture, and appendageal characteristics. However, the lack of a defined blood supply limits the size of the flap, particularly in terms of its length. Local (random) flaps normally must have no greater than a 3:1 length to width ratio to insure survival; constructing ones with greater lengths significantly raises the chance of flap necrosis at the distal end.

The planning and creation of such flaps may be among the most stimulating and rewarding of dermatologic surgical procedures. Tissue adjacent to the defect must be identified which is capable of being partially freed and then moved into the defect by advancement, rotation, or transposition. The tissue to be transferred is not only chosen for its similarities to the missing tissue, but it must be selected for its elasticity, and for its ability to be moved without creating an unacceptable level of tension on local structures. It must also be able to be moved into place without obliterating critical anatomic lines or borders that are essential for normal appearance and function. Very importantly, the flap must be planned in such a way that the secondary defect, which the surgeon creates as the tissue is transferred into the primary defect, can be closed satisfactorily.

The remainder of this article will present the major types of local flaps commonly used in dermatologic surgery. These will be demonstrated using annotated clinical photographs and with a minimum of complex geometric diagrams and theories. This brevity in regard to theory is intentional, as the authors believe that this topic has been subjected to an excessive amount of mathematical analysis and commentary, often leading to confusion and anxiety on the part of those trying to learn such procedures. Much of this dogma has arisen from surgical perspectives in which both the defect and the repair are preplanned and executed together. However, in many dermatologic settings (e.g., Mohs surgery) the defect arises first without any preconception of the subsequent repair procedure (and rarely conforms to a standard geometric shape). Furthermore, the value of a highly geometric approach to planning local flaps also seems questionable because living cutaneous tissue is not static and rigid, as are inanimate templates. Rather, it is elastic and malleable, allowing the surgeon to improvise and constantly adjust as the repair procedure progresses from planning to completion. One's hands must never be “tied” by some absolute and abstract geometric figure to which the repair must conform. Instead the surgeon should develop a sense of the local tissue environment both visually and tactilely. From that integrative approach will come the optimal flap closure.