ROTATION FLAP DESIGN: BASIC PRINCIPLES

The classic rotation flap incorporates a triangulated defect and a smooth curvilinear flap sweep. Like all flaps, rotation flaps are hindered in their movements by the inherent stiffness of the tissue at the flaps’ pivot points. Because of this pivotal restraint, even with proper flap sizing, the tip of the rotation flap will not extend to the distal margin of the operative defect unless the tip of the flap is also advanced under some tension. That is, if the flap is elevated and the primary defect is closed under no tension, the tip of the rotation falls short of the distal extent of the operative wound. In order to close the entire primary wound and also the secondary defect, it is necessary to advance the flap tip and the curve of the flap in order to close the secondary operative wound (Figure 5.1). If the surrounding tissue is mobile, this secondary motion must be considered in order to avoid unwanted displacement of adjacent structures. If the surrounding tissue is immobile, tension must be placed on the flap tip in order to achieve closure. In order to minimize tension on the flap tip and eliminate the need for undesirable secondary motion around the operative defect, the arc of the rotation can be oversized and offset so that the arc of the flap extends vertically beyond the distal extent of the operative defect.^2,3 The radius of the flap must be large enough so that the on rotation, the leading edge of the flap extends beyond the distal edge of the defect. The reason for extending the flap tip is to reduce tension and enable the flap to rotate into place without forcibly advancing the tip. This prevents undesirable tension and possible tissue ischemia at the flap’s most vulnerable point, its tip. When the flap’s rotation is subsequently executed, the extended tip of the flap then rests without tension where it meets the distant point of the primary defect (Figure 5.2). This concept has been previously eloquently reviewed, and the concept of extending the rotation arc beyond the end of an operative wound has been firmly entrenched in the reconstructive literature.

Figure 5.1 Classic rotation flap. As primary defect is closed, a secondary defect develops. Secondary flap movement closes this defect. When the tip of a rotation flap is created as a simple arc taken off of a round defect (a), the flap will “fall short” and fail to meet the superior edge of the primary defect (b). The flap’s leading edge will only meet the far edge of an operative wound if the flap tip is also advanced in a secondary motion (c). Note also that flap rotation typically produces a dog-ear redundancy at the flap’s pivot point (d). The dog-ear must be excised to achieve proper flap contour (e).

Figure 5.2 Lengthening the leading edge of the rotation arc (a) overcomes pivotal restraint and minimizes secondary flap motion. Note the lack of need to rely on tissue advancement around the primary defect with the extended leading edge design of this rotation flap (b).

A rotation flap can frequently be closed without undermining beneath the point of pivotal restraint; however, for optimal flap motion, this area of restraint should be undermined (Figure 5.3). This is particularly important with the dorsal nasal flap, where maximal rotation is required to close a defect located in the inelastic skin of the distal nose. Proper undermining of the pivot point accomplishes the release of deep restraint and usually allows substantial motion of the flap. This undermining is not without some risk, as too much undermining may interfere with deep vascular perforators. However, the reduction in tension on the flap tip usually more than compensates for any diminishment in pedicle vascularity.

Figure 5.3 For optimal flap mobilization the base of a rotation flap is undermined (shaded areas) to eliminate pivotal restraint.

Occasionally, a back cut into the rotation flap’s body can improve flap mobility, particularly on relatively immobile skin such as on the scalp.⁴ A back cut frees both deep and lateral restraint and can prove valuable in reducing closure tension, but a back cut also has the potential to compromise the vascular supply of the flap’s pedicle. The more ample the residual vascular input, the more extensive of a back cut may be created. If, as in the case of the dorsal nasal flap, the remaining pedicle contains large caliber axial vessels, the width of the pedicle may be safely narrowed and a substantial back cut will be tolerated. The defect from a back cut is usually closed with a V-to-Y repair, trimming excess tissue from the apex of the flap as indicated. Alternately, as in the original Reiger flap, the apex may be closed with a Z-plasty.⁸

Flap curvature

Most rotation flaps are designed with an arc that transects about one quarter of a circle. Such a flap design reliably redistributes tension vectors along the secondary operative defect. Rotation is limited by the surface restraint of the pivot point. The greater the curvature of a flap, the greater degree of rotation can be accomplished. Similar to a back cut, a greater curvature actually cuts into the pedicle and permits greater freedom of movement by freeing pivotal restraint. However, too great of an arc of rotation will actually redirect tension “backward” and may negate the decrease in tension that the rotation flap was supposed to accomplish (Figure 5.4).

Figure 5.4 A greater arc of rotation narrows the rotation flap’s pedicle and increases mobility (a). Note also that greater flap length minimizes the relative width of the secondary defect at any point along the flap’s arc. Rotation arcs greater than 90° redirect tension in unwanted “backward” directions (b).

Because rotation flaps require long incision lines to achieve appropriate flap motion, in many facial locations, there are often other flap repairs that are more palatable. Rotation flaps have their greatest utility in the closure of scalp, temple, and cheek defects. In select cases, rotation flaps are also quite valuable on the nose. On the scalp, a lack of adjacent skin mobility requires rotation flaps to be especially long in order to close even small to moderate-sized operative wounds. On the cheek, rotation flaps are particularly useful for the repair of medially located wounds, because the rotation flap can effectively mobilize the large reservoir of loose skin in the entire area of the lateral cheek.⁶ Infraorbital wounds can be closed with rotation flaps that recruit substantial laxity from the temple. Because rotation flaps tend to be rather “short” flaps when the distance from the flap base to the tip is considered, their vascular supply is quite predictable, and ischemic failures of the flaps are very uncommon if the flaps are handled gently and closed under minimal tension.

BILATERAL ROTATION FLAPS

Bilateral or dual rotation flaps utilize rotation from two sides of an operative defect to allow for wound closure where motion from one side would either be inadequate to close the wound or where symmetry of the repair is desired for enhanced cosmesis. Bilateral rotation flaps are most useful for large forehead wounds where a bicoronal incision is utilized (Figure 5.5) or for chin defects where the arc of the bilateral rotation lies within the mental crease.

Figure 5.5 Bilateral forehead/scalp rotation flaps for a large operative wound resulting from Mohs surgery for advanced basal cell carcinoma (a). Note that the flaps’ rotation arcs extend beyond the upper pole of the operative wound (b). The flaps are widely undermined (c), and a dog-ear redundancy is removed inferiorly (d).

SELECTED ROTATION FLAPS