ROTATION FLAPS

INTRODUCTION

Rotation flaps are pivotal flaps with a curvilinear configuration. By necessity they must be designed immediately adjacent to the defect. Thus a border of the defect becomes the advancing border of the skin flap. Although useful in many clinical situations, the configuration of rotation flaps creates curved incisions that frequently do not lie completely in relaxed skin tension lines (RSTLs). As with all pivotal flaps, rotation flaps develop standing cutaneous deformities (SCDs) at the base of the flap that cannot be easily removed without compromising the vascularity of the flap. Most rotation flaps have a random pattern blood supply; however, depending on the position of the base of the flap, they may on occasion be axial by incorporating the underlying fascia or musculature into the pedicle of the flap, which may contain an axial artery. Regardless of whether their blood supply is random or axial, rotation flaps are broad-based with a favorable length-to-width ratio and their vascularity tends to be reliable.

Although rotation flaps are pivotal flaps in their movement, most are also advanced by stretching the flap. Depending on the degree of stretching, the vector of greatest wound closure tension may be along a line extending from the base to the apex of the distal flap. When no advancement is used in movement of rotation flaps, the greatest wound closure tension is perpendicular across the peripheral border of the flap, not across the leading border of the flap. ^,

Studies by Larrabee, Jr and Galt have demonstrated minimal further reduction of skin tension at the defect site by extending the arc of rotation flaps beyond 90° from the axis of the defect. This is to say, wound closure tension is not reduced at the defect site by increasing the pivotal movement of the flap by more than 90° from the axis of the defect. Nevertheless, there is often some benefit in extending the incision to accommodate redraping of skin.

The secondary defect created by rotation flaps represents a transformation and a translocation of the primary defect. The surface area encompassed by the primary defect is equivalent to the surface area of the secondary defect. The geometry of the secondary defect is determined by the size of the flap. The larger the flap, the longer and narrower the secondary defect. The narrower the width of the secondary defect, the less tension required to close the wound and the less secondary movement of tissue adjacent to the donor site. Another way of stating this is that the greater the length of the arc and thus the larger the flap, the less wound closure tension across the repair of the secondary defect.

Rotation flaps are best suited for the repair of defects that are triangular in shape. Design of the classic rotation flap is seen in Fig. 7.1 . An SCD will develop at the base of the flap. A Burow’s triangle can be removed to facilitate repair of the donor site wound. A back cut at the base of the flap shifts the position of the pivotal point and changes the location of the SCD. When a rotation flap is converted to a two-dimensional form, it appears as in Fig. 7.2 . As can be seen in the figure, a problem encountered with rotation flaps is the unequal length of the flap’s border labeled B in the drawing compared with the width of the primary and secondary defects labeled A in the drawing. A common method to equalize this discrepancy is to excise an equalizing Burow’s triangle at some point along the periphery of the curvilinear incision. The triangles’ base is equal in width to the width of the base of the defect labeled C in Fig. 7.2 . Closure of the triangular defect resulting from the excision results in equalizing the length of the two sides of the incision. An alternative solution to the management of the discrepancy in length of wound margins is to modify the movement of the flap from one that is purely pivotal to one that is both pivotal and advancement. By advancing the flap while at the same time rotating it around its pivotal point, the flap is stretched to equalize the discrepancy ( Fig. 7.3 ). In so doing, the surgeon takes advantage of the distensibility ( Fig. 7.4 , side B) and the compressibility (see Fig. 7.4 , side A) of the skin along the wound margins. Repair is then accomplished by using the principle of halving by suturing on the bias (see Fig. 7.4, C, D ). This is accomplished by placing a suture to appose the two borders of the wound at the halfway point along the length of the flap. Succeeding sutures are placed in a manner that continues to equally divide the remaining distances along the flap’s border. An experienced surgeon will learn to suture on the bias from one end of the flap to the other without resorting to planned halving sutures.

As a general rule, when designing rotation flaps on the face, the length of the flap (see Fig. 7.2 , side B) should be four times the width of the base of the triangular defect (see Fig. 7.2 , side C). When this ratio is used, excision of an equalizing Burow’s triangle is usually not required. Undermining the base of the flap along with its pivotal point enables advancement of the flap toward the defect during wound closure. Advancement reduces wound closure tension and often necessitates a smaller flap with less movement about its pivotal point than when the flap’s pedicle is not widely undermined and advanced. In addition to reducing the overall size of the flap, undermining limits the development of an SCD by advancing a portion of the deformity peripherally away from the flap’s base.

Increasing the degree of undermining of the flap without lengthening the border of the flap does not significantly decrease wound closure tension. Likewise, enlarging the flap beyond the length of four times the width of the defect does not significantly decrease wound closure tension. When using a single flap for wound repair, the arc of the flap may be adjusted depending on a number of considerations. For instance, the arc of the flap may be shortened to maintain the incision along or inside hair-bearing tissue. The arc may be extended more than four times the width of the defect when the defect is located in areas of limited skin mobility.

To avoid an SCD at the base of a rotation flap used to repair a defect, the defect should ideally assume the configuration of an inverted triangle. The triangle should have the proportions of 2:1, height-to-width ( Fig. 7.5 ). In addition, if the arc of rotation of the flap is to be a completely symmetric curve, the height of the triangular defect should be 0.05 to 1 times the radius of the curve of the flap ( Fig. 7.6 ). To create the ideal condition for use of a rotation flap, the defect can be enlarged by removing normal tissue and converting the defect into a triangle with a height-to-width ratio of 2:1 ( Fig. 7.7 ).

There are several advantages of using rotation flaps. The flap has only two sides; as a result the surgeon can sometimes position the arced incision in an aesthetic border. The flap is broad-based and therefore its vascularity tends to be reliable. There is great flexibility in the design and positioning of the flap. The design of inferiorly based rotation flaps promotes lymphatic drainage and reduces flap congestion and edema. Similarly, arterial and venous disruptions may be minimized and sensory innervation may be maximized by appropriately positioning the base of the flap.

Rotation flaps should not be selected as a first option in situations where design of the flap will necessitate placement of incisions that cross RSTLs or aesthetic borders at right angles. This will likely result in an inadequately camouflaged scar along a portion of the donor site. Rotation flaps are not a good choice to repair central upper cheek skin defects in males because hair-bearing skin of the sideburn is moved medially into the non–hair-bearing area of the cheek covering the malar eminence. Except for the dorsal nasal flap, rotation flaps are not often used in repairing nasal defects because donor site scars do not follow the boundaries separating the nasal aesthetic units. The skin of the nasal tip is inelastic, making the use of rotation flaps difficult. Small defects over the dorsum of the nose are best repaired with transposition flaps such as a bilobe or rhombic flap. Furthermore, rotation flaps transferred from the cheek to the sidewall of the nose usually result in an unacceptable result because of the necessary bridging of the flap across the nasal facial sulcus. This partially obliterates this important landmark. Similarly, rotation flaps from the cheek are inappropriate for reconstruction of lateral lip defects because the arc of the flap must extend across the melolabial fold and crease at right angles. The melolabial crease is a prominent aesthetic border and incisions crossing it perpendicularly often create unsightly scars.

APPLICATIONS

Scalp

Rotation flaps are the preferred method to repair most scalp defects with use of local tissue ( Fig. 7.8 ). Because of its spherical topography, the scalp accommodates curvilinear incisions well and the flaps can be constructed sufficiently large without the need to regard RSTLs or aesthetic borders. Rotation flaps are transferred by a pivotal motion rather than depending on stretching of tissue for movement as required by advancement flaps. Because of the inelasticity of scalp tissue, any movement of tissue by advancement is limited. Whenever possible, multiple rotation flaps are preferred to the use of a single flap for scalp reconstruction. Each flap is designed to pivot on an independent pivotal point. When using two rotation flaps, the flaps may be designed to pivot in opposite directions creating a T configuration of the wound repair. Most defects left after micrographic surgery are round or oval. When this configuration is present, it is best to use two flaps that pivot in the same direction, either clockwise or counterclockwise. Each flap is designed with an opposite orientation on either side of the defect. The two flaps are apposed with a Z-shaped repair. This type of repair is known as an O-to-Z repair . When designing a double rotation flap in an O-to-Z pattern, the optimum design for wound closure is an acute angled flap with a length equal to four times the radius of the defect being closed. Using more than one rotation flap is advantageous because it recruits scalp tissue for reconstruction from different locations and the burden of closing the secondary defect is shared by the number of flaps used. Two or three rotation flaps work best for reconstruction of scalp defects. When using three flaps, each is responsible for repairing one-third of the surface area of the defect. Wound closure is accomplished by pivoting all three flaps in the same direction. Repair of the defect has the appearance of a pinwheel and wound closure configuration resembles the closing of a camera lens.

To use two or more rotation flaps for repair of scalp defects, the defect must be located in the central aspect of the scalp. For peripherally located defects it is often difficult or impossible to design two effective rotation flaps. In such instances, a single flap is designed larger than would be required if two flaps could be used. When using a single rotation flap, the perimeter of the arc of the flap should be at least four times the diameter of the scalp defect. Sometimes one or two back cuts at the base of the flap are necessary to reduce wound closure tension. On rare occasions, the secondary defect must in part be skin grafted or left to heal by second intention. SCDs are not resected at the base of scalp flaps at the time of transfer because resection has the effect of decreasing the width of the base of the flap and may impair vascularity. In addition, deformities tend to reabsorb over 4 to 6 weeks. Usually after 6 weeks, any remaining deformity may be removed safely without jeopardizing the vascularity of the flap.