Technique

Fig. 1 illustrates the concept of rotation and advancement of the classic z-plasty: a central vertical incision is placed in line with the long axis of the scar or line of tension. Two lateral limb incisions of the same length as the central incision are placed at its ends in a 60° angle. Next, the resulting triangular flaps are raised to the desired plane and rotated toward each other so that their tips fall into place in their respective opposite corners. The former shared sides of the triangles are now located toward flexible skin next to the limb incisions and a new, now horizontal, central limb is formed. The line of tension of the incised tissue is now perpendicular to its original direction. The costs for longitudinal elongation and elimination of 1 prominent scar are relative perpendicular tightening and 3 resulting smaller scars.

Basic principle of the z-plasty: 2 opposing triangles of equal angles to a central incision along the line of tension are transposed. The result is a break up and lengthening of scar tissue and redirection of the scar in perpendicular direction.

Although this concept may appear simple and straightforward on the pages of a surgery textbook, its execution under real circumstances can prove to be challenging. Wanzel and colleagues demonstrated that the ability of surgery residents to properly execute a z-plasty (which they termed a “spatially complex surgical skill”) correlated with their performance in visual-spacial ability testing. Those who scored lower according to their visual-spacial ability required more supplementary training and feedback to achieve comparable operative results, demonstrating how challenging this seemingly simple procedure can be.

Elongation, Remodeling, and Reorientation

Tissue lengthening in the direction of the scar contracture after z-plasty is a function of the angles of the limbs toward their central incision. Mathematically, an increase in angle will result in increased central elongation ( Table 1 ). Likewise, elongation increases with the length of the central incision, but is proportionally dependent on sufficient adjoining tissue for transposition. However, these theoretic gains in length depend on the specific conditions encountered in each patient and scar. Davis describes that the best tension relief can be achieved when an isolated contracture band is surrounded by normal lax skin, which can be transposed, guaranteeing optimal flap perfusion. However, especially in the reconstructive treatment of burn contractures, this scenario is rare, and the common findings are transpositional flaps that are composed of scarred tissue themselves. Therefore, careful planning is paramount in order to produce the best possible outcome and avoid overestimation of the technique’s potential.

It is clinically evident that scar tissue shows a tendency to thin and soften after application of a z-plasty even if the scar is merely rearranged instead of excised. Aarabi and colleagues were able to demonstrate that mere mechanical scar tension alone can cause the development of hypertrophic scars in mice, leading to manifold increases in tissue volume, cell density, and dysregulated, decreased apoptosis. On the contrary, the redirection of tension on the tissue into the perpendicular direction causes mechanical stress relief. Histologically, a reorientation of collagen fibers resembling normal skin instead of hypertrophic scar as well as a replacement of abnormally sulfated mucopolysaccharides with normal acid mucopolysaccharides was demonstrated by Longacre and colleagues through immunohistochemical analysis of biopsies of scar tissue before and 2 weeks after z-plasty. He concluded that the surgical procedure had profound impact on a molecular level.

Reorienting a protuberant scar in a more favorable direction can have great consequences for its visible appearance. Burn scars over concave surfaces such as the neck, axilla, and popliteal area tend to hypertrophy, contract, and ultimately form a bowstring structure. Through correct design of the z-plasty in a way that the transverse limb after transposition lies in a natural concavity, functional and cosmetic outcome can be maximized. Furthermore, knowledge of the location and direction of naturally occurring folds and lines across the body add valuable information to the planning process of any incision, including a z-plasty. There are numerous classic concepts for designing optimal incision placement, such as Pinkus’ main folding lines, Kraissl’s antimuscular lines, and the RTSLs described by Borges. Newer approaches combine the data of these established concepts with the distribution of striae distensae, which form perpendicular to musculoskeletal lines of tension, to create more detailed composite diagrams that are also applicable to guide incision planning in younger patients. In general, a z-plasty executed in order to camouflage or disperse an existing scar should be designed so that the resulting transverse limbs after transposition lie within a naturally occurring skin line or fold. This, on the contrary, means that z-plasty should be avoided in cases in which the initial scar to be corrected is already located along the axis of a fold or line and the resulting transverse limb would be perpendicular and thus more conspicuous. Borges formulated the practical general rule that scars located 60° or more from an RTSL should be corrected with a z-plasty with 60° angled limbs; scars situated under 60° away from an RTSL should consequently be addressed with a z-plasty whose limbs fall on the RTSL.