Z-Plasty Made Simple

A Z-plasty is a critical and reliable technique that is useful for scar revisions and correction of free margin distortion. A Z-plasty can help lengthen a contracted scar, change the direction of a scar so that it is better aligned with the relaxed skin tension lines, or interrupt and break a scar for better camouflage. This article will review the technique of a basic Z-plasty as well as provide case examples of its use in free margin distortion and scar revision.


Introduction
In order to achieve optimal aesthetic and functional results, there is no substitute for careful planning and meticulous surgical technique. Yet even in the most competent hands, surgical complications are an inevitable fact of life. In particular, areas of the face that border free margins, such as the eyes, nose, and lips, present a special challenge to the dermatologic surgeon. These areas offer little resistance to any tension created by surgical movement of nearby tissue and are not very forgiving. Any abnormality in the natural contours of these visually critical structures focuses the attention to the disruption or distortion itself. Often the distortion not only leads to an unacceptable cosmetic result but may also have functional consequences.
A Z-plasty [1] is a critical and reliable technique for the dermatologic surgeon when performing revisions or correcting free margin distortion. There are three main objectives when performing a Z-plasty: to lengthen a contracted scar, to change the direction of a scar so that it is better aligned with the relaxed skin tension lines, or to interrupt and break a scar for better camouflage. When it comes to free margins, a Z-plasty is particularly useful because it does not require excising more tissue which is often at a premium near free margins.

Design and Execution
As with all surgical reconstruction, it is essential to carefully plan, measure, and draw out the Z-plasty. Ideally this is done before any local anesthesia is injected to prevent tissue distortion. The fundamental unit of a Z-plasty is a triangular double transposition flap. However, as with most lifting flaps, there are also elements of rotation and advancement. In a classic Z-plasty three incisions of equal length create two equilateral triangular flaps (see Figures 1(b) and 1(c)). There is a central limb which is either the scar itself that needs to be redirected or an incision parallel to this scar. There are also two arms that originate from this central limb at various angles. Ideally, the angles may be measured using a protractor or they can be estimated free hand. That is, one can draw a 90-degree limb that comes off the central limb and then either bisect it to create a 45-degree angles or trisect it to create a 30-and, the more commonly used, 60-degree angles. Precise, confident incisions and delicate tissue handling are critical because the triangular flaps that are being excised and transposed are often rather small.
Undermining as in any transposition flap is also a key so that the flap can be transposed without tension. When trying to free a contracture or redirect a scar, it is especially important to undermine widely below any fibrosis that constrains the scar. If one only undermines above this plane, the flaps will transpose but the scar tissue below the flaps will prevent release of the contracture and will not significantly redirect or lengthen the original scar. In addition, for the novice, it may be helpful to place an indelible dot of ink on one of the flap tips. It is easy to sew the flaps back into their original position and not actually transpose them once they have been undermined and freed (since suturing the flaps with or without transposing will create a z or mirror image 2 Dermatology Research and Practice  of a z). After undermining, one triangular flap is transposed about its pivotal point in a clockwise direction and the other in a counterclockwise direction to create the Z-plasty. In most cases, one does not need a lot of buried interrupted sutures and must be fairly gentle with the tips of the Z-plasty to avoid vascular compromise of these small flaps [2].

Limitations and Considerations
The degree of scar directional change and lengthening is determined by the angles of the flap: the larger the angle, the greater the lengthening and the greater the change in direction of the original scar, the smaller the angle, the less the lengthening and change in the direction of the original scar ( Figure 2). Although angles between 30 and 90 degrees are possible, the 60-degree Z-plasty is most common. A 60degree Z-plasty will yield a 75% increase in scar length and a 90-degree change in scar direction. In the 45-degree Z-plasty, the resultant central limb lies in a more oblique position, approximately 60 degrees from the initial position. In the 30-degree Z-plasty, the direction of the change is even less, approximately 45 degrees from the initial position of the central limb. Z-plasties with angles less than 30 degrees will greatly increase the risk of tip necrosis. Z-plasties created by angles greater than 60 degrees will make it more difficult to transpose the two flaps without tension and also produce standing cutaneous deformities or "dog ears." It is important to bear in mind that these mathematical predictions do not bear out precisely in practice when dealing with live tissue because of factors such as pliability and tensile forces that place constraints on skin. Thus, the gain in scar lengthening or directional change is almost always less than calculated.
The limb lengths of the Z-plasty also influence the length gained: the longer the limbs, the greater the gain in scar length. Yet these limbs of the Z-plasty have some practical limitations in terms of their length. Although the broken line scar created by a Z-plasty allows for an overall less perceptible scar, this advantage diminishes with longer limbs as they will eventually create more obvious scar lines (and an unnatural appearance of a Z-shaped scar). Usually 6 to 10 millimeters is as long as any segment of the Z-plasty should be designed, particularly if the segment does not lie in a favorable direction or at the junction of two cosmetic units. In order to decrease the formation of a noticeable Zshaped scar and overcome the practical limb lengths, a longer scar can be broken up by using multiple Z-plasties ( Figure 3). Finally, mechanical dermabrasion or laser resurfacing can be performed afterwards to camouflage and make the Z-shaped scar more subtle.
Finally one should also consider the relaxed skin tension lines of the face when planning the Z-plasty such that the amount of directional change (and hence final scar lines) can be most similar to the RSTLs. For each particular scar or central limb, there are always two choices for the alignment of the peripheral arms, these being mirror images of one another (Figure 4). Both options should be considered since both designs will change the scar direction; however, one of these options will usually be a better choice for scar camouflage due to placement of the lateral limbs such that they more correctly mimic the RSTL.
Like other transposition flaps, a Z-plasties can create trapdoor or pincushion effect. Wide undermining to create an even scar contraction plate may help decrease this risk. Post-operative intralesional steroids may also help diminish such an effect should it occur.
Case Examples. Case 1. Figure 5 represents an example of Case 1. Figure 6 represents an example of Case 2.