Mastering grafts and flaps in dermatologic surgery: A narrative review

Introduction

Skin grafts and flaps are surgical techniques for wound closure. When the wound cannot be closed by primary closure, secondary intention can be tried, or if their outcomes are deemed unacceptable for a particular case, more advanced techniques such as grafts and flaps are used. The basic goal of a reconstructive procedure is to provide adequate wound coverage and anatomic replacement, but in recent times, the goals of functional and aesthetic maintenance have gained emphasis, which has led surgeons to utilise increasingly complex surgical techniques to preserve as much ‘form and function’ for the patients as possible. Hence, skin grafts and flaps are being increasingly used in practice. Advancements in tissue engineering, tissue allotransplantation, and robotics will only further bolster the utility of graft and flap reconstruction. Also, a combination of these techniques with previously mentioned techniques will allow the surgeons to deal with closures that were not adequately addressable with a single technique alone. As such, the technique of graft and flap reconstruction is an essential part of the repertoire of a dermatosurgeon.

This review presents an overarching survey of the usage of skin grafts and flaps in dermatology with respect to their history, types, techniques, and appropriate application.

History

The recorded history of flaps for reconstruction began in ancient India with Sushruta (1000-800 BC), who described a regional pedicled flap for nose reconstruction in his text Samhita.¹ In ancient Roma, Celsus and Oribasius described random circulation flaps for the reconstruction of various facial structures.

After a relatively long period of slow progress during the Middle Ages of Europe, the technique of Susruta was discovered by Gustava Branca of Italy in the 1400s. His son used distant flaps taken from the upper extremity to reconstruct the nose. During the Renaissance, there were vast improvements in anatomic descriptions, which in turn improved surgical approaches. The 18^th and 19^th centuries witnessed improvements in overall surgical practice with the introduction of aseptic techniques and antibiotics.

Thin split-thickness skin grafts (STSGs) gained popularity in the late 19th century, thanks to Ollier (1871) and Thiersch (1874). Wolfe published the full-thickness skin grafting (FTSG) technique in 1874, which was later popularised by Krause. Hence, STSGs and FTSGs have gained the eponyms Ollier-Thiersch grafts and Wolfe-Krause grafts, respectively. With World War I, there was an influx of injuries that required reconstructive techniques. A notable contribution was made by Vladimir Petrovich Filatov in 1916 and Harold Gillies in 1917 with the introduction of the tubed pedicle flap. World War II saw a further rise in machine-related casualties and an increased demand for reconstructive procedures. The modern era has continuously witnessed the development of newer and more sophisticated techniques for reconstructive procedures, including microvascular surgery, robotic surgery, composite allogenic tissue transplantation, regenerative techniques, etc.

Relevant concepts

The reconstructive ladder refers to a set of increasingly complex methods of wound management placed in an order such that the lower most rung has the least complex method of wound closure (e.g., healing by secondary intention), while higher rungs have more complex methods (e.g., flaps). Conventionally, a surgeon should start from the bottom rung and ascend to more complex techniques if required for a particular case. In contrast, the concept of ‘reconstructive elevator’ as mentioned by Gottlieb,² describes that a surgeon should be able to freely move to upper rungs or levels just like an elevator if it’s required for optimal functional and aesthetic outcomes.¹ A novel concept is that of ‘reconstructive clockwork’ as mentioned by Knobloch et al.³ It explains that the novel techniques of composite tissue allotransplantation, robotics, and regeneration/tissue engineering are best used simultaneously with traditional reconstructive techniques similar to how cogs in a clockwork work together.

Skin grafts

Three primary types of skin grafts include autografts, homografts (or allografts), and xenografts, each defined by the source of the donor tissue. Autografts are tissues transferred from one part of the body to another within the same individual. Homografts, sometimes referred to as allografts, are tissue transfers between members of the same species. Xenografts represent a more complex grafting scenario, involving tissue transfer from individuals of one species to those of another.

Types of surgical skin grafts

Based on the thickness of the tissue taken from the donor site, a graft can be epidermal, STSG (epidermis with variable depth of dermis), and FTSG (epidermis with dermis and appendages). A comparison of STSGs and FTSGs has been given in Table 1. Table 2 compares thin STSGs, thick STSGs, and FTSGs in terms of their advantages and disadvantages.

Flaps

Flap, when used as a noun in English, refers to an object that is broad, pliable, mobile, either hanging loosely or fastened by one end or side. A flap in surgery is similarly a variably shaped, flexible, and mobile sheet of tissue that, unlike grafts, can survive relying on its innate vascular network without requiring the ingrowth of vascular channels from the recipient site. Flaps can be classified as random, and non-random or axial on the basis of their blood supply. A random flap is generally based on unnamed smaller arteries that supply a particular area of the skin. Axial flaps are raised in such a fashion that they include at least one named direct cutaneous artery, providing them with a more robust blood supply. The significant robustness of a flap used in facial reconstruction is due to the fact that a single area of skin has multiple sources of blood supply.⁷

A flap can be categorised according to where the defect is located, wherein a local flap lies adjacent to the defect while a distant flap is taken from a different region of the body. A distant flap can be further divided into two categories: free (where the donor tissue is detached from the donor site by its vascular pedicle) and pedicled (where the blood supply is maintained via an intact tissue bridge). The definition of biogeometry was given by Tenta and Keyes as “the integration and summation of the biologic and geometric factors that govern the logic involved in the process of efficient selection, siting, design, construction, and transfer of a flap.”⁸ In terms of biogeometry, local flaps can be further subdivided into advancement, transposition, and rotation flaps [Figure 1].

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Figure 1:

Classification of flaps.

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Types of surgical flaps

The different types of flaps according to method of transfer and design can be classified as rotation flaps, advancement flaps, and transposition flaps. These generally use random, unnamed vessels for the blood supply. On the other hand, interpolated and free flaps are axial flaps.

Rotation flap

This kind of flap reconstructs the defect by rotating a mobilised tissue around a pivot point. The advancing edge of the flap is shared with one border of the defect. The flap biogeometry has been further explained in Supplementary Video 3. Advantages of such flaps include no secondary defect, and tissue tension is distributed over a long suture line. Furthermore, when they are used for scalp reconstructions, they don’t leave behind alopecic patches. Disadvantages include reliance of these flaps on elasticity of surrounding tissue and the fact that a large area of tissue needs to be mobilised to cover a small defect.

Supplementary Video 3

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Few modifications in standard rotational flap design include bilateral rotation flap, oval to Z or O to Z flap, Ahuja’s modified rotation flap, divine rotation flap, and snail flap.

Transposition flap

These surgical flaps are based on pivotal movement like rotational flaps, these share their advancing edge with one of the defect margins. However, they include transferring tissue to the defect from a donor site. The donor site needs to be closed by direct suturing, skin graft, or a secondary flap from more lax skin at an angle to the primary flap. This allows surgeons to transfer the incision tension vectors to more lax skin.

The length of a transposition flap is dependent upon its blood supply. An axial transposition flap will have a robust blood supply from a named vessel, allowing the surgeons to create with much greater length compared to the width of the base of the flap. On the other hand, a transposition flap with random vessel blood supply will have a relatively shorter length compared to its width to prevent tip necrosis. The flap biogeometry has been further explained in Supplementary Video 4. The biogeometry of a bilobed flap has been explained in Supplementary Video 5. Modifications of the bilobed flap include Zitelli’s and Xue’s techniques.

Supplementary Video 4

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Supplementary Video 5

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Z-plasty is a surgical method that involves the transposition of two adjacent triangular flaps. These flaps are generally of equal size. It is used to direct scars in a more favourable direction. The approach results in a length gain towards the common limb of the “Z” incision, releasing tension [Figure 2].⁹ Angles between the central limb and the two extending limbs should not be less than 30 degrees as it can cause flap tip necrosis while angles greater than 75° lead to flaps that are difficult to transpose, leading to dog ear deformity.

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Figure 2:

(a) Initial planning of the limbs of z-plasty, Note that the central limb lies along the vertical axis. (b) Right and left flaps are created after undermining. Red arrows represent the direction of motion (transposition) that the triangular flaps undergo. (c) Post transposition the right flap lies above the left flap instead of lying adjacent to it. (d) The final suture line with reorientation of the central limb of ‘Z’ in the horizontal axis.

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Other modifications of the transposition technique include note flaps, sliding transposition flaps, interpolation flaps, islanded flaps, and trilobed flaps. Rhomboid flaps, also called Limberg’s flaps, are also an example of transposition flaps [Figure 3]. Modifications in rhomboid flap design include the Dufourmental flap, Webster flap, Quaba/ Sommerland flap, and diamond flap. Pre-op, intra-op, and post-op images of an example of rhomboid flap reconstruction have been provided in Figure 4.

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Figure 3:

(a) Initial flap design stage, (b) Status after excision of the lesion and mobilisation of the flap. Red arrow represents the direction of the movement of the flap, (c) Final suture line.

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Figure 4a:

Pre-operative image of the patient with a basal cell carcinoma who underwent rhomboid flap reconstruction.

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Figure 4b:

Intra-operative photograph showing flap mobilisation.

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Figure 4c:

Post-operative photograph.

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Advancement flaps

This technique involves movement in a linear direction without any lateral or pivotal movement of the mobilised flap tissue. Undermining is, in fact, a type of advancement flap. They are useful in preventing deformity in hair bearing areas if flap reconstruction is required. Their biogeometry has been further explained in Supplementary Video 6.

Supplementary Video 6

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Extensive undermining, Burow’s triangle excision, counter incision at flap base, triangular/curvilinear design of flap, and Z plasty at base are methods that facilitate the movement of an advancement flap.

V-Y plasty is an advancement technique that involves a pivotal plane with a subcutaneous pedicle [Figure 5]. East-west flaps grant the surgeon the ability to place suture lines in favourable locations, especially in the case of nose reconstruction [Figure 6]. Pre-op and post-op images of an example of east-west flap reconstruction have been provided in Figure 7.

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Figure 5:

(a) Initial flap design stage, (b), (c) Different flap lengths for angles at the apex of 30 degrees and 60 degrees respectively. Black arrow represents the direction of the movement of the flaps and its length represents the distance that the flaps will advance, (d), (e) Status after mobilisation of the flap. Black arrow represents the distance that the flap has advanced, (f), (g) Three-point stich is applied at the apex of the triangular flaps, (h), (i) final suture lines.

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Figure 6:

(a) Initial flap design phase. Green circle represents the defect created after excision of the lesion, (b) Final suture line.

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Figure 7a:

Pre-operative photograph of the patient with a basal cell carcinoma who underwent East-West flap reconstruction.

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Figure 7b:

Post-operative photograph showing the final suture line.

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Figure 7c:

Post-operative photograph showing status post suture removal and healing of the site.

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The keystone flap is an advancement technique that derives its name from the architectural keystone that forms the central portion of the Roman bridge construction. It has been further explained in Figure 8.

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Figure 8:

Technique of keystone flap.

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Other modifications of advancement technique include O to T advancement flap (along with A to T and O to Y technique), L-plasty, H plasty (along with Harahap modification and SH plasty), bipedicled advancement flaps, and Y-V advancement flaps.

Axial flaps

Axial flaps like the median forehead flap, nasolabial flap, and glabellar flap are commonly used in surgical reconstruction. Axial supply for a median forehead flap are the terminal branches of the angular artery and supratrochlear vessels. The nasolabial flap is also based on the angular artery when it travels through the nasolabial groove. The choice of flaps for regional defects have been detailed in Table 3.

Table 3. Choice of flaps for regional defects

Zone	Flap
Scalp
Small defects <6 cm	Single or multiple rotation flaps
Larger defects	If pericranium intact: skin graft
Forehead	Bilateral advancement flaps
Cheek
Medial	Cheek rotation advancement
	Transposition flap
	V-Y advancement flap especially near the ala
Lateral	Transposition flap
Cheek	Rotation flap for larger defect
Medial
Lip
Central	Bilateral advancement flap
Lateral	Rotation Flap
Nose	Advancement of dorsal nasal skin
	Bilobed flap or nasolabial flap
	Forehead flap for large defects

Conclusion

For surgically oriented dermatologists, grafts and flaps form an indispensable part of their armamentarium. For best surgical outcomes, it is imperative to know the proper indication of these two closure techniques while following the philosophies of the surgical ladder and elevator. For applying said techniques, the surgeon needs to have a good grasp of their biogeometries. Good surgical planning and technique should include planning in reverse, designing a flap that is slightly larger than the defect, respecting the aesthetic units while designing the flap, and meticulous and gentle tissue handling.