22.1 Introduction

The goals of microsurgery reconstruction are functional outcome and aesthetic result. To achieve these goals, we often need a thin flap that is pliable and viable. Perforator flaps have been extensively used for these purposes from head and neck reconstruction, trunk reconstruction, and extremity reconstruction. But often when reconstructing for coverage, the bulk of the perforator flaps makes it difficult to achieve good contour at a single stage especially in obese patients. ¹

The current method of elevation of the perforator flap is either subfascial where the flap is elevated with the deep muscle fascia or suprafascial where the elevation is made just above the deep fascial plane. ² In either case, the flap frequently remains too bulky to resurface the defect. Immediate debulking procedures can follow but may result in partial loss of the flap. ³ Microdissection can be applied with better success to achieve a thin flap but may be to tedious and time consuming. ⁴ Thus, secondary debulking procedures are chosen to minimize flap loss, and procedures such as liposuction or surgical resection are followed to achieve better contour of the reconstruction site. But if possible, one should aim to have the ideal reconstruction at a given single stage like the concept of the reconstructive elevator. ⁵

In this chapter, we will focus on how to thin the flap based on a new plane, the superficial fascial plane, which may provide a constant safe and reliable plane. ⁶ Since the anterolateral thigh (ALT) flap and the thoracodorsal artery perforator (TDAP) flap have been discussed in detail in the previous chapters, only the superficial circumflex iliac artery perforator (SCIP) flap and the gluteal artery perforator (GAP) flap will be exemplified in this chapter. ^{7 ,​ 8 ,​ 9 ,​ 10}

22.2 Anatomical Considerations

Using the superficial fascial plane in flap elevation is a different approach from the classical subfascial or suprafascial approach. The subfascial approach is made by incising the deep fascia, and then elevating beneath this fascia, which makes it easier to identify the perforators before it penetrates the fascia. It is the easiest and, maybe, fastest way to elevate the flap. ^{2 ,​ 11 ,​ 12} The disadvantage, however, is that this approach leaves the thickest flap with possibility of muscle hernia. The suprafascial approach elevates the flap above the fascia until the perforator is reached and then opening the hiatus of the deep fascia and dissecting the perforator proximally toward the source vessel. Although it reduces the risk of muscle hernia by keeping the deep fascia intact, the risk of skin graft loss and depression of scar remains a problem if the donor site is not closed primarily. Finally, despite being thinner than the subfascial approach, it may still be too thick and not adequate for resurfacing defects with thin surrounding skin. ⁶

The critical anatomy when elevating the thin flap is the identification of layers: deep fascia, deep fat, superficial fat, and the superficial fascia that lies between the two fat layers (Fig. 22‑1). ^{3 ,​ 13 ,​ 14} According to the perforasome concept by Saint-Cyr et al, viability of the flap with the superficial fascia plane will be derived from perfusion of the perforator and the ability of indirect linking vessels connecting to each other. ^{15 ,​ 16} Based on this knowledge, a large thin flap will survive even without direct linking vessels. ^{17 ,​ 18} Therefore, despite the debulking of the deep fat where the direct linking vessels might be found, the thin flap harvested on the superficial plane will still have adequate blood supply. ⁶

The superficial fascia acts to maintain the skin integrity. Once removed, the skin can expand mimicking the full-thickness skin graft. Thus, the ability to stretch allows the flap to have thinner appearance while maintaining adequate circulation to the flap.

Another critical component of elevation on a superficial fascia plane is to identify perforators. When elevating on the superficial fascia plane, one can come across multiple perforators heading upward toward the skin. If multiple ones are identified, the perforator with the largest diameter is usually preferred. Once the perforator of choice is determined, dissection has to head toward the source vessel until an adequate length of the perforator is achieved; this is known as the freestyle approach. The final critical component of elevating on the superficial fascia can be the superficial veins. The importance of the superficial veins is known especially when elevating flaps having a potentially dominant superficial venous system. Among the commonly used flaps in the extremity, DIEP (deep inferior epigastric perforator) and SCIP flaps can be such examples. In these flaps, it is wise to include the superficial vein even when accompanying veins of the perforator allow adequate drainage.

The skin of the flap itself can vary in thickness. The only part of the skin that has a large epidermal component other than the hand and foot is the buttock skin. While the back (TDAP flap, parascapular flap) and the buttock (GAP flap) have a similar or a lightly thicker skin thickness (epidermis and dermis) compared to the plantar surface, the back skin has only half the epidermal component compared to the buttock. ¹⁹ On the contrary, the skin thickness of the anterior body may be thinner. Furthermore, the SCIP flap has one of the thinnest fat deposits as the skin is relatively tightly adhered to the deep fascia compared to other sites such as the abdomen and thigh. Thus, one can consider the skin thickness when reconstructing a defect.

22.3 Anatomical Variants and Potential Pitfalls

When elevating the flap on the superficial fascia, the identification of this layer can be tricky especially in thin patients. In a thin patient, there might be lack of deep fat as well as superficial fat, making the distinction difficult. Nevertheless, adequate tension can show the superficial fascia. Adequate tension and countertension during elevation of the perforator flap is critical to identify the superficial fascia. This maneuver allows identifying the avascular thin white film-like structure with better clarity.

The elevation in freestyle allows coping with any variant of perforator location. However, pre-elevation Doppler marking will guide you to expect where and when meticulous approach is needed. The concept of hot and cold zones of the flap may come in handy when elevating any perforator flap. Rapid elevation can occur during the elevation of the cold zone where there are no meaningful perforators and meticulous dissection is required as you come close to the vicinity of the marked perforators (hot zones).

There can be multiple perforator variants derived from the ALT, TDAP, GAP, and SCIP flaps. The perforators may not originate from the commonly known named sources. However, the freestyle approach lets you overcome these variations by quickly identifying another perforator in the adjacent region and change the flap design accordingly.

The SCIP flap can be raised as a fasciocutaneous flap known as the groin flap. ²⁰ When raised on the suprafascial plane, it is Dr. Koshima’s original description of the SCIP flap. ²¹ On this plane, one can take the SCIP flap as a chimeric flap to include lymph nodes to address patients with lymphedema or extend the dissection to the iliac bone to reconstruct small bone defects. ²² The dissection to include the bone may become very tedious as the small branches from the perforator can be difficult to identify. The donor site may have prolonged leakage of the lymphatic fluid if the lymphatic vessels and nodes are not adequately coagulated.

The GAP flap can be based on either the superior or the inferior gluteal artery. ²³ When elevating with the full fat layers, it can be used to reconstruct the breast. ²⁴ When elevating above the superficial fascia, it can be used to resurface the lower extremity or a weight-bearing foot. There can be many designs available from each GAP. ^{25 ,​ 26} It can be designed in multiple axes directing to the trochanter or toward the flank. The design variation depends on the donor site appearance or the position of the defect if it is used as a local flap to cover the defect usually originating from a pressure sore.

22.4 Flap Design

The flap design for the ALT and TDAP has been covered in the previous chapters and will not be covered in duplication.

Preoperative multidetector row computed tomography (MDCT) angiograms or conventional angiograms when hardware was used were obtained in the patients to evaluate the vascular status of the extremity. It can help identify the perforators rising from the thigh, buttock, and groin region. Preoperative markings of perforators are made based on the anatomical landmarks as described in previous chapters with the exception of the SCIP and GAP flaps. Additionally, a handheld Doppler was used to locate the actual perforator for a freestyle approach. When using a perforator as recipient, a strong visible pulse of the perforator is the main indicator for use. ²⁷ For all flaps, especially the SCIP and the GAP flaps, a pinch test of the skin should be made to maximize the chance for primary closure of the donor site. In large defects, ALT or TDAP flaps can be designed in multiple skin paddles based on multiple perforators originating from the source vessel allowing the primary closure of the leg. ²⁸

22.4.1 Flap Design for the Superficial Circumflex Iliac Artery Perforator Flap

A line is drawn from the inguinal crease to the anterosuperior iliac spine (ASIS), marking the topographical pathway of the perforator. An acoustic Doppler is used to locate and identify the perforators from the superficial circumflex iliac artery (SCIA). Multiple perforators can be traced along this axis. There are usually two major perforators originating from the SCIA along this axis. The medial (superficial) branch is a direct cutaneous branch and in 95% of cases it penetrates the deep fascia within an oval of 4.2 × 2 cm (vertical × horizontal) with the center of the oval point located 4.5 cm lateral and 1.5 cm superior from the superolateral corner of the pelvic tubercle (Fig. 22‑2, Fig. 22‑3). ²⁹

The lateral (deep) branch often travels through the sartorius muscle and then penetrates the deep fascia traveling further down to the flank region. If a large skin paddle were desired, it would be prudent to base the SCIP flap on this lateral perforator. The flap design is outlined so as to include as many perforators as possible and also to center the flap toward the medial aspect of the groin. A pinch test is done to confirm primary closure of the donor site. The maximum width of the flap that can be raised while permitting primary closure is 8 cm. The length of the flap can be extended beyond the anterior iliac spine or medially toward the buttock crease.

22.4.2 Flap Design of the Gluteal Artery Perforator Flap

To locate the SGAP perforators, a line is drawn from the posterosuperior iliac spine to the greater trochanter. Perforators are usually found adjacent to the medial two-thirds of the drawn line. A skin paddle is positioned over the most suitable perforator. In general, the more lateral the perforator, the longer the pedicle (Fig. 22‑4, Fig. 22‑5). ²⁶ To locate the inferior gluteal artery perforators (IGAPs), a line is drawn from the greater trochanter to the middle of the distance between the posterosuperior iliac spine and the medial border of the gluteal crease. The perforators are located on the middle third of this line in the marked areas (Fig. 22‑4). ²⁶ A skin paddle is positioned over a desirable perforator and dissection proceeds as a freestyle elevation.

22.5 Flap Harvest

The elevation is a freestyle approach under loupe magnification and begins from either the lateral or the medial border of the flap. The incision is made deep to the superficial fascia dividing the superficial and deep fats. The superficial fascia is between the large deep fat lobules and smaller superficial fat lobules. The small lobules suddenly become larger as it passes a very thin fascia-like structure. This may be more apparent in patients with high BMI. It is easier to identify this thin white film-like fascia while retracting the skin from both sides of the incision. The elevation technique on the superficial plane can be made easy once the white film-like layer is identified under the right traction and countertraction of the skin immediately upon incision of the skin. After locating the fascia, elevation is made on this plane until the perforator marked previously on the skin is reached (hot zone). Then the same approach is made from the contralateral side. Based on the pulse and diameter of the vessels, a single perforator can be chosen and dissected into the deep fascia and muscle. The fat around the perforator can be skeletonized or maintained with a cuff of fat. We prefer to skeletonize the pedicel as it allows identifying relevant branches to the flap. After reaching adequate length, the pedicle is cut and made ready for microsurgery. (see Video 22.1).

Related posts:

3 Indications for Vascular Intervention in Lower Extremity Reconstruction 4 Orthopaedic Evaluation of the Lower Extremity and the Concept of the Orthoplastic Approach 10 General Wound Preparation and Timing 7 Using the Flap and Angiosome Concepts to Optimize Functional Lower Leg and Foot Amputations 17 Supermicrosurgery Approach to the Lower Limb 26 Perioperative Care and Rehabilitation Specific to the Lower Limb

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