Alternative Flap-Based Breast Reconstruction: The PAP Flap

*Michael Borrero, Robert Allen and Hugo St. Hilaire*

#### **Abstract**

The profunda artery perforator flap, like many perforator-based flaps in breast reconstruction, has evolved from its initial introduction more than a decade ago. It is considered by many to be the priority alternative flap when abdominal flaps are unavailable. Several configurations of the flap may be utilized routinely, making this flap particularly versatile for mild-moderate volume breast reconstruction. Additionally, as reconstructive microsurgeons become more adept, they strive to achieve an esthetically pleasing breast in the first stage. The PAP flap is particularly suited for this endeavor, as its ability to be contoured to simulate a natural breast mound at time of inset is impressive.

**Keywords:** profunda artery perforator flap, PAP flap, autologous breast reconstruction, thigh flap, flap contouring

#### **1. Introduction**

Breast reconstruction by way of the profunda artery perforator flap, also known as the PAP flap, came to fruition in 2010. Historically, this free flap is the culmination of advancements dating back to the myocutaneous posterior thigh flap introduced by Hurwitz and Walton in 1980 [1, 2]. Subsequently, the flap was modified by Angrigiani et al. [3] and Song et al. [2] within the realm of pressure ulcer and lower extremity reconstruction.

Later, Dr. Robert Allen pioneered its use in breast reconstruction in Mexico City in 2010. He designed the flap off the first or second perforator from the profunda artery in an ellipse that extended from an anterior point at the origin of the adductor longus, to a posterior point at the end of the inferior gluteal crease [4, 5]. This would be colloquially known as the transverse PAP flap.

This flap added to the ever-growing repertoire of the reconstructive microsurgeon; specifically, it offered a perforator-based flap from the lower extremity. This was exceedingly beneficial when the abdomen, undoubtedly the most useful donor site, was unavailable for reconstructive efforts. Advantages of the PAP flap became readily apparent—good donor site location with minimal morbidity, consistent and reliable vascular anatomy, adequate pedicle length and caliber, ability to harvest from supine position—however there are drawbacks when compared to alternatives, primarily the lack of volume [4, 6]. Modern advancements in the flap, however, counter this disadvantage, especially when considering the relatively novel 'fleur-de-PAP', as well as stacked flap procedures. This chapter explores the fundamentals of PAP flap breast reconstruction.

#### **2. Patient selection and considerations**

Breast reconstruction begins at the initial consultation with patient selection and surgical planning. Modern advancements in microsurgical techniques created an impetus for innovative flap design. This includes the PAP flap, which has become our preferred alternative donor site secondary only to the abdomen. With thorough understanding of outcomes over the past decade, we have become more proficient in restoring native breast volume and esthetic contour at the first stage. When considering any patient for microsurgical breast reconstruction, a thorough history and physical exam is invaluable. Paying particular attention to body habitus and subcutaneous volume distribution of the abdomen and thighs is critical to achieving an optimal result. The indications for using PAP flaps are essentially contraindications to using the abdomen as a donor site. The only conceivable contraindication to harvesting a PAP flap is lack of perforator presence, most likely due to trauma or previous surgery (e.g. medial thigh lift).

The ideal candidate for PAP flap reconstruction is a breast with mild to moderate volume. The ideal body habitus is one who carries excess subcutaneous tissue in the hips and thighs more so than the abdomen, what is colloquially known as being "pear-shaped". In our experience a single component PAP flap weighs on average between 250 to 450 grams, depending on the quality of tissue and flap design [7, 8]. When the patient's single native breast volume exceeds this, then consideration is made for stacked PAP flaps. If bilateral reconstruction is being performed, and there is volume discrepancy, then consideration is then made for stacking the PAP flap with an abdominal flap (i.e. DIEP flap) to restore native breast volume.

#### **3. Anatomy**

As mentioned earlier, profunda artery perforators were well-described decades before the introduction into breast reconstruction, corroborated by cadaver dissection and imaging [4, 9–11]. The profunda artery branches from the common femoral artery several centimeters distal to the inguinal ligament. This source vessel runs in the posterior compartment and gives off on average three perforators that are within 7 cm from the inferior gluteal crease [4]. The most proximal perforator is often selected based on location and reliable perfusion. These perforators are invariably musculocutaneous, coursing through the adductor magnus muscle before irrigating the skin and subcutaneous tissues. The pedicle typically yields a pedicle length of 8–12 cm and caliber of 2.2 mm for artery and 2.7 mm for vein [8].

Regarding dimensions, Dr. Allen and his colleagues have reviewed their reconstructions and published in the largest clinical series using PAP flaps for breast reconstruction. The average flap weight was 367.4 g, and flap dimensions averaged 27.2 x 6.3 cm (**Figure 1**) [7].

### **4. Pre-operative imaging**

Pre-operative imaging, via computed tomography angiography (CTA) or magnetic resonance angiography (MRA) is essential in elucidating perforator course and

#### **Figure 1.**

*Anatomic depiction of profunda artery perforators coursing through the adductor magnus muscle (P—pubis; G—gracilis; and M—adductor magnus).*

#### **Figure 2.**

*MRA that displays distance from posterior border of gracilis to perforator at fascial exit on axial (left); distance from infra-gluteal gold to perforator at fascia exit on coronal (right). (Reprinted from [8]).*

assisting with mapping the dissection and incisional planning. Confirmation of the desired perforator at the skin level is performed at the time of surgery with doppler ultrasound (**Figure 2**).
