Alternative Flap-Based Breast Reconstruction: The PAP Flap

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.

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, 10, 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].

Figure 1.

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

4. Pre-operative imaging

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

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]).

5. Standard profunda artery perforator flap markings and elevation

5.1 Transverse PAP flap

Since its introduction, approaching the PAP flap has been consistent. Variability does exist regarding orientation of the flap. The initial orientation was transverse in the upper thigh. This has been studied and expanded on, with alternative orientations including vertical, oblique, and combined vertical-transverse also known as the ‘fleur-de-PAP’ [12].

The standard transverse profunda artery perforator flap begins with marking the landmarks of the groin crease, mid-axial thigh, and inferior gluteal crease. Most commonly, the preferred perforator will be found within 7 cm of the inferior gluteal fold and within 4 cm of the posterior border of the gracilis. This is often identified with pre-operative imaging and confirmed with doppler ultrasound. Standard PAP flap markings are that of a transverse elliptical pattern performed with the patient standing. The width of the flap is determined by a pinch test (Figure 3).

Figure 3.

Pre-operative picture with markings for transverse PAP flap showing the extend of posterior dissection. Perforators are marked on either side.

5.2 Vertical PAP flap

The vertical design is oriented orthogonal to the transverse design. Anatomic landmarks include marking the pubic symphysis, the adductor longus and gracilis muscle borders. The perforator is marked using the doppler. The ellipse is centralized over the perforator and a pinch test is used to determine the width of the flap. This orientation is more commonly used by the senior author for multiple reasons—able to incorporate multiple perforators, assuring the dominant perforator is captured, lower chance for wound complications, less pain when sitting [8].

5.3 Flap elevation

Elevation of the flap begins with the anterior approach. The patient is positioned supine in lithotomy. The adductor longus and gracilis muscles are palpated and transposed to the skin surface. Dissection is carried down to the muscular fascia of the gracilis and proceeds posterior. In the anteromedial thigh the greater saphenous vein and tributaries will likely be encountered. Although these tributaries, if present, may aid venous drainage of the flap, supplemental outflow is typically not required and therefore they can be ligated with impunity. Once the gracilis muscle is identified, the dissection proceeds in the subfascial plane posteriorly. Skin perforators through the gracilis may be encountered and should be ligated. The septum between the gracilis and adductor magnus is important. The gracilis muscle is retracted anterior, and the adductor magnus fascia is incised and elevated. Dissection proceeds cautiously in the subfascial plane until the perforators are identified. Meticulous intramuscular dissection is performed to isolate the perforator(s) to the source vessel of the profunda artery and vein. This typically yields a pedicle length of 8–12 cm and caliber of 2.2 mm for artery and 2.7 mm for vein [4].

After circumferential dissection is completed, the anterior incision is stapled closed, and the posterior incision is completed. Care is taken not to bevel proximally as to preserve the ischial fat pad. The flap is harvested, weighed, and transplanted to the chest for microsurgical anastomosis. Most commonly, flap coning is performed prior to inset, and the flap may be completed de-epithelialized and buried in nipple-sparing mastectomies, or a skin paddle may be retained for monitoring and/or resurfacing of the breast skin (Figure 4).

Figure 4.

Intraoperative dissection of the left vertical PAP flap. Perforators can be seen piercing the adductor magnus (AM). Flap characteristics: : 367 g; Average flap dimensions: 27 × 6 cm; Average pedicle length: 10.2 cm; Average artery diameter: 2.2 mm; and Average vein diameter: 2.8 mm.

5.4 Extended or ‘Fleur-de-PAP’ modification

The ‘fleur-de-PAP’ is a mosaic expanded modification of the standard PAP flap. Specifically, it includes both a transverse and vertical component to incorporate additional tissue [12, 13]. This increases volume at the cost of a longitudinal scar in the medial mid-axial thigh and a ‘T’-junction closure. Markings are similar, and emphasis should be placed on location of the dominant perforator to establish a central point for which the transverse and vertical components converge. Width is also determined by a skin pinch. Flap elevation is identical to that of the standard profunda artery perforator flap harvest (Figure 5).

Figure 5.

Pre-operative picture of markings for an extended PAP or ‘fleur-de-PAP’ including both vertical and transverse extension centered over the perforators (stars).

6. Flap contouring

The goal of breast reconstruction is to emulate natural esthetics. Achieving this not only requires technical finesse in microsurgery, but esthetic prowess. This often requires multiple stages of surgery, however as reconstructive surgeons become more proficient in the operating room, less time is spent on microsurgery and more time can be dedicated to contouring the breast mound at the first stage. This is evident in outcomes seen with PAP flaps. The elliptical orientation of the flaps lends itself to being molded immediately, regardless of the need for skin paddle. The fat is more supple and yields to contouring. This is often achieved on the back table prior to inset. If the patient is fortunate to have a nipple sparing mastectomy, the entire flap is de-epithelialized and folded to produce an esthetically pleasing breast mound. Otherwise, a skin paddle is left to monitor the flap. The three-dimensional construct is maintained with absorbable internal sutures and does not require the addition of supplemental materials such as meshes or slings (Figure 6).

Figure 6.

Intra-operative contouring of a single PAP flap into an esthetic breast mound.

7. Stacking flaps

Modern advancements in microsurgery have provided ample options for breast reconstruction, such that flap design can be personalized for each patient based on anatomy of both the breasts and donor sites. Trends over the last decade at our institution have shown an increase in stacked flap reconstructions. There are several variables to consider when approaching stacked flaps: (1) breast volume, (2) unilateral versus bilateral, (3) donor site availability, (4) donor site volume. An algorithmic approach can assist the pre-operative decision-making process [14, 15].

The most common scenario for performing stacked PAP flaps is either: restoration of volume in a unilateral breast reconstruction (PAP + PAP) or need for additional volume to augment bilateral breast reconstruction (DIEP + PAP).

The preferred orientation for stacking PAP flaps in a unilateral breast reconstruction is to perform the first anastomosis between the ipsilateral PAP flap and antegrade internal mammary vessels, followed by the contralateral PAP flap to the retrograde internal mammary vessels. It is important to note that contouring the flap on a sterile flap table should be done prior to the microsurgical anastomosis to facilitate ease of inset afterwards (Figure 7).

Figure 7.

Intraoperative picture of stacked PAP flaps with combined weight of 560 g.

There are multiple options for microsurgical anastomosis when combining the PAP and DIEP flap [16]. The bulk of the flap volume will come from the DIEP flap, which is centralized on the breast. If the volume between the DIEP flap and the PAP flap are similar, they can be combined to form a mound with internal sutures, and oriented such that the pedicle of the DIEP flap can lie in line with the antegrade internal mammary vessels, and the PAP flap pedicle lie in line with the retrograde vessels. Alternatively, if the DIEP flap is significantly large, it is used to reconstruct most of the central breast and upper pole, while the PAP flap augments the inferior pole volume (Figure 8).

Figure 8.

Intraoperative picture of stacked DIEP and PAP flap. The green microgrids are placed under the PAP pedicle. The DIEP flap has been de-epithelialized and inset, and the PAP flap restores the lower pole volume.

7.1 Tips and tricks

• Pre-operative imaging (CTA/MRA) is critical for perforator mapping and surgical efficiency.

• Limit flap width (~7 cm) to avoid tight incisional closure and wound healing issues.

• Identify posterior border and reflect the gracilis anteriorly, then enter the subfascial plane of the adductor magnus to identify perforators.

• Avoid beveling superiorly to retain the ischial fat pad and avoid sitting discomfort.

• For single flap reconstruction, use intra-flap absorbable sutures to create an esthetic breast mound prior to inset.

• For stacked reconstruction, align the flaps flat and side by side to gain additional base width.

• Consider two flaps for single breast reconstruction at primary procedure.

8. Donor site management

The profunda artery perforator flap harvests no muscle and therefore has minimal donor site morbidity. However, the location is in a dynamic area of the lower extremity and is prone to tensional forces and edema. For these reasons, the donor site needs to be managed appropriately. Limited undermining of skin flaps helps facilitate a tension-free closure while preventing seroma formation. A closed suction drain is always used. Quilting sutures are beneficial and involves suturing the superficial fascia to the deep fascia. Compression garments or ACE wraps are used.

9. Complications

Flap-related complications are low regarding breast reconstruction with PAP flaps. Profunda artery perforator perfusion is robust and therefore the risk of fat necrosis generally is minimal, both in incidence and volume. Fat necrosis is mostly seen at the tips of the flap and can be avoided by careful intra-operative clinical assessment and prophylactic excisional debridement of presumptive nonviable fat.

Donor site complications are more common. These include, but are not limited to, seroma, delayed wound healing, dehiscence, prolonged edema, dysesthesia, adverse scarring [5, 7].

Seroma should be distinguished easily from prolonged edema, which may also occur. This is done with a clinical exam and confirmed with ultrasound imaging. Prevention is the primary focus. This includes limiting undermining, closed suction drain, quilting sutures, layered closure, and post-operative compression garments. Persistent or recurrent seromas are treated with aspiration and/or drain placement as needed.

Due to the dynamic nature of the surgical site with ambulation, as well as being located near an intertriginous zone, delayed wound healing can occur. Dehiscence is much less common. Appropriate pre-operative planning with pinch-test and conservative skin markings support tension-free closure and routine wound healing. The Fleur-de-PAP is more susceptible to wound healing complications due to the creation of a T-junction with the skin flaps.

Prolonged edema is typically caused by disruption of major lymphatic channels in the lower extremity. The PAP flap dissection avoids the femoral triangle and major lymphatic channels; therefore, the risk is quite low. Preserving the greater saphenous vein, tributaries, and surrounding lymphatics can help prevent edema. Early ambulation with compression dressings or garments is standard of care.

Post-surgical dysesthesia, like the infraumbilical skin after DIEP flap, is a result of cutaneous nerve disruption after flap elevation and is best treated with reassurance and time.

Adverse scarring, namely widened or hypertrophic scars, can occur and is thought to be due to motion and dynamic tension at the suture line, like a thigh lift or brachioplasty.

10. Discussion

Since its introduction to breast reconstruction in 2010, the profunda artery perforator flap has been a reliable autologous alternative to the DIEP flap within the armamentarium of the reconstructive microsurgeon. It has also been an important additional method when the DIEP flap is not enough. The PAP boasts a large skin paddle (average 27 x 6 cm), ample pedicle length and good caliber, and mild-to-moderate volume of soft, pliable tissue. The ability to harvest the flap from a supine position with a two-team approach increases efficiency. The vascular anatomy is constant which has been corroborated with the routine use of pre-operative CT/MR angiography. The donor site results in acceptable scars with minimal exposure and complication rate. This is expounded by the recently described ‘fleur-de-PAP’ which enhances the volume at the cost of minimal excess scarring. Pedicle length and caliber enhances its utility in stacked flap procedures. The ability to immediately mold the flap into an esthetically excellent three-dimensional breast mound cannot be overstated.

The primary disadvantage of the flap is volume. However, this can be circumvented with proper patient selection and flap planning, including stacked flaps, hybrid procedures, and subsequent fat grafting (Figure 9A–D).

Figure 9.

(A, B) Pre and post-operative images of a patient with left breast cancer who underwent stacked DIEP and PAP flap reconstruction of the bilateral breasts. (C and D) Pre and post-operative images well-hidden PAP flap donor sites, without disruption of the infragluteal fold. (Reprinted from Artz et al. [8]).

11. Conclusion

The profunda artery perforator flap is an alternative approach to flap-based breast reconstruction. As breast reconstruction continues to advance, the prevalence of alternative approaches such as the PAP flap will increase. Familiarity with anatomy, microsurgical elevation, contouring and donor site management is critical to achieving excellent esthetic outcomes and professional success.

Acknowledgments

We would like to acknowledge Dr. Robert Allen for his incredible contributions to both this chapter and the innovation of the profunda artery perforator flap in breast reconstruction. We would also like to acknowledge his home institution, Louisiana State University Division of Plastic Surgery for their supportive efforts, and where Dr. Allen continues to contribute to the field of reconstructive microsurgery.

Conflict of interest

The authors declare no conflicts of interest.

Appendices and nomenclature

PAP	profunda artery perforator
DIEP	deep inferior epigastric artery perforator
CTA	computed tomography angiography
MRA	magnetic resonance angiography