Optimizing perfusion and volume in autologous breast reconstruction: dual-plane, conjoined and stacked flaps

Dual-Plane abdominal flaps

The variability in the perfusion of the abdomen between the deep and superficial systems is not a new concept. The concern for a superficial dominant flap, however, has primarily been focused on venous drainage and the importance of the superficial inferior epigastric vein (SIEV). Blondeel et al. first described the importance of augmenting venous outflow in congested flaps with a large SIEV in 2000^[6]. Since then, the use of additional superficial venous outflow in DIEP flaps has become common practice for addressing intrinsic congestion. While SIEV caliber has been suggested to not correlate with a dominant superficial venous system, approaches have focused on algorithmically preserving the SIEV if flap congestion is noted despite an undamaged and patent deep venous system^[7,8].

The modern “dual plane DIEP”(DP-DIEP) describes an abdominally based perforator flap where the superficial inferior epigastric artery (SIEA) and/or SIEV [Figure 1] is utilized in addition to the deep system to perfuse a flap^[9,10]. A retrospective cohort study by Sbitany et al. compared 25 DP-DIEP flaps utilizing the SIEA/V with 35 traditional DIEP flaps, and demonstrated a lower rate of fat necrosis in flaps augmented with superficial perfusion^[9]. Other authors have argued that hypoperfusion remains solely a venous outflow problem, as originally described, that is improved with SIEV augmentation, without an arterial component^[11]. While the need for venous outflow augmentation is indeed most prevalent, the utility of augmenting superficial inflow is likely to be multifactorial and continues to be elucidated.

Figure 1. Harvest of the SIEA (yellow bulldog) and SIEV (green bulldog) to their origin in a DIEP flap provides adequate length to allow for multiple different recipient vessel options (intra-flap branch or runoff, caudal IM vessels, etc.). DIEP: deep inferior epigastric artery perforator; SIEA: superficial inferior epigastric artery.

Deciding to utilize the superficial system to augment both arterial and venous outflow is multifactorial and depends not only on the size of the SIEA, but the amount of tissue harvested in relation to the number, size, row and centricity of deep perforators utilized. Sbitany et al. described assessment of flap perfusion on the deep system in situ, and hypoperfusion of the suprascarpal fat or persistent skin hyperemia as an indicator to augment with the superficial system^[9]. While the superficial system should be used in cases that demonstrate clinical hypoperfusion, it can also be utilized to minimize morbidity by limiting the number of deep perforators harvested. Larger flaps that might otherwise require multiple perforators or perforator rows can be harvested on a single dominant perforator while using the SIEA and SIEV for additional perfusion [Figure 2]. Such techniques can help to limit the fascial incisions and to optimize the perfusion of a large amount of tissue harvested on a single perforator based on individual anatomy.

Figure 2. Dual-plane DIEP flap based on single high medial perforator with the SIEA and SIEV anastomosed to the lateral branch of the deep system. DIEP: deep inferior epigastric artery perforator; SIEA: superficial inferior epigastric artery.

The use of both the deep and superficial system in DIEP flaps with a superficial dominant system or diminutive deep system has also been supported. Hembd et al. demonstrated a significantly lower rate of fat necrosis and flap failure with SIEA/SIEV DP-DIEP flaps compared with SIEA flaps^[10]. From these findings, the authors advocate for the use of a dual-plane system over superficial-only perfusion if preoperative imaging demonstrates deep system perforators <1.0 mm in size or with intraoperative findings of venous congestion or ICG hypoperfusion^[10].

Abdominal donor site

The conjoined DIEP flap utilizes the entire abdomen in a bipedicled design with both the right and left deep inferior epigastric systems to increase the amount of tissue harvested for a unilateral reconstruction while optimizing perfusion [Figure 3]. This technique was initially born out of a need to circumvent midline abdominal scars and subsequently evolved from the extended hemi-abdominal flap to improve perfusion across the midline and address a discrepancy between available donor-site tissue and desired breast volume^[14]. The conjoined DIEP is particularly useful in delayed reconstructions or in cases with damaged chest wall skin secondary to radiation, as it provides ample skin for resurfacing.

Figure 3. Conjoined or bipedicle DIEP flap for unilateral breast reconstruction. DIEP: deep inferior epigastric artery perforator.

Multiple studies have demonstrated the safety of unilateral breast reconstruction with the conjoined or bipedicled DIEP flap^[15-20]. Compared to extended hemi-abdominal flaps, bipedicled abdominal flaps have been shown to have a lower rate of fat necrosis across the midline^[21]. Importantly, donor-site morbidity has also been comparable between single pedicle and bipedicled conjoined flap designs in retrospective studies^[22].

Several anastomotic configurations can be implemented, most commonly including the cranial and caudal IM vessels or the use of intra-flap anastomoses for the secondary pedicle. Managing pedicle lie is critical to avoid kinking or twisting^[23]. In the case of IM vessel recipients, criss-crossing pedicles to the cranial and caudal IM artery and vein can help avoid sharp angles in the proximal pedicle^[21]. Inset and shaping of conjoined abdominal flaps can be challenging, but still focus on the three critical principles of the footprint, conus and skin envelope^[24]. Most commonly, conjoined flaps are either folded in the vertical dimension with the caudal flap buried or coned horizontally around the midline. Variations in these patterns can be tailored to achieve the necessary breast height, width, ptosis, projection, and skin replacement^[25].

Extended donor sites

The use of additional vessels based on adjacent known perforasomes has also expanded the volume limitations of traditional flaps. The stacked hemiabdominal extended perforator (SHAEP) flap combines the DIEP pedicle with more lateral pedicles to enable additional tissue harvest outside the zone of DIEP perfusion^[26]. Multiple perforator combinations have been described, most commonly utilizing the DIEP and deep inferior circumflex artery (DCIA) pedicles^[26]. Utilization of the lateral flank perfusion based on the superficial circumflex system can also help recruit more skin and volume when needed [Figure 4].

Figure 4. A: 35-year old female with a history of left total mastectomy and radiation planned for right prophylactic mastectomy. B: Left ShAEP flap using medial DIEP perforators and SCIA/SCIV planned to resurface and restore volume to radiated left chest (A small right DIEP flap for concomitant immediate right prophylactic mastectomy reconstruction was performed). C: 6-month postoperative photo prior to nipple reconstruction and tattooing.

The lower extremity has also been utilized for conjoined flaps. A 2023 study by Chu et al. described harvesting PAP and LTP flaps as a conjoined “L-PAP flap” to optimize coning and projection^[12]. The flap utilizes the medial, posterior, and lateral thigh tissues to improve reconstruction volume influenced by body contouring thigh-lift procedures^[12]. Additional bipedicled designs in the lower extremity include combinations of the gracilis and PAP flaps, though PAP perforators typically provide robust perfusion of the medial thigh in isolation^[27].

Single donor site

When the abdomen is utilized as a single donor site, the vast majority of reports have utilized a conjoined or bipedicled design.²⁹ However, splitting the abdomen and stacking hemiabdominal flaps is also a reported technique.¹⁴ In such cases, the flaps are often placed on top of each other with an unmonitored buried flap, though alternative means of monitoring, including flow coupler and Doppler blood flow monitors, are possible.

Some techniques preferentially call for splitting a conjoined flap into two independent stacked flaps^[31]. DellaCroce et al. suggest that the folding of the bipedicled flap may actually compromise the shared blood supply and that separation of the flaps allows for independent inset and enhanced ability to shape the reconstruction^[32]. While conjoined flap do offer less maneuverability and flexibility for inset, multiple techniques have been described to optimize shaping for both conjoined and stacked abdominally-based flaps^[25].

Multiple donor sites

Independent stacked flaps are most commonly used from multiple donor sites. In autologous breast reconstruction, the lower extremity, particularly the medial thigh, is frequently utilized^[33]. Flaps harvested from the medial thigh typically include the transverse upper gracilis (TUG), diagonal upper gracilis (DUG), and PAP flap^[33]. The PAP flap was first described for breast reconstruction in 2012 and since then has become the second or third choice for autologous breast reconstruction after DIEP^[34]. In cases where the abdominal donor site is unavailable or insufficient, the stacked PAP flap provides ample skin and soft tissue for unilateral reconstructions [Figure 5]. A retrospective series of 20 stacked PAP flaps by Haddock et al. reported an average combined flap weight of 685.5 g^[28]. The long pedicle in the PAP flaps affords multiple options for recipient vessels. Flaps are typically anastomosed to the cranial and caudal IM vessels, though the thoracodorsal system or intra-flap anastomoses can also be utilized if necessary^[28,35]. Stacked LTP flaps have similarly been described to provide adequate skin and volume in unilateral reconstructions^[36].

Figure 5. Stacked PAP flaps in a patient with prior bilateral mastectomy as well as a history of circumferential body lift with severe left chest wall radiation. A: A large proximal branch of one flap (blue background) is utilized as recipients for the second flap. B: Left stacked PAP reconstruction and right tissue expander placement in first stage of delayed reconstruction.

The use of multiple flaps per breast lends itself to many opportunities for improving volume in autologous breast reconstruction. Several different configurations and donor sites for bilateral breast reconstruction have been described with stacking flaps at each recipient site, performing “four-flap reconstructions”. Dellacroce et al. described bilateral stacked DIEP and SGAP flaps with intra-flap anastomoses effectively resulting in a body lift four-flap reconstruction^[37]. More recently, a similar configuration of stacked DIEP and LAP flaps has also been described for a circumferential four-flap body lift reconstruction^[38].

Four-flap reconstructions have classically utilized bilateral stacked DIEP and PAP flaps. In these cases, the PAP flap typically restores the lower pole contour while the hemi-abdominal DIEP is rotated 90 degrees for the upper pole, mimicking the shape of a mastectomy specimen^[39]. Recently, studies have advocated for asymmetric four-flap reconstructions in cases of bilateral reconstruction, utilizing a conjoined bipedicled DIEP on the side requiring additional skin resurfacing and stacked PAP flaps on the contralateral side^[39,40].