**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**).

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

#### **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.*
