Following mastectomy, the wounds are irrigated and hemostasis is obtained. The mastectomy flaps are evaluated by examining their thickness and assessing color and capillary refill. Areas where dermis is exposed internally should be carefully evaluated externally. Areas where the external skin is pale without capillary refill should be considered for debridement. Laser-assisted indocyaninegreen fluoroscopy has been promoted to assess mastectomy flap perfusion; however, guidelines for its use and interpretation have not been firmly established.¹

Use of tumescent solution by the extirpative surgeon makes assessment of mastectomy flaps difficult and has been shown in some studies to be associated with a higher rate of mastectomy flap necrosis.^{2, 3, 4}

When there is significant concern for mastectomy flap necrosis, or if debridement of questionable tissue will lead to closure under tension or an open wound, then aborting reconstruction is strongly advised.

If necessary, the IMF can be recreated with interrupted suture; however, the position of the inferior edge of the expander will ultimately determine the IMF, which can be adjusted further during an exchange procedure if desired. Some surgeons try to establish the native IMF during this initial procedure (which may make the exchange procedure simpler), whereas others intentionally place the expander lower than the IMF to increase lower pole expansion and projection (which requires recreation of the IMF with suture during the exchange procedure). The author’s preference is to preserve the native IMF when performing single-stage implant reconstruction, when placing a significant initial fill volume in the expander, or when the IMF is already low. When performing delayed two-stage implant reconstruction or when placing minimal initial fill volume in the expander, placing the implant below the IMF will preferentially expand the lower pole and permit the surgeon to create minimal ptosis at the exchange procedure (as described in the following text).

The tissue expander cannot be covered by the mastectomy flaps alone, which are thin and offer poor soft tissue coverage. Ideally, the surgeon should provide complete musculofascial coverage with the pectoralis major and serratus anterior muscles (FIG 2), or use an acellular dermal allograft (ADA) or other product in addition to the pectoralis major muscle.

The lateral edge of the pectoralis major muscle is pinched between the surgeon’s index finger and thumb and pulled away from the chest, revealing a loose areolar plane between the pectoralis major and minor muscles. Dissection in this plane commences with Bovie cautery, but once the subpectoral space is entered, much of the superior and medial implant pocket can be created via blunt digital dissection before using lighted retractors for direct visualization. A lighted retractor is quite helpful to finish medial dissection, as great care must be taken to ligate or cauterize the intercostal perforators of the internal mammary vessels (FIG 3).

The medial boundary is defined externally by the preoperative markings that define the patient’s native breast form. Internally, it is quite common to release the medial and inferomedial origins of the pectoralis major muscle. It is important not to release this area excessively, as symmastia can result and is difficult to correct.

After the subpectoral plane is developed, the inferior insertion of the pectoralis major muscle is examined (FIG 4). If the patient’s muscle reaches the IMF, then a submuscular pocket can be created down to the IMF with supple and adequate soft tissue coverage that will respond well to expansion (FIG 5). More commonly, however, the pectoralis major inserts above the IMF. In this scenario, to provide autologous implant coverage inferiorly, one must continue dissection past the pectoralis major insertion and under the anterior rectus sheath until just below the IMF. Transitioning from the subpectoral plane to underneath the anterior rectus sheath is sometimes technically difficult and may result in a few gaps in coverage that can be closed after the pocket is fully created. A lighted retractor is necessary for this portion of the procedure. The anterior rectus sheath is quite stiff and will not expand well unless an incision is made transversely across the sheath just below the IMF, entering the subcutaneous
plane (FIGS 6 and 7). If the anterior rectus sheath is released above the IMF, one would obviously enter the implant pocket. The goal is to provide complete and supple submusculofascial coverage without gap between the pectoralis major and the IMF. Alternatively, the pectoralis major can be released from the chest wall and a piece of ADA (or other product) can be sewn to the IMF inferiorly and the cut edge of the muscle superiorly.

Following creation of a subpectoral pocket with or without elevation of the anterior rectus sheath, inferolateral coverage must be provided. Autologous coverage is provided by elevating the serratus anterior fascia if robust, or a partial thickness muscle flap if the fascia is thin or traumatized from the mastectomy. An incision in the serratus anterior is made at the level of, and parallel to, the inferolateral edge of the pectoralis major muscle and a fascial or musculofascial flap is elevated to the anterior axillary line (FIG 8). Alternatively, one can determine the width of the implant pocket based on the width of the desired tissue expander and stop lateral dissection when a sufficient pocket width is achieved (usually 1 cm wider than tissue expander). At this point, the inferior and lateral dissections will be complete, but the inferior serratus and superolateral external oblique muscles will still be attached to the chest wall. By retracting inferiorly and laterally, this plane is exposed and the muscles can be elevated off the chest wall to open the inferolateral pocket (FIG 9).