Immediate Prepectoral Implant Breast Reconstruction

Introduction

Prepectoral implant–based breast reconstruction is a recent addition to the breast reconstructive armamentarium that is rapidly being adopted given its simplicity and reported potential benefits. The technique involves placing the implant subcutaneously over the pectoralis major muscle, as opposed to under the muscle (subpectoral), which is the current established practice. By placing the implant over the pectoralis major muscle, the prepectoral approach preserves the anatomic integrity of the muscle as it is not dissected or elevated as in the subpectoral approach. With preservation of the muscle, the prepectoral approach eliminates animation deformity, pain, and muscle spasm that are often reported with elevating the muscle in the subpectoral approach. In addition, the prepectoral approach results in a natural-looking breast that anatomically resembles a native breast.

The prepectoral concept, however, is not a novel concept. Subcutaneous implant placement was attempted more than half a century ago when silicone implants were first introduced to the market. The technique, however, was soon abandoned when it became apparent that soft tissue coverage provided by the mastectomy flap alone was insufficient to support and maintain the implant above the muscle. Complications of bottoming out; implant migration; implant visibility, palpability, rippling, and wrinkling; and skin breakdown were, thus, common with this technique.

The renewed interest in the prepectoral or subcutaneous approach began after a number of technique and device advancements were introduced over the years in breast reconstructive surgery. Mastectomies became less aggressive, deviating from radical mastectomies to skin- and nipple-sparing mastectomies that preserved mastectomy flap perfusion and viability, which are critical for the prepectoral approach. Tissue perfusion devices became available that could assess perfusion in real time, providing an objective means of evaluating flap viability. The use of acellular dermal matrices (ADMs) for lower pole soft tissue coverage in the dual-plane approach eventually led to the idea that the matrix could be used to provide total implant coverage, obviating the need to elevate the pectoralis major muscle. Improvements in implant designs, such as the highly cohesive gel implants, which are associated with less rippling and wrinkling, meant that these complications which are concerns with prepectoral implant placement could be mitigated. Lastly, advances in autologous fat grafting techniques have permitted the use of autologous fat to provide additional soft tissue coverage that is often needed in the prepectoral approach to mask implant visibility and rippling. All of these advancements taken together are credited with making the prepectoral approach a reality.

The authors and others have shown that the prepectoral approach can be an effective reconstructive option, but careful patient selection and meticulous technique are critical for successful outcomes. This chapter reviews the indications/contraindications and technique principles related to the prepectoral approach.

Indications and Contraindications

In general, ideal candidates for immediate prepectoral breast reconstruction are those who have a normal body mass index (BMI), small to medium breasts, minimal co-morbidity, and well-perfused mastectomy flaps. Many patients do not have this “ideal” candidate profile as they may be thin or obese or have mammary hypertrophy. This does not mean that prepectoral reconstruction is contraindicated in these patients but rather that it may be challenging to perform.

The availability of well-perfused, viable, mastectomy skin flaps is the single most absolute requirement for immediate prepectoral reconstruction. Given the proximity of the implant to the skin flaps, compromised skin flaps can result in skin necrosis which, in turn, may lead to infection, implant extrusion, and reconstructive failure. For this reason, any patient characteristic or factor that compromises flap perfusion or quality is considered a contraindication to immediate prepectoral approach. Thus, patient co-morbidities such as a BMI greater than 40 kg/m ² (morbid obesity), uncontrolled diabetes (HbA1c >7.5%) and active smoking are all contraindications to the immediate prepectoral approach. In addition, immunocompromised patients are also not suitable candidates because these patients are, in general, at increased risk of complications, particularly infectious complications. In patients with uncontrolled diabetes, prepectoral reconstruction can, however, be performed as a delayed procedure after controlling blood sugar with appropriate treatment. Likewise, obese patients (BMI >40 kg/m ² ) without prior radiation therapy can be considered for delayed prepectoral reconstruction.

Immediate prepectoral reconstruction is generally not recommended in patients who have undergone prior breast irradiation, particularly if the lumpectomy scar is in the lower pole. Radiation damages the skin envelope and causes dermal thickening, thus increasing the risk of skin breakdown during the tissue expansion phase. Reconstructive options for these patients have traditionally relied on autologous approaches. However, an immediate, latissimus-based, prepectoral approach can be considered in these patients. The latissimus-based approach is typically performed in two stages (expander/implant), with or without soft tissue introduction with the flap depending on the need for supplemental soft tissue. The expander stage is critical in this approach to allow for skin and subcutaneous tissue expansion.

Post-mastectomy radiation therapy (PMRT), on the other hand, is not a contraindication to immediate prepectoral reconstruction. PMRT can be delivered to the expander or the implant as in the subpectoral approach. PMRT, in general, increases the risk of short- and long-term complications, including incisional dehiscence, infection, delayed healing, seroma, hematoma, capsular contracture, implant malposition/asymmetry, and reconstructive failure. Being cognizant of potential complications of PMRT is important as proactive management can improve patients’ chances of a good outcome.

Lack of fat depots is another contraindication for immediate prepectoral reconstruction. This is of particular concern in thin patients. Thin patients have thin skin flaps that may not be adequate to mask implant visibility and rippling and require autologous fat grafting to improve aesthetic outcomes. However, alternative soft tissue fillers are an option in those without fat depots, in which case immediate prepectoral reconstruction can be considered. Further, highly cohesive gel implants are associated with less rippling and their use in thin patients may help reduce implant-related complications.

In addition to the reconstructive indications/contraindications, a number of oncologic factors also need to be taken into consideration when contemplating immediate prepectoral reconstruction. Patients with large tumors (>5 cm), posterior tumors lying near the pectoralis major muscle, chest wall involvement, axillary involvement, late-stage breast cancer, and a high risk of recurrence are not candidates for prepectoral placement. The oncologic safety of prepectoral placement in these cases is not known and it would be prudent to adhere to a conservative, cautious approach to breast reconstruction in these patients. In patients with axillary involvement and late-stage breast cancer (stage IV), aggressive adjuvant therapies may be required which preclude the immediate reconstructive option.

It should be noted that the immediate reconstructive contraindications discussed above do not apply to delayed prepectoral reconstruction. In particular, flap viability and perfusion is not a requirement for delayed reconstruction. When considering patients for delayed prepectoral reconstruction, the overall health of the patient is taken into consideration.

Preoperative Evaluation

Patient selection for immediate prepectoral reconstruction is governed by preoperative patient characteristics, co-morbidities, neoadjuvant therapies, cancer stage, and tumor location as well as intraoperative mastectomy flap perfusion and viability. The patient's BMI, HbA1c status, and smoking history are assessed and information regarding cancer stage, tumor location, and neoadjuvant therapies are obtained from patient records. In the absence of contraindications, as outlined above, patient eligibility is ascertained provisionally. Following mastectomy, assessment of flap viability is performed intraoperatively. Prepectoral reconstruction is only offered if patients have well-perfused mastectomy flaps. As alluded to above, well-perfused mastectomy flaps are an absolute requirement for the immediate prepectoral approach.

Assessment of flap vascularity and viability is ideally performed objectively with the use of a tissue perfusion assessment device. Several of these devices are currently available, most of which use indocyanine green angiography to visualize arterial and venous flow in real time. These devices not only allow the assessment of tissue viability but also help identify areas of compromised perfusion, allowing their immediate excision to minimize tissue damage.

When a perfusion assessment device is not available or easily accessible, flap viability is ascertained by clinical assessment. Clinically, a well-perfused flap is recognized by bleeding incision margins and the presence of a layer of subcutaneous tissue under the flap. The latter is indicative of a preserved subdermal vascular plexus, which suggests the overlying flap is likely to be perfused and viable. A visible dermis under the skin flap suggests that the flap is too tenuous and not likely to be well perfused and viable. Skin flap thickness should not be used to assess for flap viability because skin thickness does not necessarily correlate to tissue viability.

In order to ensure the integrity of skin flap perfusion following mastectomy, a close collaboration with the general/oncologic surgeon is undertaken preoperatively. The general surgeon is briefed about the subsequent reconstructive approach so that aggressive mastectomies that compromise the vascularity of the mastectomy flaps are avoided as much as possible.