Continuing Education Activity

Free tissue transfer has become a common technique for breast reconstruction following oncologic resection. Free transverse rectus abdominis muscle (TRAM) flaps are one option for autologous breast reconstruction. This activity reviews the evaluation and treatment of patients with a deficit of breast tissue following oncologic resection who wish to undergo autologous breast reconstruction using free transverse rectus abdominis flaps and highlights the role of the interprofessional team in evaluating and treating these patients.

Objectives:

• Describe the vascular anatomy of the rectus abdominis muscle and the overlying abdominal skin.
• Identify the indications and contraindications for autologous breast reconstruction.
• Describe the muscle-sparing options for free transverse rectus abdominis flaps.
• Outline how interprofessional teams can improve the post-operative monitoring of patients who have undergone autologous breast reconstruction with free transverse rectus abdominis muscle flaps.

Introduction

Oncologic surgeries for breast cancer often leave cosmetically significant defects. Several strategies have been developed to reconstruct acquired absence of the breast. These strategies categorized into autologous and implant-based reconstructions.

Transverse rectus abdominis muscle (TRAM) flaps are one option for autologous breast reconstruction. TRAM flaps can be used as a pedicled or free flap. The pedicled TRAM was first described by Dr. Hartrampf in 1982.[1]  However, it had high abdominal wall morbidity and was based on the less dominant superior epigastric artery and has been modified to a free version to base the blood supply off of the more dominant deep inferior epigastric artery.  This discussion will discuss the many iterations of the free TRAM flap.

Anatomy and Physiology

The blood supply of the free TRAM flaps derives from the deep inferior epigastric artery (DIEA), which itself arises from the external iliac artery. The superior epigastric artery is the continuation of the internal thoracic artery and anastomoses with the DIEA. Because of this, the flap has two separate blood supplies (the superior epigastric and the DIEA), which characterize it as a Mathes and Nahai type III muscle flap.[2]  The epigastric arteries pass along the deep aspect of the rectus abdominis muscles, which they supply, along with the overlying skin and fascia. Most commonly, the DIEA bifurcates at the level of the arcuate line, resulting in a medial and lateral row of perforating vessels (Type II vascular pattern). A single (Type I) or trifurcating (Type III) DIEA occurs less frequently.[3][4] When harvesting a TRAM flap, all of the muscular and fasciocutaneous perforators are preserved in the flap and not dissected out individually.

Several variations of muscle harvest have been described under the designations of muscle-sparing (MS) 0 through 3. MS0 refers to a flap in which there is the removal of the entire width of the rectus abdominis muscle. MS1 subdivides into medial and lateral, referring to the segment of muscle preserved. That is, in an MS1-M flap, there is the removal of the lateral segment of muscle and preservation of the medial segment. An MS2 flap preserves both the lateral and medial segments of the muscle, removing only a strip of tissue in the middle of the muscle. The term MS3 is sometimes used to denote a deep inferior epigastric perforator flap, in which there is the preservation of the entire muscle.[5]

A skin island is typically harvested with the donor muscle. Hartrampf described the zones of TRAM flap blood supply to the overlying skin. Zone I is directly overlying the rectus muscle. Zone II is across the midline; zones III and IV are the ipsilateral and contralateral lateral skin of the flap, respectively.[1] However, the deep inferior epigastric artery does not reliably perfuse the contralateral abdominal skin, and often it gets harvested for a free flap as two separate hemi-abdominal flaps. Therefore, zones I and III are the more reliable skin islands.[6] This classification was modified by Ninkovic and Holm to have Zone I directly on muscle and zone II adjacent lateral zone as it more closely relates to the free flap morphology.[5]

Indications

Acquired breast defects following treatment of breast cancer are the most common indication for reconstruction. However, it is also common for patients with BRCA1/2 or other genetic predisposition to have a bilateral mastectomy and reconstruction. Patients should receive counsel regarding the relative risks and benefits of implant-based and autologous breast reconstruction and other donor site options before choosing a free TRAM reconstruction.

Contraindications

There are few true contraindications to free TRAM breast reconstruction presuming that they have an appropriate donor site and an adequate amount of tissue.  Abdominoplasty or any other procedure in which there has been the sacrifice of the abdominal perforators is a contraindication to abdominal-based flaps.  Very thin patients who lack the tissue necessary to reconstruct an appropriately sized breast would be better suited to an alternative reconstruction.  Active smoking is a relative contraindication of microvascular free tissue transfer.[5] Obesity is associated with an increased risk of complications. BMI greater than 30 is associated with worse outcomes at the donor site, recipient site, and partial flap failure. Patients with a BMI greater than 40 are at a very high risk of flap failure.[7] Chronologic age alone is not associated with increased complications and is not a contraindication to autologous tissue reconstruction.[8]  Those with hypercoagulable states are at high risk for flap failures and problems with microsurgery.[9]

Equipment

Requisite equipment includes an operating microscope and a microsurgical instrument set. Heparinized saline should be available in the surgical field. Papaverine should be available to treat vascular spasm.  Thrombolytics might be necessary and should also be available.

Personnel

An operative team facile with microvascular equipment and the operating microscope is essential for successful free tissue transfer. An assistant skilled in microvascular surgery is preferred.  Otherwise, standard operating room personnel setup is appropriate.  It is also necessary to have adequately trained nursing staff to monitor the patient and flap afterward.

Preparation

Patients should receive counseling on the options for breast reconstruction, including the option not to under a reconstructive procedure. The risks specific to free tissue transfer should be disclosed to the patient, including flap problems and donor site complications.

Patients who have undergone abdominal surgery may receive a computed tomography angiogram to assess perforator anatomy. Patients with a personal or family history of blood clots may be referred to a hematologist for hypercoagulable workup. Finally, all patients should receive appropriate preoperative anticoagulation and antibiotics.

Technique or Treatment

The abdominal skin island is designed as an ellipse, similar to an abdominoplasty incision. A low, transverse incision and a supraumbilical, transverse incision complete the ellipse. Dissection proceeds superficial to the external oblique fascia from lateral to medial until the lateral row of deep inferior epigastric perforators is encountered. At this point, the fascia is incised lateral to the perforator row. The skin and subcutaneous tissue are then similarly elevated from the contralateral side, crossing the midline until the medial row of perforators is identified. The medial fascia is incised at this level. Depending on which variety of free TRAM (MS-0 to 3 differing amounts of muscle are taken with the flap).  The rectus muscle gets divided at the superior and inferior edge of the skin incision. The DIEA is then dissected to its origin off the iliac. After preparing the recipient site, the vessel is clipped and divided.

The internal mammary artery and vein are the preferred recipient vessels for autologous breast reconstruction. The most common access point for the vessels is between the third and fourth ribs, which can be spared or partially removed to expose the vessels.

The flap is harvested from the abdomen and placed into the chest.  Standard microsurgical anastomosis of the vein and artery are performed, and the flap is inset and shaped into a breast mound.  Many varieties of inset are possible depending on the mastectomy defect and surgeon preference. 

Breast reconstruction patients often require additional revision procedures to recreate symmetry and appropriate shape. Frequently performed procedures include fat grafting and contralateral mastopexy.

Patients who receive immediate reconstruction may require adjuvant radiation. While there is an increased risk of flap fibrosis, there is no increased risk of wound complications, fat necrosis, or infection.[10]  Overall, delayed reconstruction correlates with improved cosmetic outcomes.[11] Therefore, the general recommendation is that patients wait 12 months after radiation for autologous reconstruction.[12]

Complications

Complications include partial or total flap loss, infection, seroma, hematoma, fat necrosis, and donor site complications. Published series have shown a complete or partial flap loss rate of 0.6% to 1.3%. More commonly, poorly perfused flap segments result in fat necrosis. The development of a hematoma can threaten microvascular anastomosis. Meticulous hemostasis is requisite for free tissue transfer. Several series have considered the morbidity associated with the TRAM donor site. The literature has described hernias, abdominal wall laxity, and wound complications.[13]

Clinical Significance

TRAM flap is a viable option for autologous breast reconstruction. Various muscle sparing options are available to lessen donor site morbidity.

Enhancing Healthcare Team Outcomes

Multiple options exist for breast reconstruction following oncologic resection, and the management of oncologic breast defects has changed over time. Abdominal-based flaps have become workhorse donors for reconstruction, including free transverse rectus abdominis muscle flap (TRAM), muscle-sparing TRAM flaps, and deep inferior epigastric perforator flaps. Prior abdominal surgery, prior and planned radiotherapy, and other patient factors may complicate decision-making in the preoperative period. Collaboration with breast surgeons and the other treating oncologic teams is imperative for the best outcomes.

Intraoperatively, an operating room staff familiar with microvascular tools, techniques, and required medications is important for good outcomes. Nurses with specific surgical training are an integral part of the health care interprofessional team. Coordination with the anesthesia team, including the nurse anesthetists and anesthesiologists, is necessary for appropriate anticoagulation and blood pressure management.

In the postoperative period, the receiving nurse is of critical importance, as they are the first line in diagnosing flap problems. Pharmacists are likewise important to aid with appropriate inpatient and outpatient anticoagulation. An interprofessional team familiar with the needs of microvascular patients can minimize complications and diagnose flap problems more quickly.