Rectus Abdominis Tissue Transfer

For decades, the rectus abdominis flap has been used to reconstruct breast defects, primarily as a pedicled flap. The advent of microsurgical techniques has allowed this versatile flap to be transposed to repair soft tissue defects of the head and neck.[1]  The flap provides healthy muscle, with or without a skin paddle, that can be used to replace soft tissue bulk.

Vascularized skin and fat resist atrophy, but denervated muscle shrinks with time. Motor reinnervation of the rectus muscle, which allows for preservation of muscle bulk over time, has been described and serves to increase the usefulness of this versatile flap. Although not optimal for small or shallow defects, the rectus flap provides the reconstructive surgeon with an excellent option to reconstruct large defects. This flap is most commonly used for glossectomy defects, orbital/maxillary defects, and (as a muscle-only flap) skull base reconstruction.[2]

Advent of the rectus abdominis flap

Head and neck defects often must be replaced with soft tissue and/or bone from other areas of the body. Significant loss of soft tissue requires flaps of sufficient bulk to adequately reconstruct the defect. Pedicled myocutaneous flaps have been the reconstructive option of choice in the past. However, these flaps are often unsuitable because of restricted pedicle length. The bulk of the muscle pedicle can be unsightly and, as the muscle atrophies and scars, may tether and lead to restriction of motion.

See the image below.

Proper flap design and tailoring of the flap to fit a certain tissue defect result in optimal functional and cosmetic outcomes. The limited ability to contour pedicled flaps often leads to bulkiness in the wrong location. The pectoralis major flap, with which otolaryngologists are very familiar, has a short pedicle and, therefore, limited reach. The pedicled latissimus dorsi flap has a long pedicle and can often reach the vertex but can be quite bulky and requires patient repositioning for harvest. A free myocutaneous flap is the best option for reconstructing large soft tissue defects in difficult locations such as the orbit. Bulk is placed where it is needed, and the flap can be designed and tailored to eliminate excess tissue where it is not required. Precise contouring to fit a 3-dimensional defect can be achieved. The pedicle adds minimal bulk and can be tunneled more discreetly than that of a pedicled flap.

The rectus abdominis flap is favored for this application because of its ease of harvest and reliability. It has been used extensively as both a pedicled and free flap for breast reconstruction. It can be harvested as a muscle-only flap or as a myocutaneous flap. The muscle can be skin-grafted if the subcutaneous tissue is excessive for the defect size. The pedicle is of adequate length for anastomosis in the neck or temporal region. Blood supply to the skin depends on perforators from the underlying rectus muscle; therefore, a cutaneous free flap without muscle cannot be harvested.

Head and neck defects often must be replaced with soft tissue and/or bone from other areas of the body. Significant loss of soft tissue requires flaps of sufficient bulk to adequately reconstruct the defect. Proper flap design and tailoring of the flap to fit a certain tissue defect results in optimal functional and cosmetic outcomes.

The routine preoperative evaluation includes a full history and physical examination. Routine laboratory studies, a screening chest radiograph, and a CT scan and/or MRI are obtained as required. Consultations with appropriate specialists are included in the assessment. Evaluation by a speech therapist is usually indicated. Consider a consultation with a dental and/or oral surgeon prior to surgery. Examination of the abdomen and groin for evidence of previous surgery must be performed. In female patients, consideration of parturition is a necessity because delivery may change the vascular anatomy to the skin.

Rectus abdominis free tissue transfer allows for transfer of a large vascularized segment of skin and muscle from the abdominal wall to its intended recipient site. Patients in whom other flaps would be too thin can benefit from this flap. As a muscle-only flap, it has become indispensable for reconstruction following skull base surgery.[3] As a myocutaneous flap, it is particularly suitable for reconstructing partial and total glossectomy defects (see the image below).

Reconstruction following orbital exenteration and maxillectomy is also facilitated with a rectus flap. The muscle bulk adequately fills the defect, although globe loss and a color mismatch are apparent. Maxillectomy without orbital exenteration and large neck defects are other possible applications for this flap. The muscle component of the flap allows for obliteration of 3-dimensional defects. The muscle can also be placed into "nooks and crannies."[4, 5]

Motor reinnervation is possible to maintain bulk (see the image below).

Fat volume is well preserved in a denervated free myocutaneous flap, but it loses muscular bulk with time. Preservation of bulk can be of functional benefit in the glossectomy patient. Sensory reinnervation has also recently been reported. The ability to identify a sensory nerve for anastomosis in the recipient bed would greatly benefit the glossectomy patient.

A study by Ireton et al supported the use of pedicled transverse rectus abdominis myocutaneous (TRAM) flaps for breast reconstruction. In the study, 188 women underwent either unilateral (164 patients) or bilateral (24 patients) breast reconstruction with pedicled TRAM flaps, with polypropylene mesh used in abdominal wall repair. Over a mean follow-up period of 36 months, the flap-site complication rate was 23.2% for the unilateral reconstruction patients and 0% for those who underwent bilateral reconstruction, while the donor-site complication rates were 9.8% and 20.8%, respectively. Only 4.3% of the unilateral patients and 4.2% of the bilateral patients required an operating room visit secondary to morbidity, and there were no complete flap losses. The investigators found obesity to be significantly associated with flap- and donor-site complications, with flap-site morbidity also linked to previous or current cigarette use and treatment with at least two adjuvant therapies.[6]

The rectus abdominis muscles are paired, vertically oriented muscles that are components of the abdominal wall. Superiorly, they attach to the rib cage. Inferiorly, muscle fibers extend to the pubis. They are divided into segments by tendinous inscriptions. The rectus sheath, formed by fascial extensions of the internal and external oblique muscles and transversus abdominis muscle, encases the rectus muscle. The lateral boundary of the rectus sheath is known as the linea semilunaris, and, medially, the linea alba separates the 2 rectus muscles.

Above the arcuate line, the posterior sheath is formed by the fascial condensation of the transversus abdominis and the transversalis fascia. As such, the anterior sheath can be removed with relative impunity because closure of the posterior sheath provides sufficient structural support to prevent abdominal herniation. Because musculocutaneous perforators to the skin paddle pass through the anterior sheath, this layer must be harvested beneath that portion of the skin paddle overlying the muscle. Below the arcuate line, the posterior sheath is only composed of the transversalis fascia, which is not strong enough to prevent hernia formation. Approximation of the anterior sheath or use of mesh is required to prevent a hernia from occurring in this area.

Vascular supply to the rectus is via the superior and deep inferior epigastric vessels.[7] The deep superior epigastric vessels are not used as the pedicle for the free flap because it is of smaller caliber than the inferior vessels and a greater amount of skin can be harvested with the inferior system. The superior pedicle provides the blood supply for a pedicled flap used for breast reconstruction. During harvest, the pedicle is identified in the inferior portion of the muscle on its lateral aspect. Usually, one vein is harvested with the artery. The skin of the myocutaneous flap is vascularized through musculocutaneous perforators, which are of highest density in the periumbilical region. This area is incorporated into the flap whenever possible in order to incorporate these vessels and optimize skin vascularity.

Contraindications for a rectus abdominis flap include prior abdominal surgery in which the vascular supply may have been transected and conditions that would otherwise make the patient unsuitable for a free flap. A patient with a preexisting hernia should warrant careful consideration if a rectus flap is planned because abdominal wall strength is weakened after this surgery. Extreme obesity is not a contraindication per se, but the result may be a bulky, perhaps unsightly, flap; such patients may be better candidates for a skin-grafted rectus muscle flap or another flap from a different site.

No specific preoperative vascular evaluation is required for patients who are to undergo rectus free tissue transfer. Appropriate informed consent is obtained by both the extirpative and reconstructive surgeons.

The flap can be harvested simultaneously by 2 teams. The defect size is measured or estimated, and a flap that is slightly larger than the defect is designed. Landmarks are palpated, which include the ribcage, pubis, and anterior superior iliac spine. The dissection does not extend beyond these landmarks. A unilateral flap that includes a periumbilical portion is created. This ensures capture of these perforators.

Depending on tissue requirements, the skin paddle can be designed vertically, totally overlying the rectus muscle, or obliquely, along an axis between the umbilicus and the tip of the scapula with much of the skin paddle lateral to the linea semilunaris.[8] This latter orientation is possible because of an axial blood flow pattern from the portion of skin overlying the muscle in the periumbilical area parallel along this axis. When designed in this manner, the lateral aspect of the flap is much thinner than the portion overlying the muscle and can be useful when the defect requires soft tissue of varying thickness.

The skin is incised, and cautery is used to dissect through the fat. Use caution when working with the rectus muscle because musculocutaneous perforators may be violated. Some surgeons prefer to place tacking sutures from the skin to the anterior sheath to preserve the viability of the perforators. The anterior rectus sheath is identified. The sheath is transected superiorly and inferiorly beneath the skin incision. The inferior incision is placed above the arcuate line in order to facilitate closure without the use of mesh. Laterally, the linea semilunaris is used as a landmark for the lateral sheath incision.

Preservation of as much sheath as possible is important to facilitate primary closure. The medial fascial incision is made in proximity to the linea alba, again taking care to preserve perforating vessels with dissection. A subfascial plane is then elevated superficially to the rectus muscle superior and inferior to the skin paddle. This allows wide exposure of the entire rectus muscle. Laterally, the muscle is elevated beginning superiorly to allow posterior dissection, leaving the posterior sheath intact. With continued inferior dissection, the vascular pedicle is identified along the lateral aspect of the muscle. Cautery is used to transect the muscle superiorly. Inferiorly, the pedicle is retracted for protection as the muscle is cut. With the flap attached only by the pedicle, the surrounding fascia is cleaned and the pedicle dissected until the external iliac vessels are reached.

When the flap is ready for transfer, the vessels are clamped and the pedicle is divided. The abdomen is closed in a primary fashion. Proper and careful closure of the anterior sheath is important to prevent a hernia (see the image below). Some surgeons routinely reinforce the closure with mesh; this is particularly important if the sheath has been violated inferior to the arcuate line. A suction drain is placed in the wound.

The flap is inset in the defect site, and the pedicle is oriented to avoid tension or kinking. Suitable recipient vessels are identified and cleaned of adventitia. The anastomosis is performed under magnification in a routine fashion. At the completion of the anastomosis, venous clamps are released and retrograde flow through the anastomosis is observed. The artery is then released; papaverine may be placed on the vessels. The configuration of the pedicle is optimized, suction drains are placed, and wound closure is completed.

Patients are monitored closely in the hospital. The skin paddle is monitored frequently for signs of vascular compromise.

The ideal technique by which a flap can be assessed is only theoretical and can vary in practicality depending on the flap, patient, available equipment, and other factors. Based on individual preference, cost, and familiarity with monitoring techniques, various monitors are available. The criterion standard, direct visualization and assessment of capillary refill with or without a needle prick, is the most reliable in trained hands. Devices that may assist nurses or residents in monitoring a flap include a standard or laser Doppler device placed over the pedicle. Arterial problems usually manifest within 24 hours; venous congestion often manifests 48-72 hours postoperatively. Frequent evaluation and careful monitoring allow for early identification of problems.

Fluid balance and overall patient condition are also monitored. The authors use prophylactic antibiotics and steroids for 24 hours; many routinely use prophylactic antibiotics much longer. Aspirin (325 mg) is given rectally, orally, or per feeding tube starting on the first postoperative day; many administer the medication immediately after the patient leaves the operating room.

An oral diet is started (if the patient did not have a gastric tube) when bowel sounds are present. Postoperative ileus is common for a short time following surgery and generally resolves spontaneously. Ambulation is helpful for hastening the resolution of ileus, heralded by the return of bowel sounds.

A pillow is placed on the abdomen to assist with coughing. Stool softeners are also useful to minimize abdominal strain. We use an abdominal binder for 4 weeks.

Upon discharge from the hospital, the patient continues to take 1 aspirin each day unless contraindicated. The first postoperative visit generally occurs 1-2 weeks after release from the hospital. Flap viability is assessed. Any remaining sutures are removed. The recipient site is evaluated for complications. Removal of the feeding tube and/or tracheotomy tube, if still present, is considered. The patient is also evaluated by a speech pathologist, physical therapist, or other specialists, as required.

A study by Kagaya et al indicated that in patients who undergo reconstruction with a free rectus abdominis myocutaneous flap for total or subtotal maxillectomy, factors independently associated with flap volume loss include weight reduction, young age, and postoperative radiotherapy. The investigators also reported that fat volume remained stable in the study patients over time, while muscle volume was reduced to less than 40%, if influencing factors were absent. In addition, the report found that “the fat volume tended to gather toward the central-cranial direction, while the muscle volume gathered toward the cranial direction,” with the total flap volume gathering toward the central direction.[5]

Donor site complications are uncommon but possible. Hernias may occur when the rectus sheath has not been properly closed or is insufficient for adequate closure. Wound infections may also occur. A general surgeon may be of assistance in wound closure in patients at risk.

As with any microvascular surgery, free flap failure is a risk. A study by Kubo et al indicated that in free flap microsurgical head and neck reconstruction, disruption of the anastomosed blood vessels common after anastomosed site infection. The study, which included rectus abdominis, anterolateral thigh, radial forearm, jejunum, and latissimus dorsi flaps, found that vein disruption (without accompanying artery disruption) occurred in five out of 11 cases; artery and vein disruption, in two cases; and artery disruption (without accompanying vein disruption), in one case.[9]

Flap salvage following venous or arterial thrombosis is possible if early identification of vascular compromise leads to early (urgent) operative intervention. If thrombosis is identified and appropriately managed or pedicle geometry is optimized if twisting had occurred, the flap may be saved. Thrombectomy and revision of any thrombosed vessels are performed if required; occasionally, this necessitates vein grafting.

For flaps with venous congestion in patients who cannot be returned to the operating room immediately, leeches may be used to temporarily relieve the congestion. This technique should be used only very rarely for long-term salvage. Leeches work by removing the engorged blood from the flap and, thereafter, allowing artificial venous outflow through their bite in the patient's skin (ie, flap). An enzyme, hirudin, found in the leech saliva, enhances blood flow through the bite. This enzyme is a powerful anticoagulant and, together with removal of the tiny clot that forms at the bite site, allows flaps to slowly bleed for hours. Leeches can transmit Aeromonas hydrophila, a gram-negative rod, and patients should receive antibiotic prophylaxis that covers beta-lactamase–resistant organisms if leech therapy is used.

If one or all of the veins are thrombosed, the arterial anastomosis may be allowed to remain intact at the discretion of the surgeon. Venous drainage occurs through the unattached veins. The authors irrigate University of Washington solution (ie, streptokinase and heparin), which has been shown to improve flap survival, through the flap. Generally, systemic heparin should be started in the operating room and continued in the postoperative period for 7 days. Hematomas may occur as a result of anticoagulation. Drains should be placed carefully in the operating room and not removed until the heparin has been discontinued.

Survival of the flap is dependent on the immediate identification and treatment of complications. A flap survival rate of greater than 90-95% is expected in experienced hands. Flap complications occur in 0-20% of patients.

Patient prognosis and survival is more dependent on the primary tumor and oncologic treatment thereof than on the technique chosen for reconstruction. Postoperative radiotherapy is frequently administered when healing is complete.

Innervation of both sensory and motor supply to the flap is still being evaluated. It has yet to be proven efficacious with regard to improving speech or swallowing. It adds little to the surgery to reanastomose the nerves; thus, the drawbacks are few. Functional rehabilitation following total glossectomy or significant resection of the base of the tongue is vexing. Any advantage achieved by innervating the flap is worthwhile.[10, 11]

The routine use of mesh to reinforce the abdominal closure is also controversial. Certainly, the presence of a postoperative hernia is undesirable. Consultation with a general surgeon may be of value in achieving primary closure.