Continuing Education Activity

The latissimus dorsi myocutaneous flap or myofascial flap is a useful technique with many head, neck, and torso reconstruction applications. When there is a large soft-tissue defect of the head and neck or torso that requires pliable soft tissue for reconstruction, the latissimus flap is an excellent option. This activity reviews the latissimus dorsi muscle's anatomy, indications, and contraindications for flap transfer, and the surgical technique with its potential complications and also highlights the interprofessional team's role in evaluating and improving care for patients who undergo this procedure.

Objectives:

• Identify the anatomical structures important to latissimus dorsi flap transfer in both a pedicled and free fashion.
• Describe the technique of latissimus dorsi flap harvest, transfer, and inset.
• Outline the potential complications of latissimus dorsi flap transfer and their clinical significance.
• Review interprofessional team strategies for improving care coordination and communication to improve outcomes after latissimus dorsi flap transfer.

Introduction

The latissimus dorsi myocutaneous flap or myofascial flap is a useful technique with many head, neck, and torso reconstruction applications.[1][2] It can be harvested in a pedicled fashion or for free tissue transfer, and it can provide a large amount of pliable soft-tissue often not available with other types of flaps. Herein, we review the latissimus dorsi muscle's anatomy, indications, and contraindications for flap transfer, and the surgical technique with its potential complications.

Anatomy and Physiology

The latissimus dorsi, or "wing" muscle, is among the largest and strongest in the body. It originates on the spine and ilium and extends across the upper and mid-back to insert on the superior humerus. The latissimus lies superficial to the ribs and intercostal muscles, and it traverses inferiorly and laterally to the scapula and scapular muscles. The muscle is perfused by the thoracodorsal vessels and innervated by the thoracodorsal nerve.[3][4] 

Like the circumflex scapular artery, the thoracodorsal artery is a terminal branch of the subscapular artery; it descends accompanying the lateral aspect of the back and is typically accompanied by one, or occasionally two, venae comitantes. The thoracodorsal artery itself gives descending and transverse branches, with one branch supplying the serratus anterior muscle. The vessels enter the latissimus dorsi muscle belly approximately 10 cm from its insertion at the humerus, and they continue along the deep surface of the muscle.

Indications

Latissimus flap transfer is indicated in reconstructing large defects of the head, neck, and chest, whenever a defect requires broad soft-tissue coverage. Latissimus free tissue transfer is particularly useful for defects of the entire scalp.[5] Pedicled latissimus transfer is frequently employed in breast reconstruction after mastectomy[1], and free functional muscle transfer of the latissimus can be used in facial reanimation.[6][7] In recent years, free latissimus transfer has been used in transgender surgery to create a neophallus.[4] 

A pedicled latissimus flap, including muscle alone or muscle and skin, can be used anywhere on the chest or neck it can reach in a tension-free fashion. The pedicled configuration is particularly useful in women with neck defects who prefer to avoid pectoralis flap reconstruction that would deform the breast. The reach of a pedicled latissimus flap varies from person to person, depending on the torso's length and width. The flap itself remains pedicled at the thoracodorsal artery's takeoff, between the lateral scapula and the axilla. The pedicle can be dissected for free tissue transfer as far as the takeoff of the subscapular artery from the axillary artery, and often a substantial pedicle length can be achieved, sometimes as long as 15 cm.

The donor site is often closed primarily, but the ability to close the donor site's skin does not limit the size of the flap that can be harvested; the back can be partially or wholly covered in split-thickness skin grafts to achieve closure. Alternatively, a large myofascial flap transferred for reconstruction can, itself, be covered by split-thickness skin grafts. In rare cases, a "mega flap" involving the latissimus dorsi and the parascapular soft tissue can be harvested if the defect is huge; this flap requires the harvest of the subscapular artery, which includes both the circumflex scapular and thoracodorsal branches.[8]

Contraindications

The latissimus flap may be compromised if a patient has had prior injuries or surgery to the shoulder and back that have disrupted the flap’s blood supply; in such cases, latissimus transfer should not be undertaken. Patients should not proceed with reconstructive surgery without medical optimization first and thorough cardiovascular evaluation, as surgical time can be for an extended time, and blood loss may be significant, particularly during free tissue transfer.[9] 

Patients should be counseled to expect several days for recovery in the hospital after surgery and should be prepared for the possibilities of partial or complete flap failure, post-operative infection, and other risks of surgery. If patients require radiotherapy as part of comprehensive cancer management after surgical resection and reconstruction, then a muscle-only flap with overlying split-thickness skin grafts should not be transferred. Skin grafts require a minimum of six weeks of healing before they can be subjected to radiation, so employing skin grafts in reconstruction could delay the start of radiotherapy.[10]

Equipment

Pedicled and free latissimus transfer takes place in the operating room with sterile technique. Some surgeons prefer to harvest the flap with the patient in a prone position, then flip the patient into a supine position mid-case for flap inset. However, the flap can be successfully harvested with the patient in a lateral decubitus or even supine position with the aid of a padded bump or extra surgical tech to hold the body in a slightly rotated position. The flap can be harvested, transferred, and inset with standard surgical instruments and monopolar electrocautery. If free tissue transfer is performed, a microscope, microsurgical instruments, and a surgeon trained in microvascular surgery are required.

Personnel

Flap transfer requires a minimum of four people in the operating room:

• The surgeon
• Surgical technologist
• Circulating nurse
• Anesthetist

Having more people scrubbed in is often useful for tissue retraction and can make the surgery more efficient.

Preparation

Patients should undergo pre-operative risk stratification before any major surgery, including latissimus dorsi flap transfer. Patients should be screened for cardiovascular and pulmonary diseases that may increase the risks of general endotracheal anesthesia. Pre-operative imaging of the harvest and inset sites is not required for latissimus transfer. Blood loss from surgery can be significant, however, so a type-and-screen should be performed to prepare for the possibility of transfusion. Finally, patients' nutrition, electrolyte levels, thyroid hormone levels, and other wound healing predictors should be checked and optimized before reconstructive surgery is performed.[9]

Technique or Treatment

There are multiple methods of elevating and transferring a latissimus flap. If a pedicled flap is planned, then initially, the length of muscle required and location of a skin paddle (if needed) can be measured. A simple way of marking the distal edge of the flap to be harvested is to use a gauze strip. Gauze can be laid from the wound's farthest edge to be reconstructed to the pivot point, the area between the scapula and axilla. Then, holding one end of the gauze at the pivot point, the other end can be rotated to the back, and the edge marked to denote the edge of the flap that must be raised. The wound can also be measured, and a similar-sized skin paddle can be marked on the back. In free tissue transfer, the skin paddle harvest site is judged based on the needed pedicle length and location. The thoracodorsal artery enters the latissimus muscle approximately 10 cm beyond the muscle's attachment at the humeral head, and this entrance point must be included in any flap to ensure tissue viability.

In some cases, an initial incision is made in the mid-axillary line extending from the armpit inferiorly to the anterior-superior iliac spine. Dissection then proceeds deeply to identify the lateral edge of the latissimus muscle. The serratus anterior and rhomboids are encountered in this dissection and should be separated from the muscle. The avascular plane deep to the muscle is entered and gently elevated with blunt instruments or the surgeon's hand, permitting visualization of the thoracodorsal vessels that run along the muscle's deep surface. After verifying the vessels' location, a medial incision delineates the skin paddle to be harvested, ensuring the paddle overlies the vessels. If a skin paddle is not needed, monopolar electrocautery is used to elevate the skin and subcutaneous tissue free of the superficial surface of the muscle, and then a medial incision through the muscle, again ensuring the thoracodorsal vessels are included, is completed.In a different technique, the flap paddle's location is marked based on the approximate entry point of the thoracodorsal vessels into the muscle itself. The skin paddle is incised, and dissection is carried down to the surface of the latissimus muscle. The superficial surface is then exposed using electrocautery laterally and superiorly. The medial and inferior aspects of the skin paddle incision are then continued to reach the deep surface of the latissimus muscle. After this, the muscle is bluntly elevated in a superolateral direction until the thoracodorsal vessels are visualized. The muscle surrounding the pedicle can be narrowed as necessary so long as the vessels themselves are not violated. In facial reanimation, the thoracodorsal nerve, which runs parallel and lateral to the vessels, is then coapted to the masseteric nerve and/or a cross face nerve graft with micro sutures.

For free tissue transfer, the thoracodorsal vessels can be dissected proximally to extend the pedicle length, which requires ligation of the branches to the serratus anterior muscle and scapula. After sufficient length is dissected, the pedicle can be ligated and the flap transferred to its new position for microvascular anastomosis. In the case of pedicle flap transfer to the head and neck, it is particularly important to separate the humeral head's latissimus attachment. Further, the vessel branches to the scapula should be ligated to permit improved flap rotation and prevent vessel kinking that could compromise flap viability after transfer. A subcutaneous plane superficial to the pectoralis muscle can be developed for pedicled flap transfer to the anterior torso; for transfer to the head and neck, a similar tunnel superficial to the pectoralis muscle, superficial to the clavicle, and deep to the platysma can be developed. An intermediate incision parallel and superior to the clavicle can aid flap transfer to the head and neck. In all pedicled flap transfer cases, the tissue tunnel should be generously wide to easily accommodate the flap and not risk vascular compression.

After flap transfer, the latissimus can be inset with layers of absorbable and non-absorbable suture. Meticulous hemostasis at the inset site and donor site are necessary to prevent the development of a hematoma. If a muscle-only flap has been transferred, it should be covered by split-thickness skin grafts and a bolster. The donor site should, ideally, be closed primarily. In the case of a large skin paddle transfer, significant subcutaneous undermining may be necessary to allow advancement and closure. If the donor site's primary closure cannot be achieved; however, the remaining open wound can be covered with split-thickness skin grafts and a bolster. After pedicled latissimus transfer, patients are often placed in an arm sling post-operatively to limit the shoulder and arm movement on the flap side while initial healing is taking place.

Complications

Partial or complete flap failure can result from vascular compromise during the initial few weeks of healing.[9] In a pedicled flap, distal tip necrosis can occur due to insufficient blood supply to the flap's edges. Also, more significant flap failure can result from vessel kinking either due to failure to ligate branches to the scapula or patient positioning.

If vascular compromise is recognized early enough and corrected, flaps can often be salvaged by returning to the operating room and removing the clot from the blood vessels or correcting a kink, or by applying leeches to the skin paddle to reduce venous congestion. However, prolonged periods of venous congestion or a lack of arterial inflow can cause complete flap loss. Flaps can also be compromised due to vessel compression from a hematoma or wound infection. Intra-operative hemostasis should be meticulous, and patient activities should be limited in the first two weeks after surgery to prevent hematoma formation.

Similarly, blood pressure should be controlled with medication in the post-operative period. Antibiotics should be given before surgery and continued for several days after to prevent infection. Further, patients should be counseled about how to clean their incisions properly after discharge from the hospital.

Clinical Significance

The latissimus dorsi flap, either free or pedicled, transferred with or without the overlying skin and subcutaneous tissue, can be a technically simple flap to transfer and provide large swaths of pliable tissue for reconstruction of the head, neck, and torso. Further, the latissimus flap often provides an excellent skin match for areas of the head, neck, and torso, and so is aesthetically advantageous. Many wounds that are too large for reconstruction with other flaps are amenable to latissimus transfer, making it a useful flap to keep in the reconstructive surgeon's armamentarium.

Enhancing Healthcare Team Outcomes

A multidisciplinary approach is advantageous; involving hospital social work and nursing teams early in the surgical process can improve a patient's postoperative hospital course and discharge planning. In general, effective and continuous interprofessional communication improves patient care and outcomes, particularly for patients requiring major head and neck reconstruction.