Latissimus Myocutaneous Flap

The latissimus dorsi myocutaneous flap (LDMF) is one of the most reliable and versatile flaps used in reconstructive surgery.[1, 2] It is known for its use in chest wall and postmastectomy reconstruction and has also been used effectively for coverage of large soft tissue defects in the head and neck, either as a pedicled flap or as a microvascular free flap. The earliest application of the latissimus flap for head and neck reconstruction was described by Quillen in 1978, and microvascular free tissue transfer of the flap was described by Watson in 1979.[3]

The latissimus dorsi may be transferred as a myofascial flap, a myocutaneous flap, or as a composite osteomyocutaneous flap when harvested with underlying serratus anterior muscle and rib. For even greater reconstructive flexibility, the latissimus can be harvested for free tissue transfer in combination with any or all of the other flaps based on the subscapular vessels (the so-called subscapular compound flap or “mega-flap”), including serratus anterior, scapular, and parascapular flaps. The LDMF may be used to provide a sensate reconstruction when it is transferred with an intact neurovascular bundle. Importantly, using the LDMF does not compromise the use of other regional flaps, such as the deltopectoral flap and pectoralis major flap, which can then be used in secondary reconstructions if required.[4]

Advantages of the LDMF include the following:

• Large volume of tissue is available for reconstruction.

• Long vascular pedicle offers excellent range for pedicled flaps.

• High caliber pedicle makes free flap vascular anastomoses technically more feasible, even in patients with significant atherosclerotic disease.

• The possibility of independent skin paddles being able to address complex defects (eg, through-and-through oral cavity defects)

• Rib or scapula bone is available.

• Minimal donor site morbidity occurs.

• It can be combined with other subscapular flaps, when indicated.

These advantages allow the LDMF to address a wide array of defects in head and neck and chest wall reconstruction.[5, 6] The long pedicle length allows the flap to easily reach defects as far as the temporoparietal area. The LDMF is also appropriate to cover large scalp defects when used as a muscle-only free flap combined with a split-thickness skin graft.[7] Reconstruction of the mandible and/or facial skeleton has also been described when the flap is harvested with underlying rib . Harii has described motor reinnervation with anastomosis of the thoracodorsal nerve, which may be useful for facial reanimation or to allow functional reconstruction of the tongue. Oral cavity and oropharyngeal defects, including through-and-through defects, may also be addressed with the LDMF.

A prospective study by Yang et al found that in patients who underwent immediate breast reconstruction with a latissimus dorsi flap, shoulder strength and range of motion returned to their presurgical baseline values within 1 year postsurgery, although functional disability and quality of life associated with the flap procedure remained below baseline (as measured using the Disabilities of the Arm, Shoulder and Hand [DASH] questionnaire and the physical component of the 36-item short-form health survey [SF-36]).[8]

In a comparison of total breast reconstruction with fat-augmented LDMFs versus fat-augmented LD muscle flaps, Tomita et al found that the results of postoperative aesthetic evaluation were similar for both types of flaps. High BREAST-Q scores were associated with the muscle and myocutaneous flaps, with the muscle flaps achieving significantly higher scores for the item “Satisfaction with Back.” However, the LD muscle flaps required additional fat grafting more frequently than did the LDMFs.[9]

A study by Mericli et al indicated that following breast-conserving therapy, partial breast defects can safely and effectively be treated with LDMF reconstruction. At median 5.4-year follow-up, the investigators found an overall complication rate of 8.5% and BREAST-Q scores of 61 (Satisfaction with Breasts) and 87 (Psychosocial Well-being). As measured by plastic surgeons and laypersons using the 5-point Likert scale, a median aesthetic score of 4 was obtained.[10]

The latissimus dorsi is a flat, broad muscle measuring about 20 by 40 cm. It extends from the posterior axilla to the midline of the back and inferiorly to the posterior portion of the iliac crest. The posterior axillary fold is partially formed by the anterior edge of the latissimus (see the image below).

Outline of latissimus dorsi muscle and skin island.

Origin and insertion

The muscle originates from the posterior iliac crest and from the spinous processes of the lower 6 thoracic vertebrae, the lumbar and sacral vertebrae, and the thoracolumbar fascia arising from the dorsal iliac crest. As the latissimus extends superiorly and laterally, the muscle is adherent to the external surface of the serratus anterior muscle and the 4 lowermost ribs. The latissimus inserts anteriorly into the lesser tubercle and intertubercular groove of the humerus between the teres major and pectoralis major muscles. To reach its point of insertion, the latissimus rotates around the teres major muscle, to which it is very adherent at this level.

Function

The latissimus functions mainly as an adductor and medial rotator of the arm. It also serves to pull the shoulder inferiorly and posteriorly.

Blood supply

The latissimus dorsi muscle is supplied by 2 separate vascular systems. The dominant blood supply arises from the thoracodorsal artery, which is the terminal branch of the subscapular artery. It also has a secondary blood supply, which arises from segmental perforating branches off of the intercostal and lumbar arteries. These vessels enter the deep surface of the muscle near the posterior midline and are responsible for perfusion of the inferior and medial latissimus. Because these vessels are disrupted in the process of harvesting the latissimus, the viability of this portion the flap can be tenuous.

The subscapular artery originates from the third portion of the axillary artery. It divides into the circumflex scapular artery and the thoracodorsal artery, which enters the latissimus dorsi muscle at about 8.5-9 cm distal to the origin of the subscapular artery, as shown below. Typically, a robust branch to the serratus anterior is present and must be severed to harvest the latissimus. Alternatively, this branch can be maintained if the serratus is harvested to create a separate muscular paddle.

Arterial blood supply to the latissimus dorsi muscle.

The thoracodorsal artery and vein course along the thoracic wall on the undersurface of the latissimus muscle. The artery has a diameter of 1.5-4 mm, and the vein usually ranges from 2.5-4.5 mm. Overall, the extramuscular pedicle length varies between 6-16 cm and is about 9 cm on average. The intramuscular thoracodorsal artery reliably divides into vertical and transverse branches, which allows the flap to be divided into 2 separate muscle and skin paddles. The greatest density of myocutaneous perforators lies anteriorly along the border of the muscle, which is the ideal location for skin paddle harvest. Because these perforators are not routinely identified during harvest, a general rule is that very small skin paddles risk compromised vascular supply. If a small skin paddle must be fashioned, harvesting additional subcutaneous tissue around the skin in an attempt to maintain additional perforators is wise.

Innervation

The motor nerve to the latissimus dorsi muscle is the thoracodorsal nerve, which arises from the posterior cord of the brachial plexus and is derived from the sixth, seventh, and eighth cervical nerve roots, shown below. The nerve travels distally with the vascular pedicle and supplies only the latissimus dorsi muscle; although it is transected during the harvest, no other muscles are affected.

Relationship of arteries, veins, and nerves from the axilla to the latissimus dorsi muscle.

No absolute contraindications exist to using the latissimus dorsi muscle, provided that the vascular pedicle is intact. However, certain conditions may make the flap less reliable. In cases of radiation to the chest or axilla and in cases of previous axillary dissection, the thoracodorsal vessels may be compromised.

The latissimus dorsi muscle is considered expendable because no significant loss of adduction or rotation of the arm occurs if the other muscles of the shoulder girdle are intact. However, in certain patients in whom any loss of shoulder function would cause unacceptable disability (eg, patients who use crutches or are wheelchair bound, professional skiers), consider other options before sacrificing the latissimus dorsi muscle.

Give special attention to patients who have undergone a radical neck dissection with sacrifice of the spinal accessory nerve; these patients may experience significant shoulder problems if the latissimus dorsi muscle is harvested on the side where functional loss of the trapezius muscle has already occurred. A careful history and physical examination is standard, but pay close attention to any history of past surgery on the breast or axilla and to radiation therapy in the head and neck, chest, or axilla.[11] Determining if the patient has any history of bleeding tendencies or coagulation problems is important.

The preoperative workup is the same as for any patient undergoing major surgery. If doubt exists concerning the patency of the thoracodorsal vessels, a Doppler flowmeter could be used to trace the course of the thoracodorsal artery from its origin at the subscapular artery to the point where it enters the latissimus dorsi muscle. This is typically unnecessary given the resilience and consistent anatomy of this vessel.

Marking the flap

The flap is marked by first outlining the anterior and superior edges of the latissimus dorsi muscle. These boundaries are marked to indicate the extent of muscle that can be harvested. As previously noted, the maximum dimensions of the latissimus are usually 20 by 40 cm. A skin island can be designed anywhere overlying the muscle, but preferably it should be placed along the upper two thirds of the latissimus dorsi muscle where a higher density of myocutaneous perforators is found. The skin paddle should be a maximum of 10 cm wide to facilitate primary closure of the harvest site.

To determine the exact placement of the skin island, the distance from the surgical defect to the pectoral-humeral junction is measured. The subscapular artery arises about 1-2 cm below this area. A line is then drawn from the anterior border of the latissimus dorsi to its origin along the posterior iliac crest. The previously measured distance is then transferred to this line, indicating the location of the required skin island (see the image below).

Outline of latissimus dorsi muscle and skin island.

Patient positioning

Place the patient on his or her side in a lateral decubitus position with the operative side facing up and the shoulder abducted. An axillary roll is important in the contralateral axilla.[12]

Flap harvest

The posterior axillary fold is identified, and an incision is marked just posterior to the lateral border of the latissimus dorsi. The incision is then extended posteroinferiorly, parallel to the lateral edge of the muscle, and usually incorporates the lateral edge of the skin paddle. After the incision is made, flaps are elevated, and the lateral and superior edges of the latissimus dorsi muscle are identified. The lateral border of the latissimus is then elevated and retracted posteriorly, thus exposing the underlying serratus anterior muscle. The space between the latissimus dorsi and serratus anterior muscles is enlarged with blunt dissection.

The thoracodorsal vessels can be seen entering the latissimus dorsi about 3 cm medial to the lateral edge of the muscle. At this level, 1 or 2 branches come from the thoracodorsal to the serratus anterior muscle; these may be traced proximally to identify the thoracodorsal artery, and are divided to isolate the latissimus muscle. The neurovascular pedicle is then followed superiorly to its junction with the subscapular artery; the circumflex scapular artery arises near this junction. This artery should be preserved if possible, but if additional pedicle length is needed, the circumflex scapular vessels can be divided and the subscapular vessels harvested where they branch from the axillary vessels.

When free tissue transfer is being performed and even more arterial pedicle length is required, the proximal circumflex scapular artery can be harvested as this approach often provides more extension than harvesting the subscapular artery.

The posterior edge of the latissimus muscle is then freed, and all branches from the intercostal arteries are identified and ligated. The muscle can then be transected distally at a level determined by the amount of tissue required. The muscle is then elevated from distal to proximal and is divided at a level just proximal to the entrance of the thoracodorsal vessels. The flap is then based solely on its vascular pedicle and can be rotated and transferred to the surgical defect (see the image below) or removed for free-tissue transfer.

Harvest and arc of rotation of the latissimus dorsi myocutaneous flap.

Split latissimus dorsi muscle flap

The vertical and transverse branches of the thoracodorsal artery may be reliably used to create separate skin or myofascial paddles. These may then be used to reconstruct more complex defects (eg, full thickness defects of the oral cavity). If only a small amount of muscle is needed, the latissimus can be harvested based only on the lateral branch of the thoracodorsal artery. The dissection is the same, but once the thoracodorsal neurovascular bundle is identified, it is carefully dissected to the point where it enters the muscle. The lateral edge of the muscle can then be split and harvested based on this lateral branch. Care should be taken to maintain the innervation to the medial part of the latissimus left behind by preserving the medial branch of the thoracodorsal nerve.

Osteomyocutaneous flap

The latissimus dorsi muscle can also be harvested as a composite flap of skin and muscle with underlying rib. The skin island is designed over the ninth rib, and the dissection begins distally. When the inferior border of the ninth rib is reached, the bone and intercostal muscles are divided, leaving the attachments to the latissimus intact. The rest of the dissection of the muscle is carried out as described above.

Combination with serratus anterior (osteo) myofascial flap

The arterial branch supplying the serratus muscle may be used to co-harvest this flat, usually thin muscle with the latissimus flap. Associated rib can be included if needed. This additional muscle can be helpful in complex oral cavity and oropharyngeal reconstruction when independent bulk is needed, as it can be completely separated from the latissimus muscle while still maintaining its vascular supply.

Combination with scapular/parascapular (osteo) fasciocutaneous flap

These flaps are based on the circumflex scapular vessels and thus can be combined with the latissimus by harvesting at the level of the subscapular vessels; the combination is often referred to as a “subscapular mega-flap,” although this sometimes indicates inclusion of the serratus anterior as well. In addition to a large independent skin paddle, this approach can allow for significant bony reconstruction (eg, segmental mandibulectomy). Harvesting scapular bone is less morbid than harvesting rib and does not risk pneumothorax.

Endoscopic-assisted harvest

Advances in endoscopic surgery have been successfully applied to the harvesting of muscle flaps in an effort to minimize the morbidity of the donor site. This is often an important consideration for patients undergoing breast reconstruction using a pedicled LDMF. Many studies have shown that these techniques not only reduce the size of the donor scar but also reduce postoperative pain and problems with wound healing. A 5- to 6-cm incision is made along the posterior axillary fold. Through this small incision, the thoracodorsal vessels are identified, and the muscle is dissected in an open fashion as much as possible posteriorly. An endoscope is then used to complete the dissection. A scope with a 30° angle provides better visualization for dissection and transection of the muscle posteriorly and distally. Muscle flaps measuring up to 15 by 25 cm can be harvested with the endoscopic technique.

Transposition of the flap

If used as a pedicled flap, the distal end of the paddle is passed into the head and neck area through a tunnel created either subcutaneously over the pectoralis muscle or through the pectoralis muscle. The choice is made depending on which route places the least amount of tension on the pedicle. Removing a portion of the clavicle to reduce tension may be necessary.

Inset of the pedicled flap

Once the flap is passed through the tunnel into the operative defect, it must be inset without tension. The pedicle must be inspected to assure that no torsion or kinking of the vessels exists. The shoulder should be immobilized to avoid pinching of the tunneled pedicle with arm movement. If the oral defect is through and through, the skin paddle may be used as the inner (mucosal) or outer (skin) epithelium, with the other lining provided by a split-thickness skin graft applied directly to the muscle of the flap. Using back skin intraorally is often more straightforward because producing a fluid-tight seal with the surrounding residual mucosa is easier and does not require a bolster. Also, the color of the flap skin is often a poor match for the face.

Inset of the free flap

Standard microvascular techniques are used when selecting and performing arterial and venous anastomoses. The large caliber of the thoracodorsal artery and vein make microvascular anastomosis technically less challenging than many other free flaps. Many of the anatomic difficulties encountered with pedicled flap transposition (eg, limited range, pedicle compression in the axillary tunnel) are avoided when the LDMF is transferred in a free fashion. Additionally, for more complex defects such as the through-and-through oral cavity defect discussed above, if a free flap is performed, the option to include a scapular or parascapular flap can expand the range of reconstructive options from a single harvest.

Donor site

The donor site should be treated with closed suction drainage systems to avoid seromas and hematomas postoperatively. This is a common complication often requiring prolonged drainage.

Carefully monitor the patient for the first 24-48 hours. Postoperative monitoring of the flap can be done by many methods, some of which are more useful than others. A Doppler flowmeter can be used to monitor arterial inflow and venous outflow. Temperature strips can be placed on the flap to compare it with other parts of the body; however, unlike in digit replants, this technique is often inaccurate. Clinical examination is a reliable method of evaluating the viability of a flap, and capillary refill should be regularly monitored. Prick testing of the skin paddle or muscle with a large-bore needle with assessment of bleeding time and color is another reliable method of flap monitoring. For buried flaps, a small portion of the muscle can be brought out through a skin incision for monitoring. Recent studies have not shown a correlation between monitoring style and flap survival.

Flaps with cutaneous components are the easiest to monitor. If the flap appears tense, engorged, warm, and bluish or violaceous in color, venous obstruction should be suspected. In this situation, bleeding is dark and rapid in response to a prick, and often does not stop readily. In contrast, if the flap appears pale and cool, an arterial inflow problem is the most likely cause, and prick testing shows very slow or no bleeding. Both of these conditions may be due to torsion or kinking of the pedicle or perhaps a small hematoma at the level of the tunnel through which the flap was transferred. If detected early, these problems can be corrected in the operating room, and the flap can be salvaged.

Donor site

The most common complication following a latissimus dorsi flap is seroma formation at the donor site. The frequency is reported to be as low as 10% but has occurred in 38-50% of patients in some series. The frequency of this complication can be decreased by adequately draining the donor site with closed suction drainage and by fixating the skin flaps down with tacking sutures. The frequency of seroma is higher when extensive dissection is performed with electrocautery.

A study by Arikawa et al found that the donor site drainage time was greater for LDMFs than for thoracodorsal artery perforator (TAP) flaps, with a mean duration of 11.6 days for patients whose LDMF was used for breast reconstruction, 9.82 days for those whose LDMF was not employed in breast reconstruction, and 4.81 days for patients in the TAP flap group. The investigators also found the donor site seroma formation rate to be significantly higher in the LDMF breast reconstruction patients than in the other two groups.[13]

Some functional deficit in shoulder function can result when the latissimus dorsi muscle is sacrificed. The deficit is usually not significant, but it can be a debilitating problem in patients who are paraplegic or depend on crutches. Avoid sacrificing the latissimus if a patient has already lost the function of the trapezius on the same side.

A study by Zirk et al of donor-site bacterial infections in patients who underwent head and neck reconstruction following ablative surgery found that pedicled flaps were associated with a moderate detection ratio, ie, the number of infected sites/flaps harvested from the specific donor site. Flaps assessed in the study included pedicled LDMFs, as well as free radial forearm fasciocutaneous flaps, free fasciocutaneous anterolateral thigh flaps, pedicled pectoralis major myocutaneous flaps, and free osteocutaneous fibula flaps. The detection ratio for LDMFs was 0.27. Follow-up in the study was 12 months.[14]

Donor site cosmesis is a major concern in some patients, but with the new techniques of endoscopic-assisted harvest, the donor scar can usually be limited to a 6-cm incision. For most myocutaneous flaps, the donor site defect can be closed primarily.

Reconstruction

Depending on the site of reconstruction, a variety of complications related to repair of the defect may be encountered. Overall flap survival is very good, ranging between 95-99%. Complications related to the reconstruction site include orocutaneous fistula in about 2.5%, delayed wound healing in 7-10%, and hematoma formation in 2-4%. These rates are variable and also depend on other factors, including history of radiation exposure, smoking, diabetes, etc.[11] The flap may be initially bulky, but significant atrophy of the muscle occurs due to denervation. Secondary reduction of the flap volume can be accomplished at a later date if residual bulk is excessive.

On long-term follow-up, a retrospective study by Wattoo et al found high patient satisfaction with post-mastectomy breast reconstruction using the LDMF, with the rates of adverse events and unplanned revision surgery being relatively low. At median 7-year follow-up, median patient satisfaction with treatment outcomes was 78%, with the rate of unplanned revision surgery being 6.3% and the following adverse event rates reported[15] :

• Acute implant loss - 6.5%
• Flap necrosis - 3.4%
• Shoulder stiffness - 1.9%
• Chronic pain - 11.5%

A study by Teisch et al comparing the use of latissimus dorsi flaps with pedicled transverse rectus abdominis myocutaneous (pTRAM) flaps for breast reconstruction indicated that latissimus dorsi flaps are more likely to result in postoperative surgical site complications, while pTRAM flaps are associated with a greater risk for pulmonary complications and longer hospital stays. The study employed the Agency for Healthcare Research and Quality’s Inpatient Sample database, with data assessed from a total of more than 29,000 latissimus dorsi and pTRAM cases.[16]

The pedicled or free latissimus dorsi myocutaneous flap is one of the most versatile and reliable flaps used in reconstruction today. It can be used as a simple muscle flap or can be raised as a composite myocutaneous or osteomyocutaneous flap. Specifically, for head and neck reconstruction, its long pedicle and the large amount of available tissue are particularly useful for reconstructing large lateral temporal, scalp, or intraoral defects. The LDMF has been used extensively in the reconstruction of defects involving the trunk and chest wall, as well as following mastectomies.