OPEN ACCESS ATLAS OF OTOLARYNGOLOGY, HEAD & NECK OPERATIVE SURGERY LATISSIMUS DORSI FLAP FOR HEAD AND NECK RECONSTRUCTION Patrik Pipkorn, Ryan Jackson, Bruce Haughey The latissimus dorsi is the largest muscle in Benefits the body by surface area. It can be as large as 20 x 40cms, enabling latissimus dorsi • Easy flap to learn to harvest flaps to cover very large defects (Figure 1). • Large thin muscle that can cover very large defects • Long (5-15cm) vascular pedicle if dis- sected up to the subscapular artery • The subscapular artery has a diameter of 2-5mm • Minimal long-term donor site morbidity • Can be harvested as a muscle flap or with a skin paddle • Can be harvested as a chimeric flap (multiple otherwise independent flaps that each have an independent vascular supply with all pedicles linked to a common source vessel) along with other flaps based on a singular subscapular artery Caveats • Donor site is close to head and neck area making two team harvest difficult, though not impossible Figure 1: Large pedicled latissimus dorsi • Because the donor site is on the back, it flap makes positioning more tedious • Large wound and potential dead space The flap can be harvested as a pedicled or after harvest has high risk of a seroma free flap and as a muscular or myocuta- neous flap with an overlying skin paddle. It can also be harvested along with any other Surgical anatomy flap based on the subscapular vascular system as a chimeric or subscapular “mega- The latissimus dorsi mainly adducts and flap”. Despite its size it can be harvested medially rotates the arm. It also rotates the without significant donor site morbidity. shoulder inferiorly and posteriorly. It is a thin, flat muscle measuring about 20 x The muscle is normally about 1cm thick. 40cms (Figure 2). The muscle forms the Because it atrophies significantly if it is not posterior axillary fold together with the reinnervated, it is a popular option for scalp teres major muscle (Figure 2). It originates reconstruction and for other defects in the from the posterior iliac crest, the thoraco- head and neck area including reconstruc- lumbar fascia and spinous processes of T7- tion of skull base and total glossectomy L5. Some muscle fibres may also originate defects. from the lower ribs. Some fibres also variably originate from the tip of the scapula where they intersperse with fibers of the teres major. Supero- medially it lies deep to the trapezius muscle as the trapezius attaches all the way down to T12. Inferiorly it covers the serratus anterior and external oblique abdominis muscles (Figure 3). TM Innervation The latissimus dorsi is innervated by the thoracodorsal nerve. It is derived from the 6th, 7th and 8th cervical nerve roots and arises from the posterior cord of the brachial plexus. The nerve runs with the thoraco- dorsal vascular pedicle. It only innervates the latissimus dorsi, so no other muscles are affected despite its transection when har- Figure 2: Posterior view of Latissimus vesting the flap. dorsi muscle and Teres major (TM) Vascular anatomy The muscle fibres run in a superolateral direction and insert into the floor of the intertubercular groove of the humerus be- tween the teres major and pectoralis major muscles (Figure 3). Circumflex scapular artery Thoracodorsal artery Branch to serratus ant Figure 4: Anterolateral view of vascular anatomy; the subscapular artery is the lar- gest of 3 branches of the third segment of the axillary artery Figure 3: Anterolateral view of latissimus dorsi, teres major, serratus anterior, and The thoracodorsal artery is the main blood pectoralis major supply to the latissimus dorsi; it is a termi- 2 nal branch of the subscapular system (Fig- some variability of the branching pattern ure 4). A sound understanding of the sub- but most often a separate branch, the angu- scapular artery system is therefore impor- lar branch, arises from the thoracodorsal tant for a microvascular surgeon when har- artery and supplies the tip of the scapula vesting flaps from the back. The subscapu- (Figures 5, 6). Before entering the latissi- lar artery is a very versatile system that mus dorsi muscle a 2nd branch, the branch supplies many flaps that can be harvested to serratus anterior muscle, branches off alone or as chimeric flaps with different (Figures 4, 6). tissues based on a single pedicle. Blood supply to latissimus dorsi muscle The subscapular artery is a branch of the 3rd segment of the axillary artery after the axil- The thoracodorsal artery provides the main lary artery has crossed the pectoralis minor. blood supply to the latissimus dorsi. The The branching patterns of the subscapular thoracodorsal artery and vein course supe- system varies considerably. The subscapu- riorly along the thoracic wall on the deep lar artery divides into the circumflex scapu- surface of the latissimus dorsi towards the lar (CSA) and thoracodorsal arteries (Figu- axilla. The artery is 1.5 - 4mm in diameter re 4). The CSA continues from deep to and the vein is usually 2.5 - 4.5mm in dia- superficial in the triangular space between meter. The muscular pedicle can be be- the teres major, teres minor, the long head tween 6-16cms in length with an average of the triceps and the lateral border of the length of 9cms. It enters the muscle on its scapula. After passing through this triang- deep surface about 8-10cms distal to its ular space, the CSA divides into a hori- origin of the subscapular artery (Figure 6). zontal and a vertical terminal branch, both To gain extra length, the artery can be which can be used for cutaneous flaps dissected all the way to the axillary artery. (Figure 5). Figure 6: Right anterolateral view with latissimus dorsi (LD) retracted to demon- strate thoracodorsal vessels, nerve and branches to serratus anterior Figure 5: Subscapular artery and its branches depicted from posteriorly Just after the thoracodorsal artery enters the muscle it divides into two branches, The thoracodorsal artery continues deep to one horizontal and one vertical enabling the teres major and latissimus dorsi muscle two different skin paddles to be harvested along the thoracic wall (Figure 4). There is with the flap. The highest density of per- 3 forators is about 2cms posterior to the However, as the surgical incision is made anterior edge of the muscle, just after the on the lateral back and at no time during the artery enters the muscle. As with a pectora- surgery exposure is necessary beyond the lis major flap these perforators are small midline, it is possible to put the patient in a and are not routinely dissected when har- 30-45 degree angle with the patient’s con- vesting the flap. To ensure incorporation of tralateral side supported with a deflatable perforators into the flap, a Doppler can be beanbag (Figure 7). Once the patient is used, although it is not essential to do so. properly secured to the bed, the bed can be Designing a larger skin paddle also makes rotated back by about 15-20 degrees permit- the flap more reliable as the chance of ting adequate exposure for both the ablative incorporating perforator vessels increases. and reconstructive surgeons. This position- ing technique saves considerable time and The muscle also receives blood supply from circumvents one of the major drawbacks of segmental perforating vessels from thora- harvesting flaps from the back, namely, cic and lumbar intercostal arteries. These time-consuming repositioning, reprepping arteries are small and enter the muscle on its and redraping. deep surface close to the spine. They supply the medial and inferior extensions of the muscle. Since these vessels are transected during flap harvest, the blood supply to the distal 1/3 of the muscle may be unreliable. Informed consent Preoperative discussion should include the risk of haematomas and seromas and deve- loping an unsightly scar. Patients must be counselled about the risk of flap failure. Figure 7: Positioning to permit simulta- Shoulder strength might be slightly affect- neous cancer resection and harvesting of ted, though not noticeably in most patients latissimus dorsi flap (Courtesy Jason Rich) unless combined with other flaps that may affect shoulder strength e.g. pectoralis Key points for this positioning technique major or scapular flaps. • Once the patient is intubated and all the necessary intravenous and arterial lines, Positioning and draping urinary catheter, and ECG leads have been placed, place the patient on a bean The classic way to position a patient for any bag (Figure 7) of the flaps based on the subscapular system • Rotate the patient about 30-45 degrees is to expose the full back of the patient by to facilitate exposure of the back which placing the patient in a lateral decubitus will be used for the harvest (Figure 7) position with an axillary roll. This however • Deflate the bean bag to make a firm and makes it necessary to rotate the patient stable base to hold the patient in posi- between the ablative and the flap harvesting tion stages, which requires repositioning and • Expose the back up to the spinous redraping, and adds considerable time and processes effort to the surgery. 4 • Take care to pad any firm spots to Flap design minimise risks of pressure necrosis • Place a pillow between the knees, which • Decide whether a skin paddle is re- should be slightly bent (Figure 8) quired to reconstruct the surgical defect • If a skin paddle is needed, it must be located over the latissimus dorsi muscle • In general, a width of 10cm can easily be harvested, still allowing the defect to be closed primarily; a simple “pinch test” will give one some indication • A larger skin paddle tends to be more reliable as more perforators entering from the deep surface are incorporated The latissimus dorsi flap may be employed either as a free microvascular transfer flap Figure 8: The knee is kept slightly bent and or a pedicled flap.