OPEN ACCESS ATLAS OF OTOLARYNGOLOGY, HEAD & NECK OPERATIVE SURGERY THORACODORSAL ARTERY SCAPULAR TIP (TDAST) FLAP FOR HEAD AND NECK RECONSTRUCTION Douglas Chepeha The thoracodorsal artery scapular tip flap is Benefits of TDAST the osseous (bone) component of the latissi- mus dorsi flap. The thoracodorsal artery • Long vascular pedicle 1,2 supplies the scapular tip and the latissimus • Triangular 3-dimensional shape 2 dorsi muscle (with overlying skin). There- • Bone paddle easily shaped without fore, the scapular tip can be harvested as an osteotomy to reconstruct the infrastruc- independent osseous paddle or with the ture of the maxilla 3 latissimus dorsi muscle or with the latissi- • Bone is surrounded by attached muscle mus dorsi muscle and overlying skin or in that can be used to help close defects of some combination with the serratus muscle. maxillary and mandibular alveolus bone There are many possible combinations of • Can be harvested as a chimeric flap with skin, muscle and bone paddles that make a variety of skin and muscle paddle this arterial donor system valuable for head options 3-5 and neck reconstruction. In addition, the • Independently mobile skin paddle 2,3 thoracodorsal arterial system can be com- • Thoracodorsal artery and vein are large bined with the circumflex scapular arterial vessels and most commonly connect to system (both arteries arise from the sub- larger subscapular vessels scapular system or are directly adjacent to one another) to further increase the skin and Caveats of TDAST bone paddle options. Although it would not always be ideal, this donor site could be • Overall harvest is manageable but one used to reconstruct all defects in the head must exercise caution with the identifi- and neck. cation of the angular branch and its connection to either the thoracodorsal The scapular tip and lateral border have a artery or the serratus artery unique shape. The tip of the scapula is the • Shorter bone length (12cm) than fibula shape of the maxillary infrastructure when 6-8 inset in an axial plane. It also mimics the rim of the orbit, depending on the extent of • If the angular branch does not appear to the defect, and can be inset in axial or supply the superior aspect of the lateral coronal planes. The lateral border of the tip border of the scapula, then the circum- of the scapula is the shape of a hemiman- flex scapular artery may have to be dible and is well suited for mandibular harvested to ensure vascularity reconstruction. For posterior mandibular • Wide skin donor sites can be hard to reconstruction the tip can be used for the close and can limit shoulder mobility angle and inset in a sagittal plane to recon- • The skin donor sites may be thicker than struct the ramus. For anterior defects it can the forearm, anterolateral thigh and the be inset axially in a manner similar to lateral arm flaps depending on body maxillary reconstruction or it can be osteo- habitus and gender 9,10 tomised and inset in a coronal orientation. • Reduced shoulder mobility • Prior ipsilateral thoracotomy may limit In this chapter we address the use of the skin paddle donor options bone paddle supplied by the thoracodorsal • Two-team surgery if a hydraulic arm artery. holding device is not used 11 Anatomy 3. Subscapularis arises from the subsca- pular fossa (the part of the scapula that Harvesting the scapular tip involves tran- faces anteriorly toward the thorax) and secting a portion of, or all the origins of the inserts into the lesser tubercle of the infraspinatus, subscapularis, teres major, humerus. It rotates the humerus medial- the insertion of the serratus and, if a skin ly on the glenohumeral joint. paddle is harvested, dissection and possible 4. Teres major is encountered surgically harvesting of the latissimus dorsi flap. but is not a rotator cuff muscle. It arises Several of these muscles are part of the four from the inferior angle of the scapula muscles that form the rotator cuff that and attaches to the anterior surface of stabilises the glenohumeral joint (Figure 1). the humerus, on the medial lip of the intertubercular sulcus. It allows medial Supraspinatus Suprascapular notch (foramen) rotation and adduction of the humerus Cut edge of deltoid on the glenohumeral joint. The long head of the triceps brachii is also Cut edge of trapezius encountered in this region as it origi- Teres minor nates in the infraglenoid tubercle of the Infraspinatus Surgical neck of humerus Triangular space Medial lip of inter- scapula. It serves as an accessory adduc- tubercular sulcus tor, an extensor of the forearm and a Quadrangular space stabiliser of the glenohumeral joint Triangular Vascular Anatomy Teres Major interval Long head of triceps brachii The subscapular artery arises from the third part of the axillary artery (Figure 2). Cut edge of lateral head of triceps brachii Figure 1: Posterior view of shoulder and Subscapular artery arm Rotator Cuff and Muscle Anatomy Four muscles originate from the scapula and stabilise the glenohumeral joint (Figure 1): 1. Supraspinatus and infraspinatus mus- cles originate in fossae above and below the scapular spine and attach to the greater tubercle of the humerus. The supraspinatus initiates the first 15º abduction of the arm, whereas the infra- spinatus allows lateral rotation of the Figure 2: Origin of subscapular artery from arm on the glenohumeral joint axillary artery 2. Teres minor arises from the lateral edge of the scapula and attaches to the greater It gives rise to two branches: the thoraco- humeral tubercle. It also allows lateral dorsal artery, and circumflex scapular rotation of the arm artery (Figure 3). The thoracodorsal artery 2 and/or thoracodorsal vein can arise from the within 1.5cm of the serratus artery branch axillary vein, separate from the subscapular or from the serratus branch within 1.5cm of artery and/or the subscapular vein 12 its branchpoint with the thoracodorsal artery. The origin of the vein and artery of Dorsal scapular artery the angular artery pedicle can be divided Descending branch transverse cervical Transverse scapular between the thoracodorsal branch and the Scapular circumflex serratus branch. The total length of the dissected pedicle and bone paddle (distance from the axilla to the scapular tip) can be as long as 27cm 1,2,14. This is likely to be an overestimate; the total length is closer to 20cm. The descending and transverse thoraco- Subscapular dorsal branches are within the latissimus Thoracodorsal muscle and can be used to supply some or all of a myogenous paddle, a myocutaneous paddle, or a cutaneous perforator (if pre- sent), and can be dissected through the Termination of subscapular muscle. Figure 3: Vascular anatomy around the scapula The circumflex scapular artery (Figure 3) travels through the triangular space 3 The thoracodorsal artery arises from the created by the teres major inferiorly, teres subscapular artery, descending, roughly minor superiorly, and long head of triceps parallel to the lateral boarder of the scapula anteriorly (Figure 1). It divides into a termi- in an envelope of adipose tissue that emana- nal descending branch to the bone of the tes from the axilla (Figure 3). The thoraco- lateral border of the scapula; the circumflex dorsal artery passes between the teres major scapular artery continues toward the skin and the thoracic cage (Figure 2) 12. The and divides into transverse cutaneous and thoracodorsal artery supplies the latissimus descending cutaneous branches. The ter- dorsi, serratus anterior, and scapular tip 13. minal descending branch supplies the lateral border of the scapula and the maxi- The thoracodorsal artery gives rise to a mal bone length is 12cm. The transverse direct cutaneous branch, the serratus cutaneous branch can be used to create a artery, the angular artery to the scapular scapular cutaneous paddle 3. The descen- tip, the descending branch within the ding cutaneous branch is used to create latissimus muscle and the transverse parascapular cutaneous paddle 3. branch within the latissimus muscle. The direct cutaneous branch is present 47% of Nerve Anatomy the time (reference Taylor 1984) and supplies the skin inferior to the axilla. The The thoracodorsal nerve (Figures 4, 11) serratus branch supplies the serratus runs along the pedicle to the latissimus muscle that can be used for myogenous muscle. The nerve is about 2mm in diame- reconstruction or as an innervated subunit. ter. When harvesting the scapular tip, it should not be sacrificed and is a good guide The angular branch to the scapular tip for the direction of the pedicle and can help arises from the thoracodorsal branch 6 open the space over the pedicle. In the 3 axilla, the cords of the brachial plexus run Surgical Setup immediately superior to the axillary artery and vein. Care should be taken not to put The surgical setup is very similar to the traction on these nerves. setup described in the chapter on latissimus dorsi flaps. Patient Positioning A key advance is to avoid repositioning by putting the patient in a semidecubitus 2 and using a beanbag to secure the patient’s donor site about 20 degrees above the plane of the bed. Ensure that the entire scapula is accessible. Access to the scapula can be improved by abduction or medial rotation with the shoulder in an adducted position. Unfortunately, this setup still does not make Figure 4: Anterior view of right thora- 2-team surgery straightforward. codorsal nerve (Human Anatomy Online) A positioning device can be used to hold the 11 Preoperative Evaluation arm in position (Figure 5). These devices are in common use for rotator cuff repair No specific vascular testing is required. If and are available at many hospitals with a patient has a history of shoulder dislo- orthopaedic programs.