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1. Anatomy

 

The main blood supply to the latissimus dorsi (LD) muscle is supplied by the thoracodorsal (TD) pedicle. After giving the serratus anterior (SA) branch, the TD vessels divide into two branches, the descending or vertical branch and the horizontal branch (figure 1). Numerous perforators originate from these branches (figure 1&2) to supply the skin resulting in a multiple options of the thoracodorsal artery perforator flap (TDAP) that can be harvested and tailored according to the reconstruction needs. The largest perforator usually leaves the vertical branch of the TD artery into an intramuscular course to enter the subcutaneous tissue approximately 8 cm below the posterior axillary fold

and 2 to 3 cm posterior to the anterior border of the muscle. In most cases, the perforators are found within 5 cm of the anterior border of the LD muscle and between 7 to10 cm caudally from the posterior axillary fold. A direct TD

perforator (septal perforator) can be found around the anterior border of the LD muscle in 55% of the cases (figure 2). Although the presence of a septal perforator enables an easier and quicker dissection, it should be noted that the pedicle could be shorter than the case in intramuscular course and the flap may not be able to reach more distant defects

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The serratus artery perforator (SAAP) flap can be based on a septal or intramuscular perforator of the SA branch of the TD pedicle (Figure 3). Furthermore, vascular connection between the intercostal perforators and the serratus anterior (SA) branch is found in 21% of cases allowing to harvest the intercostal perforator flaps with the SA branch as a main pedicle (Figure 3). 

 

There are usually nine pairs of posterior intercostal arteries in the lower nine

intercostal spaces which originate from the aorta. The first and second spaces are supplied by the superior intercostal artery arising from the costocervical trunk. Every artery is accompanied by a vein of similar diameter lying above it,

while the nerve lies below it. When running deep to the external and internal intercostal muscles and superficial to the innermost intercostal muscle and parietal pleura, the intercostal artery give rise to between 5 and 7 musculocutaneous perforators at intervals of 1 to 3 cm. At the level of the midaxillary line, the vessels and nerve give off their lateral cutaneous branches emerges to the subcutaneous level, in front of the anterior edge of the latissimus dorsi muscle, which can be used in designing the Inter Costal Artery Perforator (ICAP) flap (Figure 4).

 

The intercostal (IC) perforators’ location anterior to the LD border enables the flap to be dissected without injuring the TD pedicle. The largest perforators that may be used for breast surgery are encountered in the 4th and the 5th intercostal spaces at 0.8 to 3 cm from the anterior border of the LD muscle. 

 

 

2. Surgical Technique

 

Pre-Operative assessment

 

• The flap is marked and relevant breast and flap anatomy outlined with the patient is in standing position. 

• The mastectomy technique is chosen according to oncological principles and the inframammary fold is marked. 

• Skin excess on the lateral  thoracic area and the contour of the breast are outlined.

 

Selection of most reliable perforator

 

• The patient is positioned in lateral decubitus position

• The arm is positioned in 90° abduction

• The flap is outlined on the lateral chest wall, considering the designed skin excess and breast (Figure 5a and videos below). 

• Maximum flap size is decided by pinching to allow primary closure

• The location of the perforators may be performed by Doppler evaluation but usually decided by operative exploration. 

• The flap is raised from its inferolateral border on top of the latissimus dorsi muscle fascia, proceeding forward until the different perforators are identified. 

• Once the most suitable perforator is identified (visible pulsatile artery with 2 comitant veins), the pedicle is dissected free and the skin flap is islanded (Figure 5b and videos below).

• Other perforators are not ligated till the chosen perforator is freed without injury and further evaluation has confirmed its suitability.

 

Pedicle dissection

 

• In case of a thoracodorsal perforator, a longitudinal muscle slit is made and the perforator is dissected free and isolated from the thoracodorsal nerve (Figure 1c). 

• The thoracodorsal pedicle is dissected after raising the anterior border of the latissimus dorsi muscle. This allow the flap to be pulled through the muscle, deepithelialised and transposed underneath the breast gland (Figure 1d) through a separate tunnel, taking care not to injure the intercostal nerve branches going to the breast.

• In case of an intercostal perforator (Figure 1b), the pedicle is freed up as far as possible taking care as not to injure the nerve branches. 

• The flap can be rotated 180° as in a propeller flap.

• An intercostal perforator flap is only indicated for lateral breast defects because of its short pedicle and cannot reach more medial defects

• Dissecting the pedicle within the periosteum under the rib may make the pedicle longer but it has more technical difficulties with a potential risk of a pneumothorax.

 

Flap inset

 

• After closure of the lateral part of the donor site, the patient is turned on her back to allow for definite shaping.

• The breast gland is undermined on top of the muscle fascia through an inframammary crease incision, and a pocket is created as in breast augmentation (Augmentations of 150 to 250 mL can easily be performed even in the slim patient, which covers the majority of our augmentation patients)

• When a thoracodorsal perforator is used; the other way round (posterior becomes medial, anterior lateral) in case of an 180° rotated intercostal perforator flap.

 

 

3. Technical pearls and points of significance

 

• The use of the Duplex to locate the perforators is not accurate enough because it is difficult to distinguish between the signal of a perforator and the main pedicle due to the relatively thin layer of the subcutaneous tissue. However, if  Doppler examination is done with the patient lying in a lateral position, similar to that during surgery, with a 90 degree abducted arm, perforators identification improved and an accuracy of up to 90% of the cases can be achieved.

• In thoracodorsal perforator flap dissection, a perforator originating from the descending branch is preferred as that makes the dissection easier since it is less involved with nerve branches, and the vessel course is usually shorter within the muscle fibers. 

• If two perforators are on the same line, both of them can be incorporated in the flap without cutting any muscle fibers.

• Final volume and shape adjustments can be made, as well as an additional mastopexy if the augmentation does not suffice for ptosis correction. 

• In the case of complete de-epithelialisation of the flap, a small skin paddle can be left at the recipient site for monitoring. This skin paddle is excised under local anesthetisia on the 5th postoperative day.

 

Muscle-sparing latissimus dorsi (MS-LD) flap

 

When tiny but pulsating, perforators are found, a muscle-sparing technique (MS-LD I) is used to harvest the flap with a 4 x 2 cm LD muscle segment. In this case, the perforators will be dissected within the split LD muscle but not from that muscular part which is included in the flap, so that the perforators are still attached to the LD segment. This requires direct visualisation of the perforators in order not to damage them during harvesting the muscular segment Care should be taken to free the perforator of all its branches and to rely upon 1 perforator in order not to twist different pedicles. The (MS-LD I) enables the surgeon a safer harvesting of the flap in these specific cases.

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