The first description of the pectoralis major flap for head and neck reconstruction was by Ayrian in 1978. The following year he published his work in the Journal of Plastic and Reconstructive Surgery.1
Since the description of this flap, its use quickly became widespread and within a short time it held the position as the flap of choice in head and neck reconstruction. The pectoralis muscle flap held its position as the workhorse flap in the reconstruction of defects in the head and neck for many years until the introduction of the radial forearm free flap.
The pectoralis flap has, however, not been relegated to the history books. It remains as one of the main flaps for salvage reconstruction secondary to the loss of microvascular flaps as well as in those patients in whom microvascular flaps is either contraindicated or cautioned due to existing comorbidities that diminish their ability to tolerate an extended operating time.
The location of the donor site as it relates to the head and neck makes this flap a great option for reconstructing defects in this region. The harvest of the flap can be carried out with the patient in a supine position, i.e., in the same position as the ablative head and neck operation. The potential for a two-team approach is also available, although the surgical field would be slightly crowded.
One of the greatest advantages of the pectoralis major myocutaneous flap is the quality and quantity of tissue that can be harvested. The pectoralis major muscle enables the closure of a multitude of defects in the head and neck but its robust quantity allows for the coverage of the reconstruction plates used in mandibular surgery, therefore decreasing the likelihood of plate exposure through the skin or the mucosa. At the same time, the muscle coverage in the neck provides additional protection of the great vessels. This fact is of importance in patients who have had a radical neck or a type I or II modified radical neck dissection. The coverage of the vessels becomes even more significant in those patients needing adjuvant radiation therapy or those who have already received radiotherapy and may be faced with delayed wound healing.
The main disadvantage is that the pectoralis major flap is a pedicle flap and therefore its use in reconstruction of head and neck defects is limited to sites within the arc of rotation of the flap. Equally, some of the reasons that make this flap a good option for reconstruction will also be potential downsides in certain cases. When the defect site demands a thin and pliable flap, this may not be the most ideal flap.
The tunneling of the flap in the neck to reach the defect creates a bulge over the clavicle and in the neck. This bulge has greater prominence in those patients in whom the sternocleidomastoid muscle is retained. The bulge of the muscle will eventually diminish as the muscle is not innervated and therefore will atrophy with time.
In cases where the flap is used as a myocutaneous flap with the skin island used to reconstruct a skin defect in the head and neck, there is often a very distinct color mismatch. In males there may also be a significant amount of hair growth on the skin component of the flap that may become bothersome to patients depending on the site of the reconstruction. This is often relieved, however, in patients receiving postoperative radiation therapy to the site. The radiation will affect the hair cells and therefore the affected sites will no longer have any hair growth.
An anatomical understanding of the pectoralis muscle and its vasculature is of paramount importance to the surgeon. The muscle originates along the medial aspect of the clavicle, manubrium, sternum, and the cartilages of ribs 2 to 6. The fibers of the pectoralis major muscle form a large triangular muscle which travels obliquely to insert on the greater tubercle of the humerus. The pectoralis muscle functions by providing adduction and internal rotation of the arm.
The pectoralis muscle is a type V muscle according to the Mathis and Nahai classification.2 This means that the muscle has one dominant pedicle and several segmental pedicles. The main arterial supply to the pectoralis muscle is the thoracoacromial artery which is a branch of the second portion of the axillary artery. The pectoralis muscle also receives perfusion from the lateral thoracic artery to supply the lateral aspect of the muscle. Perforating branches from the internal mammary artery supply the medial aspect of the muscle and continue to perfuse the overlying skin.
The venous drainage to the muscle and the region is by the accompanying venae commitantes, which drain in the axillary vein. On the superior aspect of the muscle, along the deltopectoral groove, the cephalic vein is encountered as it drains the upper extremity on its way to drain into the axillary vein.
The motor innervation to the muscle comes from the medial and lateral pectoral nerves. The lateral pectoral nerve, a branch from the brachial plexus, innervates the majority of the medial and sternal aspect of the muscle while the medial pectoral nerve (also a branch from the brachial plexus) innervates the lateral aspect of the pectoralis major and the pectoralis minor muscle.
The flap is harvested with the patient in a supine position. Upon completion of the preparation of the recipient site, the size of the needed skin paddle is measured. The other important information needed is the location of the defect.
- Using either a suture string or the string from the lap towel, one end is positioned over the clavicle on the ipsilateral side of the defect and pivoted lying in a passive form along the neck and into the farthest point of the defect.
- The string is then rotated caudally to the chest and the inferiormost reach is marked. This location will be the most inferior point of the skin paddle. The location of the majority of the potential skin paddle must be positioned over the underlying pectoralis muscle.
- The skin paddle is designed according to the needs of the defect and the outside perimeter of the skin island is shaped into a fusiform shape to aid in later closure of the defect.
- A point near the junction of the arm to the chest and another at the superior-lateral point of the flap are marked and a curvilinear line is marked. The curvilinear design allows for the potential use of a deltopectoral flap in the remote chance that the pectoralis muscle flap fails.
- The initial incision is made on the lateral aspect of the skin paddle and along the curvilinear line.
- The incision along the skin paddle should be made outward to insure that the base of the skin paddle is wider than the skin paddle itself.
- Once the position of the skin paddle is confirmed as being located over the muscle bed, the curvilinear extension is elevated in the suprafascial plane towards the lateral border of the muscle.
- The remainder of the skin island is completed and the skin edge is then sutured to the pectoralis fascia to prevent shearing of the skin paddle from the underlying muscle.
- Starting laterally, the lateral edge of the pectoralis muscle is elevated in the plane between the pectoralis major and minor. This is a relatively avascular plane. The inferior edge of the flap is released from its origin along the lower ribs. Perforating vessels should be clipped and hemostasis insured.
- The medial attachment of the pectoralis muscle is released beginning inferiorly in a cephalad direction. The medial release should be lateral to the row of the internal mammary perforators, especially the second and third perforators that are saved in case a bailout with the deltopectoral flap is needed.
- Once the flap is released medially, the lateral and medial pectoral nerves are divided and the thoracoacromial pedicle is identified and preserved.
- The lateral attachment of the pectoralis muscle to the humerus is then released by placing a hemostat between the muscle and sequentially segmenting the muscle. While performing the lateral release of the muscle care should be taken not to injure the cephalic vein superiorly or the lateral arterial branch to the muscle.
- The next aspect is the creation of the tunnel to transfer the flap into the neck and into the defect site. The usual circumstance is that a neck incision would have already been made to carryout the resection. A subplatysmal flap elevation is extended to the clavicle. Inferiorly from the pectoralis aspect, the skin is elevated suprafascially in a cephalad direction towards the clavicle until it communicates with the neck.
- The dimension of the tunnel should be sufficient to accommodate the flap transfer without impingement and constriction of the perfusion.