51: Pectoralis Major Myocutaneous Flap

CHAPTER 51
Pectoralis Major Myocutaneous Flap

Eric R. Carlson and Andrew Lee

Department of Oral and Maxillofacial Surgery, University of Tennessee Medical Center, University of Tennessee Cancer Institute, Knoxville, Tennessee, USA

A soft tissue reconstructive surgical procedure that provides oral lining and facial cover of soft tissue defects. Referred to as the workhorse flap of head and neck reconstruction.

Indications

  1. Immediate reconstruction of oral lining (floor of mouth, buccal mucosa, and mandibular gingiva) and lower third facial/neck cover in patients undergoing ablative cancer surgery of the oral and maxillofacial region
  2. Delayed reconstruction of oral lining and facial/neck cover tissue in patients who have experienced avulsive trauma of the oral and maxillofacial region
  3. Reconstruction of oral lining and facial/neck cover in patients undergoing surgical treatment of radiation tissue injury of the oral and maxillofacial region
  4. Immediate muscular coverage of the carotid artery in patients who have undergone radical and modified radical neck dissections
  5. Salvage reconstructive surgery for failed free microvascular flap reconstruction of the oral and maxillofacial region
  6. Primary method of reconstruction of the oral and maxillofacial region where systemic medical comorbidity (i.e., uncontrolled diabetes, cardiopulmonary failure, or renal insufficiency) precludes the execution of a microvascular flap for reconstruction

Contraindications

  1. Excessive trauma sustained by the subclavian artery during the placement of a central venous catheter, whereby the integrity of the thoracoacromial artery has been compromised. Preoperative angiography is indicated when an injury is suspected to this primary pedicle that might result in inadequate vascularity to the pectoralis major muscle if myocutaneous flap development were performed
  2. Midfacial, upper third facial, and maxillary soft tissue defects where the arc of rotation and length of the pectoralis major myocutaneous flap are insufficient
  3. Excessively large skin paddle required to perform the reconstruction. Women are able to undergo pectoralis major myocutaneous flap development with larger skin paddles than men due to the redundancy of the female breast. Skin grafting the chest wall is not advisable in the event of inability to achieve primary closure of the chest wall due to the likely development of postoperative costochondritis

Anatomy of the Pectoralis Major Muscle

Pectoralis Major Muscle

A broad, flat, fan-shaped muscle that covers the pectoralis minor, subclavius, serratus anterior, and intercostal muscles on the anterior thoracic wall.

The muscle originates from the medial one-half to two-thirds of the clavicle, the lateral portion of the entire sternum and the adjacent cartilages of the first six ribs, and the bony portions of the fourth, fifth, and sixth ribs. The muscle inserts on the greater tubercle of the humerus.

Three major segmental subunits of the pectoralis muscle have been described: a clavicular segment, a sternocostal segment, and a laterally placed external segment. The clavicular segment arises from the midclavicular area, receives its blood supply from the deltoid branch of the thoracoacromial artery, and is innervated by branches of the lateral pectoral nerve. The sternocostal segment accounts for most of the pectoralis major muscle and receives its blood supply from the pectoral branch of the thoracoacromial artery with its nerve supply from the medial and lateral pectoral nerves. The external segment has a variable blood supply with contributions from the lateral thoracic and thoracoacromial artery.

The motor action of the pectoralis major muscle is to medially rotate and adduct the humerus. The muscle is innervated by the medial and lateral pectoral nerves that develop from the brachial plexus. Development of the pectoralis major myocutaneous flap is of little functional ill consequence as the latissimus dorsi muscle compensates for otherwise lost adductor activity.

Thoracoacromial Artery

The muscle’s primary blood supply is from the thoracoacromial artery that arises as the second branch of the axillary artery coming off the subclavian artery. Secondary pedicles include the lateral thoracic and superior thoracic arteries.

Deltopectoral Groove

This represents the anatomic junction of the deltoid and pectoralis major muscles through which the cephalic vein passes.

Bony landmarks of importance in the development of the pectoralis major myocutaneous flap include the clavicle and the manubrial notch and xiphoid process that demarcate the midline of the chest wall.

Soft tissue landmarks of importance in the development of the pectoralis major myocutaneous flap include the nipple and, in the case of a woman, the inframammary crease.

Pectoralis Major Myocutaneous Flap Surgical Technique

  1. Development of the recipient tissue bed prior to the development of the myocutaneous flap is paramount in the performance of reconstruction with the pectoralis major myocutaneous flap. In the case of immediate reconstruction of an ablative soft tissue defect (Figure 51.5), the delivery of the cancer specimen (Figure 51.4) permits a quantitative measurement of the defect with the subsequent design of this exact skin paddle size on the chest wall. In the case of an avulsive traumatic defect, the release of scar tissue in the recipient tissue bed permits a more accurate appreciation and measurement of the skin paddle requirement and subsequent design of this exact skin paddle size on the chest wall. Simultaneous recipient and donor site surgeries may result in the development of a skin paddle that is of insufficient size to adequately reconstruct the defect.
  2. Following the determination of the required skin paddle size, the skin paddle is designed medial and inferior to the nipple on the chest wall. The required skin paddle size is slightly overestimated when designing the skin paddle on the chest wall so as to reduce tension on the closure at the recipient site, thereby reducing possible dehiscence at the recipient site (Figure 51.6). In the case of a woman, the inferior aspect of the skin paddle is designed in the inframammary crease.
  3. A curvilinear incision is designed that connects the medial aspect of the skin paddle to the region approximating the greater tubercle of the humerus.
  4. The dissection is initiated by incising the skin and subcutaneous tissues about the proposed incision. The deeper dissection is performed with the electrocautery unit to the level of the pectoralis major muscle fascia that is maintained on the ventral aspect of the muscle (Figure 51.7). This dissection is carried superiorly to the region of the clavicle, supero-laterally to the deltopectoral groove, infero-laterally to the free margin of the pectoralis major muscle, and medially to the region of the lateral aspect of the sternum.
  5. In the area of the skin paddle, the deep dissection is performed so as to not undermine the skin paddle and risk its viability. The circumferential dissection of the skin paddle is completed down to the pectoralis fascia superiorly and down to the rectus abdominus fascia inferiorly. Often, the inferior dissection will divulge that the skin paddle is not supported by underlying pectoralis major muscle. This realization does not jeopardize the skin paddle’s viability. The skin paddle is temporarily sutured to the underlying pectoralis major fascia and possibly to the inferiorly located rectus abdominus fascia.
  6. The elevation of the myocutaneous flap is initiated by elevating the rectus abdominus fascia off of its muscle that inserts on the inferior aspect of the sixth rib. The entirety of the pectoralis major muscle is elevated off the ribs’ superficial surfaces as well as the intercostal muscles that are encountered thereafter. This technique is continued from the free margin of the pectoralis major muscle laterally to the origination of the muscle medially. In general, approximately 1 cm of pectoralis major muscle is maintained on the lateral aspect of the sternum in the development of the myocutaneous flap. Further superior dissection will identify the pectoralis minor muscle. In addition, as the myocutaneous flap is mobilized superiorly, the axial vessels will be identified within the deep surface of the muscle. Retraction of the muscle during its elevation is important to avoid inadvertent trauma to the primary and secondary pedicles of the flap.
  7. Perforators from the intercostal />
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Jan 18, 2015 | Posted by in Oral and Maxillofacial Surgery | Comments Off on 51: Pectoralis Major Myocutaneous Flap
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