Derrick T. Lin
INTRODUCTION
Oral cavity defects including a segmental mandibulectomy can be a challenge for the reconstructive head and neck surgeon. Defects in this anatomical site may be due to oncologic resection, trauma, osteoradionecrosis, or infection/inflammation. To restore oral function, a composite graft consisting of both bone and soft tissue is ideal. The fibula, scapula, iliac crest, and osteocutaneous radial forearm are excellent donor sites for free tissue transfer. However, patient factors often play a role in decision making, such as unhealthy patients where limiting operative time and decreasing the risk of take back is essential, patients with extensive vascular disease, or patients with failed osteocutaneous free flap reconstruction. In these patients, placement of a reconstructive bar and a pectoralis major myocutaneous flap may be a safer option.
The goals of mandibular reconstruction are to reverse aesthetic deformity and functional loss. In general, lateral defects of the mandible left without reconstruction are better tolerated than are anterior defects. The use of a reconstruction bar and a pectoralis flap is usually considered in this setting. However, in the anterior mandibular defect, the use of a reconstruction plate and pectoralis flap often leads to extrusion of the plate with loss of structural support of the tongue, which results in functional deficits involving mastication and deglutition.
In the 1970s, the description of the myocutaneous circulation of the pectoralis flap led to its introduction in the use of head and neck reconstruction. The blood supply of this flap arises from the descending pectoral branch of the thoracoacromial artery. The consistency of this blood supply makes this reconstruction extremely reliable. The flap provides a large segment of skin and soft tissue, it is technically easy and efficient to harvest, it does not require a delay, and the donor site can be closed primarily. For decades, it has been the most popular flap for reconstruction after extensive resection of head and neck malignancies.
HISTORY
There are several options for managing a composite defect in the oral cavity. I find that a complete history is helpful in determining whether the patient is a candidate for free tissue transfer or reconstruction with a regional flap. Although free tissue transfer offers the optimal approach to reconstruction in select patients, regional flap reconstruction can offer an advantage. In patients with significant medical comorbidities, a surgical procedure that is less time intensive may be indicated. Other important aspects of the patient history relate to donor site availability. If the patient has had previous surgery or trauma that limit the donor site options, reconstruction with a regional flap may be indicated.
An important part of the history taking is exploring the patient’s expectations. An understanding of these expectations can impact the reconstructive options. While some patients expect dental rehabilitation with osseointegrated implants, others are less motivated and will choose a less time-intensive surgery. A careful preoperative discussion and understanding of these expectations are essential in achieving a good result.
PHYSICAL EXAMINATION
Once the decision has been made to proceed with reconstruction using a regional flap, the physical examination is important in determining if the patient is fit for this approach. The physical examination will determine if the defect can be reconstructed with a regional flap. Prior chest wall surgery may preclude use of this donor site. Similarly, if a patient has a history of external beam radiotherapy to the head and neck, a reconstruction plate may not be ideal as it often extrudes over the course of time. Other important features of the physical examination are related to the type of defect. Through and through defects involving the cheek skin, the mandible, and the buccal mucosa typically require a free flap to achieve an adequate functional result.
INDICATIONS
In general, osteocutaneous free tissue reconstruction is preferred after composite resection with segmental mandibulectomy especially for the anterior defect. The choices include fibular, scapular, iliac crest, and osteocutaneous radial forearm free flaps. However, for patients with severe comorbidities, the reliability and the relatively shorter length of surgery with the pectoralis major flap should be considered.
There are, however, disadvantages in using the pectoralis major muscle for reconstruction. The harvest of the pectoralis myocutaneous flap often results in distortion of the chest, although the inframammary crease can be used for female patients. Additionally, some degree of shoulder dysfunction is to be expected since a major function of the pectoralis major muscle is to adduct and medially rotate the arm. With early physical therapy, this level of dysfunction is usually well tolerated.
CONTRAINDICATIONS
There are rare anatomic anomalies that would preclude the use of the pectoralis flap reconstruction. Congenital absence of the pectoralis major muscle occurs in 1 in 11,000 people. Poland also described the congenital absence of the sternocostal head of the pectoralis major muscle seen in conjunction with ipsilateral syndactyly.
The anterior segmental mandibulectomy defect is a relative contraindication for the use of a reconstruction bar and pectoralis flap. The use of the reconstruction plate as an anterior projection element leads almost uniformly to extrusion of the plate resulting in deprojection and loss of support of the tongue resulting in oral incompetence.
If the patient has preexisting severe trismus from either previous radiation therapy or tumor involvement of the pterygoid muscles, reconstruction of the defect with the pectoralis flap without the reconstruction plate should be considered. The placement of the plate may worsen the trismus and downgrade oral competence. By insetting the pectoralis flap alone and letting the mandible swing, the degree of trismus will often be improved. This is not a viable choice in anterior defect since it would result in oral incompetence.
PREOPERATIVE PLANNING
The donor site and defect must be carefully evaluated. Although major surgery or previous trauma to the pectoralis muscle would be a relative contraindication, previous sternotomy for cardiac or thoracic procedures spares traumatic injury to the pectoralis major muscle and is not a contraindication.
The skin overlying the pectoralis muscle should be evaluated for concerning lesions. The muscle should be palpated to ensure that the patient does not have one of the rare congenital abnormalities mentioned above.
Under anesthesia, the inferior aspect of the pectoralis major muscle should be palpated. In general, no more than 30% of the skin paddle should be distal to this point. The lateral and medial aspect of the proposed flap is then marked out and grasped to ensure that the donor site can be closed primarily. Using the clavicle as a hinge point, the proposed distal aspect of the flap should be able to reach the most distal aspect of the defect.
SURGICAL TECHNIQUE
The skin is prepped from the clavicle down to the level of the umbilicus extending from the midline of the chest to the axilla. The skin flap is marked using a “pinch test” where the skin medial to the nipple to the midline chest is grasped, ensuring primary closure of the donor site. The superior aspect of the flap is usually marked out at the same horizontal plane as the axilla. The inferior aspect of the skin paddle is marked out with no more than one-third of the skin paddle distal to the inferior border of the pectoralis muscle (Fig. 13.1).
FIGURE 13.1 External markings on the left check for a pectoralis flap harvest.
First, the incision is made on the lateral aspect of the proposed skin paddle. The lateral border of the pectoralis major muscle is identified, which allows me to refashion the skin paddle if a significant portion is not overlying the pectoralis muscle. Once the muscle is identified, the avascular plane between the pectoralis major and the pectoralis minor muscle is bluntly dissected. This allows identification of the descending pectoral branch of the thoracoacromial artery (Fig. 13.2). Two vascular pedicles are often identified. For mobilization purposes, the lateral pedicle can be sacrificed safely. Once the pedicle is identified, the medial skin incision is made at the level of the midline of the chest and carried down to the level of the pectoralis major muscle.
FIGURE 13.2 Pectoralis flap harvest. Vascular pedicle identified between pectoralis major and pectoralis minor muscles (arrow).
The skin paddle is tacked to the underlying pectoralis major muscles using 3-0 Vicryl sutures to avoid shearing during elevation of the flap. The pectoralis major muscle is then dissected off of the chest wall using electrocautery. Intercostal perforators must be carefully ligated or cauterized.
The medial attachments to the sternum are then transected to the level of the clavicle. Care must be taken to stay lateral to the internal mammary perforators in the second and third intercostal spaces. In a similar fashion laterally, the muscular attachments to the humeral head are divided up to the level of the clavicle, being careful not injure the cephalic vein.
The nerve of the pectoralis major muscle is identified intimately associated with the vascular pedicle. Prior to its transection, the pectoral nerve can be confirmed by stimulation. In my experience, it is important to divide this nerve to avoid constriction of the venous pedicle especially if the muscular portion of the flap needs to be rotated for reconstruction. The flap is then completely harvested, keeping the vascular pedicle in view (Fig. 13.3).
FIGURE 13.3 Complete flap harvest with vascular pedicle in view (arrow).
A tunnel is created in a subcutaneous plane approximately four finger breadths in size to allow rotation of the flap into the neck without constriction of the blood supply to the flap. The flap is then brought through this tunnel into the oral cavity defect.
A 2.4 locking reconstruction plate is used. Attempts are made to achieve appropriate occlusion especially in a dentulous patient. This can be accomplished by fashioning the plate prior to the mandibulectomy. If this cannot be done due to external erosion of the mandible by tumor, an external fixator may be used. Once the plate is in place, three screws are placed on both the proximal and distal aspects of the remaining bone (Fig. 13.4).
FIGURE 13.4 Lateral segmental mandibulectomy with reconstruction bar.
The flap is then brought medial to the reconstruction bar. Every attempt should be made to try to cover the reconstruction plate entirely with the pectoralis muscle flap.
Care must also be taken to orient the pedicle properly to prevent excessive twisting during its rotation into the head and neck region. The skin portion of the paddle is then inset from distal to proximal using 3-0 Vicryl horizontal mattress sutures (Fig. 13.5).
FIGURE 13.5 Skin paddle of the pectoralis flap inset into the defect in the oral cavity.
Prior to closure of the donor site, the remaining musculature at the humeral head is clamped and ligated to prevent bleeding from this area, which is a major cause of hematoma in the donor site. Two 19 French drains are placed in the chest. 2-0 Vicryl sutures are used for the deep layer closure, and a skin stapler is used to close the skin. Elevation of the skin flaps is often necessary to allow for tension-free closure.
POSTOPERATIVE MANAGEMENT
The flap must be carefully inspected for viability. Any change in arterial or venous supply requires exploration. Leeches may sometimes be required for venous congestion. Staples in the chest are typically removed on postoperative day 7.
Tracheostomy is generally required for approximately 7 days.
Nutrition is typically given through a nasogastric tube for a minimum of 7 days in nonradiated patients. In patients who have been radiated, I usually waits 2 weeks prior to initiating an oral soft diet.
I recommend an evaluation by a speech–language pathologist in these patients to help with regaining good swallowing function.
COMPLICATIONS
Complications are relatively rare in the use of a pectoralis flap for oral cavity reconstruction. The most common complication is a hematoma at the donor site. This is managed urgently with surgical exploration and ligation of any bleeding vessels.
Should a hematoma occur in the neck, the flap may be compromised due to pressure in the blood vessels from the collection of blood. This should also be managed with urgent surgical exploration and evacuation of the hematoma and gaining complete hemostasis.
Compromise of the vascular pedicle may sometimes occur. Arterial insufficiency can be detected at the time of harvest by carefully inspecting the skin to ensure viability. Venous insufficiency may occur due to constriction of the pedicle by the pectoral nerve if it has not been transected at the level of the subdermal tunnel. Leeches may be necessary when venous congestion occurs if exploration reveals no external compression of the pedicle.
Plate extrusion occurs at a rate of 20% to 30% for lateral mandibular defects and uniformly in anterior mandibular defects in my experience. This is usually seen anywhere from 6 to 24 months postoperatively.
RESULTS
Although the ideal reconstruction of the oromandibular complex for a segmental mandibulectomy is a composite graft incorporating bone, placement of a reconstruction plate and pectoralis flap certainly has its merits. For the unhealthy patient, the shorter operative time, hospital stay, and decreased risk of reexploration is of great benefit.
Extrusion of the plate continues to be a vexing problem. For the lateral defect, there is a 20% to 30% extrusion rate, while for the anterior defect, it is almost always expected. If this occurs, the plate must be removed and the mandible allowed to swing.
PEARLS
• The distal third of the flap may be random if necessary. Rectus fascia should be raised with the flap in this location.
• The muscular attachments to the humerus should be ligated to avoid a hematoma in the donor site.
• The donor site should be closed primarily.
PITFALLS
• The flap donor site can cause distortion of the breast in females that should be discussed preoperatively. If the defect is small, the skin paddle can be placed in the inframammary crease.
• If stay sutures are not used to secure the skin paddle on the muscle, shearing may occur.
• There is a high expected extrusion rate of the reconstruction plate with this procedure.
INSTRUMENTS TO HAVE AVAILABLE
• Standard head and neck surgery set
• Titanium mandibular reconstruction plates, drill, and reciprocating saw
SUGGESTED READING
Ariyan S. The pectoralis major myocutaneous flap. A versatile flap for the reconstruction in the head and neck. Plast Reconstr Surg 1979:63:73.
Gullane PJ, Havas TE, Holmes HH. Mandibular reconstruction with metal plate and myocutaneous flap. Aust N Z J Surg 1986;56:701–706.
Cordiero PG, Hildalgo DA. Soft tissue coverage of mandibular reconstructive plates. Head Neck 1994;16:112–115.
Kensuke K, Yoshiaki T, Yojiro I, et al. Reliable, minimally invasive oromandibular reconstruction using metal plate rolled with pectoralis major myocutaneous flap. J Craniofac Surg 2001;154:34–37.
El-Zohairy M, Mostafa A, Amin A, et al. Mandibular reconstruction using pectoralis major myocutaneous flap and titanium plates after ablative surgery for locally advanced tumors of the oral cavity. J Egypt Natl Cancer Inst 2009;21(4):299–307.