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Pectoralis Major Flap in Composite Lateral Skull Base Defect Reconstruction
Vicente A. Resto, MD, PhD;
Michael J. McKenna, MD;
Daniel G. Deschler, MD
Arch Otolaryngol Head Neck Surg. 2007;133(5):490-494.
ABSTRACT
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Objective To report our experience with the pectoralis major myocutaneous flap (PMF) for the reconstruction of composite lateral temporal bone defects extending beyond the temporal line.
Design Retrospective review and illustration of specific technical modifications.
Setting Academic tertiary care center.
Patients Eight patients with composite lateral skull base defects that were reconstructed with the PMF between February 2001 and February 2006.
Intervention Reconstruction with the modified pedicled PMF.
Main Outcome Measures Reconstruction outcomes and complications.
Results Eight patients (median age, 80 years) underwent total or near-total auriculectomy, wide skin excision, and lateral temporal bone resection as part of the surgical ablation, thus requiring obliteration of the middle ear cavity as well as extensive replacement of skin cover. All patients received radiation therapy. The median postsurgical follow-up was 9 months. Complete healing of the reconstructed surgical defect with no flap loss was achieved in all cases.
Conclusion With specific technical modifications, the PMF can be reliably used for the reconstruction of composite lateral skull base defects extending up to and beyond the temporal line, making this flap an important alternative to free flap reconstruction in selected cases.
INTRODUCTION
The reconstructive management of cases involving locally advanced lateral skull base tumors remains a challenge. Surgical treatment commonly requires wide resection of bony tissues, including the lateral temporal bone, mandibular condyle, and soft tissues such as skin, auricle, parotid gland, and infratemporal fossa contents as well as dura. The resulting complex composite defect frequently requires importation of tissue for wound closure. Axial flaps remain the reconstructive substrate of choice for the management of these complex defects because they provide dependable, large-volume tissue that allows successful, watertight wound closure. These features acquire increased importance as the majority of patients undergo radiation therapy as part of their treatment plan.
A multitude of flaps have been described for the reconstruction of composite lateral skull base (CLSB) defects, including free tissue transfer from distant donor sites as well as regionally transferred pedicled flaps. The latter are often reserved for patients who are poor candidates for free flaps. Although the pectoralis major myocutaneous flap (PMF) has been a true workhorse in head and neck reconstruction for decades, its application to the reconstruction of CLSB defects has been restricted to defects below the external auditory canal because of the perceived difficulty in achieving sufficient flap length to ensure flap viability as well as a tension-free, watertight closure.1-2 Specifically, concerns have been raised regarding the reach of the skin paddle, propensity for venous congestion when flap reach is maximized, and delayed wound dehiscence associated with flap bulk and weight.
We present our experience using the PMF for the reconstruction of CLSB defects extending beyond the temporal line (supramastoid crest).3 We also describe and illustrate specific technical modifications that allow the reliable use of this robust flap and review our experience using the PMF for the reconstruction of these defects.
METHODS
The records of all lateral skull base cases reconstructed by the senior author (D.G.D.) using the described modified PMF between February 2001 and February 2006 were retrospectively reviewed. Cases were identified from a prospective database of reconstructive cases maintained by the senior author. Patient age, extent of surgical defect to be reconstructed, exposure to radiation, postoperative course, and complications were recorded and analyzed. Specific technical modifications important for the harvest and inset of the PMF when used for CLSB defect reconstruction are illustrated herein. The basic technique of PMF harvest is not presented, as it has been well described elsewhere in the literature.4-7 The institutional review board of the Massachusetts Eye and Ear Infirmary, Boston, approved this study.
SURGICAL TECHNIQUE
The PMF flap is based on the pectoralis major branch of the thoracoacromial artery.8 This report focuses specifically on 5 relevant modifications that allow enhanced reach with reliable viability: (1) the skin paddle is designed over the entire length of muscle; (2) a 5-cm cuff of the superior rectus sheath is harvested in continuity with the distal pectoralis major muscle; (3) motor nerves around the proximal pedicle are identified and severed; (4) the flap is suspended by the harvested rectus sheath; and (5) the flap skin paddle inset is incorporated into the neck incision.
Although, standard harvest of the PMF uses a curvilinear incision into the axila, thus preserving the deltopectoral fasciocutaneous flap, this modified technique for the reconstruction of CLSB defects requires the skin paddle of the flap to encompass the entire length of the muscle, with the skin ellipse extending distally over the harvested rectus sheath. The proximal aspect of the incision is then brought into continuity with the lower limb of a neck incision extended from the resultant CLSB defect. The latter incision transitions into the neck at the midpoint of the clavicle. Once the skin incisions are made, skin flap elevation is continued in the standard fashion using a suprafascial plane over the pectoralis major muscle. As the inferior aspect of the ellipse extends over the rectus muscle, the rectus fascia is exposed around and below this point, usually to the first inscription of the ipsilateral rectus abdominus muscle. Dissection in the suprafascial plane helps preserve continuity between the distal pectoralis major muscle and the proximal rectus sheath to be harvested. Once exposure is achieved, a rectangular cuff of rectus sheath measuring approximately 5 cm in length is outlined with cautery dissection through the anterior sheath, thus exposing the underlying rectus muscle fibers (Figure 1). A subfascial plane of dissection is then used to elevate the cuff of rectus sheath in continuity with the pectoralis major muscle. Care is taken to provide meticulous maintenance of the subfascial plane over the rectus abdominus muscle as the transition to the submuscular plane is made, allowing separation of the pectoralis muscle from its rib attachments. This step allows continuous elevation of the extended flap, without disinsertion of the proximal rectus muscle or violation of the rectus sheath to be harvested. Elevation of the modified flap then continues from an inferior to superior dissection following standard technique.
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Figure 1. A cuff of the ipsilateral rectus sheath is harvested in continuity with the proximal pectoralis major muscle.
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As the proximal aspect of the flap is elevated, the humeral head of the pectoralis major muscle is severed and the lateral and medial aspects of the clavicular head are isolated and severed. This maneuver requires division of the lateral thoracic pedicle to the pectoralis muscle. The pectoralis major vascular pedicle is directly visualized during this maneuver in order to avoid injury to the latter. A cuff of muscle measuring approximately 3 cm is maintained and inserted into the clavicle to protect the pedicle. Once this step is achieved, a blunt technique is used to dissect the pectoralis major vascular pedicle to its takeoff from the thoracoacromial artery, which marks the point of maximal elevation proximally. A nerve stimulator is then used to identify the motor nerve branches to the pectoralis major muscle around the vascular pedicle. The motor nerve branches are closely associated with the pedicle and usually require blunt dissection within the vascular bundle for complete identification. Once isolated, they are severed under direct vision (Figure 2). The fully elevated flap is then reflected over the clavicle.
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Figure 2. Motor nerves traversing within and around the proximal pectoralis major vascular pedicle are identified and severed. This maneuver allows rotation of the flap, without concomitant vascular pedicle compression. V indicates vein; A, artery.
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Next, flap inset geometry is assessed. By definition, the flap must be rotated 180° to position the skin paddle externally. The specific direction of rotation, clockwise vs counterclockwise, is chosen to allow maximal reach, while minimizing torsion on the pedicle (Figure 3). The harvested rectus sheath is then used to suspend the flap superiorly to available structures, usually residual temporalis fascia and muscle or pericranium (Figure 2). It provides the major tension-bearing point of inset, thus sparing the skin paddle and its associated perforators from any shearing tension. The harvested muscle can be spread, draped into position, and affixed by sutures. The inset then continues by approximating the flap skin edges to the wound edges. The paddle can be conservatively trimmed as needed, with care being taken to retain a broad subcutaneous base connection to the muscle in order to maximize and protect perforators feeding the skin paddle. An inset of the flap skin island is carried into the neck incision (Figure 4). This step allows maximal distribution of the weight of the flap. The chest wound is closed primarily in layers. Standard wound drainage is used.
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Figure 3. Flap inset geometry is assessed. Asterisk indicates zygomatic arch; arrow, superior aspect of temporal craniotomy bone flap.
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Figure 4. The flap is suspended by the harvested cuff of rectus sheath. Tension is maximally distributed by insetting the skin island throughout the entire wound, including the neck.
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RESULTS
Between February 2001 and February 2006, 8 patients (median age, 80 years) with CLSB defects after surgical ablation for tumor underwent reconstruction with the PMF. All patients underwent total or near-total auriculectomy, wide skin excision, and lateral temporal bone resection as part of the surgical ablation, thus requiring obliteration of the middle ear cavity as well as extensive replacement of skin cover. All patients received radiation therapy as part of their treatment plan. The median postsurgical follow-up was 9 months (mean, 17 months; range, 1-63 months). Complete healing of the reconstructed surgical defect with no flap loss (partial or total) was achieved in all 8 cases. Clavicle resection was not required in any case. There was 1 complication that consisted of a chest donor site hematoma on postoperative day 2. The hematoma was treated with operative drainage, without further setback. Two patients underwent secondary flap revision with the goals of reducing bulk and improving neck contour, without sequela (Figure 5).
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Figure 5. Postoperative appearance after 4 months without revision (A) and after 2 years with revision (B).
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COMMENT
As stated, repair of the CLSB defect presents specific challenges. A large dead space requires filling. Skin loss can be considerable, especially with auricular sacrifice. Dural exposure may require coverage. These issues are combined with a location more cephalad than that of other head and neck ablative defects, which are commonly repaired with pedicled flaps from the thorax. The use of free flaps for the reconstruction of CLSB defects has been well documented. Most commonly, myocutaneous or fasciocutaneous free flaps such as the rectus abdominus and the anterolateral thigh were used.1, 9-12 These flaps provide robust, high-volume tissue for closure with minimal donor site morbidity, provide long vascular pedicles, and easily allow 2-team harvesting. Such factors make them the preferred flaps for reconstruction of CLSB defects. However, free-tissue reconstruction requires longer operative times and carries the risk of multiple trips to the operating room if the flap requires reexploration during the immediate postoperative period.13 Therefore, myocutaneous or fasciocutaneous free flaps may be inadequate for patients with significant comorbid conditions who would benefit from reduced operating time and exposure to anesthesia.
Historically, regional pedicled axial flaps have been used successfully for CLSB defects. In recent years, with the advent of reliable free tissue transfer techniques, they are used less frequently but should still be considered in the setting of elderly or infirm patients who are poor candidates for free tissue transfer. Two in particular, the latissimus dorsi myocutanoeus flap and the lower island trapezius myocutaneous flaps, have been described for the reconstruction of CLSB defects.2, 14 Both provide large-bulk, well-vascularized tissue with sufficient length for the successful reconstruction of the lateral skull base. However, their use often results in poorer cosmetic results when compared with free flaps. They also require intraoperative repositioning of the patient for harvest, a maneuver that significantly lengthens the procedure. Furthermore, the use of these techniques can result in postoperative arm or shoulder dysfunction.14-16 This is important in cases involving elderly, infirm patients who may suffer the greatest impediment from such functional loss. Despite these concerns, both the latissimus dorsi myocutanoeus flap and the lower island trapezius myocutaneous flap are excellent reconstructive options in select cases.
The pectoralis major regional myocutaneous flap has found broad application for the reconstruction of head and neck defects.5 Its use for reconstruction of defects of the lateral skull base, however, has been infrequent because of the notion that the flap length is insufficient to reach this area.1-2 Modified harvest techniques for the pectoralis major flap have been reported. These techniques have included partially resecting the clavicle as well as tunneling the proximal end of the flap under the clavicle.17-20 Despite these alterations, efforts to expand flap reach to the fullest extent have been complicated by pedicle compromise, with resultant partial or total flap loss, a complication that can have significant consequence for the debilitated patient.
Herein, we present technical modifications that address the goals of (1) increased flap reach, (2) prevention of vascular pedicle compromise, and (3) tension-free closure, thereby providing reliable application of the PMF for the reconstruction of CLSB defects. Increased flap reach is primarily accomplished by incorporating a portion of the proximal ipsilateral rectus sheath into the flap elevation. This maneuver results in a dependable, inferiorly expanded skin paddle design, with resultant increased flap length. Having a large skin ellipse extending up toward the clavicle allows the capture of more proximal perforators from the muscle, which, in turn, increases the viability of the random segment of skin over the rectus sheath. Extending flap reach requires rotating the thinned clavicular muscle insertion, with its associated pectoralis muscle pedicle, within a narrow axis. This maneuver may lead to pedicle compression by the closely associated motor nerves contained within the pedicle's sheath, which can create a strangulating effect, compressing the vessels, usually the vein. Blunt dissection within the pedicle's sheath permits identification and severing of these nerves, thus preventing this complication. Finally, suspending the muscle via the harvested cuff of rectus sheath reduces the potential shear effect on the perforators to the skin island as the pectoralis muscle retracts inferiorly as a result of muscle contraction and gravity. Also, by incorporating the extended skin island completely into the neck incision, an even distribution of flap weight is achieved, a maneuver that is critical for successful wound healing. Furthermore, incorporating the entire expanded skin paddle maximally captures perforators that are important for its support.
The described technique has been successfully used for the reconstruction of CLSB defects in 8 cases. Selection of the PMF as the reconstruction modality, as opposed to free tissue transfer techniques, was based on the previous poor performance status of the treated patients. The average age of the patients in our study group was 80 years. Reconstruction was achieved expeditiously, without the need for patient repositioning, and with acceptable cosmetic and functional results.
The PMF is a robust myocutaneous flap that can be reliably used for the reconstruction of CLSB defects extending up to and beyond the temporal line (supramastoid crest).3 Within our reconstructive algorithm for CLSB defects, we use the PMF as a second option for the reconstruction of these complex defects in male patients who are not suitable candidates for reconstruction with the anterolateral thigh myocutaneous free flap.
AUTHOR INFORMATION
Correspondence: Daniel G. Deschler, MD, Head and Neck Surgical Oncology, Department of Otolaryngology–Head and Neck Surgery, Massachusetts Eye and Ear Infirmary, 243 Charles St, Boston, MA 02114 (daniel_deschler{at}meei.harvard.edu).
Submitted for Publication: June 6, 2006; final revision received September 29, 2006; accepted October 23, 2006.
Author Contributions: Drs Resto, McKenna, and Deschler had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Resto, McKenna, and Deschler. Acquisition of data: Resto. Analysis and interpretation of data: Resto and Deschler. Drafting of the manuscript: Resto and Deschler. Critical revision of the manuscript for important intellectual content: Resto, McKenna, and Deschler. Study supervision: McKenna and Deschler.
Financial Disclosure: None reported.
Previous Presentation: This study was presented as a poster at the American Head and Neck Society 2006 Annual Meeting and Research Workshop on the Biology, Prevention, and Treatment of Head and Neck Cancer; August 18, 2006; Chicago, Ill.
Author Affiliations: Departments of Otolaryngology–Head and Neck Surgery, University of Texas Medical Branch, Galveston (Dr Resto), and Massachusetts Eye and Ear Infirmary, Boston (Drs McKenna and Deschler).
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