DOI: 10.1148/rg.274055188
RadioGraphics 2007;27:975-987
© RSNA, 2007
Pedicle Muscle Flaps in Intrathoracic Cancer Resection: Imaging Appearance and Evolution1
Gregory W. Gladish, MD,
David C. Rice, MD,
Bradley S. Sabloff, MD,
Mylene T. Truong, MD,
Edith M. Marom, MD, and
Reginald F. Munden, DMD, MD
1 From the Departments of Diagnostic Radiology (G.W.G., B.S.S., M.T.T., E.M.M., R.F.M.) and Thoracic Surgery (D.C.R.), University of Texas, M.D. Anderson Cancer Center, 1515 Holcombe Blvd, Room 3B.4622, Box 0371, Houston, TX 77030. Recipient of a Certificate of Merit award for an education exhibit at the 2004 RSNA Annual Meeting. Received October 12, 2005; revision requested December 14 and received August 25, 2006; accepted November 1. All authors have no financial relationships to disclose.
Address correspondence to G.W.G. (e-mail: ggladish{at}mdanderson.org).
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Abstract
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Pedicle muscle flaps that are used to enhance surgical site integrity after thoracic cancer resections may simulate a recurrent mass at postoperative imaging. However, such flaps have a characteristic appearance and location that should allow their differentiation from a solid mass or fluid collection. The location and appearance of a flap depend on the type of muscle used (whether intercostal, serratus anterior, or latissimus dorsi) and the extent of resection. The appearance also varies according to the presence and amount of fat and calcification in the flap. Most flaps have fat strands along the flap axis that increase in size over time. Linear areas of calcification also may occur because of the inclusion of periosteum in a flap, or more extensive calcification may lead to ossification over time. Uncomplicated flaps do not show substantial radionuclide uptake at positron emission tomography (PET), but areas of extensive calcification may show increased uptake similar to that in bone. Vessels also may be seen within a flap, particularly if the flap has a high fat content; and enhancing vessels frequently are evident at contrast material–enhanced computed tomography (CT). The magnetic resonance (MR) imaging characteristics of flaps are similar to those of normal fat and muscle. Although CT is the modality most often used for follow-up imaging, PET or MR imaging may be helpful in cases in which the CT findings are questionable.
© RSNA, 2007
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:- Describe the muscle flap types most often used in intrathoracic cancer resection.
- Recognize the appearance of intrathoracic muscle flaps on images obtained with various modalities.
- Identify changes in the imaging features of intrathoracic muscle flaps over time.
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Introduction
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Soft-tissue flaps are used in a variety of surgical reconstructive procedures in various parts of the body. Flaps may contain fat, muscle, fascia, or a combination of those. A flap may be excised and moved to an entirely new location (a so-called free flap), with surgical development of a new vascular supply; or it may be rotated into position, with its vascular supply maintained through a pedicle connected to its original location. Free flaps require delicate microsurgical technique to ensure an adequate vascular supply. Pedicle flaps are more commonly used in thoracic cancer resections because the surgical procedure is less complex and postoperative perfusion is more reliable.
Indications for intrathoracic flaps include repair of tracheoesophageal fistulas, buttressing of tracheal and bronchial anastomoses, repair of esophageal perforations, repair of bronchopleural fistulas, and space obliteration after treatment of postpneumonectomy empyema (1–8).
The presence of a flap alters the radiologic appearance of the postoperative anatomy. A flap that predominantly consists of fat often is difficult to detect on postoperative images but is unlikely to be confused with a recurrent tumor. Predominantly fat-containing tissues that may be used for flaps in intrathoracic surgery include pericardial fat pads, thymus, and omentum (3). Muscle-containing flaps have a demonstrable soft-tissue component at imaging and therefore are more likely to be confused with a recurrent tumor if their characteristic features are not recognized. The muscles that are most commonly used for pedicle flaps in intrathoracic cancer resections and reconstructions are the intercostal, serratus anterior, and latissimus dorsi muscles (1,3,8).
Because each type of muscle flap has a characteristic vascular pedicle and muscle configuration, the various types have different appearances at imaging (9). In addition, the evolution of radiologic features of muscle flaps over time is different from that of recurrent tumors. Knowledge of these differences may help radiologists distinguish the type of muscle flap depicted on imaging studies and prevent a flap from being mistaken for a recurrent tumor.
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Case Review
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A waiver of informed consent and protected health information requirements was obtained from the institutional review board for this retrospective study. A surgical case database was reviewed to identify all patients in whom a pedicle muscle flap was created as part of intrathoracic cancer resection and reconstruction performed within the previous 7 years. Forty patients were identified, among whom 23 were selected for inclusion in our review because they had undergone postoperative cross-sectional imaging. Clinical records were reviewed to identify the underlying malignancy, the nature of the surgery performed, and the indication for use of a muscle flap as well as to identify the type of muscle used. The timing and type of subsequent cross-sectional imaging examinations also were determined.
A panel of five fellowship-trained thoracic radiologists reviewed the postoperative images, most of which were obtained with computed tomography (CT). Findings were determined by consensus of the panel. The panel was unaware of the surgical procedure, the indication, and the underlying malignancy. Images were reviewed to identify the location, orientation, and appearance of the flap. Specifically, the attenuation characteristics of the flap were assessed to determine the presence and amount of fat, calcification, and vascular enhancement. For patients in whom follow-up CT was performed after the first postoperative examination, additional note was made of any change in attenuation characteristics, particularly a change in the fat content or the presence and extent of calcification. Any cross-sectional images obtained with other modalities during follow-up also were reviewed.
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Case Review Results
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Patient Data
The 23 patients whose cases were reviewed included 16 men and seven women. The average age of the patients was 58 years (range, 37–79 years). The average age for men was 60 years (range, 43–79 years), and that for women was 54 years (range, 37–67 years). Eighteen of the patients had lung cancer. One patient each had esophageal cancer, lymphoma, adenoid cystic carcinoma, mesothelioma, or breast cancer.
Twenty patients underwent lung resection: 13 had a pneumonectomy, and seven had a lobectomy. Two other patients underwent an esophagectomy, and one patient underwent a tracheal resection. Three types of pedicle muscle flaps were used in these surgical procedures: An intercostal muscle flap was used in 15 patients; a serratus anterior muscle flap, in five patients; a latissimus dorsi muscle flap, in two patients; and both intercostal and serratus anterior flaps, in one patient. In one patient in whom an intercostal muscle flap was used, an omental flap also was brought into the thoracic cavity transhiatally; the omental flap was not included in this analysis because of the lack of any soft-tissue component that might be confused with tumor recurrence.
The first postoperative CT examination was performed, on average, 22 weeks after the muscle flap procedure (range, 0–80 weeks). Seventeen patients underwent further follow-up CT examinations. For the entire group, an average of 2.9 (range, 0–9) additional follow-up CT examinations were performed for each patient. These were performed an average of 46 weeks (range, 12–98 weeks) after the first examination. The final follow-up examination was performed an average of 56 weeks (range, 5–112 weeks) after the muscle flap procedure. Of the 17 patients who underwent a follow-up examination with CT, nine had at least one combined examination with CT and positron emission tomography (PET). An 18th patient underwent a magnetic resonance (MR) imaging examination.
Findings on CT Images
Findings at the first postoperative CT examination are listed in Table 1; those at subsequent CT examinations are listed in Table 2. Notably, the posterior location and course of intercostal muscle flaps allowed their differentiation from serratus anterior and latissimus dorsi flaps. Calcification was noted only in intercostal muscle flaps and presumably was related to the inclusion of periosteum in the flap. No enhancing vessels were demonstrated in latissimus dorsi flaps, but the absence of vessel enhancement might be related to the small number of such flaps included in the study and the imaging technique used for those examinations. The soft-tissue component of the muscle flaps showed enhancement that was similar to that of other muscular structures, with no areas of increased enhancement suggestive of tumor involvement or recurrence in the flap. Follow-up examinations showed an increase in the fat component of the flap in many cases. There were no cases of obliteration of previously seen fat planes. One patient had an enhancing nodule separate from the flap; the nodule proved to be a pleural metastasis. A heavily calcified intercostal muscle flap in one patient showed uptake of fluorine 18 fluorodeoxyglucose (FDG) similar to that in bone. The flaps in the other patients did not show increased FDG uptake.
Intercostal Muscle Flap.—
Intercostal muscle flaps are generally harvested from the fifth or sixth intercostal muscles and are based posteriorly on the intercostal vessels. Because these flaps are relatively small and delicate, they require meticulous harvesting before the placement of rib retractors, which frequently damage the intercostal vessels by compressing them. Intercostal muscle flaps typically are used for buttressing bronchial anastomoses or for closure of small tracheal or esophageal defects (1,6–8). Although the intercostal muscles assist in respiration, their use in flaps causes no significant functional deficit.
Because an intercostal muscle flap receives its vascular supply from the intercostal vessels, the flap originates along the posterior chest wall and extends medially toward the resection site, somewhat parallel to the ribs (Fig 1). The flap may appear as soft-tissue thickening that extends along the spine and mediastinum (9) or directly across the thoracic cavity (10) (Fig 2). Fibers of the muscle flap parallel the long axis of the flap. The flap is very short in the craniocaudal direction, whereas its origin may be several centimeters from the resection site. The soft-tissue defect at the muscle harvest site cannot usually be detected.
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Figure 1a. (a, b) Preoperative CT images from a 67-year-old woman with right upper lobe lung cancer. Axial image at the level of the ascending aorta (Ao) (a) shows a tumor (arrow) that surrounds the right upper lobe bronchus. Subsegmental atelectasis (arrowheads) also is visible. Three-dimensional volume rendering (b) demonstrates the relationship of the tumor (blue) to the airway (pink) and the native location of the fifth intercostal muscle (red). (c–h) Postoperative CT images obtained after right upper lobectomy. Cropped axial images at successively lower levels (c–f) and oblique reformatted image (g) demonstrate the typical appearance of an intercostal muscle flap (arrows) that extends from the thoracotomy site in the posterior chest wall below the fifth rib (5 on c), along the mediastinum, to the resection site in the hilum. The flap was used to buttress the bronchial staple line and separate the bronchus from an arterioplasty site. Three-dimensional volume rendering (h) shows the flap extending from the chest wall below the fifth rib to the airway at the lobectomy site. Note the thoracotomy defect (arrowhead) at the sixth rib.
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Figure 1b. (a, b) Preoperative CT images from a 67-year-old woman with right upper lobe lung cancer. Axial image at the level of the ascending aorta (Ao) (a) shows a tumor (arrow) that surrounds the right upper lobe bronchus. Subsegmental atelectasis (arrowheads) also is visible. Three-dimensional volume rendering (b) demonstrates the relationship of the tumor (blue) to the airway (pink) and the native location of the fifth intercostal muscle (red). (c–h) Postoperative CT images obtained after right upper lobectomy. Cropped axial images at successively lower levels (c–f) and oblique reformatted image (g) demonstrate the typical appearance of an intercostal muscle flap (arrows) that extends from the thoracotomy site in the posterior chest wall below the fifth rib (5 on c), along the mediastinum, to the resection site in the hilum. The flap was used to buttress the bronchial staple line and separate the bronchus from an arterioplasty site. Three-dimensional volume rendering (h) shows the flap extending from the chest wall below the fifth rib to the airway at the lobectomy site. Note the thoracotomy defect (arrowhead) at the sixth rib.
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Figure 1c. (a, b) Preoperative CT images from a 67-year-old woman with right upper lobe lung cancer. Axial image at the level of the ascending aorta (Ao) (a) shows a tumor (arrow) that surrounds the right upper lobe bronchus. Subsegmental atelectasis (arrowheads) also is visible. Three-dimensional volume rendering (b) demonstrates the relationship of the tumor (blue) to the airway (pink) and the native location of the fifth intercostal muscle (red). (c–h) Postoperative CT images obtained after right upper lobectomy. Cropped axial images at successively lower levels (c–f) and oblique reformatted image (g) demonstrate the typical appearance of an intercostal muscle flap (arrows) that extends from the thoracotomy site in the posterior chest wall below the fifth rib (5 on c), along the mediastinum, to the resection site in the hilum. The flap was used to buttress the bronchial staple line and separate the bronchus from an arterioplasty site. Three-dimensional volume rendering (h) shows the flap extending from the chest wall below the fifth rib to the airway at the lobectomy site. Note the thoracotomy defect (arrowhead) at the sixth rib.
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Figure 1d. (a, b) Preoperative CT images from a 67-year-old woman with right upper lobe lung cancer. Axial image at the level of the ascending aorta (Ao) (a) shows a tumor (arrow) that surrounds the right upper lobe bronchus. Subsegmental atelectasis (arrowheads) also is visible. Three-dimensional volume rendering (b) demonstrates the relationship of the tumor (blue) to the airway (pink) and the native location of the fifth intercostal muscle (red). (c–h) Postoperative CT images obtained after right upper lobectomy. Cropped axial images at successively lower levels (c–f) and oblique reformatted image (g) demonstrate the typical appearance of an intercostal muscle flap (arrows) that extends from the thoracotomy site in the posterior chest wall below the fifth rib (5 on c), along the mediastinum, to the resection site in the hilum. The flap was used to buttress the bronchial staple line and separate the bronchus from an arterioplasty site. Three-dimensional volume rendering (h) shows the flap extending from the chest wall below the fifth rib to the airway at the lobectomy site. Note the thoracotomy defect (arrowhead) at the sixth rib.
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Figure 1e. (a, b) Preoperative CT images from a 67-year-old woman with right upper lobe lung cancer. Axial image at the level of the ascending aorta (Ao) (a) shows a tumor (arrow) that surrounds the right upper lobe bronchus. Subsegmental atelectasis (arrowheads) also is visible. Three-dimensional volume rendering (b) demonstrates the relationship of the tumor (blue) to the airway (pink) and the native location of the fifth intercostal muscle (red). (c–h) Postoperative CT images obtained after right upper lobectomy. Cropped axial images at successively lower levels (c–f) and oblique reformatted image (g) demonstrate the typical appearance of an intercostal muscle flap (arrows) that extends from the thoracotomy site in the posterior chest wall below the fifth rib (5 on c), along the mediastinum, to the resection site in the hilum. The flap was used to buttress the bronchial staple line and separate the bronchus from an arterioplasty site. Three-dimensional volume rendering (h) shows the flap extending from the chest wall below the fifth rib to the airway at the lobectomy site. Note the thoracotomy defect (arrowhead) at the sixth rib.
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Figure 1f. (a, b) Preoperative CT images from a 67-year-old woman with right upper lobe lung cancer. Axial image at the level of the ascending aorta (Ao) (a) shows a tumor (arrow) that surrounds the right upper lobe bronchus. Subsegmental atelectasis (arrowheads) also is visible. Three-dimensional volume rendering (b) demonstrates the relationship of the tumor (blue) to the airway (pink) and the native location of the fifth intercostal muscle (red). (c–h) Postoperative CT images obtained after right upper lobectomy. Cropped axial images at successively lower levels (c–f) and oblique reformatted image (g) demonstrate the typical appearance of an intercostal muscle flap (arrows) that extends from the thoracotomy site in the posterior chest wall below the fifth rib (5 on c), along the mediastinum, to the resection site in the hilum. The flap was used to buttress the bronchial staple line and separate the bronchus from an arterioplasty site. Three-dimensional volume rendering (h) shows the flap extending from the chest wall below the fifth rib to the airway at the lobectomy site. Note the thoracotomy defect (arrowhead) at the sixth rib.
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Figure 1g. (a, b) Preoperative CT images from a 67-year-old woman with right upper lobe lung cancer. Axial image at the level of the ascending aorta (Ao) (a) shows a tumor (arrow) that surrounds the right upper lobe bronchus. Subsegmental atelectasis (arrowheads) also is visible. Three-dimensional volume rendering (b) demonstrates the relationship of the tumor (blue) to the airway (pink) and the native location of the fifth intercostal muscle (red). (c–h) Postoperative CT images obtained after right upper lobectomy. Cropped axial images at successively lower levels (c–f) and oblique reformatted image (g) demonstrate the typical appearance of an intercostal muscle flap (arrows) that extends from the thoracotomy site in the posterior chest wall below the fifth rib (5 on c), along the mediastinum, to the resection site in the hilum. The flap was used to buttress the bronchial staple line and separate the bronchus from an arterioplasty site. Three-dimensional volume rendering (h) shows the flap extending from the chest wall below the fifth rib to the airway at the lobectomy site. Note the thoracotomy defect (arrowhead) at the sixth rib.
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Figure 1h. (a, b) Preoperative CT images from a 67-year-old woman with right upper lobe lung cancer. Axial image at the level of the ascending aorta (Ao) (a) shows a tumor (arrow) that surrounds the right upper lobe bronchus. Subsegmental atelectasis (arrowheads) also is visible. Three-dimensional volume rendering (b) demonstrates the relationship of the tumor (blue) to the airway (pink) and the native location of the fifth intercostal muscle (red). (c–h) Postoperative CT images obtained after right upper lobectomy. Cropped axial images at successively lower levels (c–f) and oblique reformatted image (g) demonstrate the typical appearance of an intercostal muscle flap (arrows) that extends from the thoracotomy site in the posterior chest wall below the fifth rib (5 on c), along the mediastinum, to the resection site in the hilum. The flap was used to buttress the bronchial staple line and separate the bronchus from an arterioplasty site. Three-dimensional volume rendering (h) shows the flap extending from the chest wall below the fifth rib to the airway at the lobectomy site. Note the thoracotomy defect (arrowhead) at the sixth rib.
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Figure 2. Linear calcification in a pedicle flap in a 60-year-old woman 3 months after a right pneumonectomy for lung cancer. Cropped axial CT image at the level of the ascending aorta (Ao) shows an intercostal muscle flap (arrows) used to buttress the bronchial closure. The flap contains a linear calcification (arrowhead), presumably the remnants of periosteum; a prominent fat component; and small linear soft-tissue components. The flap extends directly through the postpneumonectomy space instead of paralleling the spine and mediastinum and is surrounded by pleural fluid.
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Intercostal muscle flaps may contain calcification if periosteum is included within the flap (Fig 2). Such calcifications are often linear and are oriented along the long axis of the flap. Calcification may be seen within a few weeks after surgery and may progress over time (9,10). Calcification may be extensive and may include ossification, with well-defined cortical and medullary bone (Fig 3). When an intercostal muscle flap is used to wrap a bronchial anastomosis, the calcification process may result in bronchial stenosis (11,12). A previously published report indicated that calcification developed in nearly all intercostal muscle flaps (10); however, we observed calcification in only about half of the intercostal muscle flaps in the cases we reviewed. The presence of calcification did not appear to be related to the time interval between surgery and imaging. The difference in the frequency of calcification therefore is likely due to differences in the techniques used to harvest these flaps.
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Figure 3. Ossification in a pedicle flap in a 43-year-old man 4 weeks after a right pneumonectomy for lung cancer. Cropped axial CT image at the level of the ascending aorta (Ao) shows an intercostal muscle flap used to buttress the bronchial closure. The flap contains marked calcification that has already progressed to ossification (arrows), with a fat component (arrowheads) between the ossified portions. The postpneumonectomy space is filled with fluid.
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Serratus Anterior Muscle Flap.—
The serratus anterior is a versatile and reliable muscle flap (3,8). The muscle receives most of its supply from terminal branches of the thoracodorsal artery, which arises from the subscapular branch of the axillary artery. To create a flap with a thoracodorsal pedicle, the muscle must be completely detached from the scapula posteriorly and from the ribs anteriorly to allow transposition to the thoracic cavity. To facilitate entrance into the thoracic cavity, a small portion of the second or third rib is usually excised to allow ample space for the muscle to traverse the chest wall. If this is not done, compression of the vascular pedicle occasionally occurs, leading to flap loss. The muscle flap is flat and fan-shaped and can be used to provide vascularized coverage over a wide area but will not reliably reach far below the level of the carina. The serratus anterior muscle provides anterior motion to the scapula and rotates the scapula upward to allow arm abduction of more than 90°. The use of this flap results in some degree of scapular winging and impairment of arm abduction, but the functional impairment is usually mild and does not interfere with normal activities (13,14).
The serratus anterior muscle flap typically fills the apex of the thoracic cavity (Fig 4). There is often soft-tissue stranding at the harvest site, with absence of the normal muscle. In patients with a serratus anterior flap, in addition, the latissimus dorsi muscle may be abnormal, because it is sometimes divided as part of the thoracotomy procedure. The soft tissue of the serratus anterior flap extends from the entrance into the thoracic cavity at the superolateral chest wall toward the resection site. The axis of the fibers in the flap is not always parallel to the long axis of the flap, presumably because of the greater breadth of the muscle and the greater degree of rotation allowed when bringing the flap into the thoracic cavity. Among our cases, serratus anterior flaps tended to have a larger fat component than did other muscle flaps.
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Figure 4a. (a, b) Preoperative CT images from a 44-year-old man with a second primary cancer in the right lung. Axial CT image at the level of the ascending aorta (Ao) (a) shows a tumor (white arrows) that surrounds the middle lobe bronchus (black arrow), which has been displaced upward after a previous right upper lobectomy. Note the normal serratus anterior muscles (S). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the right serratus anterior muscle (red). (c–f) Postoperative CT images obtained after pneumonectomy. Axial (c) and coronal reformatted (d) images at the level of the left atrium (LA) demonstrate elevation of the liver, a normal left serratus anterior muscle (S on c, arrowheads on d), and a right serratus anterior flap (arrows on d). The latissimus dorsi muscles (L on c, * on d) are in their normal positions. Cropped axial view of the upper chest (e) demonstrates the typical appearance of a serratus anterior muscle flap (arrows), which fills the apex of the thoracic cavity. The flap was used to buttress the bronchial closure. Prominent fat strands are present that are not directed toward the resection site at the hilum. Three-dimensional volume rendering (f) shows the flap (red), which extends from the upper right chest wall, through the rib cage, and into the apex of the right hemithorax, to the resection site.
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Figure 4b. (a, b) Preoperative CT images from a 44-year-old man with a second primary cancer in the right lung. Axial CT image at the level of the ascending aorta (Ao) (a) shows a tumor (white arrows) that surrounds the middle lobe bronchus (black arrow), which has been displaced upward after a previous right upper lobectomy. Note the normal serratus anterior muscles (S). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the right serratus anterior muscle (red). (c–f) Postoperative CT images obtained after pneumonectomy. Axial (c) and coronal reformatted (d) images at the level of the left atrium (LA) demonstrate elevation of the liver, a normal left serratus anterior muscle (S on c, arrowheads on d), and a right serratus anterior flap (arrows on d). The latissimus dorsi muscles (L on c, * on d) are in their normal positions. Cropped axial view of the upper chest (e) demonstrates the typical appearance of a serratus anterior muscle flap (arrows), which fills the apex of the thoracic cavity. The flap was used to buttress the bronchial closure. Prominent fat strands are present that are not directed toward the resection site at the hilum. Three-dimensional volume rendering (f) shows the flap (red), which extends from the upper right chest wall, through the rib cage, and into the apex of the right hemithorax, to the resection site.
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Figure 4c. (a, b) Preoperative CT images from a 44-year-old man with a second primary cancer in the right lung. Axial CT image at the level of the ascending aorta (Ao) (a) shows a tumor (white arrows) that surrounds the middle lobe bronchus (black arrow), which has been displaced upward after a previous right upper lobectomy. Note the normal serratus anterior muscles (S). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the right serratus anterior muscle (red). (c–f) Postoperative CT images obtained after pneumonectomy. Axial (c) and coronal reformatted (d) images at the level of the left atrium (LA) demonstrate elevation of the liver, a normal left serratus anterior muscle (S on c, arrowheads on d), and a right serratus anterior flap (arrows on d). The latissimus dorsi muscles (L on c, * on d) are in their normal positions. Cropped axial view of the upper chest (e) demonstrates the typical appearance of a serratus anterior muscle flap (arrows), which fills the apex of the thoracic cavity. The flap was used to buttress the bronchial closure. Prominent fat strands are present that are not directed toward the resection site at the hilum. Three-dimensional volume rendering (f) shows the flap (red), which extends from the upper right chest wall, through the rib cage, and into the apex of the right hemithorax, to the resection site.
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Figure 4d. (a, b) Preoperative CT images from a 44-year-old man with a second primary cancer in the right lung. Axial CT image at the level of the ascending aorta (Ao) (a) shows a tumor (white arrows) that surrounds the middle lobe bronchus (black arrow), which has been displaced upward after a previous right upper lobectomy. Note the normal serratus anterior muscles (S). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the right serratus anterior muscle (red). (c–f) Postoperative CT images obtained after pneumonectomy. Axial (c) and coronal reformatted (d) images at the level of the left atrium (LA) demonstrate elevation of the liver, a normal left serratus anterior muscle (S on c, arrowheads on d), and a right serratus anterior flap (arrows on d). The latissimus dorsi muscles (L on c, * on d) are in their normal positions. Cropped axial view of the upper chest (e) demonstrates the typical appearance of a serratus anterior muscle flap (arrows), which fills the apex of the thoracic cavity. The flap was used to buttress the bronchial closure. Prominent fat strands are present that are not directed toward the resection site at the hilum. Three-dimensional volume rendering (f) shows the flap (red), which extends from the upper right chest wall, through the rib cage, and into the apex of the right hemithorax, to the resection site.
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Figure 4e. (a, b) Preoperative CT images from a 44-year-old man with a second primary cancer in the right lung. Axial CT image at the level of the ascending aorta (Ao) (a) shows a tumor (white arrows) that surrounds the middle lobe bronchus (black arrow), which has been displaced upward after a previous right upper lobectomy. Note the normal serratus anterior muscles (S). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the right serratus anterior muscle (red). (c–f) Postoperative CT images obtained after pneumonectomy. Axial (c) and coronal reformatted (d) images at the level of the left atrium (LA) demonstrate elevation of the liver, a normal left serratus anterior muscle (S on c, arrowheads on d), and a right serratus anterior flap (arrows on d). The latissimus dorsi muscles (L on c, * on d) are in their normal positions. Cropped axial view of the upper chest (e) demonstrates the typical appearance of a serratus anterior muscle flap (arrows), which fills the apex of the thoracic cavity. The flap was used to buttress the bronchial closure. Prominent fat strands are present that are not directed toward the resection site at the hilum. Three-dimensional volume rendering (f) shows the flap (red), which extends from the upper right chest wall, through the rib cage, and into the apex of the right hemithorax, to the resection site.
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Figure 4f. (a, b) Preoperative CT images from a 44-year-old man with a second primary cancer in the right lung. Axial CT image at the level of the ascending aorta (Ao) (a) shows a tumor (white arrows) that surrounds the middle lobe bronchus (black arrow), which has been displaced upward after a previous right upper lobectomy. Note the normal serratus anterior muscles (S). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the right serratus anterior muscle (red). (c–f) Postoperative CT images obtained after pneumonectomy. Axial (c) and coronal reformatted (d) images at the level of the left atrium (LA) demonstrate elevation of the liver, a normal left serratus anterior muscle (S on c, arrowheads on d), and a right serratus anterior flap (arrows on d). The latissimus dorsi muscles (L on c, * on d) are in their normal positions. Cropped axial view of the upper chest (e) demonstrates the typical appearance of a serratus anterior muscle flap (arrows), which fills the apex of the thoracic cavity. The flap was used to buttress the bronchial closure. Prominent fat strands are present that are not directed toward the resection site at the hilum. Three-dimensional volume rendering (f) shows the flap (red), which extends from the upper right chest wall, through the rib cage, and into the apex of the right hemithorax, to the resection site.
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Latissimus Dorsi Muscle Flap.—
The latissimus dorsi muscle flap is used less frequently than is the serratus anterior (8). The latissimus dorsi muscle receives its arterial supply from the thoracodorsal artery as well as from intercostal perforating branches of the internal thoracic artery anteriorly. To completely mobilize the muscle, extensive dissection is required; but because of its large size, the muscle can be transposed to any site within the thoracic cavity. It is most often used in situations where previous intrathoracic flaps have failed or where space obliteration with vascularized tissue is required, such as in surgical treatment of postpneumonectomy empyema or bronchopleural fistula. The muscle is typically brought into the thoracic cavity through the primary thoracotomy incision, which usually is located in the intercostal space between the fifth and sixth ribs. The latissimus dorsi muscle provides arm adduction and supports the shoulder against upward displacement. The use of this flap typically results in only mild shoulder weakness that is not clinically significant (13,14).
The latissimus dorsi flap typically extends from the lateral chest wall across to the resection site (Fig 5). Soft-tissue stranding and absence of the normal muscle can be seen at the harvest site. The muscle fibers in the two flaps we evaluated were parallel to the long axis of the flap. Because its entrance into the thoracic cavity is lower and more anterior than that of a serratus anterior flap, a latissimus dorsi flap typically extends directly across the thoracic cavity rather than along the apex or the anterior or posterior chest wall to reach the resection site. The relatively infrequent use of this flap in thoracic cancer resections probably limited the range of appearances seen in our case review.
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Figure 5a. (a, b) Preoperative CT images from a 55-year-old woman with adenocarcinoma of the left main bronchus. Axial image at the level of the pulmonary artery (PA) (a) demonstrates a mass (M) adjacent to the right main bronchus (arrow), complete collapse of the left lung, and a small left pleural effusion. Note the normal positions of the latissimus dorsi muscles (L). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the left latissimus dorsi muscle (red). (c–f) Postoperative CT images. Axial image at the level of the left ventricle (LV) (c), coronal reformatted image (d), and cropped view at the level of the left atrium (LA) (e) after an intrapericardial pneumonectomy show a left latissimus dorsi flap (arrows on d and e) that extends through the chest wall and into the postpneumonectomy space. At surgery, the tumor was found to focally involve the wall of the esophagus. The flap was used to buttress the bronchial stump and cover the esophageal mucosa at the resection site. Note the strands of fat in the flap (arrowheads on e). Fluid (* on c and e) has filled the remainder of the postpneumonectomy space. The serratus anterior (S on c and d) and right latissimus dorsi (L on c and d) muscles remain in their normal locations. Surgical changes are evident at the normal location of the left latissimus dorsi muscle ( on c). Three-dimensional volume rendering (f) shows the flap (red), which extends from the left shoulder, through the rib cage, and into the left hemithorax, to the resection site.
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Figure 5b. (a, b) Preoperative CT images from a 55-year-old woman with adenocarcinoma of the left main bronchus. Axial image at the level of the pulmonary artery (PA) (a) demonstrates a mass (M) adjacent to the right main bronchus (arrow), complete collapse of the left lung, and a small left pleural effusion. Note the normal positions of the latissimus dorsi muscles (L). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the left latissimus dorsi muscle (red). (c–f) Postoperative CT images. Axial image at the level of the left ventricle (LV) (c), coronal reformatted image (d), and cropped view at the level of the left atrium (LA) (e) after an intrapericardial pneumonectomy show a left latissimus dorsi flap (arrows on d and e) that extends through the chest wall and into the postpneumonectomy space. At surgery, the tumor was found to focally involve the wall of the esophagus. The flap was used to buttress the bronchial stump and cover the esophageal mucosa at the resection site. Note the strands of fat in the flap (arrowheads on e). Fluid (* on c and e) has filled the remainder of the postpneumonectomy space. The serratus anterior (S on c and d) and right latissimus dorsi (L on c and d) muscles remain in their normal locations. Surgical changes are evident at the normal location of the left latissimus dorsi muscle ( on c). Three-dimensional volume rendering (f) shows the flap (red), which extends from the left shoulder, through the rib cage, and into the left hemithorax, to the resection site.
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Figure 5c. (a, b) Preoperative CT images from a 55-year-old woman with adenocarcinoma of the left main bronchus. Axial image at the level of the pulmonary artery (PA) (a) demonstrates a mass (M) adjacent to the right main bronchus (arrow), complete collapse of the left lung, and a small left pleural effusion. Note the normal positions of the latissimus dorsi muscles (L). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the left latissimus dorsi muscle (red). (c–f) Postoperative CT images. Axial image at the level of the left ventricle (LV) (c), coronal reformatted image (d), and cropped view at the level of the left atrium (LA) (e) after an intrapericardial pneumonectomy show a left latissimus dorsi flap (arrows on d and e) that extends through the chest wall and into the postpneumonectomy space. At surgery, the tumor was found to focally involve the wall of the esophagus. The flap was used to buttress the bronchial stump and cover the esophageal mucosa at the resection site. Note the strands of fat in the flap (arrowheads on e). Fluid (* on c and e) has filled the remainder of the postpneumonectomy space. The serratus anterior (S on c and d) and right latissimus dorsi (L on c and d) muscles remain in their normal locations. Surgical changes are evident at the normal location of the left latissimus dorsi muscle ( on c). Three-dimensional volume rendering (f) shows the flap (red), which extends from the left shoulder, through the rib cage, and into the left hemithorax, to the resection site.
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Figure 5d. (a, b) Preoperative CT images from a 55-year-old woman with adenocarcinoma of the left main bronchus. Axial image at the level of the pulmonary artery (PA) (a) demonstrates a mass (M) adjacent to the right main bronchus (arrow), complete collapse of the left lung, and a small left pleural effusion. Note the normal positions of the latissimus dorsi muscles (L). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the left latissimus dorsi muscle (red). (c–f) Postoperative CT images. Axial image at the level of the left ventricle (LV) (c), coronal reformatted image (d), and cropped view at the level of the left atrium (LA) (e) after an intrapericardial pneumonectomy show a left latissimus dorsi flap (arrows on d and e) that extends through the chest wall and into the postpneumonectomy space. At surgery, the tumor was found to focally involve the wall of the esophagus. The flap was used to buttress the bronchial stump and cover the esophageal mucosa at the resection site. Note the strands of fat in the flap (arrowheads on e). Fluid (* on c and e) has filled the remainder of the postpneumonectomy space. The serratus anterior (S on c and d) and right latissimus dorsi (L on c and d) muscles remain in their normal locations. Surgical changes are evident at the normal location of the left latissimus dorsi muscle ( on c). Three-dimensional volume rendering (f) shows the flap (red), which extends from the left shoulder, through the rib cage, and into the left hemithorax, to the resection site.
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Figure 5e. (a, b) Preoperative CT images from a 55-year-old woman with adenocarcinoma of the left main bronchus. Axial image at the level of the pulmonary artery (PA) (a) demonstrates a mass (M) adjacent to the right main bronchus (arrow), complete collapse of the left lung, and a small left pleural effusion. Note the normal positions of the latissimus dorsi muscles (L). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the left latissimus dorsi muscle (red). (c–f) Postoperative CT images. Axial image at the level of the left ventricle (LV) (c), coronal reformatted image (d), and cropped view at the level of the left atrium (LA) (e) after an intrapericardial pneumonectomy show a left latissimus dorsi flap (arrows on d and e) that extends through the chest wall and into the postpneumonectomy space. At surgery, the tumor was found to focally involve the wall of the esophagus. The flap was used to buttress the bronchial stump and cover the esophageal mucosa at the resection site. Note the strands of fat in the flap (arrowheads on e). Fluid (* on c and e) has filled the remainder of the postpneumonectomy space. The serratus anterior (S on c and d) and right latissimus dorsi (L on c and d) muscles remain in their normal locations. Surgical changes are evident at the normal location of the left latissimus dorsi muscle ( on c). Three-dimensional volume rendering (f) shows the flap (red), which extends from the left shoulder, through the rib cage, and into the left hemithorax, to the resection site.
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Figure 5f. (a, b) Preoperative CT images from a 55-year-old woman with adenocarcinoma of the left main bronchus. Axial image at the level of the pulmonary artery (PA) (a) demonstrates a mass (M) adjacent to the right main bronchus (arrow), complete collapse of the left lung, and a small left pleural effusion. Note the normal positions of the latissimus dorsi muscles (L). Three-dimensional volume rendering (b) shows the relationship of the tumor (blue) to the airway (pink) and the normal position of the left latissimus dorsi muscle (red). (c–f) Postoperative CT images. Axial image at the level of the left ventricle (LV) (c), coronal reformatted image (d), and cropped view at the level of the left atrium (LA) (e) after an intrapericardial pneumonectomy show a left latissimus dorsi flap (arrows on d and e) that extends through the chest wall and into the postpneumonectomy space. At surgery, the tumor was found to focally involve the wall of the esophagus. The flap was used to buttress the bronchial stump and cover the esophageal mucosa at the resection site. Note the strands of fat in the flap (arrowheads on e). Fluid (* on c and e) has filled the remainder of the postpneumonectomy space. The serratus anterior (S on c and d) and right latissimus dorsi (L on c and d) muscles remain in their normal locations. Surgical changes are evident at the normal location of the left latissimus dorsi muscle ( on c). Three-dimensional volume rendering (f) shows the flap (red), which extends from the left shoulder, through the rib cage, and into the left hemithorax, to the resection site.
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Fat Content.—
Many muscle flaps demonstrate a fat component at imaging. In our review, this component was often linear and oriented along the long axis of the flap (Figs 2, 5). The amount of fat within a flap often increases over time (15). An increase in fat content was seen in most of our cases with multiple postoperative imaging examinations (Fig 6) but was most prominent in serratus anterior flaps. This increase presumably was due to atrophy and fatty replacement of the muscle fibers in the flap over time. The obliteration of previously seen fat within a flap probably would be suggestive of tumor involvement. However, no recurrent tumor was seen in the flaps in our case review.
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Figure 6a. Increase in fat content in a serratus anterior muscle flap in a 61-year-old woman after a right upper lobectomy for lung cancer. The flap was used to buttress the bronchial closure and to stop a cerebrospinal fluid leak at a vertebral transverse process resection site. (a) Cropped axial CT image obtained at the level of the aortic arch (Ao), 2 weeks after surgery, demonstrates little internal fat in the flap (arrows). (b) CT image obtained at approximately the same level, 1 year after surgery, shows atrophy of the muscle fibers and an increased fat component in the flap (arrows).
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Figure 6b. Increase in fat content in a serratus anterior muscle flap in a 61-year-old woman after a right upper lobectomy for lung cancer. The flap was used to buttress the bronchial closure and to stop a cerebrospinal fluid leak at a vertebral transverse process resection site. (a) Cropped axial CT image obtained at the level of the aortic arch (Ao), 2 weeks after surgery, demonstrates little internal fat in the flap (arrows). (b) CT image obtained at approximately the same level, 1 year after surgery, shows atrophy of the muscle fibers and an increased fat component in the flap (arrows).
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Enhancing Vessels.—
Blood vessels were identified within several of the muscle flaps in our review. To our knowledge, this finding was not previously described in the literature. Vessels were depicted as enhancing curvilinear structures oriented along the fibers of the flap (Fig 7). Vessels were most frequently seen in serratus anterior flaps (Fig 8), presumably because the larger fat component in many of those flaps aided the identification of small vessels. The observation of enhancing vessels helps confirm the identification of a soft-tissue entity as a muscle flap rather than a recurrent tumor.
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Figure 7. Blood vessels in an intercostal muscle flap in a 62-year-old man 3 days after a right pneumonectomy for lung cancer. The flap was used to buttress the bronchial closure. Cropped axial CT pulmonary angiogram at the level of the ascending aorta (Ao) depicts curvilinear and punctate features that represent blood vessels (arrows) in the flap. These small vessels are most clearly demonstrated with CT pulmonary angiography. A prominent fat component also is evident in the flap.
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Figure 8. Enhancing vessels in a pedicle flap in a 55-year-old woman after a right upper lobectomy and right lower lobe superior segmentectomy for lung cancer and abscess. An intercostal muscle flap was used to buttress the right lower lobe staple line, and a serratus anterior flap was used to buttress the upper lobe bronchial closure and fill the space at the right apex to prevent abscess recurrence. Cropped axial CT image at the level of the aortic arch (Ao) demonstrates enhancing vessels (arrows) in the serratus anterior flap. Small vessels are frequently identifiable among the minimal muscle strands and prominent fat components that are common in serratus anterior flaps.
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The depiction of enhancing vessels appears to be related to the examination technique. For instance, in some cases, the enhancing vessel was not demonstrated at routine chest CT with a 3.75-mm collimation and a routine contrast agent dose but was easily identifiable on a CT pulmonary angiogram with a 1.25-mm collimation and a higher contrast agent dose and faster rate of administration. The examination parameters generally were not optimized for the visualization of small peripheral vessels; additional vessels probably would have been identified if the imaging protocol had been tailored to that purpose.
Findings on PET Images
Muscle flaps should not show significant FDG uptake at PET (10). The uptake within a flap should be similar to that in other muscle structures (similar uptake helps confirm the benign nature of the soft-tissue component); any greater uptake within the flap should be viewed with suspicion. The only exception is an intercostal muscle flap with extensive calcification or ossification (Fig 9), in which low-level FDG uptake (similar to that in normal bone) in the calcified component may be seen. It is helpful to have fused PET/CT images to accurately localize the abnormality and confirm that benign calcification is the cause of FDG uptake. After radiation therapy in areas of the lung adjacent to a muscle flap, the tissue may show increased FDG uptake due to an inflammatory reaction (Fig 10). However, careful localization with fused PET/CT images may help confirm a lack of metabolic activity within the muscle flap itself.
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Figure 9a. Calcification in an intercostal muscle flap in a 37-year-old woman after resection of a lymphomatous tracheoesophageal fistula. The flap was used to close the fistula. (a) Cropped axial CT image at the level of the thoracic inlet demonstrates prominent calcification (arrow) in the flap. (b, c) PET (b) and fused PET/CT (c) images at the same level demonstrate an area of FDG uptake in the flap (arrow) similar to the uptake in normal bone. The area of increased FDG uptake in the esophagus (*) represents a recurrent lymphoma. Tr = trachea.
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Figure 9b. Calcification in an intercostal muscle flap in a 37-year-old woman after resection of a lymphomatous tracheoesophageal fistula. The flap was used to close the fistula. (a) Cropped axial CT image at the level of the thoracic inlet demonstrates prominent calcification (arrow) in the flap. (b, c) PET (b) and fused PET/CT (c) images at the same level demonstrate an area of FDG uptake in the flap (arrow) similar to the uptake in normal bone. The area of increased FDG uptake in the esophagus (*) represents a recurrent lymphoma. Tr = trachea.
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Figure 9c. Calcification in an intercostal muscle flap in a 37-year-old woman after resection of a lymphomatous tracheoesophageal fistula. The flap was used to close the fistula. (a) Cropped axial CT image at the level of the thoracic inlet demonstrates prominent calcification (arrow) in the flap. (b, c) PET (b) and fused PET/CT (c) images at the same level demonstrate an area of FDG uptake in the flap (arrow) similar to the uptake in normal bone. The area of increased FDG uptake in the esophagus (*) represents a recurrent lymphoma. Tr = trachea.
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Figure 10a. FDG uptake due to postirradiation inflammation in a 58-year-old man after a right middle and lower lobectomy for lung cancer. (a) Cropped axial CT image at the level of the ascending aorta (Ao), 10 months after radiation therapy, demonstrates a region of consolidation and bronchiectasis (arrows) adjacent to an intercostal muscle flap (arrowheads) used to buttress the bronchial closure. (b, c) PET (b) and fused PET/CT (c) images at the same level demonstrate active FDG uptake in the irradiated lung tissue (arrows) but not in the flap (arrowheads).
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Figure 10b. FDG uptake due to postirradiation inflammation in a 58-year-old man after a right middle and lower lobectomy for lung cancer. (a) Cropped axial CT image at the level of the ascending aorta (Ao), 10 months after radiation therapy, demonstrates a region of consolidation and bronchiectasis (arrows) adjacent to an intercostal muscle flap (arrowheads) used to buttress the bronchial closure. (b, c) PET (b) and fused PET/CT (c) images at the same level demonstrate active FDG uptake in the irradiated lung tissue (arrows) but not in the flap (arrowheads).
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Figure 10c. FDG uptake due to postirradiation inflammation in a 58-year-old man after a right middle and lower lobectomy for lung cancer. (a) Cropped axial CT image at the level of the ascending aorta (Ao), 10 months after radiation therapy, demonstrates a region of consolidation and bronchiectasis (arrows) adjacent to an intercostal muscle flap (arrowheads) used to buttress the bronchial closure. (b, c) PET (b) and fused PET/CT (c) images at the same level demonstrate active FDG uptake in the irradiated lung tissue (arrows) but not in the flap (arrowheads).
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Findings on MR Images
MR images were available for only one patient in our study (Fig 11). The flap in this case had intermediate and high signal intensity on T1-weighted images and low signal intensity on T2-weighted fat-suppressed images because of its fat content. Flaps with a predominant muscle component should appear similar to muscle at MR imaging with any pulse sequence and should show enhancement similar to that of muscle after a contrast medium is administered.
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Figure 11a. Flap calcification and a metastatic pleural nodule in a 70-year-old man after pneumonectomy for lung cancer. An intercostal muscle flap was used to buttress the bronchial closure. (a) Cropped axial CT image at the level of the ascending aorta (Ao) demonstrates linear calcification in the flap (arrow) with an adjacent enhancing metastatic pleural nodule (arrowheads). Fluid fills the postpneumonectomy space. (b, c) T1-weighted (repetition time msec/echo time msec, 700/8) (b) and T2-weighted (4000/90) (c) MR images obtained 3 months later show marked growth of the nodule into a mass (M) that has displaced the flap. The flap (arrow) has intermediate and high signal intensity on b and low signal intensity on c, findings indicative of muscle and fat, respectively. Ao = aorta.
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Figure 11b. Flap calcification and a metastatic pleural nodule in a 70-year-old man after pneumonectomy for lung cancer. An intercostal muscle flap was used to buttress the bronchial closure. (a) Cropped axial CT image at the level of the ascending aorta (Ao) demonstrates linear calcification in the flap (arrow) with an adjacent enhancing metastatic pleural nodule (arrowheads). Fluid fills the postpneumonectomy space. (b, c) T1-weighted (repetition time msec/echo time msec, 700/8) (b) and T2-weighted (4000/90) (c) MR images obtained 3 months later show marked growth of the nodule into a mass (M) that has displaced the flap. The flap (arrow) has intermediate and high signal intensity on b and low signal intensity on c, findings indicative of muscle and fat, respectively. Ao = aorta.
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Figure 11c. Flap calcification and a metastatic pleural nodule in a 70-year-old man after pneumonectomy for lung cancer. An intercostal muscle flap was used to buttress the bronchial closure. (a) Cropped axial CT image at the level of the ascending aorta (Ao) demonstrates linear calcification in the flap (arrow) with an adjacent enhancing metastatic pleural nodule (arrowheads). Fluid fills the postpneumonectomy space. (b, c) T1-weighted (repetition time msec/echo time msec, 700/8) (b) and T2-weighted (4000/90) (c) MR images obtained 3 months later show marked growth of the nodule into a mass (M) that has displaced the flap. The flap (arrow) has intermediate and high signal intensity on b and low signal intensity on c, findings indicative of muscle and fat, respectively. Ao = aorta.
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Conclusions
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Pedicle flaps used in thoracic surgical oncology have characteristic appearances that allow their identification at CT. The location and presence of fat and soft-tissue strands permit the distinction of the muscle flaps from tumor recurrence and infection. Vessel enhancement along the flap axis may be seen on images obtained with thin sections and rapid contrast medium administration, but soft-tissue enhancement should not be seen. In difficult cases, PET/CT or MR imaging may be used to confirm the benign nature of the flap by demonstrating the imaging characteristics of normal muscle, fat, and calcification.
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Footnotes
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Abbreviations: FDG = fluorine 18 fluorodeoxyglucose
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References
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- Deeb ME, Sterman DH, Shrager JB, Kaiser LR. Bronchial anastomotic stricture caused by ossification of an intercostal muscle flap. Ann Thorac Surg 2001;71:1700–1702.[Abstract/Free Full Text]
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Abstract
LEARNING OBJECTIVES
