Imaging the Postoperative Neck

10.1\ Reconstruction Flaps

10.1.1  Discussion

Flap reconstruction is routinely performed for closing soft tissue, bone, and/or skin defects created by head and neck tumor resection. Many donor sites and types of flaps are available including local, regional, and free flaps (Figs. 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 10.10, and 10.11 and Table 10.1).

The pectoralis major muscle flap is often used as a rotation flap for head and neck reconstruction surgery. Due to the highly vascular nature of the pedicled pectoralis major flap, it is desirable for repairing defects in previously radiated areas. The pedicled flap is brought over the clavicle with its vascular supply and is often used to provide coverage of the carotid arteries or to reinforce primary

D.T. Ginat, M.D., M.S. (*)

Department of Radiology, University of Chicago, Chicago, IL, USA

e-mail: dtg1@uchicago.edu

E. Blair, M.D.

Department of Surgery, Section of Otolaryngology-­ Head and Neck Surgery, University of Chicago, Chicago, IL, USA

H.D. Curtin, M.D.

Department of Radiology, Harvard Medical School, Boston, MA, USA

Department of Radiology, Massachusetts Eye and Ear Infirmary, Boston, MA, USA

pharyngeal closure. Pectoralis myocutaneous flaps can also be “tubed” to create a neopharynx, in which there is a deep core of fatty tissue, a more superficial area of the muscle, and overlying skin that forms the “pseudomucosa.” Initially, the myocutaneous flaps maintain muscle bulk, but often gradually become atrophied and replaced by fat.

Osteomyocutaneous and bone grafts are mainly used to reconstruct mandibulectomy defects. The fibula is a common donor site, but the scapula, ribs, and other bones can be used as well. The bone grafts are often cut into smaller sections in order to reconstruct the curved contours of the mandible. The grafts are usually secured using plates and screws. The soft tissues attached to the bone flaps are useful for providing bulk to large surgical defects.

Colon interposition, gastric pull-through, and jejunal/ileal grafts have been used to reconstruct the upper aerodigestive tract after procedures that involve resection of part or all of the pharynx and/or esophagus, such as with pharyngolaryngoesophagectomy. On imaging, rugal folds and haustra can be identified with gastric and colon interposition, respectively. Alternatively, musculomucosal flaps, such as the FAMM flap, can be used to reconstruct relatively superficial upper aerodigestive tract defects.

Imaging with CT, MRI, and 18FDG-PET is routinely used for posttreatment imaging, particularly for tumor surveillance. Recurrence can be difficult to discern due to the altered anatomy of

the surgical bed on CT or MRI ((Fig. 10.12), such as the soft tissue components of the flaps. 18FDGPET/CT is particularly helpful in such instances, but is ideally performed no sooner than 12 weeks following surgery in order to minimize the rate of false-positive results. However, it is helpful to obtain a baseline CT or MRI soon after surgery for subsequent comparison and to correlate the findings with the operative note.

While serosanguinous fluid collections or seromas in the surgical bed after flap reconstruction are commonly encountered on early postoperative imaging, large perioperative hematomas are rare. However, these can lead to flap ischemia; therefore, prompt recognition and re-­ exploration can help salvage the flap. On CT, the hematomas can appear as mass-like heterogeneous lesions (Fig. 10.13).

Infection of the flap is a serious complication, which may require urgent debridement or revision. Diagnostic imaging is useful for delineating the extent of the infected fluid collections, which can contain gas, have peripheral enhancement, and surrounding fat stranding (Fig. 10.14). Infections in the surgical bed can be predisposed by the presence of fistulas with the skin and/or aerodigestive tract.

Anastomotic leaks are potential sources for infection. CT or fluoroscopic examinations with oral contrast administration can be useful for assessing the presence of leaks. The presence of hyperattenuation from the oral contrast material in extraluminal fluid collections is indicative of a leak (Fig. 10.15). A baseline CT without oral contrast can be useful for comparison, since surgically implanted hyperattenuating material can potentially be misinterpreted as contrast.

Fig. 10.1  Illustration of various types of tissue flaps. Fasciocutaneous (A). Musculomucosal (B). Myocutaneous (C). Bowel (D). Bone/osteomyocutaneous (E)

Fig. 10.3  Fasciocutaneous rotation advancement flap. The patient has a large defect following Mohs surgery for a cutaneous malignancy of the left cheek. Axial T2-weighted MR images (a, b) demonstrate the Scarpa’s

fascia component of the graft (arrows) as a low-signal- intensity band. The rest of the graft demonstrates normal fat signal intensity without evidence of recurrent disease. Atrophy of the left masticator muscles is noted

Fig. 10.4  Myocutaneous free flap. Axial CT image shows the skin (arrow), fat (*), and muscle (arrowhead) components of the thigh flap used to reconstruct the left oropharynx and oral cavity

Fig. 10.5  Myocutaneous rotational flap. Axial CT image shows a pectoralis flap swung over the clavicle to fill a large surgical defect in the neck. The vascular pedicle is visible (arrow), as are the muscle (arrowhead) and adipose tissue (*) components of the flap. The muscle has undergone fatty degeneration

Fig. 10.7  Myocutaneous flap neopharynx. Axial CT image shows skin lining the neopharynx (arrow), which is surrounded by subcutaneous fat and muscle

Fig. 10.8  Radial forearm free flap lip reconstruction. Axial CT image shows lower lip reconstruction utilizing radial forearm free flap and palmaris longus tendon (arrow), which provides near-anatomic contours

Fig. 10.9  Colonic interposition. Axial CT image shows a loop of large bowel (arrow) adjacent to the trachea

Fig. 10.10  Gastric transposition. Axial CT image shows the transposed stomach filled with barium, which outlines the rugal folds (arrow). Total pharyngolaryngoesophagectomy was also performed

Fig. 10.11  Facial artery musculomucosal (FAMM) flap. Preoperative coronal CT image (a) shows an infiltrative mass in the right floor of the mouth (arrow). Postoperative

Table 10.1  Types of flap reconstruction

coronal CT image (b) shows interval resection of the mass and reconstruction with a flap that closely approximately approximates the floor of the mouth

a

b

Fig. 10.12  Tumor recurrence. Axial CT image (a) shows a myocutaneous flap with subtle nodularity along the left aspect of the neopharynx (arrow) in a patient with history of head and neck squamous cell carcinoma, but no prior baseline exams available. 18FDG-PET/CT (b) was recommended and obtained 2 weeks later, which shows corresponding marked hypermetabolism (arrow)

Fig. 10.13  Perioperative hematoma. Axial CT image obtained shortly after laryngectomy shows a heterogeneous mass-like hematoma (arrow) underlying the edematous left pectoralis flap

Fig. 10.14  Infected flap. Coronal fat-suppressed post-­ contrast T1-weighted MRI shows a fluid collection with surrounding enhancement (arrow) deep to the left neck myocutaneous flap, which represents an abscess