Pharyngeal Reconstruction

Introduction

The upper aerodigestive (UAD) tract is an intricate maze of alleyways, muscular tubes, and cords that allows humans to have a common functional pathway for oral intake and breathing, as well as harmonizing vibrations into speech. Articulation of speech is dependent on the symphony of functions of these passages, influenced by the larynx, epiglottis, pharyngeal walls, soft and hard palate, the tongue musculature, salivation, lip seal or oral competence and dentition as a tightly ordered orchestra. Many of these functional elements involve the pharynx. The posterior reaches and ramifications of the UAD tract coalesce into a continuous 15 cm-long muscular collecting tube, the pharynx, which begins in continuity with the nasopharynx superiorly and connects to the esophagus inferiorly. It extends from the skull base to the esophagus and comprises three parts: upper or nasopharynx behind the nose, middle or oropharynx behind the mouth, and lower or hypo- or laryngopharynx behind the epiglottis and larynx.

Pathology

Pharyngeal cancers are predominately squamous cell carcinoma (SCC) and are of two types: HPV+ related to human papilloma virus (better prognosis) and HPV− usually linked to alcohol and tobacco. Risk factors include alcohol and tobacco, exposure to Epstein–Barr virus, and Chinese ethnicity, especially for nasopharyngeal carcinoma. Organ preservation has become the main aim in the management of UAD tract malignancy. Fortunately, early stage disease can be effectively treated conservatively with radiotherapy or chemoradiation combination so that function can largely be preserved. Given the morbidity of surgery in this most sophisticated functional zone, its place is increasingly reserved for advanced stage disease or in salvage treatment after failure of nonsurgical protocols. Sadly, most patients present at advanced stages and are associated with poor overall survival. Between 70% and 85% have stage 3 or stage 4 disease at presentation and 5-year survivals are reported around 15%–35%. The reality is that most surgery is palliative and although the prime focus here is inevitably on removal of the cancer and reduction in the risk of local recurrence, the overall focus must be on the quality of survival. By contrast, nasopharyngeal cancers have a better prognosis as they are mostly responsive to radiotherapy and rarely require surgical resection or reconstruction.

Anatomy

The nasopharynx is open to the nasal cavities anteriorly and extends from the base of the skull superiorly to the upper surface of the soft pallet where it becomes the oropharynx. The oropharynx communicates with the mouth anteriorly and includes the soft palate, the tonsils, and the tongue base posterior to the circumvallate papillae. The oropharyngeal tube extends from the soft palate above to the hyoid below. The hypopharynx is continuous below the oropharynx, extending from the level of the hyoid bone to the esophageal inlet. The larynx lies in close anterior proximity. The thyrohyoid membrane through which the internal branch of the superior laryngeal nerve gains access to the larynx is located superolaterally. The detailed anatomy of the UAD tract can be found in specialized texts. Anatomically, the area has a rich lymphatic drainage to the jugular chains as well as the retropharyngeal nodes and the node of Rouvière, with frequent crossing of the midline. The pharyngeal muscular tube, which spans from the base of the skull to the C6 vertebra, comprises circular fibers that form constrictions to propel contents into the esophagus and longitudinal fibers that lift the walls of the pharynx during swallowing.

Indications for Surgery and Reconstruction

Most commonly, major UAD tract defects result from surgical ablation of malignancies. It is accepted that radiotherapy is just as effective as surgery for eradication of early disease, and because radiotherapy is less destructive to function, it is the preferred modality of treatment. Surgery is therefore reserved for advanced stage or recurrent cancers and will be inevitably destructive. The principles of wide oncological resection, the proximity of the vital structures and the protection of the upper airway patency, speech, and deglutition dictate the indications for reconstruction of any significant UAD tract defects. Many pharyngectomies for advanced disease are associated with combined laryngectomy. Thus most advanced neoplasms involving the oropharynx, hypopharynx or cervical esophagus will result in a pharyngeal defect requiring reconstruction.

Classification of Pharyngeal Defects

A useful classification of pharyngeal defects was previously devised by Disa et al, however, this classification did not specify whether the defect involved the larynx or the base of the tongue. More recently, Urken et al, proposed a new classification scheme that addresses this issue:

• Type 0: minimal defects of the pharyngoesophageal segment that are amenable to primary closure

• Type I: non-circumferential defect with a presence of a viable strip of mucosa, measuring a minimum of 2 cm in width

• Type II: circumferential defect extended no further cephalad than the level of the vallecula

• Type III: circumferential or noncircumferential defect extended cephalad to the level of the vallecula

• Type IV: any resection that extends caudal to the level of the clavicles.

Historical Perspectives

The first attempts at pharyngoesophageal reconstruction date back to the nineteenth century. These proved notoriously unreliable, with chronic aspiration, hemorrhage, and early death in the postoperative course, followed by stricture formation in those who survived the immediate aftermath of the surgery. This led to a loss of enthusiasm for reconstruction until Wookey rekindled interest in 1948 with a random pattern anterior neck skin flap to reestablish the UAD tract. His two-stage reconstruction included using the cervical skin raised as a random flap sutured to the upper and lower ends of the defect, but left open anteriorly thereby exteriorizing the pharynx and esophagus. The sulcus thus created was closed 5 weeks later at a second-stage operation. The next surgical leap came when Bakamjian described the more reliable axial deltopectoral flap, based medially on what has subsequently been shown to be the upper second and third internal thoracic artery perforating branches. It was, however, still a two- or three-stage treatment and was not uniformly reliable.

In 1979, Ariyan’s description of a tubed myocutaneous pectoralis major flap finally made possible a single‐stage ablative reconstruction with a more predictable outcome. Subsequently, both the trapezius and latissimus dorsi myocutaneous flaps were described as alternatives for a single‐stage reconstruction, but not surprisingly did not achieve significant popularity.

Parallel with these skin tube developments, more reliable pedicled interposition gastrointestinal reconstructions were being attempted as far back as the 1930s; their primary role, however, was in total esophagectomies. Adaptation of the Ivor–Lewis gastric pull-up to the cervical esophagus and pharynx was one such procedure, which has survived as a mostly reliable option into the modern era. In addition to the gastric pull-up, the spectrum of these pedicled flap reconstructions included the left colon and the seldom used pedicled jejunum.

In 1959, Seidenberg reported the first successful harvesting and transferring of a jejunal free flap using microsurgical techniques, reportedly with threaded 6‐0 silk sutures under loupes magnification. His patient died 5 days postoperatively from a massive cerebrovascular accident, but the first successful human free flap was found to be viable at the time. The following year Hiebert and Cummings Jr performed an uneventful gastro-antral free graft joining 2 mm-diameter gastroepiploic vessels to the superior thyroid artery end to side and facial vein end-to-end. They noted the report of Jacobson and Suarez, the acknowledged founders of microvascular technique that occurred subsequent to their procedure, recommending using a microscope. These feats were performed at least a decade before the tidal wave of microsurgery began, with the works of Buncke et al, Daniel and Taylor, and O’Brien et al, and others who used other tissues, including omentum and skin. Soon, microsurgical free tissue transfer was to become a first-line mainstream reconstructive option.

Microvascular technique brought with it the promise of a reconstruction not bound by restraints of pedicle length or random proportions. The reliability of an axial flap transfer into the defect revolutionized the approach to major reconstructive challenges. Gastro-omental, gastric antral, ileocolic as well as colon free flaps have been described; however by far the most common visceral reconstruction is a free jejunal reconstruction. The earliest significant clinical series of microsurgical jejunal reconstructions were those reported by Jurkiewicz. But his daring and technical skill were not widely adopted for almost a further 20 years. The free jejunal flap, whether as a tube or patch, has since become one of the two most reliable reconstructive tools for laryngopharyngectomy and/or cervical esophagus reconstruction.

Tubed or patch fasciocutaneous flaps are the other main alternative reconstructive options for pharyngeal defects. The most common flaps used are the anterolateral thigh and radial forearm flaps.

Assessment and Planning

As with any operative surgery, planning remains the most important step in execution of the technique. This is best considered as part of a regular multidisciplinary (MDT) meeting, which includes, in addition to head and neck, oral maxillofacial and plastic surgeons, radiation oncologists, medical oncologists, pathologists, speech therapists, dieticians, physiotherapists, and social workers, as well as a radiologist specializing in head and neck malignancies. An estimation of the extent of the defect and the need for reconstruction is discussed at these meetings. The reconstructive team, in conjunction with the ablative team, can decide on the best reconstructive option and begin planning for surgery after assessment of all possible donor sites. Previous history of laparotomy and upper GI surgery is noted and the patient’s forearms and thighs are assessed.

A decision is also made at these multidisciplinary meetings in relation to the need for perioperative radiotherapy and preoperative dental surgery, as well as nutritional needs. Most, if not all, patients requiring major reconstruction have either advanced disease or chemoradiation failure for relatively advanced disease and suffer from malnutrition. The need for nutritional supplementation is almost universal, including during the radiation therapy period. This may require percutaneous endoscopic gastric (PEG) tube insertion, depending on the surgical unit. Nutritional status will influence wound healing and reduce fistula formation. Uncomplicated healing streamlines the programming of radiation therapy in the shortest time window possible for the best therapeutic outcome.

Reconstruction

The broad principles of pharyngeal reconstruction are:

• maintaining or recreating a patent airway and protection from aspiration;

• reestablishing the integrity of the pharyngeal pathway to allow swallowing and adequate caloric intake; and

• voice and speech rehabilitation.

All of these endeavors have in common the creation of a patent tube. Salvage of all these functions is possible to various extents. The advent of microsurgery has made possible transfer of large amounts of tissue sculpted to more or less reconstruct the created defect. In addition, introduction of tissues with a new vascular supply into settings of advanced disease requiring major resections and radiotherapy or following chemoradiation failure, promotes better wound healing and discourages fistula formation.

The two key determinants that influence the nature of the reconstruction are the surgery (i.e., the defect created as well as donor availabilities) and the patient’s general status. Many of these patients have life-long history of heavy smoking and drinking, with the attendant risk of cardiac or respiratory disease and malnourishment. These are all factors to be considered in the light of the length of surgery and the added morbidity from choice of donor sites. The added burden of a laparotomy or a chest flap on the respiratory reserves, the speed of skin flaps versus bowel in patients with poor cardiac reserve or malnourishment, and the benefits of donor sites that allow simultaneous access during the primary resection for two-team surgery are issues to ponder. Preoperative anesthetic, respiratory, and cardiac assessment is mandatory. Any reasonable optimization of the patient’s status should be undertaken prior to surgery.

All patients require confirmation of continuity and integrity of the UAD tract at 7–10 days postoperatively, with a contrast study before removal of nasogastric tubes and resumption of oral intake.