Indications and Contraindications

There are a variety of viable options for the reconstruction of the oropharynx, and several algorithms have been suggested in the literature. One such algorithm by de Almeida and colleagues includes a classification system based on subsite involvement and presence of adverse features (carotid artery exposure in the pharynx, communication with neck, >50% soft palate resection). Patients without any adverse features (Class I/II) were typically reconstructed with secondary intention, primary closure, or local flaps utilizing nearby tissue from the posterior pharynx and superior constrictors. Patients with adverse features (Class III/IV) required regional tissue transfer with consideration of free flap reconstruction. Regional flaps such as submental island flap, pectoralis major flap, and sternocleidomastoid flap have all been well described in the literature. Free tissue transfer was performed for extensive palatal and pharyngeal defects, and in patients likely requiring adjuvant radiotherapy based on disease severity.

The indications for TORS free flap reconstruction serve as guidelines, and each individual patient necessitates careful and tailored decision-making to select the optimal reconstructive strategy. In our experience, we perform soft palate reconstruction in individuals with at least one-third of a soft palate defect or with a resection extending anteriorly to the hard palate, therefore resulting in a break in the velopharyngeal sphincter. Lateral extension including the medial pterygoid and exposure of the internal carotid artery are also considerations for free tissue transfer. Patients with involvement of the pharyngeal constrictor and at least one-half of the base of tongue with a significant impact on postoperative dysphagia also typically undergo microvascular reconstruction. Finally, history of prior radiation therapy, which can negatively impact wound healing and is an independent risk factor for aspiration, is another important factor.

Surgical Options

There are a variety of free flaps that can be used in oropharyngeal reconstruction including enteric free flaps and fasciocutaneous free flaps. While the jejunal free flap is a viable option for the oropharynx, this strategy is typically utilized for pharyngoesophageal reconstruction due to its unique tubular, mucosal structure. Furthermore, major disadvantages include requiring a laparotomy with increased donor-site morbidity and potential for intra-abdominal complications. In contrast, the most commonly used free tissue options in the oropharynx include the radial forearm free flap (RFFF) and anterolateral thigh (ALT) free flap, 2 flaps with excellent functional outcomes and low donor-site morbidity. Other flaps including the latissimus dorsi flap, thoracodorsal artery perforator flap, medial sural artery perforator flap, and superficial circumflex iliac flap have all been reported in the literature.

The RFFF has become a widely used and popular flap for oropharyngeal reconstruction. Based on the radial artery, the flap has a reliable and long vascular pedicle, making it an ideal option to cover defects in the oropharynx. In addition, the radial forearm is pliable with the option of harvesting a thin skin paddle, allowing for appropriate coverage of the resection bed without adding unnecessary tissue bulk. Though the versatility of this flap allows for a wide range of use, morbidity at the donor site including flexor tendon exposure, skin graft breakdown, esthetic deformity, and reduced sensation and motion can occur. An alternative option for the oropharynx is the ALT flap, which is based on perforator vessels from the descending branch of the lateral circumflex femoral artery. Advantages of this flap include low donor-site morbidity, adjustability of flap thickness, and long vascular pedicle. When comparing RFFF with thinned ALT flaps in the oropharynx, one comparative study found that flap survival rates and functional results at the receiving sites were equivalent. Permanent forearm movement impairment was seen in 35% of the cases, and patient satisfaction was overall decreased in the RFFF group. Similar findings have been reported among other studies, emphasizing a lower likelihood of donor-site morbidity among patients with ALT though with no significant differences in swallowing, speech, or quality of life. However, there is no clear consensus for reconstruction in the oropharynx and surgeons need to take into consideration any pertinent patient circumstances, comorbidities, and disease burden to select the optimal flap approach.

Though free flap reconstruction after TORS is relatively safe, there are several complications associated with the procedure. One systematic review on free flap reconstruction after TORS including 23 primary studies identified infection as the most prevalent complication occurring in 9% of patients. Other perioperative complications including fistula, postoperative bleed, intra/postoperative blood transfusion, flap necrosis, flap wound dehiscence, chyle leak, hematoma, and aborted flap were also reported. There were no mortalities due to microvascular reconstruction.

Patient Satisfaction

Complex coordination of the oropharyngeal muscles is required to produce a swallow response while maintaining and protecting the airway. Extensive resection of the palate, base of the tongue, or pharyngeal muscles can impair this multifaceted process, leading to dysphagia, regurgitation, and aspiration. Patients with base of tongue resection, large tumor size, and postoperative radiation or chemoradiation therapy are particularly at risk for dysphagia. Other functional impairments including xerostomia, trismus, mucositis, salivary issues, and oral pain can further exacerbate an already limited swallowing mechanism. As swallowing function and nutritional intake impact quality of life, assessing and evaluating the role of free flap reconstructive surgery on these functional outcomes remain important.

There is a lack of randomized controlled data available assessing swallowing function in patients undergoing oropharyngeal resection with free flap reconstruction compared to primary radiation therapy. One systematic review combining oral cavity and oropharyngeal patients receiving free flap reconstruction found a positive association between postoperative radiotherapy and decreased swallowing function. Presence of aspiration on flexible nasopharyngeal laryngoscopy and videofluoroscopic swallowing study (VFSS) was reported in 15% of patients and correlated with amount of oral tongue or base of tongue resected. There was no difference in aspiration rates between flaps used, and gastrostomy dependence was reported in 8% of patients. Results from this study were used to develop a protocol for identifying low-risk and high-risk patients (defined as large resection involving base of tongue/oral tongue/soft palate with radiotherapy) and suggested that high-risk patients be monitored with validated quality-of-life metrics and VFSS postoperatively. Smaller case series and cohort studies specifically assessing swallow function following TORS with free flap reconstruction have found good long-term function with minimal intake restrictions. A review including 42 patients found that 93% of patients could tolerate oral intake postoperatively with 87% taking an entirely oral diet at 1 year. Another series reported an initial decline in functional oral intake scale at the first postoperative appointment but a progressive improvement after 1 year.

Free flap surgery for the base of tongue and palate resection allows for reconstruction and augmentation of shape, volume, and mobility to aid in speech production. One systematic review assessing free flap reconstruction in oral tongue and base of tongue cancers found a significant decline in speech in the early postoperative phase but a significant recovery to preoperative levels after 1 year. Extent of soft tissue resection can also impact speech outcomes. Patients with resections of half or greater than half of the soft palate were shown to have higher nasalance values and poorer velopharyngeal function. ^, A series of 29 patients treated with free flap reconstruction reported satisfactory speech outcomes with normal or slightly below normal speech intelligibility in 76% of patients and moderate or no rhinolalia in 72%. Mean quality of life and functioning scales were above 80%, suggesting that free flap reconstruction is a viable option with slight handicap on speech function.

Expected postoperative edema in the oropharynx often necessitates routine placement of a tracheostomy during time of surgery. Decannulation occurs in the majority of patients, with a reported overall mean airway decannulation time of 17 days. ^, As a temporary adjunct procedure for airway protection, the high rate of decannulation after free flap reconstruction is important given the profound impact of a tracheostomy on speech, swallow, and body image perception.

Challenges

The indications and options for free tissue repair of oropharyngeal defects are clear; however, there are several patient and disease characteristics that may increase the difficulty of successful reconstruction. Gaino and colleagues proposed a “Pharyngoscore” system to predict difficulty of oropharyngeal exposure during TORS. They found that male sex, increased neck circumference, smaller inter-incisor gap, and Modified Mallampati classification of class III or greater corresponded were associated with greater difficulty of exposure. Similarly, these anatomic characteristics would be expected to limit transoral visibility and range of motion during the inset of free tissue to repair oropharyngeal defects. Prior history of neck dissection or radiation can cause significant fibrosis and distortion of tissue planes, limiting options for recipient vessels in the neck and increasing the challenge of microvascular anastomosis. Radiation can also contribute to jaw trismus, further limiting intraoral access. ^,

Larger defects and those involving multiple oropharyngeal subsites require greater intraoperative planning and greater volume of tissue transfer. Some surgeons have proposed using 2 dimensional templates to guide free tissue harvesting, with distinct soft tissue domains or “petals” representing each subsite requiring reconstruction. ^, This technique may result in reconstruction that more closely resembles the native oropharyngeal configuration; however, it also requires delicate thinning and shaping of each domain, with care to avoid devascularization.

The type of free tissue utilized may also contribute to the difficulty of the flap inset. One advantage of the ALT flap over the radial forearm is the ability to harvest a thicker and broader tissue graft with relatively lower donor-site morbidity. This same thickness and bulk may also be a hindrance, limiting maneuverability and visibility within the oropharynx when compared to the radial forearm. In one study, 29% of cases using an ALT flap to reconstruct a lateral oropharyngeal defect experience early local complications requiring reoperation.

Complications

While free flap reconstruction of the oropharynx has overall high success rates, postoperative complications are not uncommon, as with all complex surgical procedures. In a recent systematic review including 132 patients who underwent TORS with free flap oropharyngeal reconstruction, the most commonly reported complications were infection (8.9%) and flap dehiscence (4.2%). In another analysis of 1115 patients who had undergone free flap reconstruction for head and neck cancer, reoperation within 30 days was necessary in 20.2% of patients. In this study, 54.3% of secondary procedures were due to urgent flap concerns, hematoma, or wound closure, 32.1% were for infection control, and 13.6% were for enteral or airway intervention.

Several studies have attempted to identify risk factors and special patient populations that may predispose to greater flap complications. One study of 1643 head and neck free flaps from the American College of Surgeons—National Surgical Quality Improvement Project dataset found that greater operative time was associated with both greater overall complications and serious complications (reoperation, deep surgical-site infection, death, cardiac arrest, etc.). Another study assessed the association between body mass index and complications after head and neck free flap surgery; they found that significant weight loss and underweight status were associated with greater 30 day mortality, though neither were associated with greater flap loss.

Several studies have shown that greater time to perform microvascular anastomosis was associated with a higher incidence of flap necrosis or dehiscence, suggesting that ischemic time should be limited to 30 minutes per vessel. At the same time, it is undetermined whether greater ischemic time is directly responsible for these complications and is therefore a modifiable risk factor, or if the ischemia reflects baseline characteristics of the donor and recipient vessels that predispose to subsequent complications.

Current Controversies

Given the relative infrequency of oropharyngeal free flap reconstruction, the postoperative management of these cases is not uniform, with considerable variation based on institution and individual surgeon preference. This variation is particularly prominent with regard to the use of prophylactic anticoagulation, routine flap monitoring, and blood pressure management.

It is well known that vascular compromise after free flap reconstruction is most likely to occur in the first 72 hours after surgery, and early detection is associated with greater chances of flap salvage; however, there is little agreement in the literature as to the optimal frequency and total duration of flap monitoring. Furthermore, there is no consensus as to the best method of monitoring, with myriad options including direct clinical assessment, implantable Doppler ultrasonography, handheld Doppler ultrasonography, and microdialysis. ^, Each of these options requires significant effort and time from skilled clinicians, the proportions of salvaged free flaps attributable to each method of postoperative monitoring have not been thoroughly compared. At the same time, a unique advantage of using implantable Doppler probes is the detection of intraoperative vascular compromise, which can be repaired immediately. Even so, there is inter-surgeon variability in the use of implantable Doppler probes to measure arterial signals, venous signals, or both.

Anticoagulation is commonly used after free flap reconstruction to prevent thrombosis of the pedicle anastomosis. One systematic review of postoperative anticoagulation techniques among patients with head and neck cancer undergoing free flap reconstruction found that anticoagulation protocols included heparin, low molecular weight heparin, aspirin, dextran-40, prostaglandin E1, and, in some cases, no anticoagulation. This study included several types of donor sites and was not limited to oropharyngeal reconstruction; however, it is reasonable to assume that similar variation in postoperative anticoagulation protocols exists within the context of oropharyngeal reconstruction. Across all methods, the rate of postoperative thrombosis was low, ranging from 0.8% for aspirin to 7.8% for dextran-40. Interestingly, the thrombosis rate among patients who did not receive anticoagulation was 4.3%. The heterogeneity of the anticoagulation protocols among the studies included in this review precluded a meta-analysis. Another review of 8 studies on postoperative anticoagulation after head and neck free flap reconstruction found that anticoagulation did not significantly decrease the rates of flap thrombosis and subsequent failure, while the rate of hematoma formation significantly increased. Prospective studies may be warranted to directly compare different methods of postoperative anticoagulation and determine whether any anticoagulation is warranted at all.

Maintaining adequate perfusion to free flaps in the immediate postoperative period is paramount to flap viability, though the acute blood loss and lingering effects of anesthesia present several challenges. Common interventions to maintain perfusion such as fluid resuscitation and blood transfusions can alter the viscosity and coagulability of blood in the flap microvasculature, impacting blood flow. Several studies have found that aggressive crystalloid resuscitation, typically with more than 130 mL/kg per 24 hour period, was associated with free flap compromise and general medical complications among patients with head and neck cancer. At the same time, it is unclear whether the resuscitation efforts or the hemodynamic circumstances that necessitated these interventions are responsible for the observed impact on flap outcomes. Furthermore, while maintaining an adequate hematocrit is beneficial to tissue oxygenation, blood transfusions may increase blood viscosity and decrease circulation through microvascular anastomoses. At present, no prospective studies have determined optimal protocols for hemodynamic intervention among patients with head and neck free flap.

Future Developments/Considerations

While the success rates of oropharyngeal free flap reconstruction are high, quantitative data on functional outcomes after reconstruction are limited in the present literature. One recent systematic review of studies describing reconstruction after TORS found that only 3 of 26 included studies characterized postoperative swallowing function using quantitative measures, concluding that further investigation with quantitative measures is warranted to describe functional outcomes after oropharyngeal reconstruction. The M.D. Anderson Dysphagia Inventory and the Functional Outcomes of Swallowing Scale are 2 examples of validated metrics that could be used to characterize speech and swallow function prior to and following oropharyngeal reconstruction. ^, In particular, these tools could be useful in allowing direct comparison of quantitative functional outcomes between different methods of reconstruction (eg, ALT vs radial forearm).

As previously stated, the postoperative management protocols of oropharyngeal free flap reconstruction are highly variable, which presents an opportunity for greater standardization through outcomes-focused prospective studies. Furthermore, many of the aforementioned studies regarding postoperative protocols included all head and neck free flaps and were not limited to the oropharynx. ^, Optimization of postoperative anticoagulation and fluid resuscitation protocols has the potential to lead to greater rates of successful reconstruction and decreased complications.