Eric J. Moore
INTRODUCTION
The base of the tongue (BOT) is a subsite of the oropharynx (OP). It consists of that portion of the tongue that lies posterior to the circumvallate papilla, and it extends to the vallecula at the base of the epiglottis posteriorly. The BOT contains squamous mucosal-covered lymphoid tissue (the lingual tonsil), skeletal muscle, and minor salivary glands and mucous glands. Squamous cell carcinoma and neoplasms of salivary gland origin frequently involve the BOT. Treatment of advanced cancer of the OP often involves removal of all or part of the BOT. The BOT plays a role in the oropharyngeal phase of swallowing. Its presence and function aid in formation of a food bolus and proper positioning of that bolus prior to the pharyngeal phase of swallowing. The BOT also aids in posterior displacement of the epiglottis and closure of the laryngeal inlet, thereby preventing aspiration of oral contents. Quality of life studies have demonstrated diminished swallowing function in patients undergoing treatment of oropharyngeal carcinoma. As the degree of the BOT involvement with cancer increases, the ability of the patient to develop an aspiration-free swallow is diminished.
Following resection of the BOT, the resulting defect can heal by second intention or be reconstructed with a local flap, a regional pedicle flap, or a microvascular free flap. While the first two options are often sufficient for subtotal defects in the BOT that involve less than 50% of that structure, more substantial subtotal and total defects of the BOT require major flap reconstruction to rehabilitate the patient. Pedicle flaps, such as the pectoralis major myocutaneous flap, have been used extensively for reconstruction of the BOT. They have as their major advantages ease of harvest, reliability, consistent anatomy, and minimal donor site morbidity. Pedicle flaps, however, have been associated with a higher rate of flap dehiscence, tissue necrosis, and fistula formation than microvascular flap reconstruction of the OP. The radial forearm free flap (RFFF) and the anterolateral thigh flap (ALTF) are the microvascular flaps employed most often in BOT reconstruction. They both provide vascularized soft tissue that can be folded and contoured to reconstruct the complicated three-dimensional geometry of the BOT and pharyngeal defect that is often created in resection of advanced OP tumors. While the RFFF has a longer history of use, the ALTF has been employed more often recently. The major advantage of the ALTF is the ability to close the donor site defect primarily. It provides a thicker amount of subcutaneous adipose tissue that can be an advantage or hindrance in flap design and contouring depending on the patient’s body habitus.
HISTORY
When considering the ALTF donor site for reconstruction, I take not only a thorough general history but also a history focused on physical limitations related to the lower extremity including a history of prior injury or surgery that may preclude the ALTF donor site.
PHYSICAL EXAMINATION
In addition to a general physical examination, I also evaluate the lower extremity for scar, prior surgery, and muscular tone and evaluates the patient’s gait. Because either leg can be used as a donor site, a history of knee instability, hip injury, or prior surgery may dictate which leg I use as a donor site. I also like to evaluate the thickness of the skin and the anatomy of the leg to determine whether the thigh is an appropriate donor site. If the tissue is too thick, I may consider an alternative such as the radial forearm flap. In contrast, if the thigh is too thin, I may consider a technique to add bulk to the flap or consider another donor site.
INDICATIONS
The indications for this technique include any BOT defect that requires bulk and epithelial lining. The ALTF was described in 1984 by Song et al., but it failed to gain popularity for some time, particularly in the Western literature and operating rooms. Two factors may have been responsible for this tempered enthusiasm: (1) The flap is associated with some variability in the vascular perforators and (2) the flap can be associated with extensive subcutaneous adipose tissue that can make contouring of the tissue difficult during the reconstruction of defects of the head and neck. Wei and others popularized the ALTF by clarifying the vascular anatomy, demonstrating the advantages of the long pedicle, and exploring the versatility of the generous cutaneous, fasciocutaneous, and myocutaneous tissue paddles that could be based on that pedicle.
Today, the ALTF is one of the most frequently employed microvascular flaps for BOT reconstruction. Adequate rehabilitation of a BOT defect requires maintenance of volume in the reconstructed tissue. While muscle and skin contract substantially in maturing flaps, subcutaneous adipose tissue is more reliably preserved. The abundance of subcutaneous adipose tissue in the ALTF allows the surgeon to design a flap of appropriate bulk and remain confident that the tissue volume will be preserved over the lifetime of the patient.
The ALTF is based on the descending branch of the lateral femoral circumflex artery, which arises from the profunda femoris artery. The artery is usually accompanied by two venae comitantes that occasionally join into one vein as they ascend. The vascular pedicle runs with the nerve to the vastus lateralis muscle in a space between the vastus lateralis and the rectus femoris muscles. The vascular pedicle supplies perforators to these muscles. The perforators to the anterolateral thigh skin can arise either as septocutaneous perforators (incidence approximately 15%) between the muscles or as musculocutaneous perforators (incidence approximately 85%) passing through the vastus lateralis muscle. In the case of septocutaneous perforators, the flap can easily be harvested as a thin septocutaneous tissue paddle. In the incidence of musculocutaneous perforators, the flap can be harvested as a musculocutaneous paddle by including a superolateral portion of the vastus lateralis muscle around the perforators or as a cutaneous perforator of the fasciocutaneous flap by meticulously dissecting the perforators through the vastus lateralis muscle.
The descending branch of the lateral femoral circumflex artery has a length between 8 and 16 cm in the adult patient. The arterial diameter is between 2 and 2.5 mm at its proximal portion, and the flap vein diameters are typically between 1.8 and 3 mm. These factors are favorable for most BOT reconstructions. The flap can be harvested as a sensate flap by including the anterior branch of the lateral cutaneous nerve of the thigh. Theoretically, the flap could be harvested as an innervated musculocutaneous flap by including the nerve to the vastus lateralis muscle.
Variability in the vascular anatomy of the ALTF has been studied, and this variability can make flap harvest difficult and, sometimes, not feasible. Shieh et al. described four variations in the skin perforators from the lateral circumflex femoral arterial system. The classic situation of vertical musculocutaneous perforators off the descending branch of the lateral circumflex femoral artery was observed in 56% of the patients. Variations included horizontal musculocutaneous perforators off the transverse branch of the lateral circumflex femoral artery (27%), septocutaneous perforators from the descending branch (10%), and horizontal septocutaneous perforators from the transverse branch (5%). Rarely, no suitable skin perforators can be found during elevation of ALTF, or the transverse branch will be of insufficient caliber or length to allow microvascular anastomosis. In these situations, the partially elevated flap is returned to the donor site and an alternative reconstructive flap will have to be elevated.
CONTRAINDICATIONS
Contraindications to reconstruction of the BOT include patient health factors, tumor factors, and donor site factors. As in all major ablative surgery of the head and neck and reconstruction, the length and extent of the procedure can put stress on the patient. Patients should have adequate cardiovascular and pulmonary function to tolerate this stress without the anticipation of major morbidity or mortality. Hypercoagulability conditions, extensive peripheral vascular disease, severe malnutrition, immunodeficiency, and surrounding tissue trauma from previous operative and nonoperative treatments can all complicate microvascular reconstruction. Previous surgery or trauma to the lower extremity needs investigation preoperatively to anticipate vascular or soft tissue damage that may preclude successful ALTF harvest.
PREOPERATIVE PLANNING
Preoperative planning includes assessment of fitness of the patient for a major surgical procedure, but this likely will have been done in consideration for tongue resection. No preoperative imaging studies or vascular studies need to be done, but the surgeon should ensure that the patient has not had a previous surgical procedure or any trauma on the lateral leg that would interrupt the vascular supply of the perforators from the lateral femoral circumflex artery.
SURGICAL TECHNIQUE
Study of swallowing function after subtotal and total glossectomy and microvascular reconstruction by Kamata et al. correlated improved function with protuberant tongue flaps that maintained their bulk. These reconstructive flaps were able to contact the posterior pharyngeal wall and obturate the oral space better than tongue reconstructions that were flat or depressed and of insufficient volume. I recommended designing a flap that was 30% wider than the resected soft tissue in order to ensure adequate postoperative volume. In design of the flap to reconstruct a BOT defect, I formed a template of the resected tissue that frequently forms an L shape owing to the fact that most BOT resections include a portion of the tonsillar fossa, lateral pharynx, and occasionally soft palate that also needs to be reconstructed. The height of the “L” is determined by measuring the most inferior aspect of the pharyngeal defect to the most superior aspect of the pharyngeal or palatal defect. The width of the widest portion of the “L” is determined by the width of the tongue base and pharyngeal wall defect. The width of the template at this level is increased by 25% to 30% to allow for anticipated flap contraction and atrophy (Figs. 12.1 to 12.3). The flap is typically 8 cm × 10 cm in the average base of tongue defect. With experience, the surgeon can estimate the extent of the defect and design a flap with generous proportions without waiting for a template, thereby harvesting the flap simultaneously with tumor extirpation by another team and decreasing the operative time. Excess flap tissue can be de-epithelialized and folded on itself for additional bulk or discarded as appropriate.
FIGURE 12.1 Base of tongue tumor exposure via mandibulotomy. Tumors can also be removed through transhyoid or transoral resection.
FIGURE 12.2 Resection of the tumor of the BOT. Flap design should be 30% wider than the width of the defect to provide adequate soft tissue bulk.
FIGURE 12.3 ALTF designed to include perforators from the descending branch of the lateral femoral circumflex artery.
With the patient in the supine position, a line is drawn from the superolateral patella to the anterior superior iliac spine. A handheld Doppler is used to mark the position of the perforators. The perforators usually lie within a circle with a diameter of 5 cm from the midpoint of this line. The flap is designed as an oval centered on two to three of these perforators with the long axis of this oval parallel to the long axis of the thigh. The L-shaped tissue to be used is designed within this oval. The flap elevation begins with an incision of the medial side of the flap. Care should be taken to ensure that the initial incision is generously medial so as not to end up lateral to the perforators supplying the flap. Dissection is carried down to the fascia of the rectus femoris muscle. Dissection can then proceed laterally in a suprafascial or subfascial plane depending on the surgeon’s preference to harvest a fasciocutaneous or cutaneous flap. Dissection is carried meticulously laterally to identify either the septocutaneous perforators in the septum between the rectus femoris and the vastus lateralis or the musculocutaneous perforators piercing the vastus lateralis muscle lateral to the intermuscular septum. If the perforators are septocutaneous, the dissection proceeds easily along the medial side of the septum between the muscle bellies to identify the pedicle. If the perforators are musculocutaneous, the surgeon follows the septum to expose the pedicle, and then the medial side of these perforators is finely dissected through the muscle to their takeoff from the pedicle. Care is taken to preserve a thin cuff of muscle over the perforators to protect their integrity. Dissection of the perforators and the pedicle is easiest if it proceeds from distal to proximal. The perforators give off branches to the surrounding vastus lateralis on their lateral and posterior sides, and these branches must be clipped if the muscle is not to be included in the specimen. Alternatively, a cuff of vastus lateralis muscle can be harvested with the flap by incising the muscle lateral and posterior to the perforators after the circumferential incision of the skin flap.
After identification of the perforators and pedicle, the incision is completed around the skin paddle, and dissection is carried through the lateral vastus lateralis fascia. The distal continuation of the descending branch of the lateral circumflex femoral artery is clipped and divided. Dissection continues by freeing the perforators or muscle completely from their lateral and posterior attachments all the way to the pedicle, and then the pedicle is raised from distal to proximal with care to clip and divide the medial branches supplying the rectus femoris muscle. The flap elevation continues to the origin of the descending branch of the lateral femoral circumflex artery. Care should be taken to support the weight of the flap so as not to put tension on the pedicle during elevation. The flap can be left in situ without vessel division until the tumor extirpation is complete and the insetting for reconstruction can begin.
Prior to division of the flap pedicle, excessive subcutaneous adipose tissue can be trimmed away down to the level of the subcutaneous vascular plexus. Care should be taken not to thin the flap excessively around the perforators to prevent vascular compromise. The pedicle artery and veins are doubly clipped with microvascular clips for identification, and the flap is separated from the lower extremity and brought to the head table. Contouring is followed by insetting. The flap is inset with horizontal mattress 3-0 resorbable sutures with care to take large enough bites of native tissue to prevent the sutures from pulling through resulting in tissue dehiscence. The closure should be watertight (Fig. 12.4). If a mandibulotomy has not been performed, the surgeon may have to perform some of the insetting through the neck as well as the mouth, and an endoscope may be necessary to ensure adequate closure of the oral cavity and pharynx. The mouth should be flooded with saline at the completion of closure to ensure that no oropharyngeal leak occurs into the neck, as this can result in neck infection, vessel thrombosis, and flap failure.
FIGURE 12.4 Flap inset for base of tongue reconstruction.
After complete flap inset, the vessels are draped into the neck with care to prevent tension or kinking. The reconstructive team should communicate with the resecting team regularly to ensure that adequate arterial and venous donor vessels are preserved for vascular anastomosis. The long pedicle of the ALTF gives the surgeon multiple options for vessel placement, but kinking can occur, and the geometry of the vessel placement in the neck deserves careful consideration. Both veins are anastomosed if possible to ensure adequate venous return. After vessel anastomosis, the neck is irrigated with sterile saline, and the neck wound is closed with adequate drainage. I prefer to monitor the flap with implantable Doppler placement, as the skin paddle of the OP reconstruction may be hard to visualize if a monitoring segment has not been externalized.
The donor site can nearly always be closed with skin undermining and primary closure with resorbable sutures over a drain. For reconstruction of the OP, the size of the skin paddle does not necessitate grafting of the donor site defect, but in the event of excessive donor site tension, the thigh wound could be reconstructed with a skin graft.
POSTOPERATIVE MANAGEMENT
The patient is monitored in the hospital with close surveillance of flap perfusion, wound drainage, and vital signs. Adequate nutrition is provided by a nasogastric feeding tube until oral intake can be initiated in 7 to 10 days. If enteral nutrition is needed past this point, then consideration should be given to placement of a gastrostomy tube. A tracheostomy tube is used until edema has resolved enough to allow the patient to breathe easily through the nose and mouth. Drains are removed from the neck and leg once their output decreases below 20 mL/d.
Early speech and swallowing physiotherapy and physical therapy are essential for maximal return to function both with OP function and ambulation. The patient should be encouraged to participate actively in speech and swallowing exercises. Motivated patients make more rapid progress than patients who are not encouraged.
COMPLICATIONS
Immediate postoperative complications such as hematoma in the donor site or recipient site, wound infection, flap partial or total necrosis, orocutaneous fistula, and wound dehiscence can occur. They are best managed by prevention, and this is best accomplished by careful preoperative patient selection and planning, meticulous execution, and attention to operative detail. Close postoperative management can identify problems when they first start to occur, and early recognition usually results in better management of complications. In the event of significant postoperative wound complications and flap failure, the surgeon may need to employ long-term use of antibiotics and chronic wound management, hyperbaric oxygen therapy, and revision surgery and flap design.
RESULTS
Patients who undergo greater than 50% resection of the BOT and reconstruction never achieve “normal” speech and swallowing, but they can expect to recover the ability to maintain nutrition with an oral diet and communicate effectively. The extent of swallowing recovery is inversely proportional to the amount of tongue resected, and it is loosely related to age, comorbidities, and baseline swallowing function before treatment.
Studies by Yanai et al. showed that 85% of patients undergoing total or near-total (>75%) resection of the BOT with laryngeal preservation were able to swallow an oral diet after tongue base reconstruction. With a carefully planned and executed ALTF tongue base reconstruction, the experienced surgeon can provide meaningful rehabilitation for the patient.
The donor site defect with the ALTF is well tolerated. The scar in the leg is lengthy and difficult to conceal, but the patient should expect to return to vigorous and unlimited leg activity after healing and a period of rehabilitation. Extensive resection of the vastus lateralis or injury to the nerve to the vastus can diminish leg strength and alter gait.
PEARLS
• Greater than 50% resection of the BOT requires reconstruction to preserve function.
• Maintenance of the bulk of the flap and the ability of the flap to contact the posterior pharyngeal wall and obturate the upper OP during swallowing improves function. The ALTF provides a long pedicle, adequate subcutaneous adipose tissue that maintains its bulk, and the ability to allow a simultaneous two-team approach to BOT resection and reconstruction.
• The ALTF is supplied by musculocutaneous perforators of the descending branch of the lateral femoral circumflex artery the majority of the time.
• The surgeon should consider a template of the defect and plan for some atrophy of the flap by designing the flap slightly wider than the defect.
• The flap should be meticulously inset in a watertight closure.
• Early speech and swallowing therapy and donor site physical therapy maximize function.
PITFALLS
• Failure to Doppler the perforators and begin the incision medial enough on the thigh may place the surgeon lateral to the perforators with the initial incision.
• Patients who require a skin graft for closure of the donor site have been shown to experience donor site morbidity.
INSTRUMENTS TO HAVE AVAILABLE
• Standard head and neck surgery set
SUGGESTED READING
Song YG, Chen GZ, Song YL. The free thigh flap: a new free flap concept based on the septocutaneous artery. Br J Plast Surg 1984;37:149.
Shieh SJ, Chiu HY, Yu JC, et al. Free anterolateral thigh flap for reconstruction of head and neck defects following cancer ablation. Plast Reconstr Surg 2000;105:2349–2357.
Wei FC, Jain V, Celik N, et al. Have we found an ideal soft- tissue flap? Experience with 672 Anterolateral thigh flaps. Plast Reconstr Surg 2002;109:2219–2226.
Yanai C, Kikutani T, et al. Functional outcome after total and subtotal glossectomy with free flap reconstruction. Head Neck 2008;30:909–918.
Chepeha DB, et al. Oropharygnoplasty with template based reconstruction of oropharyngeal defects. Arch Otolarynglo Head Neck Surg 2009;135(9):88.