Master Techniques in Otolaryngology - Head and Neck Surgery: Reconstructive Surgery, 1ed.

3. The Floor of the Mouth Defect: Radial Forearm Free Flap

Eben L. Rosenthal

INTRODUCTION

Reconstruction of the oral cavity, particularly the floor of the mouth, can be a challenging task for numerous reasons. The complex anatomy of this area as well as its spatial relationship to surrounding structures, in particular the mandible and tongue, are definite obstacles for the reconstructive surgeon. The goals of reconstruction of the floor of the mouth are to separate the oral cavity from the neck, to restore unrestricted mobility of the tongue, and to construct a platform for bolus preparation to assist with oral intake.

An adequate reconstruction can be accomplished in numerous ways depending on the size of the defect. Smaller defects with residual, viable soft tissue can be closed primarily or with a split-thickness skin graft, which can provide a water-tight closure. Various regional flaps have been described for larger defects, the most common of which is the submental island pedicled flap, the facial artery musculomucosal flap, or the platysma flap. The radial forearm fasciocutaneous flap is the free flap most frequently used for the reconstruction of the oral cavity. The focus of this chapter is to describe the use of the radial forearm free flap for reconstruction of the floor of the mouth.

A positive history of tobacco and alcohol exposure is typically present in patients with cancer of the oral cavity. The smoking is thought to interfere with healing due to small vessel obliteration. Patients often present with pain, dysphagia, and weight loss resulting from limited oral intake.

The physical findings in patients with cancer of the floor of the mouth may include ulcerative, exophytic lesions or simply irregular mucosa with subtle surface changes. In more extensive lesions, limited mobility of the tongue or disruption of dentition may be present. The physical examination should always evaluate two important factors: involvement of the tongue and invasion of the mandible. The degree of bone invasion is important to determine preoperatively in order to plan for possible mandibulectomy requiring bone reconstruction. The findings on physical examination are also helpful for the reconstructive surgeon in predicting the size of the defect. The forearm donor site should be examined, taking into account the handedness of the patient and any previous surgery or trauma. An Allen test should be performed on the donor arm to assess for patency of the collateral circulation to the hand via the ulnar artery. Venipuncture should not be performed on the planned donor arm, and any evidence of intravenous drug abuse, recent radial artery puncture, or failure of the Allen test is a contraindication to harvesting a radial forearm flap from that arm. The neck must be evaluated for possible cervical lymph node metastasis. A neck dissection is usually necessary and may impact the reconstruction options.

The main goals of reconstruction of the floor of the mouth are to separate the oral cavity from the neck, restore unrestricted mobility to the tongue, and provide a solid platform upon which bolus preparation can occur. Adequate postoperative function of speech and swallowing remains a major challenge for the reconstructive surgeon. Ideally, reconstruction should be performed with an adequate amount of soft, mobile tissue with the anticipation of some degree of contracture upon healing. Radial forearm fasciocutaneous free flaps are particularly useful due to their thin, pliable nature.

The only contraindications to reconstruction of the floor of the mouth using the radial forearm free flap are related to those patients with an inadequate Allen test (incomplete vascular palmar arch).

Routine anatomic imaging, in the form of CT or MRI, is usually performed preoperatively to assess the size of the primary tumor or depth of invasion into the tongue or mandible. An MRI is typically superior to CT in evaluation of soft tissue and nerve involvement; however, CT scans can more accurately predict invasion of the mandible. A CT scan can also be useful in preoperative modeling of the contour of the mandible to define the architecture of the titanium plate that will be used in the reconstruction.

Regardless of the preoperative evaluation, one should always be prepared to deviate from the plan as new information is presented from intraoperative findings. This may be due to numerous factors including growth of the cancer prior to surgery or false-negative/-positive physical or radiographical findings. For intermediate-size defects of the floor of the mouth, it is often best to consider several options for reconstruction.

Patient selection is important in determining whether they are a candidate for free tissue transfer. Advanced age alone is not a contraindication to this procedure, but age-related comorbidities, particularly significant atherosclerosis with poor cardiac function, should be considered prior to surgery. Patients with coagulopathies, collagen vascular diseases, and other vascular disorders are not good candidates for free tissue transfer. Malnutrition should also be addressed because of its detrimental effects on wound healing.

Prior radiation therapy to the head and neck often results in decreased patency of vessels secondary to vessel fibrosis and endothelial cell disruption. Hypothyroidism may also occur following radiation to the neck.

The availability of the appropriate surgical and nursing personnel should also be addressed during preoperative planning. These individuals play critical roles in both the initial procedure as well as the postoperative period. This varies based on the institution, but the patient should have a monitored bed available for at least the first 24 to 48 hours for hourly flap assessments. Either a conventional intensive care unit or “step-down” intensive care bed should be arranged prior to the day of the procedure.

The blood supply to the radial forearm flap is based on the radial artery and is a well-vascularized and pliable flap that has a low incidence of failure when used for reconstruction of the floor of the mouth. Outflow from the flap is via the paired venae comitantes, which accompany the artery as well as various subcutaneous veins of the forearm. Generally, the vascular pedicle may be up to 18 cm in length, and the vessel diameters are usually large (2 to 4 mm). A common radial vein can usually be identified to allow a single venous outflow microvascular anastomosis. The medial and lateral antebrachial cutaneous nerves can be harvested to create a sensate flap, although the added benefit of this technique remains controversial. A bilobed design in the flap design creating a flap in the shape of a mitten has been described to improve mobility of the tongue. The vascular pedicle can be easily identified and marked at the beginning of the procedure prior to the elevation of the flap.

The skin paddle should be fashioned to overlie the distal radial artery and usually encompasses numerous muscular perforators of the radial artery. The flap design should be with the distal and proximal end tapered to allow the flap to inset into the V-shaped defect of the lateral gingivolingual sulcus on either side of the defect. It is best to fashion the skin paddle wider (add 1.5 to 3 cm) and slightly longer than the measured defect because contracture of the graft results in significant tongue immobility (Fig. 3.1). Loss of a segment of the mandible can be managed by harvesting a portion of the distal aspect of the radius.

FIGURE 3.1 Floor of the mouth repair using the radial forearm free flap. The cancer is demonstrated (A) prior to resection. The defect included the floor of the mouth with invasion of the gingival surface with exposed bone and a connection into the neck (B). The 6-month postoperative appearance of the flap with blunting of the alveolus and appropriate healing (C).

Although the distal aspect of the flap should be set proximal enough to be covered by the shirt sleeve, thinner tissue is often present in the distal aspect of the arm and may be required in obese patients. The arm is then exsanguinated, and a tourniquet is inflated to approximately 250 mm Hg. The first skin incision is made at the distal end of the skin paddle along the ulnar border down to fascia, and a subfascial dissection is performed toward the flexor carpi radialis tendon. Care should be taken to preserve paratenon over the tendon to prevent loss of the skin graft. The use of suprafacial dissection has been described that results in improved take of the split-thickness skin graft without vascular compromise to the skin paddle. The distal ends of the radial artery and venae comitantes are isolated and ligated with suture, and the radial margin of the flap is incised down to brachioradialis preserving the distal branches of the radial nerve. The lateral intermuscular septum is identified, and the flap is raised from distal to proximal following the course of the vascular pedicle to the antecubital fossa. Small branches from the pedicle are isolated and taken along the way with bipolar cautery and/or small vascular clips. The ulnar artery is identified and preserved and a common radial vein isolated where possible and the tourniquet lowered and hemostasis obtained using bipolar cautery and clips on the pedicle. The vascularity of the thumb and forefingers should be assessed prior to dividing the pedicle. The flap is transferred to the recipient site for inset. Total ischemia time should be less than 6 hours for optimum flap survival.

The distal forearm defect can be closed in a number of ways. A split-thickness skin graft harvested from the forearm prior to raising the graft or from the lateral thigh is pie crusted and inset into the donor site defect. This is typically held in position with absorbable suture. The skin graft site is bolstered into place with a nonadherent dressing and the forearm splinted with the wrist slightly extended for 5 days. This improves survival of the split-thickness skin graft by limiting movement between the skin graft and the underlying muscles and tendons. Other options for repair of the distal forearm defect have been described. These include cadaveric skin grafting or placement of a skin graft with a negative pressure dressing to improve take rate. The advantage of a negative pressure dressing is elimination of a splint, which allows better postoperative monitoring of the distal extremity; however, it is associated with significantly higher costs. The negative pressure dressing is typically left in place for 3 to 5 days. Take rates are relatively equivalent, although significant contracture of the wound can occur with the negative pressure dressing resulting in overall improved appearance.

The recipient site is prepared, and the flap is transferred to the floor of the mouth. The harvested forearm tissue is arranged in a manner so as to fully fill the defect and inset is begun. The flap is sutured to the mucosa of the oral cavity with interrupted Vicryl suture using great effort to provide a watertight seal. If no mucosa remains on the surface of the mandible, suture can be placed around the base of the remaining teeth or small holes can be drilled directly into the mandible to hold the flap securely in place.

Once the flap is inset or nearly so, attention is turned to the neck for the microvascular anastomosis. The facial, lingual, or superior thyroid arteries are preferred based on vessel size for the arterial anastomosis. Venous anastomosis is usually performed end to end with any of the branches from the internal jugular vein. My preference is the use of the continuous suture technique using 8-0 nylon suture, which involves placement of two interrupted sutures placed opposite each other and then a simple running suture applied around the vessel. A drain can be placed through the mylohyoid muscle to lie underneath the closure to monitor for a salivary leak postoperatively. A microvascular coupler is most commonly used to anastomose the veins in an end-to-end fashion.

Patients are monitored in a specialty nursing “step-down” type of intensive care unit for 24 hours where the flap can be checked hourly. The pedicle vasculature can be monitored via external or implantable Doppler. The skin paddle is typically easily visible in the floor of the mouth for visual and tactile assessment of flap viability as well. The average hospital stay is 5 to 7 days. Patients are given 3 doses of perioperative antibiotics (clindamycin or piperacillin–tazobactam) and daily low-dose aspirin therapy for 3 weeks. The wounds and drains are carefully monitored for signs of salivary contamination.

The splint is removed from the donor site on postoperative day 4 or 5, and a lightweight plastic splint is fashioned and worn for 10 to 14 days after which aggressive passive and active range of motion exercises are performed to prevent limitation of movement even if tendon exposure does occur. The skin graft site is kept covered with Xeroform gauze, and the arm is lightly wrapped with gauze underneath the splint. The patient should resume oral intake only once a complete seal is assured in the oral cavity. Typically, the patient is fed via nasogastric or gastrostomy tube for the first 5 days while swallowing therapy is initiated. Management of patients in the hospital and anticipated complications can be predicted depending on the postoperative day (Fig. 3.2). Aggressive postoperative speech therapy is critical in ensuring a safe return to an oral diet. A modified barium swallow may be required, especially in elderly patients, who are more likely to have silent aspiration and significant pulmonary sequelae as a complication. The majority of patients are discharged home on pureed or soft oral diets.

FIGURE 3.2 In-hospital management of patient and anticipated complications of patients undergoing radial forearm free flap reconstruction. Typically, the first 24 hours are at highest risk for hematoma, and anytime in the first 3 days, there is a risk of vascular complications. After postoperative management follows a relatively routine course in the absence of a surgical or medical event.

The most significant complications associated with radial forearm free flap reconstruction of the floor of the mouth are dependent on flap viability. Early flap failures should be noted immediately and taken to the operating room for management. Microvascular complications are typically reported to be between 4% and 6% with approximately half of those being salvageable. Occasionally, leech therapy is used to assist with venous congestion if the anastomosis has been explored and no thrombus was seen and/or the patient’s medical comorbidities do not allow for another general anesthetic.

Salivary leak into the neck is another complication and can be managed based on severity. Treatment options range from conservative observation with oral antibiotics to aggressive debridement and irrigation. A fistula can be managed with a Penrose drain in place or negative pressure dressings (Fig. 3.3). I have found that application of the negative pressure dressings to rapidly promote granulation tissue in severely compromised wounds and placement of the dressing directly over the pedicle or carotid to be safe. Drains should be left in the neck until a salivary leak is of minimal threat to wound healing.

FIGURE 3.3 Use of negative pressure dressings to manage fistulas after floor of the mouth reconstructions. The patient had viable tissue in the neck but developed a salivary leak in the floor of the mouth (A). Application of a negative pressure dressing within the defect for a limited period of time (3 to 7 days) allows for contraction of the wound site and promotes healing (B).

Donor site tendon exposure is reported in approximately 10% to 30% of forearm defects, but these wounds usually heal over a period of 2 to 6 weeks. To prevent long-term complications, movement of the wrist should be encouraged with passive and active range of motion. Limited functional deficits of the donor site are reported even in the presence of significantly delayed healing secondary to tendon exposure (Fig. 3.4). Typically, patients will have measurably decreased strength in the donor arm in comparison to the contralateral side; however, this does not tend to interfere with daily activities of life.

FIGURE 3.4 Tendon exposure after radial forearm free flap. Immediate postoperative view at 1 week demonstrates some discoloration of the graft, but otherwise appropriate healing (A). However, at 3 weeks, significant loss of the graft has occurred particularly over the flexor carpi radialis (B), which is the most common site for loss due to the mobility of this surface tendon and low vascularity.

The results with this technique are excellent. The pliable nature of the radial forearm skin makes it an ideal choice for reconstruction of the floor of the mouth.

• Limited mobility of the tongue is difficult to treat secondarily, and management is often delayed for 4 to 12 months after completion of radiation therapy.

• Tethering of the tongue can be improved by releasing the tongue with placement of a split-thickness skin graft in the floor of the mouth as a secondary procedure.

• In large cancers of the floor of the mouth, it may be best to wait until pathology reports indicate that the cancer has been completely resected because there may be unrecognized involvement of deep tongue and/or bone, which can significantly change the choice of the flap.

• Harvesting a flap slightly larger than the size of the defect is helpful in preventing tethering of the tongue.

• Thinning of the flap may be required postoperatively to improve control of oral secretions.

• The remaining mucosa of the gingiva, if available, can provide sufficient strength to hold sutures. If dentition is present, sutures placed circumferentially around the teeth can be used intermittently to relieve tension on the relatively thin mucosa of the floor of the mouth.

• If the deep tongue muscle attachments to the mandible are resected, their reattachment can be helpful in preventing retraction of the posterior tongue, which can limit the diameter of the oropharyngeal airway.

• A tracheostomy is not always required in limited resections of the floor of the mouth.

• If the patient has undergone previous radiation therapy, however, he or she may experience unpredictable postoperative edema making a tracheostomy necessary.

• Excessive bulk in the reconstructed tissue should be avoided anteriorly to avoid glossoptosis and/or obliteration of the lower lip sulcus.

• Scar contracture may tether the tongue; therefore, ample tissue should be transferred to the defect primarily, which can be debulked at a later time if necessary.

• Injury to the lingual nerve during the ablative operation may limit tongue sensation or mobility that is perceived as decreased mobility by the patient but cannot be surgically corrected.

• Premature return to oral intake may compromise the integrity of the wound in the floor of the mouth and lead to salivary fistula.

• Dental rehabilitation in the floor of the mouth defects remains controversial and costly to the patients. It may be best to defer in-depth preoperative discussion of options until several months after surgery.

• Standard head and neck surgical set

• Dermatome

I gratefully acknowledge the contributions of Hillary White, MD.

SUGGESTED READING

Ko AB, Lavertu P, Rezaee RP. Double bilobed radial forearm free flap for anterior tongue and floor-of-mouth reconstruction. Ear Nose Throat J 2010;89(4):177–179.

Huang JJ, Wu CW, Lam WL, et al. Anatomical basis and clinical application of the ulnar forearm free flap for head and neck reconstruction. Laryngoscope 2012;122(12):2670–2676.