Management of Palatal Defects after Free-Flap Reconstruction and Radiotherapy

Abstract

Palatal fistulas have significant effects on quality of life. Traditional prosthetic rehabilitation and surgical reconstruction of palate defects in radiation-naïve tissues are well described. However, palatal fistulas developing after initial tumor extirpation, free-flap reconstruction, and adjuvant radiation or chemoradiation are associated with challenging secondary tissue effects. In this review, we will discuss the management of palatal fistulas after surgical reconstruction and radiotherapy.

Surgical extirpation is the primary treatment modality for benign and malignant lesions of the oral cavity or paranasal sinuses that involve the palate. Traditional reconstruction of palatal defects includes local flaps, regional flaps, and free-flap reconstruction. Over 15 individual systems have been developed to describe defects and reconstructive principles of the maxilla. ^{1 2 3 4 5 6} Free-flap reconstruction is usually performed for moderate to large defects of the maxilla. Malignant lesions of the maxilla often present with unfavorable pathological features requiring adjuvant radiation with or without chemotherapy. ⁷ The development of local wound complications following reconstruction and adjuvant therapy can create significant functional consequences of the midface.

A palatal defect can develop as one of these complications and is defined as an abnormal communication between the oral and sinonasal cavities. This communication leads to nasal regurgitation, taste disturbances, hypernasality, and reduced quality of life. ⁸ Palatal defects occurring following free-flap reconstruction and adjuvant radiotherapy present with unique challenges. Radiation results in damaged cellular mechanisms in nonmalignant cells, leading to progressive loss of cellularity, vascularity, and tissue integrity in the irradiated field. ⁹ These effects are intensified with the addition of chemotherapy. These palatal defects can be associated with tissue atrophy, trismus, osteoradionecrosis (ORN), recurrent infections, plate exposure, and occult recurrence. ^{8 10} Aggressive surgical management is typically required for these palatal defects. ¹¹

In this article, we describe the management of palatal defects that develop following free-flap reconstruction and adjuvant radiotherapy. We will discuss considerations for palatal obturation versus reconstructive surgery, and the role of endosseous implantation in a previously irradiated field.

Initial Management of Palatal Defects

Radiotherapy should not be interrupted if a palatal defect develops during treatment. Instead, the area should be observed to allow the inflammation to subside to determine the full extent of the palatal defect. During this time, initial management should include routine oral saline or chlorhexidine rinses. Many patients have sinonasal concerns including crusting, rhinorrhea, facial pain or pressure, and foul odor. Patients can also perform nasal saline irrigations. ¹² Culture-directed antibiotic therapy can be considered if there is evidence of persistent infection. Malnutrition, hypothyroidism, anemia, vitamin deficiency, and substance abuse should be addressed to maximize healing and to minimize the development of more complications. ^{13 14} Speech-language pathology should be consulted to assist with oral intake and communication strategies. The ensuing priority is to biopsy any concerning lesions to exclude persistent or recurrent disease; however, occult recurrences can still occur. A temporary palatal obturator can be fabricated to assist with oral intake, if tolerated. The patient's prognosis, underlying functional status, and motivational goals should be considered when deciding how to definitively manage the palatal defect in this setting.

Palatal Obturator

A palatal obturator, whether temporary or permanent, is a nonsurgical option for palatal defects. A palatal obturator is a prosthetic device that has been used as the traditional mode of restoring function to a palatal defect. An obturator can restore a patient's dentition while simultaneously separating the oral and sinonasal cavities. ¹⁵ The use of an obturator can be advantageous in poor surgical candidates or elderly patients, provided they have good manual dexterity. It can facilitate earlier oral intake and not interfere with adjuvant therapy. The retention of an obturator is determined by the status of the remaining palatal bone, the obturated cavity, and the patient's remaining dentition. ¹⁶ Patients with missing premaxilla or bilateral canines are typically poor candidates for obturation. ⁵ Obturators in partially dentate patients function as a removable partial denture, whereas edentulous patients usually require endosseous implants in the residual alveolar bone to provide a platform for the fabrication of a retention bar to support the overlying prosthesis. ¹⁷ Fabrication of an obturator requires a referral to a maxillofacial prosthodontist, who works closely with speech-language pathologists to optimize speech and swallow outcomes.

An obturator has noteworthy disadvantages. Obturators have poorer retention in larger defects. Nasal regurgitation can develop over time due to tissue contractures or poor fit. Adequate placement can also be complicated by significant trismus. Inspissated secretions from an irradiated maxillectomy cavity can coat the obturator, leading to foul smells and secondary infections. ¹ Patients with heavily irradiated facial skin have increased risk of obturator erosion and exposure. Obturators do not provide orbital support or assist with restoring midface projection. Finally, a patient can experience psychological stress and anxiety if they constantly must place a removable prosthesis for frequent daily functions of oral communication and eating. ¹⁰ Despite these disadvantages, patients may be reluctant to undergo another surgical procedure for closure of a palatal defect after already undergoing free-flap reconstruction with adjuvant radiotherapy. Moreover, these patients may have malnutrition and diminished functional status after cancer treatment. Therefore, an obturator should be considered for these patients.

Reconstruction Principles of Palatal Defects

In general, creating a barrier between the oral and sinonasal cavities is the primary surgical objective for reconstructing a palatal defect. Depending on the size and location of the defect, other objectives include the following: preserving soft palate function to decrease the risk of velopharyngeal insufficiency; restoring mastication and articulation with a prosthesis; restoring volume to midface projection; removing all affected sinonasal mucosa; obliterating the dead space; and determining the extent of orbit and/or skull base involvement. ³

Palatal defects that develop after maxillary free-flap reconstruction and irradiation are more complex to reconstruct than defects addressed secondary to cleft palates, dental procedures, or tumor ablation not requiring adjuvant therapy. The remaining irradiated native maxillary mucosa and recipient free-flap tissue develop turgor and rigidity, so the tissue does not tolerate extensive dissection, advancement, or rotation for reconstruction of these defects. Subsequently, palatal defects repaired with irradiated tissue are at much higher risk of impaired wound healing. Multiple systematic reviews have shown that preoperative radiotherapy is associated with an increased risk in postoperative complication rates, including flap failure and recurrent fistula formation. ^{18 19 20}

Surgical reconstruction options are based on the size, location, and extent of surrounding tissue involvement. However, each of these defects in previously reconstructed irradiated palates is unique. Well-described algorithms for primary maxillary tumor extirpation and reconstruction do not necessarily apply in these cases. Ideally, double-layer closure of the oral and sinonasal cavities should be attained to minimize the risk of further soft-tissue contracture, recurrent palatal defect formation, and bone and/or hardware exposure. ²¹ The previous flap inset may be modified to assist with closure of the defect. ²² Local flaps should be designed with more generous dimensions than one would normally use. We recommend using twice the normal flap dimensions to achieve the same tension-free closure as one would have in normal tissue not previously exposed to reconstruction or radiation. The flaps should be raised with approximately 2 to 4 mm of thickness, if possible. Raising the flap with a wider base allows for increased vascularity to the distal tip of the flap, which should be used as an indicator of how robust the tissue is prior to inset. ⁸ Of note, minimizing oral intake is beneficial during the healing process. Use of a nasogastric tube or a preexisting gastrostomy tube may be required to optimize nutrition postoperatively.

Small Palatal Defects

Small palatal defects (<1.5 cm) may heal on their own with time using the conservative measures mentioned previously. If healing spontaneously does not occur, we recommend minimal local debridement with pathological evaluation of any diseased tissue. If the surgeon feels like healing is unlikely, then consideration can be given to local flap reconstruction.

A turn-in flap can be considered to assist with double-layer closure of the sinonasal side of the defect. A turn-in flap utilizes a partial-thickness dissection of the surrounding native maxillary mucosa or recipient free-flap tissue. This tissue is subsequently rotated and sutured closed on the sinonasal cavity surface of the defect. ²³ For small fistulas, the palatal island flap can be considered to close the oral surface of the defect. The palatal island flap is a posterior-based rotational mucoperiosteal flap supplied by the palatine artery. This flap has been shown to be versatile in reconstructing postoperative palatal and retromolar trigone defects in tissue not previously exposed to radiation. ²⁴ However, radiotherapy and/or extensive oral cavity surgeries are relative contraindications to this flap due to impaired wound healing by secondary intention of the hard palate and its potential compromised vasculature supply. ^{23 25} While this flap has decreased elasticity after radiotherapy, it can be considered to assist with closure of small palatal fistulas in combination with a turn in flap and/or minor tissue rearrangement of the initial flap's inset. ²⁶

Moderate Palatal Defects

Moderate-sized palatal defects (1.5–3 cm) often require nonpalatal tissue for reconstruction. In general, classically described intranasal flaps, such as the nasoseptal flap or inferior turbinate flap, are compromised during the initial tumor extirpation and are not reliable for closure of sinonasal surface of the defects. Similar to the small palatal defects, we prefer a turn-in flap made from tissue immediately adjacent to the fistula followed by a second layer of coverage with an intraoral rotational flap. The most applicable intraoral rotational flaps include the facial artery myomucosal (FAMM) flap and the buccinator myomucosal flap. If a regional flap is desired, a temporalis flap can be considered.

FAMM Flap

The FAMM flap is a reliable local flap based on the facial artery. It is composed of the mucosa, submucosa, buccinator muscle, and the deeper plane of the orbicularis oris muscle. ^{27 28} The advantages of the FAMM flap include its pliability, strong vascular supply, minimal postoperative pain, improved functional outcome, and the ability for primary site closure if the width of the flap is less than 3 cm. ²⁷ In the case of palatal defects, the FAMM flap can be a superior flap based on the angular artery with retrograde flow. Although studies are limited, the FAMM flap has been shown to be successful in patients with prior neck dissection or history of irradiation. ²⁹

Buccinator Myomucosal Flap

The buccinator myomucosal flap is a horizontal flap based on the buccal artery, a distal branch of the maxillary artery. ³⁰ Classically, this flap has been shown to be a reliable flap for posterior oral floor defects, but it has been used for posterior hard palate and/or soft palate reconstruction. ³¹ As with the FAMM flap, its use is limited in patients with severe trismus and history of irradiation.

Temporalis Flap

The temporalis flap is a robust regional flap that was used to reconstruct palatomaxillary defects before the advent of microvascular surgery. ³² It is readily available even in the setting of previous irradiation given its strong inferior vascular supply arising from the internal maxillary artery. The temporalis muscle can tolerate 180 degrees of rotation with an approximate length of 12 to 16 cm to fill an intraoral defect. The zygomatic arch can be temporarily removed to allow more mobility. The flap has favorable functional recovery in swallowing and speech. ³³ The major disadvantage is the risk to the frontal branch of the facial nerve and facial asymmetry secondary to temporal hollowing. ³⁴ Typically, the temporalis region has received less radiation compared with the primary tumor site, making this flap a robust and reliable regional flap option in patients who otherwise are not candidates for microvascular reconstruction.

Large Palatal Fistulas

Large palatal defects often require another free tissue transfer flap. Prior to reconstruction, these defects typically require aggressive tissue debridement secondary to chronic infection, exposed bone, and/or ORN. ³⁵ Any nearby hardware should be removed given the risk of biofilm formation and infection. ⁸ Free tissue transfer has significant advantages in this setting, as it can provide enough bulk to fill any remaining dead space, close the palatal defect, and provide a vascularized bone flap if considering endosseous implants. When considering free-flap reconstruction of the midface, it is pertinent to understand the anticipated vascular pedicle length and the vascular anatomy in a previously operated neck. We will highlight the pertinent free flaps to be considered for reconstructing palatal defects.

Fibula

The fibula free flap can be harvested as a bone-only, osteocutaneous, or a myo-osteocutaneous flap. It is our recommended flap of choice for reconstructing the midface due to its extent of bone stock, long vascular pedicle, ability for multiple osteotomies, and reliability of endosseous implantation. It is based on the peroneal artery and vein, and osteotomized segments should ideally be at least 2 cm. The height of the fibula is on average approximately 13 to 15 mm, giving a reliable stock of bone for endosseous implantation. ³⁶ The tibialis posterior and soleus muscle can be harvested to assist with dead space obliteration, but its mobility is typically limited. Also, it is important to take into consideration the pliability of the lateral calf skin to reconstruct the palate. In the case with an unreliable cutaneous perforator or nonpliable lateral calf skin, a fibula free flap can be used to restore the neoalveolus and midface volume, and a second fasciocutaneous flap can be used as a double closure technique to close the palate. ^{1 6 36 37 38 39 40} Fig. 1 shows a patient who required a complete maxillectomy with orbital exenteration and cranialization of the frontal sinus for an extensive mucosal melanoma. The initial skull base and orbital defect was reconstructed with a radial forearm free flap with a beavertail modification. Subsequently, the patient had reconstruction of the maxilla with an osteocutaneous fibula free flap with immediate implant placement.

Fig. 1.

This patient had extensive mucosal melanoma requiring a complete maxillectomy with orbital exenteration and cranialization of the frontal sinus. The initial skull base and orbital defect were reconstructed with a radial forearm free flap with a beavertail modification. Subsequently, the patient had reconstruction of the maxilla with an osteocutaneous fibula free flap with immediate implant placement. This patient has plans to receive an ocular prosthesis.

Scapula

The scapular system has many options for reconstruction of the midface. This is a versatile flap system that can be harvested using two separate bone grafts, the serratus anterior or latissimus dorsi muscle, and multiple skin paddles. The lateral border of the scapula, based on the superficial circumflex scapular artery, can be used for endosseous implants. The scapula tip has a reliable shape to reconstruct the palatal shelf. The scapular tip has a longer pedicle due to the angular artery coming from the thoracodorsal artery or its serratus branch. The scapula bone can be cut into nonlinear shapes to customize the bone segment to the maxillary defect. The serratus anterior or latissimus dorsi muscles can be harvested for dead space obliteration. The skin paddles can be based on the ascending, horizontal, or descending branches of the circumflex scapular artery, or a skin paddle can be harvested with the thoracodorsal artery. ⁴¹ The vascular supply to this flap is not normally compromised by arteriosclerosis or diabetes. The disadvantage to the scapular system is that the bone stock is not as comparable to the iliac crest or fibula for endosseous implantation. The scapular system initially was not favorable due to position difficulties preventing simultaneous tumor ablation and flap harvest, prolongating operative times. However, newer supine positioning techniques described allow a two-team approach to minimize the operative times. ⁴² In Fig. 2 , this patient had a large palatal fistula following irradiation that was addressed with an osteocutaneous scapula free flap using the parascapular skin paddle.

Fig. 2.

This patient had recurrent sinonasal squamous cell carcinoma with previous surgery and adjuvant radiation who subsequently underwent salvage surgery with a total maxillectomy. The fistula was closed with a parascapular skin paddle and lateral scapular border osteocutaneous free flap.

Iliac Crest

The iliac crest can be harvested as a bone-only, osteocutaneous, or a myo-osteocutaneous flap. This flap is based on the deep circumflex iliac artery and deep circumflex iliac vein. The pedicle is short, so vein grafts may be required for this flap when reconstructing the midface. The internal oblique muscle can be harvested to restore intraoral and nasal linings while obliterating the maxillectomy defect. ^{43 44} The bone volume is reliable for endosseous implantation, and its vertical height allows restoration of the alveolus, malar prominence, and infraorbital rim. The reconstructed infraorbital rim can serve as a shelf to facilitate orbital floor reconstruction. The donor-site morbidity is worth noting due to gait disturbances and the risk of abdominal wall herniation. Therefore, this flap is primarily used for large-volume defects amenable to its accompanying soft-tissue bulk and bone stock. ⁴⁵ In general, a free nonvascular iliac crest bone graft is not recommended for consideration when reconstructing these complex wounds due to the unpredictable degree of graft resorption and secondary infection.

Radial Forearm

The radial forearm can be harvested as a fasciocutaneous or osteocutaneous free flap. This flap has a long pedicle encompassing the radial artery, cephalic vein, and venae comitantes. The fasciocutaneous free flap is a workhorse for midface reconstruction due to its thin, pliable skin suitable for intraoral and intranasal lining. Moreover, the beavertail modification of the radial forearm flap can also be used to provide more bulk. When harvesting using the beavertail modification, the standard skin paddle and vasculature are designed and elevated. However, dissection in the proximal forearm proceeds subcutaneously and the underlying fibrofatty contents are mobilized from the underlying flexor tendons and muscles. Once the beavertail and skin paddle are elevated, the vascular pedicle can be dissected free from the beavertail. The beavertail portion of the flap can be folded over to provide a second layer of closure for the palatal defect. ⁴⁶ If the fibula skin paddle is not reliable to reconstruct the palate, this flap can be used in a two-flap technique to ensure an adequate closure of the palatal defect. ³⁹

The osteocutaneous radial forearm flap is also an option for midface reconstruction. During flap harvest, the flexor pollicis longus muscle belly is divided longitudinally to allow access to the volar aspect of the radius. Approximately 50% of the width of the radius bone is harvested by joining the longitudinal osteotomy with beveled osteotomies at the proximal and distal end, ensuring at least 3 to 4 cm of distal radius remains for three-screw fixation. ⁴⁷ Some surgeons also use iliac crest free bone grafts to the remaining radius for quicker healing and mobilization. ²¹ Miniplates should be used for inset of the flap, as larger plates and screws can compromise the vasculature supply to the radius. This flap initially fell out of favor due to concerns of postoperative radius fractures, but the rate of this complication is low with proper keel-shaped osteotomies and prophylactic plating of the radius. ^{48 49} Likewise, it has been used for successful nasomaxillary, palatomaxillary, and orbital reconstruction. ^{39 50 51}

Anterolateral Thigh

The anterolateral thigh (ALT) flap is a versatile fasciocutaneous or myocutaneous flap that can be used for isolated palatal defects for which a large dead space needs to be obliterated, but without the need for support of implant prosthesis or orbital floor reconstruction. This flap is based on the descending branch of the lateral circumflex artery with two veins, with a pedicle length between 8 and 16 cm. The overlying skin paddle is supplied predominantly by musculocutaneous perforators through the vastus lateralis. ⁵² For small infrastructure palatal defects only, an ALT cutaneous flap can be used. An ALT musculocutaneous flap using the vastus lateralis muscle can be used to assist with dead space obliteration. In either scenario, the ALT can be partially deepithelialized if needed. An ALT myocutaneous flap can also be used to cover a free bone graft if the orbital floor needs reconstruction. ⁵³ In Fig. 3 , this patient had an ALT flap to cover a large palatal fistula following irradiation.

Fig. 3.

This patient had extensive history of sinonasal squamous cell carcinoma with multiple ablative and reconstructive surgeries. He also had irradiation and was disease-free for many years. The secondary soft-tissue effects of radiation and multiple local flaps resulted in a persistent oronasal fistula that impaired his quality of life. He had a myocutaneous ALT flap to close his fistula.

Endosseous Implant Considerations

Prosthodontic rehabilitation is a major goal for patients with midface malignancies. Endosseous implants are used either to support a palatal obturator or for dental rehabilitation following reconstruction of the maxilla. In malignancies, endosseous implant placement is typically delayed 6 to 12 months after completion of radiotherapy, due to concerns of decreased vascularity of the recipient bone for osseointegration. As mentioned before, we recommend waiting 6 months following completion of radiotherapy prior to reconstructing palatal defects. Therefore, consideration can be given to developing a surgical plan for reconstructing the palatal defect that involves immediate endosseous implant placement. Of note, the extra cost, extended operative times, and patient motivations are major barriers for implant placement. ^{15 54}

If a palatal obturator is planned for the primary treatment of a palatal defect, implants can be placed in available bone surrounding the defect (e.g., residual maxilla, pterygoid plates, or zygoma) to improve prosthetic retention and stability. Implants not placed in the alveolus have worse osseointegration and are difficult to restore and maintain. Studies have shown that the failure rate of zygomatic implants in maxillectomy defects is as high as 21%, with likely higher failure rate in the setting of previous irradiation. ^{55 56} Because of this high failure rate, we typically do not recommend placing implants into an irradiated zygoma if this is the primary means for obturator retention.

Endosseous implants can also be used for dental rehabilitation after bone reconstruction of the maxilla. ¹⁷ Implant placement can be accomplished during the inset of the vascularized bone free flap. In appropriately selected patients with palatal defects following radiotherapy, vascularized bone reconstruction with immediate implant-supported prosthetic rehabilitation can be considered ( Fig. 1 ). ^{57 58} Virtual surgical planning (VSP) has revolutionized implant placement by formulation of a patient-specific cutting and implant placement guide of the fibula free flap. The increased cost of VSP is offset by reduced operating time, greater use of placed implants, higher rates of tertiary prosthetic rehabilitation, and improved patient satisfaction and quality of life. ⁵⁷ Therefore, discussing these goals with the patient is imperative to potentially shorten the time and number of procedures to prosthodontic rehabilitation while simultaneously reconstructing the palatal fistula.

Conclusion

The reconstructive surgeon must consider many complex factors in managing irradiated palatal fistulas in previous free-flap reconstruction of the maxilla. We recommend waiting at least 6 months after completion of radiotherapy before reconstructing the palatal fistula. Small to moderate fistulas may be addressed with more robust local and regional flaps, but larger fistulas require a second free-flap reconstruction. An obturator can be offered depending on the status of the remaining palate and dentition. Endosseous implantation should be considered to improve stability of a palatal obturator and/or during vascularized bone free-flap reconstruction in the appropriately selected patient.