Hard Palate Resection

Introduction

The oral cavity functions as the interface between the respiratory/digestive tracts and the outside world. It contributes to a complex array of functions that include speech, mastication, salivation, early digestion, and oral/oronasal competence. Tumors of the hard palate are uncommon. Resection of the hard palate may be necessary for the management of benign or malignant tumors or as a donor site for a mucosal graft.

Key considerations

Although squamous cell carcinoma is the most common primary malignant tumor of the oral cavity, the most common tumors of the hard palate are of minor salivary gland origin. These include benign tumors such as pleomorphic adenomas, as shown below, and malignant tumors such as mucoepidermoid carcinoma, adenoid cystic carcinoma, and polymorphous low-grade adenocarcinoma. Other histologies less frequently encountered include verrucous carcinoma, sarcoma, melanoma, and lymphoma. The lung, kidney, breast, and skin are the most common sites of primary carcinoma that metastasize to the oral cavity. ^{[1, 2, 3]}  Classification of oral cavity tumors has been created by the American Joint Committee on Cancer (AJCC) and is reviewed in Table 1. ^[4]

Pleomorphic adenoma of hard palate in Asian woman.

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Table 1. The American Joint Committee on Cancer (AJCC) TNM classification of oral cavity tumors ^[4] (Open Table in a new window)

When used as donor grafts, hard palate tissue offers the advantages of an epithelial lining, minimal postoperative graft shrinkage, and ready availability compared to other donor sites/materials. Although it is a stiff graft, it is moist and flexible, thus allowing appropriate functioning as a tectonic support in facial reconstruction such as in the lower eyelids, lower lip, nasal ala, and in mucosal defects in oral surgery. ^{[5, 6, 7, 8, 9]} The hard palate mucosa exists as a keratinizing squamous epithelium on a dense, collagenous lamina propria, very similar in structure to native tarsus in the eyelid.

Indications

The indications to perform hard palate resection include excision of malignant and benign tumors, to alleviate complications from tumor burden that compromise the function of the oral cavity, and for facial reconstruction such as in cases of eyelid, lip, and nasal ala deformities.

Contraindications

Contraindications to hard palate resection include inability to tolerate general anesthesia, extensive lesions that may require more radical surgical intervention, and tumors that may be more appropriately treated with local irradiation and/or chemotherapy.

Relevant Anatomy

The oral cavity (see the image below) is oval shaped and is separated into the oral vestibule and the oral cavity proper. It is bound by the lips anteriorly, the cheeks laterally, the floor of the mouth inferiorly, the oropharynx posteriorly, and the palate superiorly. The oropharynx begins superiorly at the junction between the hard palate and the soft palate, and inferiorly behind the circumvallate papillae of the tongue. The bony base of the oral cavity is represented by the maxillary and mandibular bones.

Schematic representation of oral cavity and floor of mouth. A: philtrum; B: upper labial frenulum; C: opening of Stensen's duct; D: labial commissure; E: hard palate; F: soft palate; G: intermaxillary commissure; H: base of tongue; I: lateral border of tongue, dorsal view; J: tip of tongue, dorsal view; K: tip of tongue, ventral view; L: lateral border of tongue, ventral view; M: ventral surface of tongue; N: lingual frenulum; O: floor of mouth; P: opening of Wharton's duct; Q: vestibular gingiva; R: vestibule. Teeth are numbered according to international classification.

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The palate is the horseshoe-shaped, domed roof of the oral cavity. It is divided into a hard portion and a soft portion. The hard palate belongs to the oral cavity and separates it from the nasal cavities. The soft palate belongs to the oropharynx and separates it from the nasopharynx.

The hard palate is concave, and this concavity is occupied mostly by the tongue when it is at rest. The hard palate is subdivided into the primary and secondary palates. The primary palate is separated from the secondary palate by a small depression behind the central incisors termed the incisive fossa, where the incisive foramen opens.

For more information about the relevant anatomy, see Mouth Anatomy.

Anesthesia

Examination under general anesthesia is usually necessary for tumor mapping and surgical planning. Consultation with an experienced anesthesiologist is useful to ensure safe intubation that allows appropriate exposure of the surgical field while not compromising the patient's respiratory status during the case. Paralytic agents may help to improve oral cavity exposure during the case. Local anesthetic with vasoconstriction is often used around the resection site to improve hemostasis.

Special Equipment

See the list below:

• Headlight

• Mouth Gag

• Cheek Retractors

• Oscillating Bone Saw

• Chisels

• Electrocautery

• Saline irrigation

• Periosteal Elevators

Positioning

The patient is placed in the supine position with the head stabilized in a doughnut holder. However, if a scapular tip free flap graft will be used, the patient will be placed in the 30º lateral decubitus position with a rolled-up towel under the inferolateral border of the latissimus dorsi muscle.

Prophylactic antibiotics (to cover gram-positive and anaerobic organisms) are often given during the induction of general anesthesia and continued for at least 48 hours postoperatively. Anticoagulation is stopped or bridged when medically appropriate. A mouth gag is inserted to retract the tongue and endotracheal tube away from the surgical field and to provide optimal visualization of the mouth. If necessary, malleable cheek retractors can be used to improve the view. The periphery of the lesion is noted visually or marked graphically. Local anesthetic with vasoconstriction is injected along the surgical plane to promote hemostasis.

An incision down to the periosteum with wide margins away from the peripheral extent of the lesion is performed to allow for tumor-free surgical margins. Periosteal elevators are used to lift the tissue and allow bone-cutting instruments to be introduced in such a way to avoid nearby soft tissues. If bone resection is needed, the area to be resected can be isolated with an oscillating saw or high-speed Midas Rex drill. After the lesion has been circumscribed by bony cuts, the specimen can be rocked free and excised. Frozen section examination of the surgical specimen is often necessary to ensure complete surgical removal.

After resection, electrocautery is used to achieve hemostasis, and the wound is irrigated with copious amounts of saline. Small defects can be closed primarily by the advancement of adjacent mucosa or by reconstruction using a local palatal island mucoperiosteal flap based upon the descending palatine artery pedicle, which exits from the greater palatine foramen. ^[9] Alternatively, small defects may be packed with Xeroform and left to allow healing by secondary intention. ^[10]  Larger palatal or palatomaxillary defects can be categorized using the Mount Sinai classification system, with reconstruction options differing between classifications (Table 2). ^{[11, 12]}

Table 2. Mount Sinai Classification System of Palatomaxillary Defects ^{[11, 12]} (Open Table in a new window)

For squamous cell carcinomas of the hard palate, the regional lymph nodes must be carefully inspected. Although the rate of occult metastases in hard palate cancer is lower than in most other oral cavity subsites, advanced-stage (T3 and T4) tumors do have a significant risk of occult metastases and elective neck dissection should be considered. It has been shown that nodal observation post-tumor resection is associated with a two-fold increase of disease recurrence compared to resection plus elective lymph node dissection, even when controlling for factors such as age and tumor classification. Performing an elective lymph node dissection for patients with squamous cell carcinomas of the hard palate may improve overall survival, as well as recurrence-free survival rates. ^[13]

For hard palate mucosal grafting, the prospective donor site is marked and injected with local anesthetic with epinephrine. The nasopalatine neurovascular bundle and the greater palatine vascular bundle may be anesthetized for further post-operative pain control. The hard palate mucosal donor site is infiltrated with local anesthesia. The graft is harvested by outlining the mucosal site, staying lateral to the median raphe with a cutting Bovie on a sharp pointed tip such as a Colorado needle. The graft is harvested using a right-angle sharp blade such as a super blade or crescent knife or #57 beaver blade. The graft is undermined, but an attempt is made to keep it thin. Hemostasis is obtained with cautery or a pressure dressing.

Hard palate reconstruction can be performed using a variety of reconstructive modalities. Consideration as to the type of defect is essential in selecting an appropriate reconstructive option (Table 2). Prior to the implementation of free flaps, obturator prosthetics were relied on for restoring oral function and facial form. With the development of flaps, reconstruction of defects involving less than one third of the hard palate may be perfomed using local flaps, such as palatal island flaps and buccal mucosal flaps. 

Larger defects, however, require more extensive reconstruction, including the use of free flaps. Fasciocutaneous free flaps may be used for patients with defects greater than one third of the hard palate or for smaller defects within a previously irradiated field. Other free flaps, including radial forearm free flaps and anterolateral thigh flaps, can be used for patients who will require dental rehabilitation, as both are pliable flaps and can accommodate dental prosthetics. For defects of larger volume, myocutnaeous flaps, including latissimus dorsi and rectus abdominus flaps, can be used and are helpful in maintaining contour of the cheek. 

Osseocutaneous flaps can be used for defects with significant bony loss. Radial forearm osseocutaneous flaps may be considered in patients with defects involving most or all of the maxilla with loss of the premaxilla and nasal spine. Fibular free flaps can be of use for defects involving the tooth-bearing maxillary alveolus including one or both canines or if the defect is greater than 50% of the palatal surface.  Near-total or total maxillectomy defects can be reconstructed using subscapular vessel-based flaps. 

Using scapular tip free flaps can be beneficial when compared to a fibular or iliac crest free flap. This includes the chimeric nature of the scapular tip free flap, which lends itself to more complex head and neck reconstruction, a longer pedicle length from the thoracodorsal artery to the angular branch, decreased donor site morbidity, reduced rate of vein grafting, and the ability of the patient to ambulate shortly after the operation without limitations. Morphologically similar bone grafts to the mandibular angle, maxilla, and palate can be obtained using the scapular tip flap technique, thus improving the aesthetic outcome of head and neck reconstruction. ^[14]

The decision to use an obturator prosthetics versus a free flap remains a topic of debate. Using obturator prosthetics post-tumor resection can decrease hospital length of stay and cost, decrease the time to restore oral function, and make it easier to detect tumor recurrence. ^[15]  However, free flap transfer can provide definitive reconstruction and better functional outcomes, especially for larger defects. The facial contour can be reconstructed with free flaps, which also allows for fixture of dental prosthetics. Free flap reconstruction has been associated with improved patient-perceived quality of life. When implemented, there appears to be a preference towards using prosthetic rehabilitation for hard palate and upper gum defects compared to lower gum and soft palate defects. ^[16]

Complications

As with other surgical procedures, excessive bleeding and postoperative infection remain the most commonly feared complications. Surgical planning to avoid damage to local structures, potentiate missed tumor margins, and ensure oronasal competence is necessary for optimal recovery.

When used for facial reconstruction, hard palate grafts may not completely reapproximate native tissues. Proper handling of grafts is necessary to prevent tissue extrusion and compromise of the graft's integrity.

Long-term monitoring

Patients are followed closely during the postoperative period to avoid the previously mentioned complications and to treat them aggressively when they do occur. In the case of tumor resection, direct inspection of the resected site is necessary following surgery, along with palpation of lymph nodes of the head and neck during the period of surveillance. In this respect, a potential advantage of prosthetic obturator reconstruction is the ability to carefully inspect the surgical site for local recurrence.

When grafted, the reconstructed area is examined for areas of tissue necrosis that may indicate failure and/or rejection.

Post-operative oral intake

After resection of hard palate lesions, patients are often left with difficulty in deglutition. Reconstruction with either obturator or tissue reconstruction leave patients with the need to adapt to the structural changes in order to maintain function of swallow. ^{[17, 18]}  For those with obturators, patients can be started on oral intake trials soon after surgery. Those with free flap reconstructions typically remain without oral diet until post-operative day 5 and then are started on clear liquid diets with further advancing as tolerated. For patients with obturators and tissue reconstruction, few patients have complaints regarding chew or taste differences. Many patients with tissue reconstruction do report higher satisfaction in regard to speech, comfort, and social interaction compared to those with obturators. ^{[19, 20, 21]}