Sandra Manfra Marretta, DVM, Diplomate
Palatal surgery in dogs and cats can be subdivided into several different categories including: management of oronasal/oroantral fistulas, management of congenital and acquired palatal defects and the ventral approach to the nasal cavity and nasopharynx through the palate.
The most common cause of oronasal/oroantral fistulas is periodontal disease and the most frequent tooth causing oronasal fistulas is the maxillary canine tooth. The maxillary third and fourth premolar and the first molar may cause oroantral fistulas. These fistulas may be closed with either single or double-layer flaps.
Single-Layer Oronasal Fistula Repair
A single-layer flap is recommended for the repair of most fistulas. Recurrent or large fistulas may require the use of a double-layer flap. A single-layer flap repair of oronasal or oroantral fistulas is initiated by the removal of the entire epithelial edge of the fistula using a #15 blade to remove a thin layer of mucosa around the perimeter of the fistula. Divergent incisions are made from the mesial and distal aspects of the fistula through the mucogingival line extending into the buccal mucosa. The mucoperiosteal flap is gently elevated using a periosteal elevator. The mucoperiosteal flap is retracted laterally and apically to expose the periosteum of the apical region of the flap. The periosteal layer of the flap is incised distomesially in the apical region to improve flap mobility. The flap is positioned over the fistula to ensure that there is no tension on the flap prior to closure. The mucoperiosteal flap is sutured to the palatal and gingival mucosa with a simple interrupted pattern using 3-0 absorbable suture material.
Double-Layer Oronasal Fistula Repair
Recurrent or large fistulas may require the use of a double-layer flap. Several techniques for repair of oronasal fistulas have been described including a double reposition flap technique.1 The double reposition flap is initiated by excising the entire mucosal edge of the fistula except the palatal edge. A large semi-circular palatal mucoperiosteal flap is created palatal to the defect and elevated using a periosteal elevator. The palatal flap is rotated on its basilar attachment into the fistula and sutured in place with 3-0 absorbable suture material. The second layer of the flap is similiar to the single-layer flap technique except that it is particularly important in the creation of the second layer of the flap to adequately incise the periosteal layer of the flap to ensure no tension is present on the flap following closure since this second layer of the flap is sutured to a more palatal location than a single-layer flap. The buccal mucoperiosteal flap is advanced palatally to cover the inverted flap and denuded palatine bone and sutured in a simple interrupted pattern.
Congenital Palatal Defects
Congenital palatal defects can be subdivided into several different categories including cleft hard palate, cleft soft palate, and hypoplastic soft palate.2 Cleft hard palatal defects are usually associated with cleft soft palatal defects. Cleft soft palatal defects may occur without hard palatal defects. Hypoplasia or the congenital absence of the soft palate has a guarded prognosis for resolution of clinical signs since the function of the soft palate cannot be surgically restored.
Two basic techniques for the repair of palatal defects are most commonly utilized. The first technique involves removal of the epithelium from the edges of the defect and complete periosteal elevation of the palatine mucosa bilaterally on each side of the cleft. Bilateral releasing incisions are made along the upper dental arcade to permit apposition of the edges of the midline defect. The overlapping flap technique, the second basic technique, is preferred by most surgeons because there is less tension on the suture line, the suture line is not located directly over the defect, and the area of opposing connective tissue is larger which results in a stronger scar. The need for releasing incisions is also unnecessary with the overlapping flap technique.
The overlapping flap technique is performed by creating two mucoperiosteal flaps. One flap is hinged at the end of the palatal defect and is turned beneath the other flap. Vest-over-pants type sutures of synthetic absorbable suture material are utilized to maintain the connective tissue surfaces of both flaps in apposition. This technique provides a wide area of connective tissue contact without tension.
Cleft soft palatal defects are repaired using a double flap technique in which incisions are made along the medial margin of the palatal cleft on each side. A small scissors is utilized to divide the palatal tissue into a dorsal and ventral component. The two dorsal flaps are sutured together using aborbable suture material in a simple interrupted pattern with the knots located intranasally. The two ventral flaps are sutured using a similiar material and pattern with the knots located intraorally. The edge of the repaired soft palate should reach the midpoint or caudal end of the tonsils and oppose the tip of the epiglottis when the tongue is in normal position.
Acquired Palatal Defects
Acquired palatal defects that have etiologies other than dental disease are usually located in the hard palate. These acquired palatal defects are caused by various types of trauma including dog bites, blunt head trauma, electrical shock, gunshot wounds, foreign body penetration and pressure necrosis. The acute inflammatory reaction and the overall clinical status of the patient with acute trauma should be managed prior to surgical correction of the palatal defect. Various surgical techniques can be utilized to repair acquired palatal defects including rotation flaps, advancement flaps, tongue flaps, and split palatal U-flaps.2,3 The technique selected for repair of an acquired palatal defect depends on the location of the defect. In general the technique that will provide the largest flap with no tension is recommended.
Rotation flaps are recommended for small circular defects especially defects located lateral to the midline. Large caudal defects that cross the midline can be repaired using an advancement flap. The defect is repaired by excising a thin section of mucosa from the perimeter of the defect and then creating a large mucoperiosteal flap caudal to the defect, incising the periosteal layer of the flap caudally, advancing the flap rostrally and suturing the flap over the defect with monofilament absorbable suture material in a simple interrupted pattern.
Tongue flaps may be used to repair large rostral palatal defects. The edges of the dorsal aspect of the tongue are excised and apposed to the debrided edges of the palatal defect. Approximately four weeks later the tongue is separated from the palate leaving enough tongue with the palate to close the defect without tension. Alternative techniques to tongue flaps are recommended whenever possible because of the high incidence of dehiscence associated with tongue flaps.
The split palatal U-flap can be used to repair acquired hard palatal defects located in the caudal hard palate.3 The edges of the palatal defect are debrided and a large U-shaped flap is created rostral to the defect. The major palatine arteries should be preserved during the creation of the U-flap. The U-flap is divided on the midline. One side of the U-flap is rotated 90 degrees into the defect and sutured in place. The second side of the U-flap is rotated 90 degrees and sutured to the previously rotated flap. The site from which the U-flap is harvested fills with granulation tissue and will be covered with epithelium in 4-8 weeks.
Ventral Approach to Nasal Cavity/Nasopharynx
The ventral approach to the nasal cavity or nasopharynx can be used in the removal of foreign bodies and in the treatment of nasopharyngeal stenosis and choanal atresia. The ventral approach to the nasal cavity has been previously described.4
A ventral approach to the nasopharynx is utilized primarily for increasing exposure of the nasopharynx as is needed in the treatment of nasopharyngeal stenosis in cats. The diagnosis and treatment of acquired nasopharyngeal stenosis in cats has been previously described.5,6 Cats with acquired nasopharyngeal stenosis usually present with a history of nasal obstruction of several months duration. The most significant clinical sign in these cats is stertorous breathing or wheezing upper respiratory noise. When the cat's mouth is held open the respiratory noise and distress are relieved indicating that the clinical signs are nasal in origin. Definitive diagnosis of nasopharyngeal stenosis is confirmed with a small-bore, flexible fiberoptic endoscope. The endoscope is placed dorsal to the caudal edge of the soft palate and directed rostrally. In normal cats the caudal nares are seen at approximately the level of the hard palate and form an ovoid orifice. In cats with acquired nasopharyngeal stenosis the caudal nares is reduced to a pinhole-sized orifice by the presence of a thin but tough membrane. Attempts to pass a thin catheter from the external nares through the ventral meatus on each side will be unsuccessful in cats with nasopharyngeal stenosis. The treatment of choice for acquired nasopharyngeal stenosis is surgery. The cat is placed in dorsal recumbency with the mouth taped open. A midline incision is made in the soft palate and the cut edges are retracted laterally. The stenotic nasopharyngeal opening is enlarged by carefully excising the abnormal membrane with a fine iris scissors, alternatively the abnormal tissue may be removed with laser surgery. The soft palate is sutured with 4-0 PDS in two layers.
The ventral approach to the nasal cavity has been utilized to remove ventrally located nonendoscopically retrievable foreign bodies, biopsy nasal tumors, and to attempt surgical correction of choanal atresia in the dog.7 A ventral rhinotomy for retrieval of a foreign body or for removal of choanal webbing is initiated by making a midline incision in the palatal mucoperiosteum from the level of the second premolar through the rostral one-third of the soft palate. The mucoperiosteum is elevated from the midline with a periosteal elevator exposing the caudal aspect of the hard palate perserving the major palatine arteries as they exit through the major palatine foramina one cm palatal to the fourth premolars. A large round bur is used to remove a 1 centimeter wide by 2 centimeter long section of midline palatal bone to expose the caudal aspect of the nasal cavity. The foreign body or anomalous choanal atresia membrane is removed through the defect created in the hard palate. The rhinotomy is closed in two layers using 4-0 PDS in a simple continuous pattern in the nasal mucosa-submucosa and 3-0 PDS in a simple interrupted pattern for the nasal mucosa-submucosa layer. Removal of the anomalous choanal atresia membrane may result in nasopharyngeal stenosis from scar/stricture formation following surgery. The potential for development of this surgical complication may be decreased with laser surgery. Treatment of severe or recurrent nasal obstruction may be treated with permanent tracheostomy in symptomatic cases.
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3. Manfra Marretta S, Grove TK, Grillo JF. Split palatal U-flap: A new technique for repair of caudal hard palate defects. J Vet Dent 1991;8(1):5-8.
4. Nelson AW. Upper respiratory system. In: Slatter D, ed. Textbook of Small Animal Surgery, 2nd ed., Philadelphia: WB Saunders 1993:733-776.
5. Mitten RW. Nasopharyngeal stenosis in four cats. J Small Anim Pract, 29:341, 1988.
6. Mitten RW. Acquired nasopharyngeal stenosis in cats. In: Kirk RW, Bonagura JD, eds. Kirk's Current Veterinary Therapy XI, Philadelphia: WB Saunders, 1992:801-803.
7. Coolman BR, Manfra Marretta S, McKiernan BC, Zachary JF. Choanal atresia and secondary nasopharyngeal stenosis in a dog: a case report. J Am Anim Hosp Assoc 1997