Oronasal communications may be the result of congenital bone defect, traumatic separation of bone, and resorption associated with dental diseases. Congenital and traumatic palatal defects are most of the time characterized by a midline (sagittal) defect. Communications of dental origins are located along the maxillary dental arch, most of the time at the level of the upper canine or fourth premolar teeth.
1. APPLIED ANATOMY
The hard palate is composed of paired bones fused on the midline. They are, from front to back, the incisive (premaxillary), maxillary, and palatine bones. Bones are covered by a thick mucoperiosteum. Most of the hard palate is made by the palatal shelves of the maxillary bone. Palatal congenital defects result from the lack of fusion of the palatal shelves of the maxillary bone during embryologic development. Traumatic palatal disjunction occurs most of the time at the level of the fusion between the two palatal shelves (sagittal palatal suture). Fracture of the maxillary or palatine bones may also occur.
2. PALATAL CLEFT
Congenital palatal defects may not be detected until the slow growth of one of the puppies is noticed. Associated problems (nasal discharge, aspiration pneumonia) may also be indicative of a cleft palate in a puppy. Some animals have trouble sucking. The more caudal the defect is, the more likely the dog is to develop nasal discharge and pneumonia. Owners/breeders should be informed of the potential inheritance of the condition. Secondary lesions (pneumonia) may jeopardize the prognosis and have to be treated with antibiotics early in the process. Young animals should be fed with a long nipple bringing the food into the oro-pharynx. Surgery must be delayed as much as possible to allow for more cranial growth. If possible, waiting until three to four months of age is advised. More than one surgery is likely, especially if performed at a young age. In young animals, fibroblastic activity associated with healing may disturb further facial/palatal growth.
Traumatic palatal defects mainly occur in cats that have sustained a “high-rise syndrome.” It may also occur in dogs following gunshot injuries and hunting injuries. Surgical repair is never an emergency in animals with severe maxillo-facial trauma. In cats with palatal disjunction, if the palatal shelves are not too spread apart following the injury, the vomer bone and nasal structures located underneath may help in retaining the blood clot and healing may occur whether or not sutures have been placed on the mucoperiosteum. The best treatment in this case is to wait a couple of weeks and to perform surgical repair only if needed.
Surgical repair of congenital and traumatic palatal defects can be performed using different techniques:
Surgical Techniques (Palatorrhaphy)
Usually, the palatal defect is closed with soft tissue. Palatal axial pattern flaps are used. Direct vascularisation of the flap is due to the major palatine artery exiting on the medial surface of the upper fourth premolar tooth. With congenital defects, no effort is made to create an osseous partition between the nasal and oral cavity, though techniques involving bone grafts have been described. With recent traumatic injuries, one can attempt to close the bony midline defect with intraosseous ligatures. The flap can be protected by an acrylic plate fixed on the upper teeth.
Modified Van Langenbeck or Veau-Wardill-Kilner Techniques
An incision is made on both parts along the cleft margin, parallel relaxing incisions are made along the dental arches on both side, and the mucoperiosteum is dissected from the palatal shelves until approximation over the cleft defect is possible. Care is taken not to sever the major palatine artery exiting on the palatal (internal) side of the upper fourth maxillary premolar tooth. The soft tissue are sutured in a watertight manner over the defect and allowed to heal. When possible, a two-layer closure is performed by suturing the nasal mucosa first. If it becomes necessary to free up more of the mucoperisoteum from the palatal shelves, additional transverse relaxing incisions can be made at the most rostral location of the cleft. This results in two large U-shaped pedicled grafts centered on the palatine artery. This enables the surgeon to completely mobilized the mucoperiosteum toward the midline and backwards. The disadvantage of these techniques is that the suture line is located above the bony defect, which is more likely to be associated with dehiscence. The advantage of the technique is that very little maxillary bone (hard palate) is left uncovered, decreasing the likelihood of abnormal facial growth or bone necrosis.
It consists in a double rotation flap technique based on the palatine artery. On one side, two transverse incisions are made at the most rostral and the most caudal extent of the cleft, and an incision is made along the dental arch allowing free dissection of the mucoperiosteum from the palatal shelf until the cleft is reached. Care is taken not to lacerate the mucoperiosteum at this level, as it will be used as the hinge for the rotation of the flap. On the other side, an incision is made along the cleft and the mucoperiosteum dissected over a few millimetres. The flap is rotated upside down and the free end is introduced under the mucoperiosteum on the other side of the cleft. Sutures are placed over the bony edge on this side of the cleft. By doing this, the connective surface of the flap, and the palatine artery, is exposed in the oral cavity. This technique gives very predictable results in various types of palatal clefts (congenital or traumatic). The side effect of the technique is that a large part of the palate is left exposed and heals by second intention within weeks. This type of healing on a large part of the hard palate could lead to abnormal palatal development in young animals.
3. ORONASAL FISTULA OF DENTAL ORIGIN
This type of defect occurs on the dental arch following bone destruction by periodontal disease. Small size dogs are mostly affected. Most commons locations are the canine tooth and the upper fourth premolar tooth. The tooth (teeth) responsible for the deep pocket must be extracted first. Granulation and necrotic tissue must be curetted. This does include nasal conchae whenever necessary. Closure of the defect is simply performed with a large triangular or trapezoidal muco-gingival flap. Horizontal incision of the periosteum on the inside surface of the flap is mandatory to help mobilizing the flap towards the defect. An incision is made on the opposite side of the defect and the mucoperiosteum is dissected over a few millimetres. Monofilament resorbable suture material is used to close the flap.
4. POST-OPERATIVE CARE
An E-collar is place to avoid scratching of the wound. Analgesics are given as needed. Soft food is given for a week and if needed, an oesophageal tube may be placed for nutrition. Healing of the wound can best be evaluated after 10 days.