Palatine defects are very challenging to treat and create a lot of morbidity for the patient. Defects arise from failure of midline fusion or congenital absence of the palate, or may result from trauma after falls, motor vehicle accidents or dogfights. Removal of teeth or oral tumours can result in oronasal fistulae. Food and other debris such as vegetable material lodges in the nasal cavity or nasopharynx, causing immediate irritation and sneezing. Chronic inflammation of the nasal passages leads to halitosis and infection of the nasal turbinates. Nasal regurgitation of food and liquids is uncomfortable for the patient and leads to chronic changes including hyperplasia of lymphoid tissue. Otitis media may be seen if obstruction to the Eustachian tube occurs. Upper respiratory obstruction as a result of chronic rhinitis can complicate the situation by generating excessive negative inspiratory pressure, putting stress on any surgical repair as animals may breathe primarily through the fistula. Attempts to breathe exclusively through the nose after repair of the fistula may concentrate forces upon the suture lines, contributing to wound breakdown. Placement of a gastrostomy tube is beneficial in some animals as it ensures appropriate nutrition and delivery of medications while reducing mechanical trauma to the palate.

The surgical closure of oronasal fistulae can be frustrating and recurrence of fistulae, in some cases weeks after the surgical repair, is common. Local tissue is usually inelastic and may be scarred from previous surgeries. The tissues may be poorly vascularised and tension at the site of wound closure may result in breakdown of the repair.

Traditionally, two-layer closure is attempted to avoid leaving suture lines directly over the fistula. This usually requires the use of mucoperiosteal flaps, based where possible on the major palatine arteries. Tissues used in the repair must have a good blood supply and the suture line should be under minimal tension. In some cases, distant tissues are utilised, including corticocancellous grafts. A variety of silicone or acrylic obturators have also been described. A silicone nasal septal button, trimmed to size, can be used for short- or long-term management of fistulae if surgery is not feasible or must be delayed.

Auricular Cartilage Grafts

Ear cartilage was first used to repair a palatal fistula in a 7-year-old boy and has been used extensively in human patients since then. Cartilage from the pinna or the external ear canal has recently been reported for repair of palatine fistulae in five cats.

Surgical Technique

The pinna or external ear canal may be used:

 Pinna: the pinna is prepared for aseptic surgery and a skin incision made over the outer (caudal) surface of the pinna. A round piece of cartilage is excised, leaving the rostral skin and surrounding cartilage intact and therefore not affecting the cosmetic appearance of the pinna.

 Vertical ear canal: after aseptic preparation, the lateral two-thirds of the vertical ear canal is excised. The mucosa of the horizontal ear canal is sutured to the skin using single interrupted sutures (1 metric polyglycolic acid). The cartilaginous tube of the vertical ear canal is unfolded to produce a flat square ~1.5 x 1.5 cm and as much of the mucosa of the ear canal as possible is removed by sharp scissor dissection.

The oronasal fistula is prepared to accept the graft by separating the oral and nasal mucosa around the defect, creating a 2-5 mm pocket for the graft edges. The cartilage is positioned with its original inner surface (with small amounts of remaining epithelium in the case of ear canal cartilage) facing dorsally into the nasal cavity, and the external surface (from which the skin has been elevated before excision) facing into the mouth. It is secured at each corner and midway between each corner using vertical mattress sutures (2 metric polydioxanone). The cartilage graft completely closes the oronasal fistula. Local mucosal flaps are created to cover as much of the cartilage graft as possible.

The success of this technique is dependent on the conchal graft providing a scaffold upon which granulation and re-epithelialisation of the oral and nasal side can take place, as well as support for local mucoperiosteal flaps. The graft presumably acquires a vascular supply from the surrounding tissue and becomes incorporated into the healing local tissues.

Not only is the technique relatively simple, it involves little tissue dissection and is not dependent on vascularity and elasticity of local tissues, unlike conventional techniques. Because of the relatively limited local trauma, delays between surgical attempts should not be required if initial repairs fail. In cases with large fistulae, the graft should be covered with a local mucoperiosteal flap. Full coverage of the conchal graft is, however, not required for the technique to be successful.

References

1.  Coles BH, Underwood LC. Repair of the traumatic oronasal fistula in the cat with a prosthetic acrylic implant. Veterinary Record, 1988; 122: 359-360.

2.  Cox CL, Hunt GB, Cadier MM. Repair of oronasal fistulae using auricular cartilage grafts in 5 cats. Veterinary Surgery, 2006; 35: 284-286

3.  De Souza HJ, Amorim FV, et al. Management of the traumatic oronasal fistula in the cat with a conical silastic prosthetic device. Journal of Feline Medicine and Surgery, 2005; 7: 129-133

4.  Matsuo K, Kiyono M, Hirose A. Simple technique for closure of a palatal fistula using conchal cartilage graft. Plastic Reconstructive Surgery, 1991; 88: 334-337