Introduction

Oronasal fistulae are most commonly seen with maxillary bone loss secondary to extraction of maxillary canine teeth, or to severe periodontal disease. They can also be the consequence of cleft palate repair, or different types of trauma (fall, electrical, surgical, radiation therapy, etc.).^1,2 Several methods have been used to correct these defects with variable success rates: single- or double-layer mucoperiosteal flap techniques, free tissue graft (allograft), use of synthetic or natural (xenograft) tissue or bone regeneration material, and permanent or removable obturator.^1-6

Method

Single-layer technique is by far the most commonly employed technique. A mucogingival flap is elevated, the affected area is debrided, the periosteum is fenestrated to release the tension, the flap is sutured closed carefully, simple. The main problems surgeons encounter are: 1) Flap is too small resulting in sutures being on top of the hole and dehiscing. 2) Tension is still present when suturing the flap and repair fails in the next 5 to 7 days.

Now, if the single-layer technique is performed proficiently, it succeeds in over 90% of the cases. When it fails, you are now faced with a recurrent fistula. The first thing to do is try to figure out why it failed. It may be due to surgical deficiency (most common), or to some other factor such as necrotic tissue left behind, bone sequestrum in the nasal passages, lack of bony support in the area.

Several techniques were designed to deal with recidivist fistulae.

Double layer technique. A mucogingival flap similar to the one used in the single-layer technique is created. The edges of the bone defect are debrided. A palatal flap is elevated. It cuts through the palatine artery and thus will require careful ligation. The palatal tissue is flipped over the defect and sutured to the bony edge through preset holes. The mucogingival flap is then mobilized to cover, without tension, the fistula and the defect created by the palatal flap. In other words, the mucogingival flap now has to cover twice the area it would have with the single-layer technique. The main advantage of this technique is that it covers the hole with two layers instead of one. It also provides palatal epithelium facing the nasal cavity and mucosal epithelium facing the oral cavity. Its greatest disadvantage is doubling the size of the defect, making the elevation of the mucogingival flap much more difficult. For that reason, it is the author's least favourite.

Recently, the use of auricular cartilage for oronasal fistula (ONF) repairs has been reported in both human and veterinary literature. On the veterinary side, three studies are of particular interest to us. In the first, auricular cartilage (pinna and annular) grafts were used on five cats, resulting in 5 out of 5 successful ONF repairs (1 cat, however, required a second graft after the first was dislodged).⁷ The second study, involving 33 rabbits with 2 to 3 mm ONF, demonstrated that after one year, only 25% of the rabbits in the group without surgery had healed, compared to a 96% (24 out of 25) success rate of healing in the group with autograft repair. The same group applied the technique on the human side with a 91.7% (22 out of 24) success rate and were able to conclude that the surgery was simple and reliable.⁸ More recently, in 2009, the same procedure using auricular cartilage was attempted in a dog with success.⁹

Procedure

Prior to proceeding with the surgery, it is important to obtain two radiographic views of the affected area to ascertain that there is no bone loss, bone growth, or bone lysis that could be attributable to other pathosis.⁶

Harvesting of the Auricular Cartilage

 The pinna is shaved on its dorsal aspect and an incision is made longitudinally on the skin parallel to the major blood vessels, with a no. 15 blade (the length of the incision depends on the size of the desired cartilage flap).

 The tissues are dissected in order to separate the skin and the subcutaneous mucosa from the cartilage. Once this is completed, a rectangular incision, larger in size than the defect to be covered, is made in the cartilage (Because cartilage does not shrink, the graft only needs to be a few millimeters larger, in all directions, to allow for placement of anchor sutures in the corners). One side is lifted and the rest of the cartilage is peeled off using the no. 15 blade. The cartilage graft is removed and placed on a piece of gauze generously humidified with physiological saline.

 The skin of the pinna is closed using poliglecaprone 5-0 in a subcuticular uninterrupted manner.

Repair of the Oronasal Fistula

 The edges of the defect are incised, debrided, and mobilized. The palatal mucosa is elevated from the periosteum by blunt dissection.

 The auricular cartilage graft is inserted in between the gingival mucosa and the bone of the maxilla and sutured in place with horizontal mattress sutures placed in its four corners using poliglecaprone 4-0.

 The gingival mucosa, on either side of the defect, is sutured together with inverted cross mattress sutures, in order to bury the knots, using poliglecaprone 4-0.

 The patient needs to be examined 7 to 10 days postoperatively to ensure that the surgical sites are healing properly. A further recheck visit 2 to 3 weeks later is also recommended to make sure that the fistula has not reopened.

Discussion

Several cases of ONF, varying from 10 mm to 22 mm in length and situated around the area of the maxillary canines, were included in this report. The patients were geriatric and had concomitant periodontal pathology. All the previous surgeries consisted of variations of the single-layer mucoperiosteal flap technique; except for one patient where polypropylene meshes were tried. In half of those cases, two previous surgical attempts had been made to repair the defects. In a few cases, only one surgical attempt was made before, while in others 3 or more attempts had been made. Over 95% of the ONFs healed completely, usually within two weeks (from 1 to 4) following the surgery. There was no complication or permanent deformation noted at the donor sites.

When dealing with oronasal fistula, it is recommended to try to repair the defect on the first surgical attempt. This minimizes interference with vascular supply, reduces time and cost associated with surgery, and more tissue is always available on the first procedure. In general, the standard flap techniques (simple or double) constitute a reasonably efficient way to achieve success. However, in refractory cases, the use of an auricular graft provides many advantages over other techniques. It offers a support for epithelialization, especially in the region where bone is lacking, such as the palatine fossae, or where it has been destroyed secondary to pathology. The technique is fairly simple and rapid, and with practice, one should be able to obtain the auricular cartilage graft within 20 to 30 minutes. The graft is harvested on the dorsal surface of the pinna through a single longitudinal incision; this allows easier access, easier surgical preparation, easier dissection of the cartilage, and does not damage possible ear tattoos. Moreover, the auricular cartilage can be custom fitted to the size of the wound and, in cases of bilateral defects, cartilage flaps can be harvested from both ears. Normally, the donor site heals without complication and does not leave permanent deformation of the pinna, preserving the esthetic of it. The use of auricular cartilage is also economical when compared to the cost of synthetic materials or xenografts. From the results obtained, we are able to conclude that the use of an auricular cartilage graft constitutes an excellent alternative for surgical repair of ONF when conventional methods are not successful. Very recently, a commercially produced lamellar bone membrane has become available and has proved useful in the repair of recurrent ONFs. The membrane is used in the same way as the auricular cartilage graft.

References

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2.  Kapatkin AS, Marretta SM, Schloss AJ. Problems associated with basic oral surgical techniques. Prob Vet Med. 1990;2(1)85–109.

3.  Holmstrom S, Frost P, Eisner E. Exodontics. Veterinary Dental Techniques for the Small Animal Practitioner. 2nd ed. Philadelphia, PA: Saunders; 1998.

4.  Gorrel C. Emergencies. In: Veterinary Dentistry for the General Practitioner. Philadelphia, PA: Saunders; 2004:131–155.

5.  Wiggs RB, Lobprise HB. Oral surgery. In: Veterinary Dentistry: Principles and Practice. Philadelphia, PA: Lippincott-Raven; 1997:232–258.

6.  Fossum TW. Surgery of the digestive system. In: Small Animal Surgery. St. Louis, MO: Mosby-Year Book, Inc; 1997;200–366.

7.  Cox CL, Hunt GB, Cadier MM. Repair of oronasal fistulae using auricular cartilage grafts in five cats. Vet Surg. 2007;36(2):164–169.

8.  Ohsumi N, Onizuka T, Ito Y. Use of a free conchal cartilage graft for closure of a palatal fistula: an experimental study and clinical application. Plast Reconstr Surg. 1993;91(3):433–440.

9.  Soukup JW, Snyder CJ, Gengler WR. Free auricular cartilage autograft for repair of an oronasal fistula in a dog. J Vet Dent. 26(2):86–95.