How to Use an Allograft Membrane to Fix Oral Trauma

A case study.

Originally published in the December 2015 issue of Veterinary Practice News. Did you enjoy this article? Then subscribe today!

Halo, an 8-week-old female pit bull mix, was presented as a referral to the Dentistry and Oral Surgery Department at North-Star VETS. Halo had been attacked by an adult pit bull, suffering injuries to her head and face.

She was stabilized at a specialty hospital and sent to me for evaluation of fractures of her right maxilla and hard palate. A physical exam revealed normal findings except for mucoid discharge from the right nostril, sneezing and puncture wounds over the right muzzle. Halo refused a conscious oral examination.

Figure 2: Initial suture placement of an allograft bone membrane before trimming the membrane to a size slightly larger than the size of the defect

John Lewis, VMD, FAVD, Dipl. AVDC

Figure 2: Initial suture placement of an allograft bone membrane before trimming the membrane to a size slightly larger than the size of the defect

After preoperative CBC and chemistry screen proved to be unremarkable, Halo was placed under anesthesia for an oral examination. It revealed a defect of the palatine process of the maxilla and a large defect of the palatal soft tissue that should cover the hard palate (Figure 1)

A right midmaxilla fracture extended through the furcation of the right maxillary deciduous second premolar tooth (tooth 506). Teeth 604 and 606 were fractured and 504 was discolored.

Imaging 

A CT scan showed multiple maxillary fractures exhibiting sharp margins and moderate displacement. The left half of the nasal bone contained a fracture resulting in ventral displacement of the rostral portion of the bone into the nasal cavity.

In the right side of the maxilla, a large segmental fracture was present just cranial to the canine tooth (tooth 504), extending caudally to the level of tooth 506. Immediately caudal to the palatine fissures, the hard palate contained multiple fractures, which resulted in a communicating hole between the oral and nasal cavities.

Figure 3: Bone membrane sutured in place.

John Lewis, VMD, FAVD, Dipl. AVDC

Figure 3: Bone membrane sutured in place.

Treatment

The displaced left nasal bone was reduced in a closed fashion by inserting an instrument into the left nostril and levering the displaced bone dorsally. Puncture wounds of the skin were debrided and lavaged.

The soft tissue over the right lateral maxillary fracture site was closed after removing tooth 506, but there was not sufficient soft tissue to close the palatal defect. Recruiting soft tissue from the adjacent hard palate was considered, but due to the comminuted fractures in these areas, there were concerns about raising flaps in this area.

A buccal mucosal flap was considered, but since the adult teeth still needed to erupt, this was not pursued. Instead, an allograft bone membrane (Ossiflex, Veterinary Transplant Services) was utilized to encourage mucosa adjacent to the defect to migrate across the defect, with the plan to close any residual defect when the patient was older and larger.

Free-floating bone was removed from the defect, and the area was debrided and lavaged. The palatal mucosa was undermined around the defect and edges were freshened. Rigid fixation of the segmental right maxillary fracture was not pursued due to degree of displacement and age of the patient. A 2-by-3-centimeter allograft bone membrane was tucked between the bone surrounding the palatal defect and the edges of the soft tissue defect (Figure 2)

The membrane was trimmed to size and sutured in place with multiple securing mattress and simple interrupted sutures (Figure 3). An esophagostomy tube was placed to allow for minimally invasive feeding and administration of medications. 

Follow-up 

Halo was re-examined 10 days after the procedure. A sedated oral examination revealed a nice bed of granulation tissue over a large portion of the defect. A piece of plant material was retrieved from a central area of the granulation bed. The esophagostomy tube site was clean and its bandage was changed.

Figure 4: The hard palate 3½ months after placement of the bone membrane. A 3-millimeter defect remains, which may require closure in the future. The right maxillary canine, first premolar and second premolar teeth have not erupted, and some evidence exists of developmental abnormalities of the right maxillary incisors that may require further treatment.

John Lewis, VMD, FAVD, Dipl. AVDC

Figure 4: The hard palate 3½ months after placement of the bone membrane. A 3-millimeter defect remains, which may require closure in the future. The right maxillary canine, first premolar and second premolar teeth have not erupted, and some evidence exists of developmental abnormalities of the right maxillary incisors that may require further treatment.

Twenty-five days after the procedure, Halo presented for another scheduled re-examination. The previously seen bed of granulation tissue had been replaced by epithelium, with only a small 3-millimeter area of residual communication between the mouth and the nose.

The site was rechecked 14 weeks postoperatively and the palatal defect was still 3 millimeters in diameter. Teeth in the area of the trauma showed evidence of developmental abnormalities (lack of normal formation and eruption, enamel hypoplasia) that will likely require further treatment in the future (Figure 4)

A New Technology 

Canine and equine allograft bone membranes are available for a variety of uses, including providing scaffolding for palatal defect repairs. Often, a mucosal flap will be placed over the membrane if used for palate defects.

However, in this case, due to issues with the surrounding available tissue, only the bone membrane was used as a barrier to the nasal cavity and encouraged re-epithelialization of palatal mucosa to reduce the size of the defect as the underlying maxillary fractures healed. The degree of epithelialization obtained with this technique was impressive.

Similar results have been obtained with use of auricular cartilage autografts in dogs and cats,1-2 though use of the bone membrane prevents the need for harvesting the autograft. Though further treatment may be necessary to repair the small remaining palate defect and address dental issues from the prior trauma, Halo shows no signs of nasal discharge and is eating and drinking well with only occasional sneezing. 

References

1. Cox CL, Hunt GB, Cadier MM. Repair of oronasal fistulae using auricular cartilage grafts in five cats. Veterinary Surgery 36: 164-169, 2007. 

2. Soukup JW, Synder CJ, Gengler WR. Free auricular cartilage autograft for repair of an oronasal fistula in a dog. J Vet Dent 26(2): 86-95, 2009. 

 

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