The main way for a jaw to fracture is by a traumatic insult (hit by car, a fall, fighting). However, there are instances called pathologic fractures where the jaw is weakened by another disease process, and can be broken with out any real trauma (eating for instance). The two most common causes are
advanced periodontal disease and malignant oral tumors.
There are numerous techniques for the fixation of jaw fractures. The type of fixation selected depends on the type of fracture as well as surgeons preference. This listing is a brief summary of techniques and is not complete or exhaustive. I have set it up as to the type of fracture and followed by the types of fixation available.
The most common type of fracture in the cat is a mandibular symphaseal separation. This is also seen not infrequently in the dog. The easiest way to fix this fracture is by
circum-mandibular wiring. This is done by placing a wire around both mandibles just behind the canines and tightening under the skin below the chin. If the jaw is still unstable a figure 8 wire can be placed around the canines in the mouth, or an acrylic splint can be placed to stabilize the separation further.
The most common type of fracture in a dog is a mandibular body fracture, although it is not uncommon in the cat either. There are numerous techniques that work for this type of fracture, but my favorite is an acrylic splint. This works by using the teeth to stabilize the fracture. A dental acrylic (similar to epoxy) is applied to the teeth in the involved area. This uses the teeth as the posts to hold the teeth in alignment. The advantage to this form of fixation is that it is relatively quick and is non-invasive, as the bone itself is not involved. In addition, removal does not require surgical removal, as it is removed by cutting the splint and removing with forceps. If the fracture is on one side, and fairly stable, a muzzle can be used to stabilize the jaw enough to allow healing. This is reserved for relatively stable fractures. Interdental (between the teeth) or interossues wiring can be used as well, depending on the type of fracture. Interdental wiring is more difficult in animals due to the fact that they do not have much of a neck to the tooth, and the wire can slide up when tightened. The interosseus wires are slightly more invasive, and will need to be surgically removed later. Bone plating is rarely used, due to the difficulty in avoiding the tooth roots with the fixation screws. However, it can be useful when there is a large bony defect. External fixation with pins in the bone attached to a bar outside the mouth can be used in these situations as well.
Fractures of the vertical ramus are fairly common in cats and also seen in dogs. They can often be managed with a soft muzzle since they muscles in the area will hold the jaw fairly stable. If this is not the case, then surgical fixations with plates or wires can be used, or if the fractured piece is small it can be removed.
Maxillary fractures are often stabile enough to be treated by suturing the soft tissues only. If additional stabilization is needed, an acrylic splint, interosseus or interdental wiring or external fixation can be used.
Pathologic fractures are very difficult to treat due to the fact that the bone is very diseased to begin with. Fractures from periodontal disease are usually treated by first extracting the offending tooth, and placing the patient in a soft muzzle. Unfortunately this usually only forms a fibrous and not a bony union. Another option following extraction is to attempt external fixation with pins and bone grafting material, this MAY work, but the prognosis is not good.
Comminuted fracture of the
left mandible in a dog.
Open reduction and osseous wiring avoiding the roots of the teeth in the above patient was used to repair this fracture providing excellent stability and quick return to function.
Severely comminuted maxillary fracture with extensive soft tissue and nasal cavity damage in a dog.
A combination of soft tissue imbrication, wires and acrylic splints were used to reconstruct the maxilla
Several weeks postoperatively the patient is fully functional and pain free