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.