When a dog or cat presents with a jaw fracture, trepidation often sets in—not unlike watching “Jaws” the movie. Ready to step into the waters of jaw fractures and symphyseal separations? We’ll hold off on temporomandibular joint fractures until “T” is for TMJ disease. For now, let’s embrace jaw anatomy, terminology and a few straightforward concepts.
The maxillary bones form the lateral parts of the face and the part of the hard palate that holds the canines and upper cheek teeth. The maxilla articulates with the incisive bone rostrally, the nasal bone dorsally, the vomer bone medially, and the lacrimal and zygomatic bones caudally.
The palatine bone forms the bony part of the hard palate together with the maxillary and incisive bones. The incisive bone located rostrally holds the upper incisors and forms about one-sixth of the hard palate.
The hard palate separates the oral and nasal cavities. The primary palate is the incisive portion of the palate and associated soft tissues. The secondary palate includes the remaining hard and soft palatal structures. Firmly attached heavily keratinized mucosa covers the hard palate.
The large bones articulating with the skull that support the lower teeth are the mandibles. Each mandible is composed of a horizontal body and a vertical ramus. The body supports the lower teeth. The ramus has three processes (coronoid, condylar and angular). The condylar process articulates with the cranium in the temporomandibular joint (TMJ). The mandibles are connected to each other by a strong fibrocartilaginous joint at the mandibular symphysis.
Jaw fracture pointers
Keep in mind that jaw fracture repair options include simple suturing, external fixation, plates and screws, elastics, interfragmentary wiring and acrylic splinting. But let’s look at some particulars.
• Generally, the lower jaw deviates toward the side of the fracture (Figures 1A and 1B).
• Determining whether the fracture is favorable or unfavorable is important in deciding which method of fixation is best. Attached jaw muscles either compress (favorable) or distract (unfavorable) the fractured segments.
Favorable mandible fractures run dorsocaudal to ventrocranial. These fractures compress because of the upward pulling of the masseter and temporalis muscles, and downward and caudal pulling of the digastricus. Stabilization of the tension surface may be all that is required for bony healing.
Unfavorable fractures run dorsocranial to ventrocaudal and distract the fracture fragments. The alveolar crestal bone is considered the tension surface, while the ventral cortex is considered the compression surface (Figure 2).
• Unless you’ve had advanced training, avoid plating jaw fractures for fear of compromising tooth roots. Also avoid placing intramedullary pins into the mandibular canal. The mandibular canal carries the neurovascular structures—it’s not an intramedullary canal.
• Removing teeth (or parts of teeth) in the fracture line is usually a good idea (Figures 3A-3C and 4A and 4B).
• For many minimally displaced jaw fractures, you can use a tape muzzle or loose-fitting commercial muzzle that allows for food lapping to stabilize the area.
• External fixators work well in many mandibular fractures (Figure 5).
• Mandibular symphyseal separations are not true fractures. The symphysis is a joint. If needed, the separation can be stabilized with suture, wire or light cured composite (6A-6I).
• Midline maxillary fractures without displacement often only need to be sutured (Figures 7A-7C).
• Maxillary fractures with displacement often need much more then suturing the tissues overlying the hard palate (Figures 8A-8D).
Time to stop jawing and start doing!
Jaw fractures don’t have to be overwhelming when you concentrate on creating a stable means of fixation to maintain alignment and quick return to function. Feel free to contact your local veterinary dentist (avdc.org) for help.