Pubic Symphysis Diastasis

Figure 1. Diagram of the canine mandible. Adapted from Evans HE: Miller’s Anatomy of the Dog, 3rd edition. ©1993

In healthy dogs and cats, a substantial amount of force (trauma) is necessary to cause a fracture of the mandible (lower jaw). A fracture refers to a disruption of bone continuity and may range from a greenstick fracture (an incomplete break) to severe comminution, where the bone is fragmented into multiple pieces. Trauma related to motor vehicles is the most frequent cause of mandibular fractures.

Because mandibular (lower jaw), maxillary (upper jaw), or skull fractures are usually associated with high-energy trauma, injuries are often not confined to the facial area alone. As a result, pets frequently require evaluation and treatment of other traumatic injuries before definitive repair of the jaw fracture can be undertaken. Your primary veterinarian may therefore recommend radiographic evaluation of additional body regions prior to focusing specifically on the mandible.

Thoracic (chest) injuries commonly occur concurrently and may include pulmonary contusions (bruising of lung tissue), pneumothorax (air leakage due to lung puncture), diaphragmatic hernia, and traumatic myocarditis (cardiac bruising leading to arrhythmias). A thorough whole-body assessment is essential, as these associated injuries may be immediately life-threatening.

In some instances, no traumatic event is reported. Under these circumstances, a pathologic fracture—one resulting from underlying disease—must be considered. Conditions such as advanced dental or jaw bone disease and neoplasia can weaken the mandible and predispose it to fracture. Pathologic fractures are more frequently observed in older animals compared with younger ones.

The mandible and maxilla possess unique anatomic characteristics that make fracture management more complex than fractures elsewhere in the skeleton. The mandible consists of two bones joined at the midline by a symphysis, which is a non-movable joint (Figure 1). Tooth roots, nerves, blood vessels, and salivary ducts are located within or adjacent to the mandible, and these structures are often injured concurrently with mandibular fractures.

Figure 2. Dog presented for treatment of a mandibular fracture following an encounter with a bull. The fracture is located just caudal to the canine teeth. Notice the oral bleeding, persistently open mouth, and exposed canine tooth roots.

Clinical signs associated with mandibular fractures include:

• reluctance or refusal to eat
• bleeding from the oral cavity
• abnormal alignment of the jaw
• wounds around the mouth, localized pain and swelling, and a persistently open mouth
• excessive drooling, which may contain blood (Figure 2)

Figure 3. Preoperative radiographs of a dog showing concurrent symphyseal separation (A) and a mandibular body fracture (B).

Due to the pain associated with mandibular fractures, your veterinarian may recommend sedation or general anesthesia prior to palpation of the affected area and further diagnostic procedures. Because the mandible is covered by minimal soft tissue, these fractures are frequently open. An open fracture is defined as a fracture in which the protective soft tissue envelope surrounding the bone has been disrupted, exposing the fractured bone ends to the external environment (Figure 2).

Once your pet is deemed stable enough to proceed with evaluation of the jaw injury, radiographs of the mandible are recommended to confirm the fracture and assist in treatment planning (Figure 3). Owing to the complex anatomy of the mandible, dentition, and skull, radiographs are typically obtained under heavy sedation or general anesthesia to minimize stress and allow accurate positioning. In certain cases, computed tomography (CT or “CAT” scan) may be advised to better define the anatomy and facilitate optimal surgical planning.

Figure 4. Internal fracture reduction and stabilization using a bone plate and screws. Adapted from Fossum TW et al: Small Animal Surgery, 3rd edition. ©2007

Figure 5. Application of external skeletal fixation (ESF) for comminuted mandibular fractures. Upper images depict linear ESF constructs, while lower images demonstrate pin fixation connected with acrylic material. From Fossum TW et al: Small Animal Surgery, 3rd edition. ©2007

External immobilization may be applied in certain cases. Reduction refers to the manipulation of bone fragments into proper alignment to reduce pain and improve healing. External immobilization typically consists of a muzzle, either custom-made using medical tape or a commercially available device. In select cases, this method alone is sufficient for treatment.

Surgical management is recommended when mandibular fractures are unstable, involve multiple fragments, or affect both sides of the mandible. The goals of surgery include restoration of normal dental occlusion (scissor-like contact of the teeth), improved comfort and cosmetic appearance, and rapid return to normal jaw function.

Several surgical techniques are available for treating mandibular fractures. A board-certified veterinary surgeon (Diplomate of the American College of Veterinary Surgeons) or a veterinary dentist (Diplomate of the American Veterinary Dental College) will determine the most appropriate approach. One commonly used method is internal reduction and stabilization with bone plates and screws (Figure 4). This technique involves surgically exposing the fracture, realigning the bone segments, and securing them with a plate and screws. Benefits include early functional recovery and reduced postoperative management compared with other methods.

Another option is external skeletal fixation (ESF) (Figure 5). This technique involves inserting pins through the skin into the bone fragments and connecting them externally with a rigid bar to maintain stability during healing. Most of the fixation apparatus remains outside the body, requiring some postoperative care. Advantages include less invasive placement and complete removal of implants after healing.

Additional techniques include intraoral splints, interosseous or interfragmentary wiring, interdental wiring, and interarcade wiring (Figures 6a, 6b, 6c). Veterinary dentists may offer further specialized treatment options. In some cases, placement of a feeding tube may be recommended to ensure adequate nutrition during healing.

Potential complications following mandibular fracture treatment include:

• dental malocclusion
• infection
• delayed or incomplete bone healing
• nonunion (failure of bone healing)

Dental malocclusion is the most frequently reported complication and may result in temporomandibular joint dysfunction, excessive tooth wear, trauma to oral soft tissues, periodontal disease, pain, and difficulty eating. Once malocclusion develops, correction can be challenging.

Analgesic medications are routinely prescribed after treatment. Many veterinarians also recommend non-steroidal anti-inflammatory drugs (NSAIDs) formulated specifically for dogs or cats. Antibiotics are commonly prescribed due to the high incidence of open fractures.

Pets should be prevented from playing with toys, interacting roughly with other animals, chewing bones, or engaging in activities that place stress on the healing fracture. When external immobilization is used, regular inspection of the muzzle area is advised to detect irritation or food accumulation, as dermatitis is common. For pets with restricted jaw movement, physical activity should be limited, and outdoor exposure should occur during cooler times of day. Dogs rely on panting for thermoregulation, and restricted mouth opening can rapidly lead to overheating.

Dietary modification is recommended during recovery. Pets fed dry kibble may benefit from a softened diet or from soaking kibble in warm water prior to feeding. This reduces stress on healing bone and minimizes trauma to oral soft tissues. For pets with feeding tubes, detailed instructions regarding tube care and feeding will be provided.

When intraoral splints or wiring techniques are used, food debris may accumulate, and gentle oral flushing may be recommended to maintain cleanliness. If external skeletal fixation is employed, the fixation apparatus may require regular cleaning and, in some cases, bandaging with routine bandage changes.

The overall prognosis is generally excellent when complications are avoided. However, as noted, malocclusion may necessitate additional procedures such as tooth reconstruction or extraction.