Mandibular fracture

What it is

Mandibular fractures account for a significant share of fractures of the head in the dog and are more common than maxillary fractures. They are often open to the oral cavity. Most result from trauma (vehicle accidents, falls, kicks, bites). In small and toy breeds, severe periodontal disease destroys the alveolar bone around the roots of the teeth and leaves the mandible so thin that it may break with minimal force, including during extraction of a tooth (pathological fracture).

Who it affects

Dogs of any age and breed after trauma. Pathological fractures are typical of older toy and small breeds (Yorkshire terrier, Chihuahua, toy poodle, Maltese) with advanced periodontitis.

Anatomy involved

Each half of the mandible has a body, which carries the teeth, and a ramus, with the coronoid process (insertion of the temporalis), the condylar process (temporomandibular joint) and the angular process. The two halves are joined rostrally by the mandibular symphysis, a fibrocartilaginous joint that normally does not ossify in the dog. Inside the body runs the mandibular canal, with the inferior alveolar artery, vein and nerve, which leave through the mental foramina. In small dogs the roots of the mandibular first molar occupy most of the height of the body, so this is a weak point and a frequent site of pathological fracture. The alveolar (oral) border is the tension side of the bone.

Clinical signs

Malocclusion, inability to close the mouth, mandibular asymmetry, drooling with blood, pain, crepitus on palpation, reluctance to eat and halitosis in open or chronic fractures.

Diagnosis

• Evaluation of the trauma patient first: thorax, neurological status, other injuries.
• Oral examination under general anaesthesia, checking occlusion and the teeth in the fracture line.
• Intraoral dental radiographs and, ideally, CT of the head, which avoids the superimposition of skull radiographs and shows fractures of the ramus and temporomandibular joint.

Treatment

The priority is to restore normal occlusion, so the jaw must be reduced with the teeth in their normal relationship. Options include a tape muzzle for minimally displaced fractures, interdental wiring with an intraoral acrylic or composite splint, intraosseous wiring, miniplates and external fixators. Implants must avoid the tooth roots and the mandibular canal. Teeth in the fracture line are kept if they are healthy and stabilise the fragments, and extracted if they are loose or periodontally diseased. Pathological fractures heal poorly and need treatment of the periodontal disease; in some cases partial mandibulectomy is an option. A feeding tube may be needed while the fracture heals.

In the cat

In the cat mandibular fractures are caused mainly by falls from height, road traffic accidents and fights. The most common injury is mandibular symphyseal separation, part of high-rise syndrome together with fracture of the hard palate. Fractures of the ramus, the condylar process and the temporomandibular joint are also common; temporomandibular joint injuries are usually unilateral, and bilateral ones are more typical of falls from height.

The feline mandible is small and the roots of the canine teeth take up much of its rostral part, so little bone is left for implants. The most used techniques are:

• Circumferential cerclage wire around the mandible, caudal to the canines, for symphyseal separation; it is removed once the symphysis has stabilised.
• Maxillomandibular fixation with composite or acrylic bonding the upper and lower canines, leaving the mouth slightly open so the cat can lap soft food; useful in caudal and temporomandibular joint fractures.
• Intraoral splints, miniplates or external fixators for fractures of the body.

An oesophagostomy tube is almost always placed to feed the cat while the fracture heals. Pathological fractures from periodontal disease are less common than in small dogs, but can be associated with tooth resorption and oral tumours such as squamous cell carcinoma.

Key studies in the cat

• Knight and Meeson (2019), CT of 75 cats with skull fractures. 89% had fractures in several bones, mostly of the mandible, upper jaw and craniofacial region, and 56% had temporomandibular joint injuries. Road traffic accidents caused 89% of cases and were associated with ocular, neurological and thoracic injuries. Half were managed without surgery; mortality was 8%, complications occurred in 22% and occlusion problems after treatment were uncommon.
• Mestrinho et al. (2022), CT of 158 temporomandibular joints in 79 cats from six centres. 70.9% of injuries were unilateral. The mandibular condyle was fractured in 55.7% of joints, mostly intra-articular and through its medial half, and 32.9% of cats had a luxation, mostly rostrodorsal. Bilateral injuries were 13.1 times more likely after falls from height.
• Evenhuis et al. (2025), 109 cats with mandibular trauma. The sites most often injured were the symphysis (55.0%), the condylar process (49.5%) and the mid ramus (48.6%). Open reduction and internal fixation healed better than maxillomandibular fixation and left less persistent malocclusion (9.1% versus 53.9%). An oesophagostomy tube did not change weight trends, and 94.5% of cats survived. Treatment was not randomised.