Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
Introduction
Mandibular fractures in small animals are a common occurrence in veterinary practice. The frequency varies between the species. Surveys conducted showed that mandibular fractures in dogs make up 1.5 to 2.5% of all fractures, whereas in the cat this figure varies between 11.5% and 23.1%.1,2 The higher incidence in cats is related to the fact that they present with a high percentage of symphyseal separation (fracture), usually due to "high-rise syndrome."1 Fractures occur most commonly in both species in the age group less than 1 year of age and small to medium-breed dogs.3 The mandibular molar is the site of most fractures in the dog.3 In both species, automobile trauma accounts for the majority of fractures;1,2,4 however, in a recent South African study, dog bites accounted for the majority of jaw fractures3. "High-rise syndrome" (HRS) in cats and dog fights in dogs are the next most common reasons for mandibular fractures, respectively. A high percentage of iatrogenic mandibular fractures also occur during dental procedures.
Fracture Biology
Most mandibular fractures are open to either the oral cavity or the skin. The anatomical location of fractures differs between the species. In the dog, fractures are most common in the premolar region followed by the molar region and then the symphysis. In cats they occur most commonly in the symphysis and then the premolar/molar region.1,2,4 Kitshoff et al. in the South African study however showed that the most common site for jaw fractures in their study was the mandibular first molar.5
The two main forces acting on the mandible are the digastric muscle opening the jaw and the masseter and other masticatory muscles which close the jaw. The tension surface of the mandible is at the gingival border (oral) and the compression side is at the ventral border (aboral).6 Stable fractures are those where minimal displacement has taken place, and the forces acting on the fracture line force the fracture line closed. Unstable fractures tend to displace when masticatory muscles contract.
Initial Fracture Site Evaluation/Treatment
The initial fracture site evaluation may only be a very cursory one where the animal is not even sedated, depending on the other injuries sustained during the trauma. As soon as it is possible a thorough evaluation of the oral cavity under general anaesthesia or at least a heavy sedation should be performed. This will frequently include skull radiographs and/or dental radiographs and/or skull computed tomography (CT) scans. In acute fractures I will attempt repair under this anaesthetic opportunity; however, if the fracture is due to an infectious process (osteomyelitis or periodontitis), I will only do extractions, curettage and soft-tissue closure initially. The patient is then maintained in a canvas muzzle until results from cultures etc. have been received and the appropriate antimicrobial drugs started.
Non-Invasive Fracture Repair Techniques
|
Tape/canvas muzzle2
|
|
Indication
|
Tape muzzles be used as temporary, definitive or adjunctive therapy. This is a good method in cases of pathological fractures or where the bone is very porous and will not support a fixative device. Where fractures are stable this is also a good technique.
|
|
Advantages
|
Will not disrupt blood supply and does not require the presence of teeth.
|
|
Disadvantages
|
Movement occurs at the fracture site, therefore not indicated with unstable fractures. There is an increased risk of pneumonia due to syringe feeding these patients and inadvertently feeding down the trachea. Due to the fact that the animal cannot open its mouth, the capacity to exchange heat is reduced due to restriction of panting. The latter is the reason why this technique is contraindicated in brachycephalic breeds. Food and water accumulation on the muzzle can increase the risk of dermatitis around the face.
|
|
Circumferential wiring7
|
|
Indication
|
Symphyseal separations and oblique stable fractures.
|
|
Advantages
|
Wire or thick nylon may be used depending on the species. This technique may also be combined with the indirect acrylic method in areas where teeth were lost.
|
|
Disadvantages
|
Increased risk of damage to healthy tissue, malocclusion if wire is too tight.
|
|
Interarcade bonding8
|
|
Indication
|
Stable or unstable fractures of dentate areas and caudal mandible.
|
|
Advantages
|
No disruption of blood supply to fracture segments. With proper application the acrylic device does not interfere with occlusion. Acrylic/composite can be applied directly to the teeth (bonded) or indirectly by stabilising interdental wires or as a mould that can be fixed perimandibularly. Canine to canine fixation can be used for symphyseal separations and other stable fractures.
|
|
Disadvantages
|
Dentition is a prerequisite. Food can get trapped under the device and can lead to increased gingivitis/periodontitis. Excessive salivation and improper grooming may lead to increased risk of dermatitis. As the patients are unable to masticate, the owner care increases. Acrylic/composite failure can occur if the animal bumps the jaw. Extra instrumentation is needed if light cure acrylic/composite is used.
|
|
Reinforced interdental wiring techniques5,9
|
|
Indication
|
To act as a temporary means of stabilising the fracture before a definitive repair is performed.
|
|
Advantages
|
Inexpensive technique that acts at the tension surface and can combine with other techniques. It does not disturb local blood supply.
|
|
Disadvantages
|
Due to the conical shape of carnivore teeth and the lack of a prominent tooth neck, these wires are difficult to place and maintain in place. Notching the teeth can help to overcome this problem but this damages the teeth. This technique requires intact dentition.
|
Care and Removal of Non-Invasive Oral Devices
Since we are placing devices either around or in the mouth, the owner involvement with these patients increases significantly.
Canvas Muzzles
Muzzles should be removed - after eating - and washed. At the same time, owners should clean the face of the dog with water, dry it, and replace with a dry muzzle. I therefore dispense 2 canvas muzzles with each patient. I have found this the best method of keeping the perioral areas clean and dry, therefore preventing complications like perioral skin infections.
Intraoral Devices
Where these devices have been placed, I dispense a chlorhexidine-containing oral rinse to flush into the oral cavity daily. Owners are also motivated to improve oral hygiene (toothbrushing) in order to remove plaque efficiently. Any intraoral device will increase the retentive areas for plaque and can increase the risk for periodontitis.
Once the desired effect has been reached, extreme care should be taken when removing the intraoral devices. Since they are attached to underlying teeth, sections should be made interdental to prevent cutting healthy teeth when the device is being removed. Composite that is attached to the teeth after removal can be removed using extraction forceps and any remainder should be ultrasonically removed or smoothed with a white Arkansas stone.
Complications10
Malocclusion, osteomyelitis, delayed or nonunion, malunion, soft-tissue infection, and appliance failure are all complications commonly seen. Infections occur significantly less frequently in cases where antimicrobial treatment was started perioperatively and continued for a period of 5–7 days. Antimicrobials should be broad-spectrum to cover the variety of bacteria present in the oral cavity.
References
1. Umphlet RC, Johnson AL. Mandibular fractures in the cat. A retrospective study. Veterinary Surgery. 1988;17(6):333–337.
2. Umphlet RC, Johnson AL. Mandibular fractures in the dog. A retrospective study of 157 cases. Veterinary Surgery. 1990;19(4):272–275.
3. Kitshoff AM, de Rooster H, Ferreira SM, Steenkamp G. A retrospective study of 109 dogs with mandibular fractures. Veterinary and Comparative Orthopaedics and Traumatology. 2013;26(1):1–5.
4. Lopes FM, Gioso MA, Ferro DG, Leon-Roman MA, Venturini MA, Correa HL. Oral fractures in dogs of Brazil - a retrospective study. Journal of Veterinary Dentistry. 2005;22(2):86–90.
5. Kitshoff AM, de Rooster H, Ferreira SM, Burger D, Steenkamp G. The comparative biomechanics of the reinforced interdental crossover and the Stout loop composite splints for mandibular fracture repair in dogs. Veterinary and Comparative Orthopaedics and Traumatology. 2013;26(6):461–468.
6. Boudrieau RJ, Verstraete FJM. Principles of maxillofacial trauma repair. In: Verstraete FJM, Lommer MJ, eds. Oral and Maxillofacial Surgery in Dogs and Cats. Chapter 25. 1st ed. Edinburgh, UK: Saunders Elsevier; 2012: 233–242.
7. Matis U, Köstlin R. Symphyseal separation and fractures involving the incisive region. In: Verstraete FJM, Lommer M, eds. Oral and Maxillofacial Surgery in Dogs and Cats. Chapter 28. 1st ed. Edinburgh, UK: Saunders Elsevier; 2012: 265–274.
8. Zacher AM, Marretta SM. Oral and maxillofacial surgery in dogs and cats. The Veterinary Clinics of North America Small Animal Practice. 2013;43(3):609–649.
9. Legendre L. Intraoral acrylic splints for maxillofacial fracture repair. Journal of Veterinary Dentistry. 2003;20(2):70–78.
10. Manfra Marretta S, Schrader SC, Matthiesen DT. Problems associated with the management and treatment of jaw fractures. Problems in Veterinary Medicine. 1990;2(1):220–247.