Mandibular Fracture - Horse
Introduction
Mandibular fractures often occur when animals catch their lower jaw for example on wire fencing, the rings on the stable walls or under a manger. Normally the rostral mandible is avulsed as they try to free themselves by pulling backward. Fractures can also occur in the ramus of the mandible, however these are much less common.
Signalment
It is most common in young animals, particularly horses.
Clinical Signs
The horse usually presents with a history of inappetance. Clinical signs include dysphagia, halitosis, salivation, oral haemorrhage, crepitus, abnormal incisor occlusion and discharging-tracts.
The fracture can be visualised on oral exam; it is normally open and located in the rostral mandible, caudal to the incisor teeth (with or without involving the incisors). This avulsion fracture can be unilateral or bilateral. Soft tissue structures adjacent to the fracture may also be damaged. Care should be taken when using a gag as this may displace the fracture.
Diagnosis
Diagnosis should be achievable from clinical signs alone, however radiography is a useful ancillary test - multiple views should be taken to show the extent and position of the fracture and also reveal any additional fracture that may be present.
Treatment
Initially, contamination of the site should be grossly removed and then lavaged with copious amounts of isotonic fluids. Then the fracture should be reduced and stabilised using wires looped around the incisors, which are then anchored either to the canines or to bilateral cortical screws located in the diastemal region. This should be performed under general anaesthesia. Due to the high level of contamination, antibiotic treatment is recommended. Implants should be removed if the fracture is stable after 6-12 weeks to avoid chronic infection.
Prognosis
The prognosis is good. The excellent blood supply to the head, in particular the mandibular region, means that these fractures almost always heal quickly and without complications. there is usually acceptable cosmetic appearance despite being grossly contaminated. This can be compared to open contaminated fractures elsewhere in the body, which, unless they have small fragments that can be easily removed, carry a very guarded prognosis due to the high incidence of osteomyelitis at the fracture site.
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References
May, SA & McIlwraith, CW (1998) Equine Orthopaedics and Rheumatology Self-Assessment Colour Review Manson Publishing Ltd
RVC staff (2009) Urogenital system RVC Intergrated BVetMed Course, Royal Veterinary College
Tremaine, H (1997) Dental care in horse In Practice 1997 19: 186-19
Tremaine, H (2004) Management of skull fractures in the horse In Practice 2004 26: 214-22
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