La Salle University, Bogotá, Colombia; Postgraduate specialization in veterinary dentistry, University of São Paulo, Brasil; Director, DentalVet veterinary dentistry service, Bogotá, Colombia
The temporomandibular joint is formed by the condyle of the mandible and the mandibular fossa of the temporal bone.1 This joint has the ability to make movements of flexion, extension and translation. Since the translational motion refers to the ability of the jaw to move both rostral and laterally, the degree of ability to perform translation movements is directly related to the eating habits of the animal, being strictly carnivorous animals that have less rostral and lateral movement than omnivores.2
Dislocation is a temporary displacement of the bone from its normal position in the joint, while a complete dislocation in which the joint surfaces are separated, is known as luxation.3
In cats, temporomandibular joint luxation is often the result of trauma and usually occurs in association with other maxillofacial injuries. Usually it is a problem of unilateral presentation and usually occurs in rostral direction; when this occurs, the jaw can be deviated in the opposite direction to the affected side, while in cases of bilateral luxation, the jaw can be shifted rostral.3
When a luxation of the temporomandibular joint occurs, it is common a history of trauma before the injury. The most common finding in cases of luxation or fracture in the temporomandibular joint is the inability to close the mouth completely.3
In these cases an initial oral examination without anesthesia is painful and limits the assessment of occlusion and the ability or inability of the animal to open and close the mouth, so it is necessary to anesthetize the patient to perform both complete oral examination and radiographs of the skull, which will help confirm the diagnosis.3
With the patient under general anesthesia the luxation must be corrected; this can be done in two ways:
The first is closed correction, in which the goal is to pry an object positioned between the mandible and maxilla, crossing from one side to the other, at the level of the second and third molars, as caudal as possible.5 With the positioned object, the goal is to try to close the patient's mouth, so that the condylar process that is luxated, will be shifted ventrally; after this, the jaw is pushed caudally to the side of the dislocation to reincorporate the condylar process in the mandibular fossa. After achieving the reduction, the joint should be stabilized with a tape muzzle for 1–2 weeks to prevent recurrent dislocation.6
When the luxation can not be corrected with closed reduction, or recurrent luxations occur, must consider the open reduction, in which the joint is accessed laterally and using a wire from the base of the mandibular condyle to the zygomatic arch, to ensure reduction.4
References
1. Evans HE. Miller's Anatomy of the Dog. 3rd ed. Philadelphia, PA: WB Saunders;1993.
2. Reiter AM. Symphysiotomy, symphysiectomy, and intermandibular arthrodesis in a cat with open-mouth jaw locking: case report and literature review. J Vet Dent. 2004;21:147–158.
3. Lantz GC, Verstraete FJ. Fractures and luxations involving the temporomandibular joint. In: Verstraete FJM, Lommer MJ, eds. Oral and Maxillofacial Surgery in Dogs and Cats. Edinburgh, UK: Saunders;2012;321–332.
4. Gemmill T. Conditions of the temporomandibular joint in dogs and cats. In Practice. 2008; 30:36-43.
5. Schulz K. Diseases of the joints. In: Fossum TW, editor. Small Animal Surgery. 3rd ed. St. Louis, MO: Mosby;2007:1143–1315.
6. Niemiec BA. Small Animal Dental, Oral and Maxillofacial Disease: A Color Handbook. London, UK: Manson Publishing Ltd; 2011.