The temporomandibular joint has a hinge-like function and is stable as a result of the close congruity between the condyloid process and the deep mandibular fossa. Bony processes prevent rostral and caudal condylar displacement.
A fibrocartilagenous meniscus is interposed between the articulating surfaces and divides the joint into two separate compartments.
Luxation occurs when there is traumatic overextension of the temporomandibular joint. It may occur as an isolated injury or be associated with other maxillofacial injuries. Generally the mandibular condyle luxates in a rostrodorsal direction. If it luxates caudally, luxation is usually associated with a fracture of the retroarticular process.
Luxation is usually unilateral, but bilateral luxation can also occur.
The condition has been reported in cats and dogs, particularly in St Bernards, Basset Hounds and Irish Setters.
The animal will present with an inability to close the mouth and, in unilateral cases, with the lower jaw deviated away from the luxated side.
If the luxation is caudoventral, the jaw will be deviated towards the luxated side.
If other fractures or significant head trauma is present, TMJ joint luxation may be more difficult to diagnose, but should be suspected in any head trauma case which is unable to close its mouth.
If bilateral luxation occurs, there will be no deviation of the mandible.
Radiographs will help to confirm the diagnosis and help evaluate for concurrent injuries and fractures which may complicate treatment.
On the dorsoventral view, the most useful radiographic sign is an increased temporomandibular joint space. Right and left lateral oblique projections can usually permit further evaluation of the joints.
Closed reduction of the temporomandibular joint should be attempted with the patient under general anaesthesia.
A fulcrum, such as a syringe case or a dowel, should be placed transversely across the jaw at the level of the molars. The rostral mandible and maxilla are then squeezed together, partially closing the jaw and levering the caudal mandible against the fulcrum to disengage the luxated condyle. While maintaining pressure on the rostral mandible, it is pushed in the appropriate direction to reduce the luxation.
For the more common rostrodorsal luxation, the rostral mandible is pushed towards the side of the luxation, whereas for caudoventral luxations, the rostral mandible is pushed away from the side of the luxation.
The mandible can be release after reduction and the occlusion of the upper and lower canine teeth should be examined. Radiography can also be used to confirm reduction.
A tape muzzle or interarcade wiring can be used after reduction for 1-2 weeks to prevent recurrence.
With refractory or recurrent luxations, open reduction and suture imbrication of the joint capsule, or a mandibular condylectomy, are indicated.
NSAIDs should be administered for the pain and inflammation associated with the condition.
|Temporomandibular Luxation Learning Resources|
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|Veterinary Dentistry Q&A 01|
Lobprise, H (2007) Blackwell's Five-minute consult clinical companion Wiley-Blackwell
Niemiec, B. (2010) A colour handbook of small animal dental and oral maxillofacial disease Manson Publishing
Scott, H. (2007) Feline Orthopaedics Manson Publishing
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