How I Treat Rostral Luxation of the Temporomandibular Joint in a Cat
Learning Objective
Presenting diagnostic challenges and solutions for TMJ rostral luxation in a cat.
TMJ Dorso-Rostral Luxation
Only stabile patient may undergo diagnostic procedure followed by preliminary or definite treatment.
Temporomandibular joint (TMJ) luxation in the cat is usually the result of trauma, and is often associated with other maxillofacial injuries. It may occur unilaterally or bilaterally. The most common presentation is unilateral rostrodorsal displacement of one mandibular condyle, with the mandibles shifted to the side opposite the luxation. Less commonly, bilateral luxations can result in both mandibles displaced rostrally.
The signalment of luxation of TMJ is easily visible as the animal has malocclusion, cannot close the mouth. Caudal mucosa and soft palate is the place where signs of TMJ injuries as the heamorrhages may be observed.
Diagnosis require at least 3 projections: lateral oblique left, lateral oblique right. These two techniques provide general view of left and right canine, premolars, and molars, TMJ and mandibular body. Additionally, it is helpful to obtain dorso-ventral projection which will show the symmetry of TMJ, mandibular body, and incisors. The superior diagnostic techniques for any TMJ pathologies is 3D imaging like CT, MRI, or CBCT.
The differential diagnosis of TMJ lunation includes: acute arthritis due to injury, mandibular fracture, mandibular neurapraxia teeth luxations.
The goal of treatment is to return the luxated condylar process into the joint cavity. While the patient is under general anesthesia, a fulcrum (a tuberculin syringe, pencil or non-metallic tubular device) is inserted between the maxillary fourth premolar and mandibular molar on the side of the luxation. The mandible of the luxated side is gently pulled rostrally to disengage the condyle from the dorsal surface of the articular eminence. Then the jaws are opposed on the fulcrum. This action usually causes the affected condyle(s) to pass over the articular eminence to insert into the mandibular fossa. Radiographs are exposed and examined to confirm reduction.
The success in reduction of luxated TMJ depends on time between injury and repairing procedure. If the reduction is not possible or with refractory or recurrent luxations, open reduction and suture imbrication of the joint capsule, or a mandibular condylectomy, are indicated.
Closed reduction under general anesthesia is used to correct acute, uncomplicated rostrodorsal luxations. The movement of the TMJs should be restricted during the healing period following difficult or unstable reductions. This may be achieved with rigid composite-used maxillomandibular fixation or non-rigid fixation, such as a tape muzzle. Use of a tape muzzle for management of TMJ luxation in the cat is challenging and candidates for muzzle application should be chosen carefully. A tape muzzle or maxillomandibular fixation can be used after reduction for 1–2 weeks to prevent recurrence.
Post-traumatic ankylosis of TMJ often appears as the reason of insufficient postoperative care and/or complete lack of treatment due to improper primary diagnosis. Ankylotic TMJ may cause an emergency when the animal cannot breathe with the open mouth and decrease the internal temperature. It is important to figure out if the limitations of jaw movement are caused in (true ankylosis) or outside TMJ. Sometimes local intracapsular administration of betamethasone can improve mobility and functioning of the joints. Removal of the ankylosed tissue may be also considered and require either unilateral or bilateral condylectomy.