Management of Temporomandibular Joint Problems and Differentials

Introduction
Temporomandibular joint (TMJ) disorders more commonly encountered in the cat and dog include luxation, open-mouth jaw locking, and ankylosis. Luxation of the TMJ is often confused with open-mouth jaw locking. Both conditions may present with inability to close the mouth, but their causes, manifestations and treatments differ. A diagnosis is made by means of clinical examination and radiography (e.g., dorsoventral view). Luxation of the TMJ can usually be resolved with a pencil placed between the maxillary and mandibular carnassials and then closing the mouth. However, the same treatment modality is impractical and will cause further trauma and pain to the patient with open-mouth jaw locking. Trauma to the TMJ in young animals may lead to joint ankylosis and progressive inability to open the mouth.

Temporomandibular Joint Luxation
Luxation of the TMJ occurs as a result of trauma, with mandibular condyle usually displaced in a rostrodorsal direction. The lower jaw then shifts forward and to the contralateral side, resulting in the inability of the animal to close its mouth fully due to abnormal contact between the maxillary and mandibular teeth. Caudal displacement of the mandibular condyle is rare, but may occur with fracture of the retroarticular process of the temporal bone.

Radiographic examination facilitates diagnosis of TMJ luxation. A dorsoventral radiographic view will show increased width of the joint space and (rostral) displacement of the mandibular condyle. Lateral oblique views are also useful in establishing a diagnosis. Reduction of rostrodorsal TMJ luxation is achieved by placing a pencil between the maxillary fourth premolar and mandibular first molar teeth on the affected side only and closing the mouth. Following reduction the TMJ capsule may be lax and the mandibular condyle unstable. A tape muzzle for 2 to 4 weeks will prevent the patient from opening the mouth wide, thus reducing the likelihood of recurring displacement. Chronic luxation is treated by condylectomy.  [...]