Temporomandibular joint dislocation represents the condyle of the mandible being abnormally displaced, with a loss of the normal articulation with the temporal bone's mandibular (glenoid) fossa.
Epidemiology
Dislocations of the temporomandibular joint (TMJ) are common and occur in as many as 7% of the entire population, at some point in their lives 3. They can occur at any age but are most common between 20-40 years of age 3.
Pathology
Dislocations can occur in a number of directions 1:
anterior dislocation (common)
cranial dislocation (uncommon)
posterior dislocation (rare)
Anterior dislocation
Anterior dislocations are most common and represent either an exaggerated and often recurrent (also known as habitual) normal anterior translation of the condyle out of the glenoid fossa and onto the condylar eminence (see TMJ dysfunction), or the result of acute and forceful opening of the mouth (e.g. trauma, intubation etc.) 1-3. In some settings, the dislocation may not be reduced and becomes chronic.
Cranial dislocation
Cranial dislocations are quite uncommon and are usually the result of an upward blow to the mandible such that the condyle fractures the glenoid fossa and protrudes into the middle cranial fossa 1.
Posterior dislocation
Posterior dislocations are rare.
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