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  • Dr Stephen Gilmartin

Temporomandibular Joint (TMJ) Dislocation

Updated: Mar 20

Dr Stephen Gilmartin Emergency Registrar

Peer review: Dr Mehul Srivastava

Editor: Dr David McCreary


THE CASE

A 22-year-old female medical student attends the emergency department. She is unable to close her mouth after yawning in one of her biochemistry lectures. She is in some distress and is struggling to speak clearly.

You have seen many a bored medical student, so you are able to quickly diagnose a temporomandibular joint (TMJ) dislocation. Before we get down to the fun part of relocation let’s explore the background of this injury.


ANATOMY

The TMJ is a ginglymoarthroidal (yes, that's a real word) joint, this means it is made up of two joints, one moving in a hinge motion and the other in a gliding motion. The Condylar process articulates with the glenoid fossa and is cushioned by an articular disc.


Image 1: Anatomy of the TMJ(1)

HOW IS STABILITY NORMALLY MAINTAINED?

The synergistic movement of the joint’s dynamic stabilisers (pterygoid and masseter muscles) ensures the TMJ remains stable during opening and closing of the jaw.

Image 2: Anatomy of Pterygoid Muscles

Image 3: Anatomy of Masseter Muscles


DISLOCATION

Spontaneous anterior TMJ dislocation has a reported annual incidence of 5.3 per 1,000,000 patients who present to the emergency department (ED)(2).  Dislocation is most commonly bilateral but can also be unilateral.


MECHANISM

When movement of the st