Mandible or temporomandibular joint (TMJ) dislocations usually
occur in the setting of prior musculoskeletal problems of the jaw.1–3 This
includes joint laxity, prior injury or dislocation, inherent hypermobile
syndromes (e.g., Marfan, Ehlers-Danlos), or neuromuscular problems
(e.g., dystonic reactions) that pull the mandible out of its joint.
The mandibular dislocation typically results from TMJ hyperextension
or trauma. The Emergency Physician must be able to reduce a TMJ
dislocation. The procedure is easy, simple, and straightforward.
The TMJ is an unusual joint (Figure 161-1). It is composed of
two joints separated by an articular disk. The TMJ functions as
a hinge and gliding joint. A discussion of the mechanics of the
TMJ is beyond the scope of this chapter. Anterior dislocations
are most commonly seen in the Emergency Department. The etiology
of the dislocation includes laughing, chewing, opening the mouth
wide (eating, for procedures, yawning, vomiting), seizures, and
trauma. All of these actions can result in the mandibular condyle
sliding forward and anterior to the articular eminence of the temporal
bone. The muscular attachments of the mandible result in a pulling
of the condyle superiorly and in front of the articular eminence
(Figure 161-2). This causes the mandible to become fixed in dislocation
and rarely spontaneously reduce.
Anatomy. A. Lateral view
of the head and temporomandibular joint. B. Anatomy
of the mandible. C. Sagittal
section through the temporomandibular joint. D. The
attachment of the muscles of mastication to the mandible. The arrows
represent the direction of pull of the muscles.
Anatomic relationships of the mandible. A. The fully opened mandible. B. The anteriorly dislocated mandible.
TMJ dislocations are commonly anterior, but may be in any direction.
Anterior TMJ dislocations may occur spontaneously in normal individuals
and can occasionally reduce spontaneously. Dislocations of the TMJ
are usually bilateral, but can occur unilaterally. Posterior, superior,
and lateral dislocations are much more rare. They are seen in the
context of direct trauma to the mandible, with or without an associated
The diagnosis can often be made clinically in a cooperative patient
with a nontraumatic history. The patient will present in pain with
an open mouth, protruding mandible, and malocclusion. A unilateral
dislocation will cause the mandible to protrude towards the non-dislocated
side. A depression, palpable and visible, will be noted in the preauricular
area. Mandibular radiographs are indicated when trauma is involved
to rule out an associated fracture. The dislocation is often best
seen on the Panorex view ...