Temporomandibular Joint Dislocation
Hypermobility disorders of the temporomandibular joint
(TMJ) present in two major forms:
1. Dislocation
2. Subluxation [1]
The differences between dislocation and subluxation have
been highlighted in Box 64.1.
The condyle may be displaced either anteriorly, posteriorly, medially, or laterally of which anterior dislocation is the
most common [1]. The incidence of TMJ dislocation constitutes about 3% of the dislocations occurring in other joints of
the body with female predilection. The reported incidence of
TMJ dislocation is 7% with a preponderance in people in the
second and third decades [2]
1. Acute
2. Chronic
Dislocation recurring more than once is termed as chronic
recurrent dislocation. The term chronic protracted dislocation is used to describe dislocation persisting for more than 1
month, while dislocation present for more than 6 months is
called extra-long-standing dislocation [4].
Based on the direction of displacement [2],
Classifcation (Box 64.2)
Dislocation has been classifed by numerous methods. Rowe
and Killey [3] based it on the duration of the dislocation episode as:
• Anterior
• Posterior
• Lateral
• Superior
Anterior dislocation is the most common type of dislocation due the weakness of the capsule in the anterior region.
Posterior dislocation occurs following fracture of the
external auditory canal and skull base. Allen and Young
classified lateral dislocation into Type I and Type II. This
type of dislocation occurs in mandibular trauma
(Fig. 64.1a, b):
• Type I refers to lateral subluxation.
• Type II indicated lateral and superior dislocation into the
temporal fossa [2].
Superior dislocation results when condyle is pushed into
the middle cranial fossa accompanied by glenoid fossa fracture. Small and round-shaped condyle is predisposed to this
type of dislocation [2].
Etiopathogenesis (Table 64.1)
A multitude of causes have been described in the etiopathogenesis of TMJ dislocation including congenital,
iatrogenic, anatomical aberrations, spontaneous, pharmacological, neurological, neuromuscular, etc. Proper diagnosis of the etiology is important to institute problemspecifc treatment
Daily activities which involve wide mouth opening such as
laughing, yawning, and biting may induce TMJ dislocation. It
may also occur spontaneously during epileptic seizures, vomiting, yawning, and singing. Trauma is another cause which
might cause posterior, superior, and lateral dislocation in addition to anterior dislocation [5]. Iatrogenic causes include dental procedures which require wide mouth opening for
prolonged time, intubation procedures, gastrointestinal endoscopy, and laryngoscopy/bronchoscopy. Anatomical aberrations such as small condyle, underdeveloped glenoid fossa,
shallow/steep articular eminence and laxity of ligaments and
capsule are more prone for dislocation.
Predisposing risk factors include connective tissue disorders such as Ehlers-Danlos disease and Marfan’s syndrome
which predispose to laxity of the joint and hypermobility.
Muscle spasms occur in neurodegenerative or neurodysfunctional diseases, namely, Huntington disease, Parkinson disease, multiple sclerosis, muscle dystrophies, or dystonias.
Medications which induce dislocation are antipsychiatric
(phenothiazines) and antiemetic (metoclopramide) drugs which
produce unwanted extrapyramidal reactions which eventually
lead to muscular imbalance attributed to dislocation.
Reduced vertical dimension due to loss of posterior teeth
in advanced age may also predispose an individual to dislocation [5].
Though various theories of pathogenesis have been
described in literature, the most accepted was muscular incoordination during mandibular movements. In the initialstages of mouth closure, elevators are activated prior to the
relaxation of depressors mainly lateral pterygoid which pulls
the condyle forward. This initial dislocation facilitates the
further dislocation [5].
Clinical Features
(Mentioned in Box
64.3; Figs. 64.2a, b, 64.3, 64.4a, b,
and 64.5a, b)
Investigations
• Orthopantomogram (OPG) (open and closed) (Fig. 64.6)
This is the commonly used screening modality for the
examination of TMJ. Morphology of condyle, articular
eminence, and joint space can be evaluated. Open mouth
OPG shows the position of the condyle in relation to the
articular eminence.
• TMJ tomogram
Open and closed mouth TMJ images can be obtained in
different slices.
• Computed tomography(CT)
Evaluation of the morphology of osseous TMJ components—condyle, articular eminence and the glenoid
fossa—are better assessed with CT.
• Cone beam computed tomography CBCT
CBCT facilitates accurate measurement of condylar
height, width, and length as well as inclination of articular
eminence.
• Magnetic resonance imaging (MRI)
MRI demonstrates the soft tissue morphology, particularly disc shape, displacement, and effusion of the joint
frequently associated with dislocation.
• Electromyography (EMG)
EMG evaluates the activity of the muscles which may be
hypoactive, normoactive, or hyperactive.
• Ultrasonography (USG)
Thickness and length of the muscles can be evaluated
both at rest and clenching by USG.
cle spasm persisting for longer duration. In diffcult situations, reduction can be facilitated with the help of local
anesthesia, conscious sedation, and general anesthesia.
Following reduction, a Barton’s bandage, chin strap, or intermaxillary fxation is advised for 3–6 weeks to prevent further
dislocation. Several reduction techniques have been
employed with varying rates of success.
Management of Dislocation
Acute Dislocation
Reducing the dislocated condyle poses a great challenge.
Reduction is more complicated with the accompanied muscle spasm persisting for longer duration. In diffcult situations, reduction can be facilitated with the help of local
anesthesia, conscious sedation, and general anesthesia.
Following reduction, a Barton’s bandage, chin strap, or intermaxillary fxation is advised for 3–6 weeks to prevent further
dislocation. Several reduction techniques have been
employed with varying rates of success.
Hippocratic/Nelaton’s Technique
(Fig. 64.7)
This is the conventional method of reduction of acute dislocation in which physician stands in front of the patient, with
the thumb placed either on the external oblique ridge or on
the lower molars and other fngers positioned along the lower
border of the mandible. A steady downward, backward, and
superior force should be given to reduce the dislocated
condyle. The thumb should be protected either with a plastic
splint or gauze wrapped around it to prevent injury to the
thumb while reducing dislocation.
64.6.1.2 Gag Refex [3]
Gag refex is induced by probing the soft palate using mouth
mirror. In alert individuals, this refex relaxes the lateral pterygoid muscle through coordinated neuromuscular activities
which reduces dislocation in natural way.
64.6.1.3 Wrist Pivot Method [7] (Fig. 64.8)
This method utilizes existing myospasm of the elevators for
reduction. The thumb is placed under the chin, while other
fngers are placed over the occlusal surfaces of lower teeth.
Then upward movement is applied by the thumb, and concomitant inferior force is given by other fngers with pivoting
the wrist. The advantage of this technique is that it utilizes
the force created by the muscles of mastication rather than
overcoming this force as in Nelaton’s technique.
64.6.1.4 Extraoral Method [8] (Fig. 64.9a, b)
Intraoral methods described previously have the risk of
human bite in which there are chances of infection transmission. To overcome this, extraoral method has been described.
In the dislocated mandible, coronoid process comes forward
which is easy to palpate. On one side, the thumb is positioned over the coronoid process which pushes the mandible
backward, while the other fngers are located over the mastoid process to deliver counteracting force (Fig. 64.9a). On
the other side, the mandible is pulled further forward with
the thumb on the malar eminence and rest of the fngers on
the mandibular angle (Fig. 64.9b). Pulling the mandible on
one side with simultaneous pushing of the mandible on the
other side reduces the dislocation on one side frst and then
subsequently on the other side. This technique is applicable
in unilateral dislocation as one side is reduced frst and then
the other is reduced thereafter
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