Re: Internal derangements of the temporomandibular joint

[Anonymous]

Dislocation of TMJ
Dislocation of a joint is a displacement of one component of the joint beyond its normal limits,
without spontaneous return to its normal position.

The condyle moves to articular eminence that marks the anterior limit of the condylar excursion. Once the condyle slips over the articular eminence to come and lie anterior to the eminence in the infratemporal space, it is known to be dislocated. The capsule of the joint along with temporomandibular ligament is either sufficiently relaxed or torn to let this all happen.
If both joint are dislocated and the patient is dentate the mouth remains wide open, although
sometimes the patient may be able to close toward a protruded position.

If only one joint is dislocated then there is a marked deviation to the opposite and the teeth may be brought closer together but still nowhere near back into occlusion. For a few hours after the event there remains a depression just in front of the ear where the condyle would normally be found, but in times that fills with oedema.
Classification:

1. Acute
2. Chronic
3. Subluxation
Causes:
1. Over-opening of the mouth to its extreme positions such as during a yawn, hefty laugh or mastication
of large object (biting a full apple).
2. When the jaws are forcibly opened during general anaesthesia, during bronchoscopy or while using a
mouth gag injudiciously.
3. Due to blow on the chin when the mouth is wide open.
Treatment:
A) Acute dislocation can usually be reduced as an outdoor procedure.
Reduction of dislocation of the TMJ:

Have the patient supine
Stand behind the head
Place the thumbs on the posterior teeth and the fingers under the chin
Press increasingly firmly on the posterior teeth while pulling gently up anteriorly
If there is great resistance concentrate on one side at time
When reduced hold the mouth shut for 30 sec or so
Advice restricted mouth opening for at least 24 hours

At times muscle spasm is so strong that it does not allow the manipulation of the condyle back to its original position, it is advisable to sedate the patient by administration of the muscle relaxant or local anaesthetic solution or even general anaesthesia can be administered.
B) In majority of the chronic cases, dislocation of long standing usually requires an open reduction.
The patient is taken to the operation theatre and under general anaesthesia jaw is manipulated for closed
reduction.

If it fails, joint is opened through a conventional preauricular approach. The dislocated condyle is exposed and manipulated under direct vision. The manipulation can be reinforced by exposing the angle of the mandible through a submandibular incision. A hole is drilled there to facilitate the additional downward pull with the help of a wire passed through this hole.
If the above procedure fails, an eminectomy may be performed. This will allow the comfortable
repositioning of the condyle into the fossa since the obstruction stands removed.