Temporomandibular Joint Dislocation

Temporomandibular joint dislocation is the displacement of the mandibular condyle anterior to the articular eminence, so that the jaw is locked open and cannot close without manipulation. It accounts for under 3 percent of joint dislocations. Anterior dislocation is by far the commonest; posterior, lateral and superior types occur with trauma and are often associated with fractures.

Causes include:

• wide mouth opening (yawning, laughing, vomiting, dental procedures, endotracheal intubation, endoscopy)
• trauma
• drugs (antipsychotics and metoclopramide causing dystonia)
• seizures
• joint hypermobility conditions (Ehlers-Danlos syndrome, Marfan syndrome)
• a shallow glenoid fossa
• ligamentous laxity

Acute dislocation is the condyle jammed in front of the eminence with masseter and pterygoid spasm. Recurrent (habitual) dislocation arises when capsule and ligaments are stretched.

Chronic locked dislocation, unreduced for weeks, leads to fibrosis and needs surgery.

• Inability to close the mouth, with the jaw protruded and an open bite.
• Pain and spasm of the masseter, difficulty speaking, drooling, and difficulty swallowing.
• Bilateral: the chin is displaced forward and downwards; a depression (hollow) in the preauricular region; condyles palpable anterior to the tragus.
• Unilateral: chin deviates to the opposite side.
• Recurrent: repeated painless dislocation self-reduced by the patient, clicking.
• Red flags: trauma with facial injury (mandibular fracture), neurological deficit, dislocation in a patient taking antipsychotics (acute dystonia), inability to reduce after repeated attempts, and posterior dislocation (external auditory canal injury).

• Clinical diagnosis from the typical appearance and inability to close.
• Panoramic radiograph or CT of the TMJ is not needed for typical uncomplicated atraumatic anterior dislocation, but is required before reduction when trauma is possible: shows condylar head anterior to the eminence; excludes fracture of the mandible or skull base.
• Assess the drug history and medical cause (dystonia, seizure, connective tissue disorder).
• MRI for chronic or recurrent cases to evaluate disc and capsule.
• Exclude mandibular condylar fracture, acute dystonic reaction, tetanus (trismus is the opposite picture), and temporomandibular disorder with locking.

• Reduce promptly: the earlier the reduction the easier it is, as muscle spasm increases with time.
• Analgesia and relaxation: lidocaine 1 percent 2 to 3 mL infiltrated into the preauricular region (the TMJ capsule) or auriculotemporal nerve block; oral analgesia (ibuprofen 400 mg, paracetamol 1 g); for muscle spasm, diazepam 2 to 5 mg intravenously or midazolam 1 to 2 mg intravenously titrated, or procedural sedation (propofol, ketamine) when manual reduction fails.
• Classic extraoral manoeuvre: seated patient with head supported against a wall; clinician stands in front, thumbs wrapped in gauze placed on the lower molar occlusal surfaces (or on the mandible external oblique ridge), fingers wrapped around the mandibular angle; apply firm downward pressure to disengage the condyles from the eminence, then push the mandible backward; the jaw reduces with a clunk; protect thumbs from biting by placing them lateral to the molars.
• Alternative: syringe technique (patient bites down on a 5 mL syringe; patient rolls it) or the wrist pivot method; extraoral approach with thumb pressure on the zygomatic prominence and downward chin pressure (Gorbatov method).
• After reduction: confirm occlusion; head bandage or elastic chin support for 24 hours; soft diet for 2 weeks; avoid wide opening (limit to 2 fingers) and yawning against a hand; NSAID analgesia for 3 to 5 days.
• Drug induced dystonia: benztropine 1 to 2 mg intravenously or intramuscularly (children 0.02 mg/kg), or procyclidine 5 to 10 mg intravenously; stop the offending drug.
• Recurrent dislocation: autologous blood injection (2 to 4 mL into each joint space, with 2 to 3 mL into the pericapsular tissue) with intermaxillary fixation for 1 to 3 weeks; dextrose prolotherapy 20 to 25 percent 1 to 2 mL repeated every 4 weeks for 3 to 4 sessions; botulinum toxin A 25 to 50 units into each lateral pterygoid every 3 to 6 months.
• Surgery for chronic or persistent recurrent dislocation: eminectomy (removal of articular eminence), eminoplasty, capsular plication, or augmentation (block bone graft or implants) of the eminence; open reduction for chronic unreduced dislocation with traction.
• Follow up: review at 1 and 4 weeks; recurrence risk 10 to 30 percent within 1 year after first acute dislocation.
• Counselling: when yawning support the chin, avoid large bites, and seek immediate help when the jaw locks.