Recurrent TMJ Dislocation

Recurrent temporomandibular joint dislocation is repeated episodes of the condyle displacing in front of the articular eminence, with the jaw locked open and difficult reduction, usually after earlier subluxations. It can be self-reducing or need manipulation.

It is related to joint hypermobility, ligament laxity, a shallow glenoid fossa, a flattened or small eminence, and conditions such as Ehlers-Danlos syndrome and Marfan syndrome, neurological disorders and long term antipsychotic use. It is seen at any age, with a peak in young adults.

Pathophysiology. An incompetent capsule and ligaments, with a shallow eminence and a dysfunctional disc, allow the condyle to cross the eminence with little resistance.

Each episode stretches the capsule and ligaments, so dislocations become easier, so a cycle of increasing instability is created, and chronic lock can follow.

Episodes of the jaw locking open on yawning, laughing, eating or dental treatment, either self-reduced or needing help, with pain, anterior open bite and drooling. Between episodes the joint may click or pop, and the opening range is wide (over 50 mm).

Ask about frequency, triggers, connective tissue disease, neurological conditions and drugs. Features of generalised hypermobility, such as skin laxity and joint hypermobility, support the diagnosis.

Associated facial trauma, head injury or neurological signs need assessment, and a fixed dislocation lasting over days is a chronic or long standing dislocation requiring surgical treatment.

• Clinical diagnosis from history, with wide opening and hypermobility.
• Panoramic radiograph or CT: shows condylar position in front of the eminence during dislocation, a shallow fossa, a flat eminence, and a small or high eminence in some.
• MRI for disc position and capsular laxity when planning treatment.
• Screening for connective tissue disease (Beighton score) and for neurological and drug causes.
• Exclude fracture after trauma.

Differential diagnosis.

• Isolated first dislocation
• Subluxation that reduces itself
• Drug induced dystonia
• Disc displacement and internal derangement
• Mandibular fracture
• Seizure related dislocation
• Tetanus

• Education: limit mouth opening, support the jaw when yawning (a hand under the chin), avoid wide opening and prolonged dental procedures, and learn self-reduction with the manoeuvre taught by a specialist.
• Treat reversible causes: review antipsychotic and other drugs, and treat neurological disease.
• Elastic bandage or chin cap for a few weeks after an episode.
• Minimally invasive options:
  • Autologous blood injection: 2 to 3 mL of the patient's venous blood into the superior joint space and 1 to 2 mL into the pericapsular tissue, under local anaesthesia, followed by limited opening (intermaxillary fixation or bandage) for 1 to 2 weeks. Reported success is about 70 to 90%, with repeat injection if needed.
  • Dextrose prolotherapy: 20 to 25% dextrose 1 to 2 mL into the joint and capsule at intervals of 2 to 4 weeks for 3 to 4 injections.
  • Botulinum toxin type A into the lateral pterygoid muscles to limit hyperactivity, with doses depending on the product (the total for both sides is often 50 to 100 units of the product used), repeated every 3 to 4 months. Evidence is limited.
• Surgery for persistent recurrence: eminectomy (reduction of the articular eminence, with a success rate of about 90%), eminence augmentation with a block or plate, capsular plication, lateral pterygoid myotomy, and in selected severe cases condylectomy or joint replacement.
• Analgesia: ibuprofen 400 mg three times daily with food and paracetamol 1 g every 6 hours (maximum 4 g daily) during episodes.

Special groups. Connective tissue disease needs care in surgery because of poor healing and recurrence, and genetics input. Older adults need review of drugs.

Monitoring. Review at 2 weeks, 3 months and 6 months, recording episodes and opening range. Repeat imaging for failed treatment or before surgery.

Referral and escalation. Refer to oral and maxillofacial surgery for recurrence. Emergency referral for a lock that cannot be reduced.