Anterior Disc Displacement Without Reduction

Anterior disc displacement without reduction is a condition in which the temporomandibular joint disc remains in front of the condyle on both closing and opening, blocking forward translation of the condyle. It is the cause of a closed lock.

It follows displacement with reduction in some patients, or begins abruptly after trauma or heavy parafunction. It is most frequent in women aged 20 to 40 years, and it is a recognised route to degenerative joint disease.

Pathophysiology. Chronic stretching of the discal attachments and distortion of the disc allow it to fold in front of the condyle. The condyle is then unable to translate beyond the disc and opening is limited.

With time, the retrodiscal tissue stretches and adapts, the disc may deform or perforate, and the range of opening improves in many patients despite the persistent displacement.

Sudden loss of a previous click with a catch or lock, limited mouth opening to about 25 to 35 mm, pain on attempts to open wide, and deviation of the jaw to the affected side on opening. Excursion to the opposite side is restricted. The click is absent.

Acute locking is often painful, and over weeks the pain falls and the opening increases as the joint adapts. Ask about the onset, trauma, a history of clicking, bruxism, and the effect on eating.

Fever, joint swelling, a changing bite and recent trauma point to septic arthritis, haemarthrosis or fracture and need urgent assessment.

• Clinical examination: opening range in millimetres (usually 25 to 35 mm), deflection to the affected side, restricted lateral movement to the opposite side, and a hard end feel without a click. Passive stretch adds only a few millimetres.
• MRI in closed and open mouth positions: shows the disc anterior to the condyle in both positions, with a deformed disc, effusion, bone marrow change and retrodiscal tissue change.
• Cone beam CT for bone change.
• Exclude other causes of limited opening: muscle splinting, coronoid hyperplasia, ankylosis, infection and fracture.
• Joint aspiration, bloods and cultures when infection or inflammatory arthritis is suspected.

Differential diagnosis.

• Anterior disc displacement with reduction
• Masticatory muscle trismus and myofascial pain
• TMJ ankylosis
• Osteoarthritis and inflammatory arthritis
• Septic arthritis
• Coronoid process hyperplasia or fracture
• Condylar fracture
• Tumour of the joint or infratemporal fossa

• Acute closed lock (under 3 months): attempt manual manipulation under local anaesthesia or sedation, with traction on the mandible downward and forward and gentle jaw movements to release the disc, followed by a stabilisation splint and a graded jaw exercise programme. Success is variable and best in the first weeks.
• Analgesia: ibuprofen 400 mg three times daily with food, or naproxen 250 to 500 mg twice daily with food, for 2 to 4 weeks, with a proton pump inhibitor in people at risk of ulcer. Avoid NSAIDs in renal impairment, peptic ulcer and anticoagulation. Paracetamol 1 g every 6 hours (maximum 4 g daily). Short course of a muscle relaxant such as cyclobenzaprine 5 to 10 mg orally at night for up to 2 weeks in selected patients, avoided with arrhythmia, heart block, recent myocardial infarction and monoamine oxidase inhibitors.
• Arthrocentesis with lavage of 100 to 300 mL of sterile saline or lactated Ringer solution, with or without an injection of hyaluronic acid 1 mL, for lock that does not respond within 2 to 4 weeks. Success is about 70 to 90% in published series, and the figure is of lower certainty.
• Arthroscopy for adhesions and persistent pain, and open surgery (discoplasty, disc repositioning or plication, or disc removal with replacement) for refractory pain and limitation.
• Chronic lock with good function and little pain needs no surgery, with exercise and splint therapy.
• Physiotherapy with stretching, using a jaw exerciser, started early and continued for at least 3 months after any procedure.

Special groups. Children and adolescents need assessment for juvenile idiopathic arthritis and a conservative approach to protect condylar growth.

Monitoring. Review at 2 to 4 weeks, then at 3 months for pain, opening range and function. Repeat imaging if symptoms progress or a procedure is planned.

Referral and escalation. Refer to oral and maxillofacial surgery or an orofacial pain clinic. Urgent referral for trauma, fever with swelling or an acute change in the bite.