Idiopathic Condylar Resorption

Idiopathic condylar resorption is a progressive loss of condylar bone, usually bilateral, in adolescents and young women, producing a retruded mandible and an anterior open bite that worsens over months to years. It is also called progressive condylar resorption.

It is found mostly in girls and women between 15 and 35 years of age (female predominance of about 8 to 1 or higher), often after orthodontic treatment or orthognathic surgery. It may be unrecognised until the bite changes.

Pathophysiology. The cause is not known. Proposed contributors are hormonal factors (oestrogen receptors in the joint), mechanical overload from disc displacement and parafunction, a reduced remodelling capacity of the condyle, and an inflammatory or autoimmune process.

Resorption is active for months to years and then stops. Disc displacement is present in most affected joints, and cytokines such as IL-1 beta and TNF-alpha, and matrix metalloproteinases are raised in the joint fluid.

A progressive anterior open bite with only the molars in contact, a receding chin and a class II facial profile, a shorter ramus, a steep mandibular plane, and a change in the bite over months. Joint pain, clicking, headaches and limited opening may occur, but many have no pain.

The bite change after orthognathic surgery or orthodontic treatment, or a gradual onset in a young woman, are typical. Ask about arthritis, hormonal treatment and previous treatment.

Rapidly progressive changes with joint swelling, morning stiffness and other joint symptoms need rheumatological assessment.

• Clinical examination of bite, opening and joint, with serial photographs and bite records.
• CT or cone beam CT: flattened, eroded or reduced condyles with loss of height, and a shortened ramus. Comparison with earlier imaging shows progression.
• MRI: disc displacement, effusion and marrow oedema in active disease.
• Bone scintigraphy (single photon emission CT) for activity, with increased uptake in active resorption.
• Bloods to exclude inflammatory arthritis: C-reactive protein, ESR, rheumatoid factor, anti-CCP, antinuclear antibody, HLA-B27, and thyroid function.
• Serial cephalometry at intervals of 6 months to show whether the resorption is still progressing.

Differential diagnosis.

• Juvenile idiopathic arthritis and rheumatoid arthritis of the joint
• Psoriatic arthritis and ankylosing spondylitis
• Osteoarthritis
• Post-traumatic condylar changes
• Avascular necrosis of the condyle
• Scleroderma and other connective tissue disease
• Skeletal open bite of other cause

• Confirm stability before definitive surgery: no further progression on imaging or bite records for at least 6 to 12 months (often longer).
• Symptomatic and stabilising treatment during active disease: stabilisation splint at night, soft diet, physiotherapy, and a short course of NSAIDs (ibuprofen 400 mg three times daily with food or naproxen 250 to 500 mg twice daily, for 2 to 4 weeks, avoided in renal impairment, peptic ulcer and anticoagulation).
• Surgical treatment once stable: orthognathic surgery (mandibular advancement with maxillary impaction or Le Fort I) with orthodontics. Disc repositioning with stabilisation has been used, and total alloplastic joint replacement is the treatment for severe or recurrent resorption in adults. Results are less predictable than for stable skeletal disease.
• Drug treatments (tetracyclines, hormonal agents) have no proven benefit, and are not advised.
• Treat any inflammatory arthritis with rheumatology, which is the cause in a subset.
• Perioperative antibiotic: cefazolin 2 g intravenously (3 g if over 120 kg) at induction, or clindamycin 600 mg intravenously in penicillin allergy.

Special groups. In adolescents, orthognathic surgery is delayed until growth and resorption have stopped. Pregnancy and hormonal treatment need review of the joint.

Monitoring. Review at 3 to 6 month intervals with bite records, photographs and cephalometry, and imaging every 6 to 12 months while active. Review after surgery at 1, 3, 6 and 12 months and annually, as relapse can occur.

Referral and escalation. Refer to oral and maxillofacial surgery and orthodontics, and to rheumatology for suspected inflammatory arthritis. Urgent referral for rapid progression, severe pain or systemic features.