Condylar Hypoplasia

Condylar hypoplasia is underdevelopment or absence of the mandibular condyle and ramus, producing mandibular retrognathia, asymmetry and a restricted jaw movement. It can be congenital or acquired.

Congenital causes are hemifacial microsomia (the second commonest facial malformation after cleft), Treacher Collins syndrome and Pierre Robin sequence. Acquired causes are condylar fracture in childhood, joint infection, juvenile idiopathic arthritis, radiotherapy and ankylosis.

Pathophysiology. The condylar cartilage is the main growth site of the mandible. Failure of development (congenital) or damage (injury, infection, inflammation, radiation) reduces ramus height and mandibular length.

Facial growth is affected progressively, with a shortened ramus, deviation of the chin to the affected side, a canted occlusal plane and compensation of the unaffected side.

Short ramus and a small chin, a receding mandible (class II malocclusion), chin deviation to the affected side in unilateral cases, a flat cheek and fullness of the opposite side, a canted occlusal plane, and limited mouth opening or deviation on opening.

Congenital cases may have ear anomalies, a macrostomia and other facial defects. Sleep disordered breathing with snoring and apnoea occurs with severe retrognathia. TMJ pain, clicking or locking may be present.

Airway symptoms in infancy (feeding problems, stridor, apnoea) need urgent assessment.

• Clinical examination of the face, bite and opening range, with photographs.
• Panoramic radiograph, cephalometry and CT with 3D reconstruction: small or absent condyle, short ramus, and deformity of the glenoid fossa. Grading by the degree of ramus and condyle deficiency (three grades, from small and shortened, to a rudimentary joint, to absent ramus, condyle and fossa).
• MRI for the disc and soft tissue.
• Sleep study (polysomnography) for suspected obstructive sleep apnoea.
• Genetic assessment, hearing tests, and examination of the cervical spine and heart in congenital cases.
• Bloods for inflammatory arthritis (C-reactive protein, ESR, rheumatoid factor, anti-CCP, antinuclear antibody) in acquired cases.

Differential diagnosis.

• Condylar hyperplasia on the opposite side
• Hemifacial microsomia and other syndromes
• Mandibular deficiency from a skeletal class II pattern
• Ankylosis and condylar resorption
• Juvenile idiopathic arthritis with growth disturbance
• Post-radiotherapy growth deficiency
• Parry-Romberg syndrome

• Treat the cause: control of inflammatory arthritis with the rheumatology team (intra-articular corticosteroid and disease modifying treatment), and early management of fractures and infection.
• Growing patients: functional orthodontic appliances to stimulate growth and improve the bite, and distraction osteogenesis or costochondral graft to lengthen the ramus in severe cases.
• Adults and those with stable growth: orthognathic surgery (bilateral sagittal split mandibular advancement with a maxillary Le Fort I and genioplasty) with orthodontics. Total alloplastic joint replacement in severe, deficient or damaged joints.
• Obstructive sleep apnoea: maxillomandibular advancement, positive airway pressure treatment or adenotonsillectomy as appropriate.
• Perioperative antibiotic: cefazolin 2 g intravenously (3 g if over 120 kg) at induction, or clindamycin 600 mg intravenously in penicillin allergy.
• Physiotherapy and splint therapy for TMJ dysfunction, and analgesia: paracetamol 1 g every 6 hours (maximum 4 g daily) with ibuprofen 400 mg every 8 hours with food.

Special groups. Children need coordinated craniofacial team care (surgery, orthodontics, ENT, audiology and speech therapy), with review of the airway at birth in congenital cases.

Monitoring. Review every 6 months during growth, with cephalometric and clinical records. After surgery, review at 1, 3, 6 and 12 months and annually.

Referral and escalation. Refer to a craniofacial or oral and maxillofacial service. Urgent referral for airway compromise or feeding failure in infants.