Congenital radial head dislocation

Congenital radial head dislocation is the most common congenital elbow abnormality. It can occur in isolation, or more commonly may be associated with other conditions or syndromes.

Epidemiology

Overall, congenital radial head dislocation is rare ².

Clinical presentation

Congenital radial head dislocation is often asymptomatic, which may result in a delayed presentation. Patients usually present in adolescence, when the child starts using the limb more. 

On examination there may be mild loss of flexion with radial head prominence just below the antecubital fossa in anterior dislocation or mild loss extension in a posterior dislocation. There may also be subtle decrease in range of pronation and supination.

Pathology

Congenital radial head dislocation is bilateral in the majority of cases. Posterior dislocation (~70%) is more common than anterior and lateral dislocations (15% each) ^{1, 2}. 

Etiology

The underlying abnormality is hypothesized to be failure of development of a normal capitellum, causing loss of contact pressure required for normal development of the radial head. This results in malformation of the radiocapitellar joint leading to altered biomechanics at the proximal radioulnar joint and abnormal development of the ulna.

Associations

• Apert syndrome
• Klinefelter syndrome
• Ehlers-Danlos syndrome
• Nail-patella syndrome
• Klippel-Feil syndrome
• scoliosis
• lower extremity anomalies

Radiographic features

Plain film

Diagnostic criteria have been proposed by McFarland ²: 

• absent or hypoplastic and flattened capitellum
• prominent ulna epicondyle
• partially abnormal trochlea
• domed radial head articular surface with a long neck
• negative ulnar variance

Ultrasound

Limited application in infants with unossified epiphyses and suspected dislocation.

Treatment and prognosis

Treatment is largely non-operative in the majority of cases ³ with analgesics and follow-up. Surgical treatments include:

• radial head excision (contraindicated in skeletally immature patients)
• radial head reconstruction ¹
• shortening of proximal radius

Differential diagnosis

Other causes for chronic radial head dislocation should be considered including post-traumatic and developmental causes ².