Congenital
- Rare (? familial)
- Often associated with other abnormalities :
- Congenital below elbow amputation (hemimelia)
- Arthrogryposis
- Ehlers-Danlos syndrome
- Usually lateral, may be anterior or posterior
- Usually bilateral
- Patients usually notice a lump which moves on rotation of the forearm
- X-Rays show the dislocated radial head, which is dome shaped
- Treatment: If the lump limits elbow flexion, it can be excised
Developmental or Acquired
- Unilateral dislocation of the radial head may follow an untreated or unrecognised Monteggia fracture-dislocation, where the radial head can become dome shaped
- Monteggia lesion is a fracture of proximal shaft of the ulna with dislocation of the radial head and diastasis of the proximal radio-ulnar joint
- Up to 1/3 of Monteggia injuries in children are missed initially
- Ulnar injury may be a complete fracture, greenstick fracture or plastic deformation (~10%)
- 75% are anterior dislocation of the radial head with the ulna fracture angled anteriorly due to an extension / pronation injury
- Closed reduction is usually possible in a child
- If radial head not reduced or ulna unstable, operative intervention is indicated
- 25% are associated with posterior interosseous nerve injuries due to compression in the arcade of Frohse, which usually recover spontaneously
- Myositis ossificans and radioulnar synostosis may complicate post reduction
