CONGENITAL
DISLOCATION OF RADIAL HEAD
Congenital dislocation of the
radial head is typically not diagnosed until 2 to 5 years of age, when parents
notice a mild limitation of elbow extension and an abnormal lateral prominence
of the elbow in their child. The abnormality can be unilateral or bilateral,
and the most common direction of dislocation is posterior or pos-terolateral,
although anterior or lateral dislocations can occur. Approximately half of all
cases are bilateral, and in approximately 60% of patients the deformity occurs
in association with a specific syndrome or a connective tissue disorder.
Therefore, a search for other anomalies should be made whenever this
abnormality is diagnosed. Most congenital dislocations of the radial head are
asymptomatic and cause no functional disability, because the limitation of
elbow motion is mild. Congenital subluxations of the radial head are less
common than congenital dislocations but are more likely to be associated with
pain. Anterior dislocations cause a slight decrease in flexion and supination,
whereas posterior dislocations result in a slight limitation of extension and
pronation.
Plain radiographs reveal the
abnormality, and the radiographic features considered to be characteristic of a
congenital dislocation are (1) a dislocated or subluxated radial head, (2) an
underdeveloped radial head, (3) a flat or dome-shaped radial head (rather than
the normal concave cup shape), (4) a more slender radius than normal, (5) a
longer radius than normal, (6) an underdeveloped capitellum, and (7) a lack of
anterior angulation of the distal humerus. A shortened ulna may also commonly
occur with a congenital dislocation of the radial head. These associated
findings may help to distinguish a congenital dislocation from an acquired
postnatal or traumatic dislocation, as will the presence of bilaterality and
other musculoskeletal anomalies. However, a traumatic dislocation occurring in
an infant and left untreated may result in deformities over time that appear similar
to a congenital dislocation.
The lack of symptoms and
functional limitations make treatment of congenital dislocation of the radial head
largely unnecessary. Attempts at open reduction have been reported, but often
with recurrence. If an unacceptable appearance or pain can be attributed to the
dislocation, or painful arthritic changes develop, the radial head can be
excised when growth is complete. This procedure relieves pain but does not
usually improve range of motion because long-standing soft tissue contractures
persist.
