This deformity is associated with hip dysplasia and metatarsus adductus, resulting from contracture of the sternocleidomastoid muscle. The etiology remains uncertain but studies suggest that it is caused by an intrauterine Compartment Syndrome. The muscles of most affected children respond to ongoing, passive stretching within the first year. This disorder involves the middle third of the clavicle. It does not have an associated fracture callus and almost always occurs on the right side.
Surgical repair is needed if the child suffers severe pain.