Double-layered manubrium sterni in young children with diastrophic dysplasia.

A review of the roentgenograms, which included a lateral view of the sternum in 12 children with diastrophic dysplasia, revealed that 4 children (2 newborns, and 2 aged 1.5 years) had a double-layered manubrium with the accessory ossification located ventral to the normal manubrium. In the other 2 children, aged 5 and 11.5 years, the manubrium showed a deformity consistent with a previous double-layered manubrium in which the ventral ossification had fused with the normal dorsal element. The nature of this anomaly is not certain, but a survey of the embryology of the manubrium raises the possibility of a persistence and ossification of a primitive midline embryonic structure that normally is resorbed in its cartilaginous state.