3D CT Reconstruction of Lumbar vertebral column with L1 hemivertebra in case of congenital scoliosis

There are two main causes of congenital scoliosis:

• Hemivertebra: Failure of formation of half of the vertebral body. Each vertebral body typically forms from two chondrification centres in week 6 of embryological development. If one of these chondrification centres fails to form, only half of the vertebral body will ossify resulting in a left or right-sided hemivertebra. This may occur at more than one vertebral level resulting in multiple hemivertebrae.

In hemivertebra formation one of the chondrification centres in the body of the vertebra fails to form leading to failed ossification on one side of the vertebral body.

• Block vertebra: Failure of segmentation of the paraxial mesoderm to form discrete somites results in a merging of multiple vertebral levels which may occur unilaterally or bilaterally.
• Both hemivertebra and block vertebra.

Left = hemivertebra formation; Middle = Unilateral block vertebra; Right = Bilateral block vertebra.

Both causes of congenital scoliosis result in disproportionate growth on the right and left side of the vertebral column ultimately resulting in the lateral curvature. Often this curvature becomes more severe with age as the vertebrae continue to grow. 

Lateral curvature of vertebral column characteristic of scoliosis.

Coronal MRI of vertebral column of child with congenital scoliosis caused by hemivertebra formation

Congenital scoliosis is often associated with other developmental anomalies within the foetus including:

• 40% incidence of other bone anomalies such as fused or bifid ribs
• 10% incidence of cardiac abnormalities
• 25% incidence of urinary and/or reproductive abnormalities

A child with congenital scoliosis demonstrating both hemivertebrae and block vertebra. Also note presence of fused ribs.