Abul Cranial Shift

Homeotic transformation[1] is defined as the transformation of a spinal segment (Cervical-Thoracal-Lumbar-Sacral) into a different segment. Homeotic changes in spine identity occur at vertebral transition boundaries such as the lumbosacral transitional boundary and are associated with Homeobox (Hox) gene expression.

Vertebral precursors or somites acquire cervical, thoracic, lumbar, sacral, or coccygeal features during early development, depending on the anteroposterior axis of the embryo and Hox gene expression, and form 'segments' of these names. Homeotic shifts in the spinal transitional boundaries can be classified as cranially oriented (towards the head) or caudally oriented (towards the coccyx), depending on the direction of the change in regional identity.

Abul Cranial Shift[2] is a description for the coexistence of cranially-directed homeotic transformations in the thoracolumbar and lumbosacral regions that occur simultaneously with idiopathic scoliosis. It occurs in one in five patients, especially in idiopathic scoliosis requiring surgical treatment, and it is clinically very important to recognize it because of the risks of 'wrong level surgery' and additional loss of motion level because of the selected surgical levels.

References:

1.  Williams SA, Russo GA. Evolution of the hominoid vertebral column: The long and the short of it. Evol Anthropol. 2015;24(1):15-32. doi:10.1002/evan.21437

2.  Abul K, Özmen BB, Yücekul A, Zulemyan T, Yılgör Ç, Alanay A. If you look this way, you will see it: cranial shift in adolescent idiopathic scoliosis. Spine Deform. Published online August 3, 2022. doi:10.1007/s43390-022-00560-2