Notching of the ribs is a radiological finding where the surface of the rib is deformed. It can be characterized as unilateral or bilateral. It can also be characterized as affecting the upper or lower surface of the rib.It can be at the superior and inferior border of the ribs.

Inferior rib notching can be associated with aortic coarctation

Aortic coarctation

Coarctation of the aorta, or aortic coarctation, is a congenital condition whereby the aorta narrows in the area where the ductus arteriosus inserts.-Types:There are three types:...

 (as a result of dilatation of intercostal arteries

Intercostal arteries

The intercostal arteries are a group of arteries that supply the area between the ribs , called the intercostal space.* Highest intercostal artery - first and second intercostal spaces...

), superior vena caval obstruction, arteriovenous fistula

Arteriovenous fistula

An arteriovenous fistula is an abnormal connection or passageway between an artery and a vein. It may be congenital, surgically created for hemodialysis treatments, or acquired due to pathologic process, such as trauma or erosion of an arterial aneurysm....

, or following a Blalock Taussig shunt.
Some causes of superior rib notching are: poliomyelitis, osteogenesis imperfecta, neurofibromatosis, Marfan's syndrome, collagen vascular disease & hyperparathyroidism.