A case of bifid rib and additional intercostal space

Introduction The thoracic cage is made up of twelve vertebrae, sternum and twelve pairs of ribs. The ribs articulate with the vertebrae posteriorly and with the sternum through the corresponding costal cartilages anteriorly. The spaces between the adjacent ribs are called intercostal spaces. There are 11 intercostal spaces on each side. The intercostal spaces are filled with three layers of intercostal muscles and are also occupied by the intercostal nerves and vessels. It is very rare to see variations of the ribs and intercostal spaces. Knowledge of variations of ribs and intercostal spaces is important for clinicians and radiologists.