Dealing with normal variations in human body

Normally there are five lumbar vertebrae in normal human subjects. But occasionally there are six! In such a situation, a radiologist need to discern between lumbarization of S1 (S1 vertebra becomes segmented and mimics L5) or due to hypoplastic 12th ribs, hence the T12 vertebra is wrongly assumed to be L1.

This distinction matters little to the health of the patient himself but can have disastrous effect if the surgeon decides to operate on him and there is misconception of the level. Hence it is my habit to label the level of the vertebrae in the spine to avoid this.


Pictures shown in this article is one such example. At first glance, there are six lumbar vertebrae (judging from where the 12th ribs ends). But on closer inspection (see picture on the right), the 12th ribs are actually present but are hypoplastic. Hence the apparent L1 (the first vertebra without the ribs) is actually a T12 (with hypoplastic ribs).