What does asymmetric transitional segment at L5 with left-sided sacralization mean?

Answer 1

This is a description of a congenital deformity or congenital malformation at the very bottom of the spine that rests on the sacral part of the pelvis, just above the tailbone. This type of deformity is fairly common, and is perhaps the most common type of spinal abnormality a person can have from birth.

What this explanation is saying is that the very last spinal bone, the 5th lumbar segment, on the left side appears to be attempting to look like part of the sacral segment that it is resting upon. Asymmetry means that the right and left sides of the L5 vertebra look different; the right side is normal and the left side is abnormal to some degree as it attempts to look like part of the sacrum. Typically, in a case of sacralization the part of L5 called the transverse process is broader and taller than it should be and might be trying to touch or articulate with the sacrum.

The explanation does not mention the degree of asymmetrical sacralization present; it could be very slight or mild or severe and extensive. The more asymmetrical a congenital deformity is, the more unstable and prone to causing pain it tends to be.

This kind of spinal malformation is not necessarily painful, but it can pose a degree of instability to the lower back and when stressed might lead to a painful low back in some people.